Need Expert Help on home-brew project
Kman2ya
want to build a guitar amp from it. This will be my first attempt at
anything tubular electronic, so please bear with me as I am determined
to learn this stuff. Hell I put this 12 node NT 4 network together at
home from parts so....maybe with some direction I can learn this too. I
presently play guitar through a Fender Tone-Master w/4x12, a Fender M-80
Chorus 2x12 (ss) and a Crate Vintage Club 20 with a 10". Lately, in a
smaller venue I will play the Crate through the Fender Tone-Master 4x12
bottom. It always gets the guitar guys asking questions about the "rig"
when they hear me play. It really sounds good and most won't believe it
is a stock VC20. I think it's just that the little amp is turned all the
way up making my guitar tone and harmonics come alive. (can I ruin
something here?) To reproduce this feel with the 100 watt Tone-Master is
really too loud (killer sound though). It has knocked things off of the
walls to the dismay of club owners. I bought and use the VC20 by itself
at practice but am gigging with it now. I will use all three together
sometimes in a stereo config in bigger situations. I play a Strat Deluxe
Plus w/lace sesnsors, a 53 tele, a late 60's gretsch CGent, a 56
Danelectro re-issue and various acoustics - all top $ wood. I use the SS
M-80 chorus for the acoustic guitar clarity in the mix. It just works
better. Cuts right through.
Ok my problem is I need to learn to bias and maintain these two tube
amps, and cannot afford to learn on the Tone-Master and really don't
want to mess with the Crate. I am possesed with the urge to wire
something up from scratch. As for my wattage and tonal needs - I need an
in between and considered a VC30 because of the tone of my VC20. I read
all the tube FAQ's I could find and decided I want to build something
special that gives me:
1. 30 or so tube watts.
2. Good power tube saturation
3. ability to use with 4x12 2x12 1x12 1x15 1x8 and 1x5 cabs
4. power attenuation. I want to use this as a power amp for my isolation
cabinets also.
5. some way to vary the wattage to reduce it for recording flexability
with total saturation at lower volumes and smaller speakers.
My dinosaur egg is a Bell Carillon Model 35-A 35 watt amplifier with:
2 RCA 6L6GC's
3 12AX7's (two DOA)
1 12AV6
3 HI-Z microphone inputs
1 aux phono input
4 - 8 - 16 ohm speaker connections
The front panel has 7 knobs:
Mic 1, 2 and 3
Program
Master
Bass
Treble
(I would want to add a midrange.)
The amp was mfg. by Bell P/A Products at 1209 N. Fifth St. Columbus, OH
43201
It sounds cool to me, but is this feasable? Am I nuts? Should I look for
another amp? What about schematics? Adding 2 more 6L6's?
Resonses Please: Lord Valve? Tremolux? AmpTech? Anybody? What would
ToneHog2 say?
I'm here to stay 'til I get it done!!!
Thanks so much. Kman2ya
}:~
Please remove NO SPAM from address to email.
Mutantmoose
<3660611C...@SPAMconcentric.net>...
> I need some help here. I acquired an old beat up 35 watt tube PA and
> want to build a guitar amp from it. This will be my first attempt at
> anything tubular electronic, so please bear with me as I am determined
> to learn this stuff.
Well, as usual, here's what I do - give an address!!
There's an article on doing this kind of conversion - it may explain much
more than I could, and is probably clearer.
Good luck!!
Mark
Kman2ya
I was there and looked to find this URL
http://www.wwu.edu/~n9343176/docs/old2new.html cannot be found and it is
what I might need.
Exerpt from http://www.eden.com/~keen/tubeampfaq/tube_amp.htm#Section1:
What is the easiest way to get tube sound at a good price?
Back to the index...
Obtain an old piece of tube gear, perhaps intended for another purpose,
like mono hifi, at no or low cost. Modify this
to duplicate to a certain extent the circuit of an existing amplifier.
Tinker to your heart's content.
There is a document on exactly this at
http://www.wwu.edu/~n9343176/docs/old2new.html The document goes into
excellent detail on the in's and out's of building from old tube gear
and the possible and useful variations of which
stages with how much gain go where in the amp.
Build a tube preamp from scratch, and use this to drive another larger
amplifier which does not necessarily have to be
tube based. I have designed things like this, so have others. Good tube
sound, and inexpensive. Really convincing
tube distortion, especially if you add some lowpass filtering to
simulate the high frequency cutoff of guitar speakers.
This is what the Hughes and Kettner Blues Master and Cream Machine tube
preamps did (they've been
discontinued). These were entire tube amplifiers with maybe 2 or 3 watts
output, a simulated load, and a line level
output in addition to the speaker output. They did a VERY respectable
job.
Do you know of any other locations?
Thanks Kurt.
Mike Schway
<kman...@SPAMconcentric.net> wrote:
[lots snipped]
> My dinosaur egg is a Bell Carillon Model 35-A 35 watt amplifier with:
> 2 RCA 6L6GC's
> 3 12AX7's (two DOA)
> 1 12AV6
> 3 HI-Z microphone inputs
> 1 aux phono input
> 4 - 8 - 16 ohm speaker connections
>
> The front panel has 7 knobs:
> Mic 1, 2 and 3
> Program
> Master
> Bass
> Treble
> (I would want to add a midrange.)
> The amp was mfg. by Bell P/A Products at 1209 N. Fifth St. Columbus, OH
> 43201
>
> It sounds cool to me, but is this feasable? Am I nuts? Should I look for
> another amp? What about schematics? Adding 2 more 6L6's?
>
> Resonses Please: Lord Valve? Tremolux? AmpTech? Anybody? What would
> ToneHog2 say?
> I'm here to stay 'til I get it done!!!
> Thanks so much. Kman2ya
Dunno if you'll get any good info from TH2, so I'll chime in here.
If it were my chassis, first thing I'd do is to try and get the original
circuit in working condition. Replace cordset to 3-wire type. Replace
obvious bad tubes and caps, change input load to 68K ohm in series to grid
of V1, 1M ohm to ground, and 1000-1500 ohm at cathode (bypassd with a 25uF
cap). Plug in and play. If it sounds good, dont change a thing (except
maybe upgrade the coupling and filter caps and resistors which have gone
far off-value). If B+ is 415V or less, try 6V6's instead of 6L6's for
smoother and earlier overdrive and a honey-like clean tone. (you'll have
to rebias if it's a fixed bias).
If it's real tubby, noisy or otherwise not to your liking, you may save
time in the long run by gutting the thing entirely. Remove everything
from the tube sockets, get rid of rust, build up a good star ground and
put together a circuit from scratch. Old-style terminal strips work well,
but you really have to thoroughly plan your component layout well in
advance. Other possibilities for a one-off job might be perfboard. If
you do a good job, it'll fly right for the long haul, although replacing
components can be hassle.
Don't add another pair of 6L6's! Your power and output trannies may not
handle it and (if I read your post correctly), you're after a managable
overdrive.
Hopefully the power and output trannies are still good. Find a good ol'
classic to clone. Good candidates for a first time project might include
a late tweed Deluxe or BF Deluxe. Personally, I'm partial to the BF
deluxe preamp and phase splitter with a cathode biased power stage. With
a cathode bias, you don't have to worry about a bias supply, but it's no
biggie to derive a bias supply from the rectifier plates. A cathode bias
has a sweeter sounding overdrive but a fixed bias has a tad more clean
headroom.
On second look, it appears you don't have a rectifier tube. That true?
If so, then you probably will have to do a cathode bias unless the power
tranny has a convenient bias tap.
I could babble on and on, but obviously shouldn't. Check out websites for
Duncan's Amp Pages, Ampage, and Keen's effects page.
Good sources for schematics are Ampage, Ned Carlson's site, The Pittman
book, Dave Funk's Tube Amp book (my favorite for all things Fender), and
Gerald Weber's Desktop Guide to Hip amps. Folks like to slam Torres for
his mods and his attitude, but his book has lots of useful info for
first-time homebrews.
Good luck. It'll be worth it in the long haul (though dont expect to save
any money!) Hope this helps.
--Mike Schway
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Mike Schway | [watch this space]
msc...@nas.com |
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