| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 924.1 | don't mess with vintage gear!! | ANT::JACQUES | | Fri Oct 14 1988 11:06 | 22 |
|
Most Bassman amps carry, to some degree, a high resale value
due to their "Vintage" appeal. Bottom line, I wouldn't mess with
one, even if I was a tube expert. It is much more practical to
use a stomp box, or rack mount preamp for this purpose. The chandler
and Realtube units are very reasonably priced. Dean Markley just
came out with a tube preamp that is probably inexpensive as well.
Some of the transistorized stomp-box distortion units are known
to produce a nice tube-like distortion, and most can be purchased
for around $50. I doubt you could build a good one cheap enough
to make it worth your while, but I guess it wouldn't hurt to
try. Over the years, I have done quite a few home-brew projects
but eventually, I have replaced most home-made gear for store-bought
as the money became available. You have to keep in mind that if
you have a nice guitar and amp, you want to use accessories that
will enhance, rather than detract from, your gear.
Mark
|
| 924.2 | Eq/Twin | PIWACT::JMINVILLE | Dig It Up | Fri Oct 14 1988 11:17 | 6 |
| Would it be possible to somehow put Eq between the amplifier and
the speakers of my early 70's Fender Twin? I would not want to
make any *permanent* modifications to the amp. Does this even
make sense. I'm not up on this type of thing at all.
joe.
|
| 924.3 | Well, perhaps not the fender, then | ROLL::BEFUMO | It's a happy FIZZIES party! | Fri Oct 14 1988 11:27 | 11 |
| Hmmm, I hadn't realized that Bassmans (bassmen?) had any intrinsic
value. In any case, I also have a Traynor tube head with 2 EL34s,
which I do know has little value, and hence might be a better
candidate for modification. Presumably, the procedure would be
similar for either unit. Actually, I rarely use effects at all,
and for the times I do I find that my homebrews are usually adequate.
I've yet to find a distortion box that gives me just that little
extra thickness without that grinding fuzz box sound, though I've
admittedly not auditioned them all. In any case, thanks for the
tip.
joe
|
| 924.4 | Go for it..... | VOLKS::RYEN | Rick Ryen 285-6248 | Fri Oct 14 1988 11:44 | 31 |
| Joe,
I think your idea of redoing one of the Bassman channels
as an overdrive is neat! I've forgotten most of what I
might have known about electronics but it sounds feasable,
to me. After all, Mesa engineering started out in much the
same way.... Fooling around with vintage fender Amps,
beefing up components and restructuring the basic design,
to get new sounds. Experimentation is the "mother of invention".
(or maybe it was necessity, anyway...)
If I'm not mistaken (and I often am), the first Mesa
amps were modified Fender Bassmans. (Anybody out there
who knows more about this, feel free to correct me)
Yeah, sure it's a bit risky, and you might end up smoking
the whole damn thing, but as long you don't electrocute yourself,
WTF, go for it!
I think I have a schematic for a Mesa. I'll make a copy of
it for you if you'd like. You might get some inspiration there on
how the pre-amp is set-up.
The library might have some reference books on tubes. And, there aught
to be some ole EE out there in DECland with knowledge of tubes
who might be able to review what you are doing before you throw
the power switch. I have a pile of old tubes (from a 1960's
stereo and TV) that you are welcome to have also.
Rick
|
| 924.5 | Learning from mistakes | ROLL::BEFUMO | It's a happy FIZZIES party! | Fri Oct 14 1988 12:35 | 12 |
| Hi Rick,
Yea, some schematics would be great, thanks (I'm at HLO2-1/F10).
I heard the same thing about the origins of the Mesas, which started
me thinking about this. I'd never consider doing it to a pre-CBS
unit, but the one I have is a newer model. Besides, I've ruined
more valuable instruments/amps before, and, as Peter Cook says :
"I've learned from my mistakes and can repeat them exactly". In
any case, when I had the bassman open everything in there looked
pretty simple. I'd like to get some bassman schematics, that way
I can always put it back the way it was (yea, right!). See ya.
joe
|
| 924.6 | MV mod | ELESYS::JASNIEWSKI | Our common crisis | Mon Oct 17 1988 09:25 | 29 |
|
Hi,
I'd think that you wouldnt want to tear up your Bassman. Just
cause it has "Fender" on it means it's "worth" big bucks - especially
around here. If you look, you can find equivalent amplifiers that
say "EICO" or "Heathkit" or "Knightkit" or "Capehart" or "Scott"
that are all worthless to musicians just cause they dont happen to say
"Fender". I'd rip into one of those instead.
The easiest mod to make on an existing amp is the "classic"
MASTER VOLUME! All you need is a good, dual section, 500K ohm, audio
taper potentiometer and a place to put it on the front panel. *ALL*
amplifiers with two output tubes are capacitively coupled to the
previous stage, with a resistor to ground. This resistor is usually
big in value, between 100K and 1M. Just replace these (one on each
tube) with the potentiometer, and you're there! (Hint: connect one
end of each pot section to ground, the other ends to the coupling
caps and the wiper to the grids of the tubes. Make it so that as
you turn the pot clockwise, the wiper moves from ground to the cap
connection.)
Once you have your master volume in place, you can provide
sufficient gain to overdrive the pre amp stages externally. There
are a number of "stomp-box" devices that can do this, one is a small
MXR micro amp, another is a graphic EQ that happens to have gain.
Joe Jas
|
| 924.7 | Slave labor | ROLL::BEFUMO | It's a happy FIZZIES party! | Mon Oct 17 1988 10:06 | 19 |
| Well, whetever I do, I'm definitely going to try it on the traynor
first. However, if I decide to do it on the bassman, what I had
in mind was to mount the pot on a bracket in the back, so as to
avoid chopping up the chassis, and to make sure the mod is reversable.
Im sure it's an oversimplification, but it's been my understanding
that the coveted Mesa sound was largely a result of their using
two preamps (and eq). Since I don't see myself affording a Boogie
any time soon, I'd like to try adding an additional preamp stage
& see how that works. This weekend I threw together a Craig Anderton
solid-state preamp, which seems to work & be fairly quiet. I tested
it on my Peavey practice amp, which sounds pretty crappy to begin
with, so it's hard to tell. I'll bring it to practice tomorrow
& try it on on the tube amps. If that doesn't do it I'm going to
try to cook up a tube preamp of some kind - perhaps working from
the fender or mesa schematics, & see how that works out.
joe-who-would-have-to-work-for-2-cents-an-hour-to-make-these-projects-worth-while
|
| 924.8 | Tthis month's GP | ANT::JACQUES | | Mon Oct 17 1988 10:12 | 5 |
| This month's issue of Guitar Player is dedicated to Amps.
There are sections on New amps, Vintage amps, mods, care
and feeding, etc. Check it out !
Mark
|
| 924.9 | a quick one | RICKS::CALCAGNI | | Mon Oct 17 1988 10:53 | 25 |
| A real easy "mod" you might want to try is linking the channels.
This is most often done with Marshalls but will also work with a
four input Fender. Each pair of inputs is a separate channel with
its own volume and tone controls; the top input is high sensitivity
and the bottom one is low. To link channels, plug into the high
sensitivity input of one channel, probably the NORMAL channel on
your Bassman, and run an ordinary guitar cord from the low sensitivity
input of the same channel to the high sensitivity input of the other.
You're now basically driving signal into both channels and you can
experiment with different combinations of volume and tone controls
(on a Marshall its everything wide open :-). The effect is usually
to thicken up the sound and increase sustain, although it varies
on different amps. Try it, you may like it.
Note that you can use this same technique to link multiple amps
together as well as channels on the same amp; just keep linking
from the low sensitiviy input of one to the high sensitivity input
of the other. Be careful with ground polarity on older amps with
two prong power plugs; you want both amps properly grounded and
this doesn't necessarily mean the switches are in the same position.
Also note that this only works for standard four input Fenders and
Marshalls (which are based on old Fenders) and maybe some other
amps of similar design.
/rick
|
| 924.10 | FYI | MARKER::BUCKLEY | Leftist Liberal | Mon Oct 17 1988 11:10 | 2 |
|
The `mod' described in .9 is refered to as Channel Strapping.
|
| 924.11 | I always change to 3-wire | ROLL::BEFUMO | It's a happy FIZZIES party! | Mon Oct 17 1988 14:39 | 6 |
| Thanks all,
I'll have to try the patch-cord method first, definitely.
RE:2-wire cords, the first thing I do when I get an older amp is
replace the cord with a 3-wire - tends to quite them down too, I
think.
joe
|
| 924.12 | its a mod mod world | RICKS::CALCAGNI | | Mon Oct 17 1988 14:41 | 20 |
| re adding a pot for master volume or some other purpose:
instead of mounting a bracket in the back of the amp, you might
want to try putting the pot in one of the unused input jack holes.
The jack can be unscrewed and disconnected, or even left hanging
(just secure it) and you've got a perfect hole to mount your pot.
This puts the master right out in front where you need it, doesn't
look too bad, and doesn't require any serious or permanent modification
to the amp at all. This is the way I've seen most pro master volume
mods done.
re this month's GP:
as Mark Jacques mentioned, this month's GP is devoted to amps.
There's an article on people who've become mildly famous for their
amp mods; Lee Jackson, Harry Kolbe, Paul Rivera, and some others.
I'm curious, has anyone out there in netland ever had their amps
reworked by one of these guys? Were you happy with the result?
/rick
|
| 924.13 | A hike !! | ANT::JACQUES | | Tue Oct 18 1988 09:24 | 7 |
| I have never been to any of them. The closest to New England
would be Harry Colbe in NY, or Dennis Electronics in Union
City, N.J.
The rest are in Ca, Or, and Ms.
Mark
|
| 924.14 | Dennis? I've known them for years! | SALEM::ABATELLI | Set/Mode=No_Think | Tue Oct 18 1988 15:29 | 21 |
|
I've delt with "Dennis Electronics" in N.J. for years.
Good people to deal with. When I needed parts for old Fender
amps that I was repairing, "Fender" (parts were out in Chicago) gave
me the phone number for Dennis Electronics when Fender didn't have
parts in stock. Interesting... don't you think?
You can order C.O.D. also, at least I used to.
Good Luck!
Fred
P.S. Last I spoke with these guys, they informed me that Fender
parts might be hard to get. Transformers, for example were
going to be hard to get, altho they always had the stuff I
needed. Just something to keep in mind. How about a main power
transformer from a Fender Twin and put it into a Deluxe Reverb!
Yea, then rip out that old Jensen speaker and replace it with a
Celestion, or an E.V.!! Yea...yea... that's the ticket! :^)
|
| 924.15 | How To Build a 50 Watt Deluxe | AQUA::ROST | Canned ham, that's for me | Tue Oct 18 1988 17:27 | 10 |
|
Re: .14
Don't laugh, a friend has two Deluxes and one sounds nice and dirty
at about 7 while the other one is still clean and *really* loud.
So I go take a look inside...the louder one has an Altec 12", a pair
of 6L6s and new (bigger) transformers. Kick-ass...
|
| 924.16 | RAP sez less is more sometimes | MARKER::BUCKLEY | RCMP, PMRC - No similarities | Tue Oct 18 1988 17:31 | 5 |
| R. Aspen Pitman sez most of the time he just replaces the tubes
and filter caps and cleans the connections up a bit and most amps
sing like a big time mod was done to them. Of course he replaces
the tubes withg GT's!
;^)
|
| 924.17 | low voltage | RICKS::CALCAGNI | | Tue Oct 18 1988 18:23 | 8 |
| Supposedly there are people who change (reduce?) the line voltage
into their Marshalls with a variac and get a wicked distortion sound,
although its not too cool for the amp healthwise. GP article says that
Harry Kolbe in N.Y. does a pre-amp mod that duplicates this effect
without the variac.
Of course, I occasionally get this mod free of charge, courtesy of
the local power company :-)
|
| 924.18 | Tame it! | ELESYS::JASNIEWSKI | Our common crisis | Wed Oct 19 1988 10:58 | 21 |
|
What this does is to reduce the dynamic range capability of
the preamp amplification sections, by reducing the voltage value
they have to work *within*. The stages clip sooner because they
no longer have the voltage excursion range they did at their intended
B+ power supply voltage value.
If you really wanted to, it's possible to provide this as a
function of a control setting, say, next to the pre-volume control.
However, it would reduce the gain somewhat and no-one would understand
it's function. It'd likely be "cranked to 10" along with the rest
of the controls...
If you amp has so much gain that it's unmanagable (feedsback
with the strings muffed - microphonic feedback) you could "tame"
it somewhat by increasing the value of the filter resistors in the
power supply, which would reduce the gain and dynamic range, by
reducing the voltage to the preamp tubes.
Joe Jas
|
| 924.19 | Bassman mod a snap! | ELESYS::JASNIEWSKI | Our common crisis | Wed Oct 19 1988 17:50 | 13 |
|
Judging from the schematic of the fender bassman-50 I have here,
it'd be a snap to wire the pre-amp sections in series. You could
do it so that a small patch cord, inserted into two of the 4 inputs
available, would complete the jump. By using contacting 1/4" jacks,
the amp would assume normal operation without the jumper. You just
wouldnt have two inputs *per* channel anymore - only one.
With the preamps in series, you would have two bass and two
treble controls, two pre volumes, effecting the same input signal.
Joe Jas
|
| 924.20 | DID IT! | ROLL::BEFUMO | I chase the winds of a prism ship | Mon Oct 24 1988 08:32 | 10 |
| Well, I took the plunge and installed a master volume in my bassman
this weekend. I followed the procedure described in note #256,
and the sound is super. My only concern is that some resistors
in the vicinity of the ones replaced seem to be heating up - not
a whole lot, but enought to cause the material on which they're
mounted to accumulate a shiny, waxy substance. Any advice? Would
anyone who has schematics for a bassman with master volume happen
to know if the method described in note 256 is the same as that
used in the stock amp? Thanks.
joe
|
| 924.21 | | RICKS::CALCAGNI | | Mon Oct 24 1988 10:32 | 11 |
| Although I haven't checked the Bassman schematics yet, every factory
installed master volume I've ever seen puts the pot further back
(i.e. away from the output stage) than the one you installed. The
mv mod in note 256 sounds better than factory mv's for just that
reason; you're getting a more "natural" overdrive distributed through
more stages in the signal chain.
What's the value and wattage of the resistors that seem to be cooking?
/rick
|
| 924.22 | Maybe I'm just a worrywart | ROLL::BEFUMO | I chase the winds of a prism ship | Mon Oct 24 1988 16:22 | 10 |
| I'll have to check tomorrow, but I do know that they're 1/2 W, and
fairly large, ~47-100K. I remember that cause I checked on the
availablility of 2W replacements & found that they didn't come in
that value (At least not from Active). I should explain that this
may just be a matter of paranoia - They're not getting THAT hot,
nor is anything smoking. I'm not even sure that the shiny spot
that I'm noticing in the fiberboard wasn't there before. It's just
that I want to be certain before I start using the thing - it's
not much, but it's what I got & I'd like to keep it healthy.
joe
|
| 924.24 | MESA .22 MODS | GIDDAY::COOK | | Tue Apr 11 1989 05:50 | 15 |
|
I have a Mesa Boogie .22 with a graphic eq.
My problem is that when I change between the lead and rhythm
preamp's, the volume change is to dramatic with the lead channel
being heaps louder than the rhythm. At this point in time I am
using an ME-5 to make the changes while staying on rhythm
channel.
In Australia there is only one Mesa dealer and they wouldn't
have a clue as to what can be done.
Dont get the wrong idea , the amp is a beast and I wouldn't
get rid of it for the world.
Brian
|
| 924.25 | need more input | CASV05::PELLERIN | | Wed Apr 12 1989 13:14 | 15 |
| First off, what is an ME-5?
Next, I'm not intimately familiar with the .22, but I know that
even the 2-channel (non Mark III) Boogies have a seperate lead master
volume. And I believe that the main master controls the overall
volume of the amp. It would help (unless I get to a music store
tonite and look at the front panel of a .22) if you could help me
to visualize the front panel (what knobs are there and in what order
from left to right). My hunch is that the .22 is like the old Mark
II style as follows:
preamp 1...treble...mid...bass...master 1...preamp 2...master 2
with reverb and/or presence on the front or back depending on space.
let me know and maybe I can help....
|
| 924.26 | .22 front panel | HAZEL::STARR | Like a fool, fell in love with you... | Wed Apr 12 1989 13:44 | 9 |
| I have a .22, but as I usually only use the lead channel, I can't comment on
the difference in volume. But as I remember, there wasn't too much of a
differenc when I switched....
The front panel goes like this:
gain - master - bass - mid - treble - reverb - presence - (five band EQ)
Alan S.
|
| 924.27 | Me and my Boggie | MEO34A::COOK | | Thu Apr 13 1989 04:24 | 4 |
| An ME-5 is the new (or new in oz) multi effects processor.
As the last note says , the .22 Boogie doesn't have a seperate lead
and rhythm volume.
|
| 924.28 | Call them!! | CASV05::PELLERIN | | Thu Apr 13 1989 08:50 | 22 |
| Well then, the .22 is a little different than any Boog I've own(ed).
I would be willing to bet that when you are in lead mode you are
getting the entire saturation of the preamp, and when you switch
down to rythym, the signal is tapped at a certain % of the preamp.
Since the two channels use the *same* preamp you're limited.
The only sure way is to call Boogie. I have MANY MANY times and
they are always a big help, and they *WILL* return your calls.
Any of the technicians at Mesa will help, but Steve Kimloc's name
comes to mind as someone who has always given me straight forward
clear answers to any questions.
I realize this may be expensive from the moon or wherever you are,
and it may not actually *help* (my guess is that if you run gain-1
too hot you can't effectively balance the volumes) but you *will*
get the technical reasons (in english) of how and why it works the
way it does.
Good Luck...
-BAP
|
| 924.29 | experiment | ANT::JACQUES | | Thu Apr 13 1989 09:58 | 40 |
| I'm not familiar with Boogies, but I would still suggest a little
experimenting with your amp.
First of all, does the eq affect both settings, or just the lead
setting ?? If it only affects the lead setting, you may be getting
a lot of your gain from the eq. If this is the case, try backing
all bands down equally. I would set up the eq so that the curve
is centered around 0db, rather than driving all bands above 0db.
Even if the eq affects both the rhythm and lead settings, it may
have a more dramatic affect when switched to the lead setting, since
the gain may be exponentially higher. The ME5 you are using ALSO
has an equalizor built into it which gives you even MORE gain.
You should experiment with the ME5 to make sure that all your
patches have the proper amount of eq for the amp setting you are
going to be using. If I were you, I would probably erase all the
factory programs and make up all your own from scratch. with 64
programs, you can pretty much cover all the sounds you could ever
want, but remembering all 64 patches, and what they are intended
for may be more than most people want to think about, especially
on stage.
If this is not the case, I would experiment with the gain and master
controls. I assume the gain pot only affects the lead setting. Start
with the gain pot at 0, and switch to rhythm setting. If you want the
guitar to really scream in the lead mode, the controls on the guitar
itself should be on 10. Set the amp to a rhythm setting you like, then
switch to lead mode and crank up the gain until the *volume* is where
you want it. You may find that the amp gets loud on a relatively
low gain setting, and is not distorting as much as you would like.
Chock it up to a limitation of having only one preamp. I wouldn't
fret it, since you have the ME5. You can set the ME5 to give you
all the differant distortion sounds you like. You also have the
option of running the amp with the gain set high for that singing
boogie crunch, but switch to a custom patch on the ME5 with the
master volume parameter set lower than your rhythm patches.
I'd be interested to hear if any of this pans out.
Mark Jacques_from_the_land_up_over
|
| 924.30 | volunteer.... | VIDEO::BUSENBARK | | Thu Apr 13 1989 12:39 | 6 |
| If someone will send me a set of Schematic's I'll
give it shot at modifying the amp to give you more tweaking
ability.....
Rick
|
| 924.31 | what's wrong at MB? | TOOK::SUDAMA | Living is easy with eyes closed... | Thu Apr 13 1989 13:49 | 18 |
| One of the main reasons I didn't buy a Boogie amp was because of this
limitation. Even though they claim to have a separate rhythm channel,
there is only one master volume switch for both channels. In theory you
can set the levels differently by setting the master volume to the
desired volume for the rhythm channel, and then adjusting the overdrive
to get the appropriate level for the lead channel. But in practice, in
order to get the right level of gain going into the lead channel for
the amount of sustain you want you have to adjust the master volume as
well, and cannot therefore adjust the rhythm volume independently.
Since I switch back and forth between rhythm and lead all the time I
found this very limiting. Of course, there are ways to get around it if
you are into pedals and such, but I'm not. I want an amp that does the
basics well, and I really don't understand why they don't just add
another pot to control the level on the rhythm channel independently of
the lead channel.
- Ram
|
| 924.32 | Offered Here | DNEAST::GREVE_STEVE | If all else fails, take a nap... | Thu Apr 13 1989 13:57 | 7 |
|
As a matter of fact, the guitar shop where I usually go offers
rythmn channel level control as mod, before your new amp leaves
the shop.... I could ask for his schematic, I guess.
Steve
|
| 924.33 | | DNEAST::BOTTOM_DAVID | and let the purges begin | Thu Apr 13 1989 16:29 | 13 |
| As long as we're airing why we dislike Boogies ;_), I don't care
for any amp that doesn't give me tone controls for each channel.
On the boogie, in particular if I get a good clean tone, it sounds
lousy dirty and vice versa. Now my musicman had the same problem
sorta, the dirty channel just had way too much bass, even with the
bass set to 0, so I tore it open, changed a couple of caps and now
it sounds much better to my ear, this weekend I'm gonna field test
the mods at our gig. If it still has a bass overload problem I'll
mod it somemore....
for what it's worth
dbii
|
| 924.34 | We can boogie down under | GIDDAY::COOK | | Thu Apr 13 1989 20:10 | 18 |
|
Hmmm
If anyone has a Boogie schematic I could be laughing but no one
wants to know about here. I know there is a mod to the calibre 50
to do the same thing but the design is totally different.
Regarding eq , you can set up the eq to only work on lead mode but
to get the volume down I have to cut everything dramatically which
sound pretty terrible. The ME-5 overcomes the problem but the
overdrive and distortion are not as nice as the boogie on its own.
By the way I use an 87 strat which lacks pickup volume, I have
found that this does effect the lead/rhythm ratio. The .22 Boogie
does have a seperate lead and rhythm preamp so there must be a way.
BC
|
| 924.35 | | DECWET::CARSTENSEN | | Thu Apr 13 1989 22:01 | 6 |
|
If someone has a copy of the .22 schematic, would they mind
sending me one?
Thanks,
Frank
|
| 924.36 | direct help in your area? | HAZEL::STARR | Like a fool, fell in love with you... | Thu Apr 13 1989 23:45 | 24 |
| > In Australia there is only one Mesa dealer and they wouldn't
> have a clue as to what can be done.
Brian,
I have a listing of Mesa Boogie Repair Stations, and they list two in
Australia. Maybe you can try one of these for direct advice?
PRO AUDIO
Nunzio Gambale
15 Woolley Street
Dickson, Canberra ACT 2602
Australia
062 49-7766
and
FM AUDIO SERVICES
7 Daphne Street
Prospect, SA
Australia 5082
Alan S.
|
| 924.37 | Fixed in next release | DREGS::BLICKSTEIN | Conliberative | Fri Apr 14 1989 10:25 | 17 |
| Ram,
This WAS a classic problem with boogies, but has been, IMO, adequately
addressed by the Mark III series which have three settings: lead,
rhythm (as before) and "crunch".
I've tried a few Mark III's and it certainly was an adequate solution
to the problem I have with my Mark II. I was offered the opportunity
to get my II upgraded to a III but my Boogie is (now) sorta
semi-vintage (1979) and the guys at Boogie said that in terms of
value, I'd be better off leaving it alone.
I still would NOT trade a Boogie for anything. I still haven't
tried anything else that has that "singing" quality to it and I
can't do without it.
db
|
| 924.38 | | VLNVAX::ALECLAIRE | | Fri Apr 14 1989 15:23 | 4 |
| I played a boogie last week and was disappointed. I tried a Marshall
150 W transistor head throught the same cab and liked it better.
Too bad, the cost of a power amp (2 x 200 @1300) is cheaper in boogie.
( Marshall 2 x 50 @ 1000 ). Need to look more.
|
| 924.39 | Mesa/Boogie Studio Preamp | XERO::ARNOLD | A few days older than Digital itself | Fri Apr 14 1989 17:41 | 18 |
| re: the last few
Not that I want to bog this down but, the bit about level control
on the .22 intrigued me. Thus, I dug out my relatively recent Boogie
catalog, etc. and checked it out. I was surprised to see that (as
mentioned earlier), the .22 does NOT have a separate lead drive
and lead master volume like the Mark II and III have.
I did notice, however, that the newest version of the "Studio Preamp"
(a non-power amp version of the .22) DOES have separate lead drive and
lead master controls. I think this would allow it to be easier to
balance the rhythm and lead volumes. (Not perfect, maybe, but easier.)
FYI, the "Studio Preamp" sells for $549 and, as of a few weeks ago,
they had one at Daddy's in Shrewsbury. (not that I want to go down
that path again, either).
- John -
|
| 924.23 | $? | CSC32::G_HOUSE | Back to the front | Wed Sep 27 1989 21:09 | 9 |
| Anyone know what a reasonable shop would charge to add a power amp
(line level) input to an older tube amp?
If it makes a difference, the amp that this would *probably* be done to
is a Hiwatt 100wt.
Thanks,
Greg
|
| 924.40 | Amp Modifications | OTOA01::ELLACOTT | Freddie's Revenge | Mon Dec 04 1989 12:53 | 7 |
| Can anyone out there help with this. I'm looking to collect
amp mods as there aren't many people doing them around here. I would
like ANYTHING that ANYONE might have. Comments on tone, amp life,
etc would also be appreciated.
Thnx Much
|
| 924.41 | How about a name? | GERBIL::PELKEY | Loco Boy Makes Good. | Mon Dec 04 1989 13:21 | 12 |
| There's a guy named Guy Clarret. He used to work out of Towsend,
and now, I believe he's in Groton ma. (could be wrong)
He has researched and patented several modifications to both solid
state and tub amps.
A very (no, extremly) smart, handy guy to know about.
I'm not sure if he'd give you anything on his patents, but he'd
certainly not be ojbect to some casual conversation.
|
| 924.42 | Pat's yer man! | RAVEN1::DANDREA | Fry Zsa Zsa, Free James Brown | Mon Dec 04 1989 16:05 | 6 |
| Here ya go Pat! Dump on this guy, he'll love ya!
(Pat = Raven1::Blair) who I heard in a rumor was THE EXPERT on fine tuning
Kitty Hawk cabinets!
Steve
|
| 924.43 | Too far to walk | OTOA01::ELLACOTT | Freddie's Revenge | Wed Dec 06 1989 14:41 | 6 |
| BTW I'm up in Canada....the telephone bills to Mass would kill my
budget...but I'll mail you the postage for the hardcopy stuff
Thnx FJE.
|
| 924.44 | TUBE OVERDRIVE! | JUPITR::TASHJIAN | | Thu Oct 11 1990 06:32 | 43 |
| Here is the 1st stage overdrive idea I talked about. It was 1st
done on the Vox V125 head, and allows the 1st stage to adapt to
any pickup/effect loading of the input.
Look on the schematic of your amp, and the 1st stage of preamp
tube, 1/2 of a 12AX7, has a resistor (from 800 ohm to 1,5K)
from cathode to ground. Also, there would be a small cap (25 uf on
Fenders, from 200uf to .68uf on Marshalls) accross this resistor
too. Cut the resistor, and replace it with the circuit below:
connect to tube
|
|
| | 0
| |
22K Pot | | <----
| | |
| | |
| |
|-------
| 10
| |
| |
| | 1K resistor
| |
| |
|
|
|
=====
===
-
Turn to 0 for no gain, and 10 for high gain. The british press
when reviewing the V125 LOVED this idea!!!!! I've instaled about
50 of these, and it works on most any amp.
NEXT::: the MOSFET/TUBE input stage!!!
Jay Tashjian
|
| 924.45 | Cheapo fuzz mod... | JUPITR::TASHJIAN | | Sat Oct 13 1990 05:01 | 53 |
| HERE IS ANOTHER TOY.
Add this to any tube preamp stage, the 1st tube is best, and it
works great with the input buffer item a few replys back...
Connect after output cap from 1st tube
\ /
|
|
|
-----------------
| |
| |
----- ---
/ \ \ / 1-1n9148 diodes
--- ----- or 1n4004 diodes
| |
| |
-----------------
|
|
|
---
| |
| |
10K pot | | <----
| | |
| | |
--- --- .01uf, 500vts
| ---
| |
|-------|
|
=====
===
=
This will 'soft' clip the preamp stage, and give a neat-o fuzz type
sound. and it cost zipp!
To switch it in/out, connect an on/off switch from the bottom of the
pot and cap to ground.
Till next time...
Jay Tashjian
|
| 924.46 | FENDER MOD.... | JUPITR::TASHJIAN | | Mon Oct 15 1990 05:13 | 40 |
| HERE IS A MOD FOR YOU FENDER FREAKS....ADAPTED FROM A BOOGIE DESIGN,
AND SOOOOOOOOOOOOOO CHEAP, IT SHOULD COST UNDER $2.
IN ALL 3-TONE CONTROL FENDERS, THE MID CONTROL IS CONNECTED TO
GROUND ON ONE PIN. DISCONNECT THAT GROUND WIRE, AND CONNECT THE PIN OF THE
MID POT TO THIS......
TO MID CONTROL, REPLACING GROUND WIRE------|
|
-----------------|
| |
| |
| -----
/ ----- .005 UF CAP, 200+ VTS
ON/OFF SWITCH / |
| |
-----------------|
|
|
|
=====
===
=
THIS GIVES A NICE MID BOOST. NOT A RIP OFF OF THE BOOGIE, BUT THEY
'INSPIRED' ME TO THINK OF IT...
MORE COMING SOON....POST WHAT YOU WOULD LIKE HERE.
NEXT TIME, POWER SUPPLY MODS....
JAY TASHJIAN
|
| 924.47 | FENDER MOD PART II.... | JUPITR::TASHJIAN | | Mon Oct 15 1990 05:18 | 9 |
| YES, YOU WHO ASKED, EXPERIMENT WITH DIFFERENT CAP VALUES, FROM
.005 TO .05 ON THE FENDER MOD. OUTSIDE THAT RANGE, IT SOUNDS BAD.
RUMOR: JAPAN IS LOOKING FOR TUBE AMP COMPANIES TO BUY, WITH
$$$$$$$$$$$$$$$$$$$$$ IN HAND. THOSE BEING LOOKED AT? FENDER
(AMPS ONLY), BOOGIE, BEDROCK. PEAVEY ALREADY SAID "NO".
JAYTASHJIAN
|
| 924.48 | POWER SUPPLY MOD... | JUPITR::TASHJIAN | | Mon Oct 15 1990 05:49 | 32 |
| HERE IS A POWER SUPPLY MOD FOR THOSE WHO WANT TO BOOST ATTACK ON
ANY TUBE AMP.
**WARNING** NEVER WORK ON A TUBE AMP UNLESS IT HAS BEEN OFF,
UNPLUGGED FOR OVER 3 HOURS!! I DISCLAIM ALL PROBLEMS AND INJURYS
RESULTED FROM ANYONE WORKING ON AMPS. DEATH CAN HAPPEN!!!
******* BE CAREFULL! IF YOU ARE UNSURE, ASK A TECH TO DO IT *******
ANYWAY, ALL POWER SUPPLY CAPS HAVE A + AND A - TERMINAL. ACROSS THESE
TERMINALS WIRE A .1 UF/800VOLT CAP AND A 1 UF/800VOLT CAP LIKE THIS:
+ ----------------------
| |
| |
| |
--- ---
--- ---
| |
| |
| |
- ----------------------
THIS HELPS THE POWER SUPPLY SEND VOLTS TO THE AMP FASTER, AND ALSO
QUIETS THE AMP. DO THIS TO EVERY ELECT. POWER SUPPLY CAP, BIAS
CAP (200 VOLT UNITS ARE OK FOR THE BIAS CAPS) AND YOU WILL NOTICE
THE CHANGE RIGHT AWAY! ALSO, CHANGE THE BIAS CAPS TO ANOTHER LARGER
SIZE UNIT HELPS ANY AMP. 1000UF/200VOLTS FOR EACH BIAS CAP IS A
START. REMEMBER: ANY TUBE AMP IS ONLY AS GOOD AS IT'S POWER SUPPLY!
JAY TASHJIAN
|
| 924.49 | FACTS & RUMORS.... | JUPITR::TASHJIAN | | Mon Oct 15 1990 07:17 | 28 |
| FACTS.....
FACT: THE EL34 RUNS BETTER, WITH MORE CRUNCH AT LOWER VOLTAGE LEVELS,
BUT ANY AMP WITH 1K SCREEN RESISTORS ON EL34'S RUNS BETTER WITH
IT CHANGED TO 500 OHMS. EXPLAIN?
TIP: IF YOU HAVE A 2-OUTPUT TUBE MARSHALL WITH A 1K SCREEN RESISTOR,
REMOVE THE RESISTOR AND CONNECT THE WIRE DIRECTLY. THIS WILL
BRING IT CLOSER TO 'PLEXIGLASS' SPECS. DO *!NOT!* TRY THIS
WITH 100 WATT UNITS.!!!!!
FACT: 200 WATT MARSHALL MAJORS WITH THE BIAS CUT IN HALF MAKES
THE BEST 100 WATT MARSHALL AMP AROUND. USING KT88s AT
LOWER BIAS GETS IT ALMOST TO CLASS-A. LOWER BIAS TILL
THE AMP HUMS. THEN RAISE A SLIGHT BIT.
FACT: HIWATT ONCE MADE A 400 WATT GUITAR AMP, WITH 8-KT88s!
FIND ME ONE, I'LL BUY IT.
FACT: CORAL (THE DANELECTRO FOLKS) ONCE MADE A 1000 WATT RMS HEAD!
I HAVE 2, I NEED SCHEMATICS! HELP!!! ALSO, IF YOU HAVE
DANELECTRO GUITARS, AND WANT TO SELL THEM, LET ME KNOW!
RUMOR: PEAVEY WILL DROP TUBE AMPS BY END OF 1991! FROM GOOD SOURCE!
RUMOR: AMPEG WILL DROP TUBES BY END 1990!
JAY TASHJIAN
|
| 924.50 | Top-Cut a la Vox AC30... | JUPITR::TASHJIAN | | Wed Oct 17 1990 00:34 | 43 |
| Here is the VOX AC30 'top-cut circuit' I promised:
In the output inverter stage of the power amp, a 12AX7A or 12AT7A
is used to split the signal. Output from both 1/2's of the tube are fed
into 2 caps, ranging from .01 to .47uf. After these caps, place
this circuit across the caps as shown:
| |
----------------| |-------------|-------------------------->
| | |
|
| |
| |
| |<----|
| | | 250K pot
| | |
| |
| |
| |
|------|
|
|
|
---
--- .0047 600vt cap
|
|
| | |
--------------------| |-------------|-------------------------->
| |
This just adds a simple filter to the output stage, but was very
successful for VOX from the 60's till now.
Note: On the 1st stage limiting overdrive stage, try increasing
the cap accross the pot/resistor unit to 100uf/50vt. On some
amps this helps. It also does not work well with 7025 tubes.
I'll try a few varations, and report back. More later tonight..
Jay Tashjian
|
| 924.51 | Noticed on moved notes | ICS::BUCKLEY | Racism sux! | Wed Oct 17 1990 11:00 | 8 |
|
I have moved some notes from note 1994 (TUBES, TUBES, TUBES) to here,
the Amp Mod topic, as I feel this is a more appropriate topic for that
information. 1994.0's base note was to discuss tubes and tube
amps...if you have an amp modification, please post it here in topic
924.*, thanks!
B.
|
| 924.52 | Mosfet tube bias regulator..... | JUPITR::TASHJIAN | | Thu Oct 18 1990 04:31 | 51 |
| Here is the Mosfet Tube Bias supply Regulator:
IN OUT
>---|----------|------------|--------------| |---------------------->
| | | C| |E
| | | | |
| | | -------
| | | |B ECG 262 Transistor
50uf | - | |--------| |-----
----- --- | |
----- | | | |
| + 2K | | D | | S
| | | | |
| | | -------
| --- | G ECG 2382 MOSFET
| | |
| |-------------|---------|
| | | |
| ----- | |
| \ Z / | - - |
| \ \ / 50uf ----- ----- 1uf
| ----- _____ -----
| | \ | + + |
| | | |
| | | |
|----------|-------------|---------|------>Ground
Select the Zenar diode (Z) to the - bias voltage + 10% 1-watt
Select all caps to a MIN of 100 volts!!!
This isolates the bias voltage from the signal by over 150db!!!!
Reset the bias pot after construction.
Try everything outside the amp before you hitch it up, but it is
a easy design, and works quite well. Tube life increases over 30%!
If you have any problems, e-mail me and I'll try to help. This works
up to -60 volts, over that it needs a differant Mosfet, a SJ series
would work fine. Since most amps run about -44 to -55 volts bias,
there should be no problems.
We are having fun now, by the way....
The IDEAL system would be 1 regulator to EACH TUBE !!!!!
Jay Tashjian
|
| 924.53 | MOSFET BIAS ??????s | JUPITR::TASHJIAN | | Thu Oct 18 1990 06:48 | 36 |
| To answer the 1st few ?? on the bias regulator:
1: The final output is +/- .01vt of the set -voltage. Not too bad.
2: To get the same stiffness of voltage regulation, one would need
a total of 180,000uf of caps, and you still would not have the
isolation we have here, no to mention the cost.
3: Yes, if you reverse the poles of the caps, change to a ECG 2382
Mosfet and a ECG 261 transistor, & reverse the Zener, you can do
the same for a + voltage. Try both with rack mount effects, say
+/- 15vts, or one with battery powered effects.
4: Yes, if you run your preamp tubes (not power) on +12.6vts, this
quiets it up greatly. Be carefull of current draw!
5: And yes, using one (single or set) for each channel will increase
channel seperation over 50db. I have built them into 12 channel
boards (+ & - per each channel) and it is amazing.
If you all want more, I'll try a combo MOSFET/TUBE/TRANSISTOR high
voltage B+ regulator that makes this one look like old hat!
I hope I'm not gettig too tech-ish here, but I think we got to go
forward in out quest, beyond what has been designed by others.
IF you need parts, try Mouser Electronics. The ECG ### are the same
as NTC ###. If you STILL have problems, e-mail me.
I will try to get to my back mail soon, all who send me a SASE request
get the going back towards them the same day. And, there are only now
8 packs of tube info left, after that, there is no more.
Jay Tashjian
P.O. Box 189
Worcester, Ma. 01602
PS: Thanx to Digital for allowing me to use the system to this means.
|
| 924.54 | mod help please | OTOA01::ELLACOTT | non_teenage_mutant_ninja_bassist | Wed Dec 05 1990 10:44 | 12 |
| Need two things:
1. Can a presence control be added to an Ampeg V2 (or V4), if so
how ?
2. Mesa Boogie MkII uses what kind of preamp tubes? I've got the
schematic but it doesn't say. Also it list LDR (led driven relays).
What are these and what's the chip number, they're used in the preamp
for signal switching.
Thnx
FJE
|
| 924.55 | | MOMUNY::64288::COLLUM | Oscar's only ostrich oiled an orange owl today | Wed Dec 05 1990 15:15 | 3 |
| My Mark-IIC uses 12AX7's.
Will
|
| 924.56 | | OTOA01::ELLACOTT | non_teenage_mutant_ninja_bassist | Wed Dec 05 1990 16:29 | 4 |
| Thanks much... and now the next question. How can I get a transformer
(power supply) with enough voltage for just the preamp without going to
the orginal transformer that has the current capacity for the power amp
section????
|
| 924.57 | I wanna MOD OUT my Marshall top to high-tech specs! | ICS::BUCKLEY | and he shall reign for ever and ever | Wed Dec 12 1990 10:22 | 10 |
| Can someone offer help, suggestions here (Jay Tashjian, anyone?)...
I'm looking for advice on how to MOD out my Marshall JCM 900 head to
better specs. I mean, the amp alreay sounds amazing, but I can't help
thinking that, like the KH M1 users, that there would be subtle changes
available to make the amp run more reliably, and sound more intense!!
If I get the schematics on it, anyone wanna take a shot at it???
Lemme know...
Buck, on a tone quest for the ultimate heavy rock TONE!
|
| 924.58 | | PNO::HEISER | love inhalation | Wed Dec 12 1990 11:16 | 5 |
| Buck, send me a copy of the schematics and I'll have my hardware
engineering consultant (Bob Sanders) take a look at it (same guy
helping me with my M1).
Mike
|
| 924.59 | On a Kitty I can see it, but a MARSHALL ?? | GSRC::COOPER | MIDI Rack Puke | Wed Dec 12 1990 11:33 | 3 |
| Sheeesh Buck, it's brand new !
<thud!>
|
| 924.60 | | PNO::HEISER | love inhalation | Wed Dec 12 1990 12:02 | 4 |
| It's been my experience that EVERYONE tries to get away with cheap
parts to make a profit. Even DEC! (ahhh blasphemy!)
Mike
|
| 924.61 | | POLAR::KFICZERE | | Wed May 10 1995 17:38 | 4 |
| Some pretty cool idea's in this conference.Looking for Silver-face
Bassman schematics.
-kev
|
| 924.62 | expensive experiment | POLAR::KFICZERE | | Sat Jun 03 1995 17:35 | 21 |
| Question:
I recently went to a tech and had him install a master volume in my
silverface Bassman head. I told him i wanted my amp to sound like it's
running wide open on 10,but just be able to control the volume of that
sound. He hummed and mumbled and said i can do a volume mod,but can't
gaurantee you will like the sound. I said ok,so your gonna put a pot
betwee the out-put tubes right?( an idea i got from the notes-file) He
say's he wouldn't do it like that but a vol. mod is no problem. I
figure he knows what he's talking about and say go for it. Iget it back
and i have to wind the thing to 10 (still) to get my "sound". I don't
under stand and call him.He say's it was an experiment and i'll have to
deal with it. The sound you want is from the out-put tubes being over
driven (no shite). So i'm wild!! If that original mod i was asking for
was done, would i get my sound and be able to control the volume.
I'm pretty much electrnically illeterate but can somone answer this
question?
thanx,
-kev
|
| 924.63 | experiments are expensive..... | NETCAD::BUSENBARK | | Mon Jun 05 1995 07:52 | 52 |
| Kev,
> I recently went to a tech and had him install a master volume in my
> silverface Bassman head. I told him i wanted my amp to sound like it's
> running wide open on 10,but just be able to control the volume of that
> sound. He hummed and mumbled and said i can do a volume mod,but can't
> gaurantee you will like the sound. I said ok,so your gonna put a pot
> betwee the out-put tubes right?( an idea i got from the notes-file) He
> say's he wouldn't do it like that but a vol. mod is no problem. I
> figure he knows what he's talking about and say go for it. Iget it back
> and i have to wind the thing to 10 (still) to get my "sound". I don't
> under stand and call him.He say's it was an experiment and i'll have to
> deal with it. The sound you want is from the out-put tubes being over
> driven (no shite). So i'm wild!! If that original mod i was asking for
> was done, would i get my sound and be able to control the volume.
> I'm pretty much electrnically illeterate but can somone answer this
> question?
I don't think so....
I guess your question can be answered in a variety of ways,even though
I'm not sure why anyone who is knowledgeable about amp's would have sold you
this mod. Someone correct me if I'm wrong as I need some new memory chips....
Master volume # 1 is very common in Fender amps of the early 70's
whereas single ganged master volume control came right after the preamp stage
and before the phase inverter stage of there tube amps.
Master volume # 2 is a dual ganged control replacing two resistors in
the phase inverter stage of the amp.
Mesa Boogie's have a master volume 1 but originaly in the MKI ran one
channel into the second channel. Increasing gain through several stages of the
amp. Fender ran there two channels in parallel to a single point prior to the
phase inverter/power stage. There are several similiarities between Mesa and
Fender.
People have used Tom Scholtz's power soak to overdrive the power stage
of there amp's until they realized that it decreased reliability of there
amp. Prior to Tom's soak,Jim Kelley designed an amp called the Jim Kelley FACS
amp which provided you two channels one which could be setup as a lead channel
and a second rythmn. When you changed from rythmn to lead with a footswitch
a relay would kick in a variable resistive load preset by the player. The
amp from the beginning was designed at the power stage to handle the extra load
used to decrease the volume and overdrive the power section of the amp. He
used a higher gain preamp tube in the first stages of the amp and 4 6V6 power
tubes instead of 6L6's.
Your Fender bassman is not designed to do what you want it to do. At
best you could have modified the amp to handle 6V6 power tubes instead of
the 6L6's you are using. I'm not sure if this is a reliable mod as I don't
know of anyone who has had an amp modified like this for any length of time.
Rick
|
| 924.64 | What's the diff? | POLAR::KFICZERE | | Wed Jun 07 1995 07:44 | 6 |
| Thanks Rick.Just one more quick question.Regarding #2,does it produce a
significant difference in tone/sound? Will it cause on overdrive
situation to occur faster or sr sound more pronounced than #1,or will
they basically sound the same.
-kev
|
| 924.65 | buzz factor | NETCAD::BUSENBARK | | Wed Jun 07 1995 08:01 | 10 |
| #2 provides more "buzz factor" than #1. The only time #1 worked for
me was when I used a pedal to overdrive the amp's frontend and had
hot pickups. #2 does not provide more tone/sound. If you want "preamp
overdrive" there are things you can do,such as the "mender" mod which
I'm not familiar with,but someone else in notes probably is. If you
are looking for power amp distortion/overdrive other people in notes
may know whats on the market.
Rick
|
| 924.66 | | POLAR::KFICZERE | | Wed Jun 07 1995 10:04 | 3 |
| THanks again
-kev
|