| Title: | GUITARnotes - Where Every Note has Emotion |
| Notice: | Discussion of the finer stringed instruments |
| Moderator: | KDX200::COOPER |
| Created: | Thu Aug 14 1986 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 3280 |
| Total number of notes: | 61432 |
OK, like I picked up this Altec amplifier for $20 the other
day, it's one of those old 4 input mixer monophonic PA amps. The
gentleman I bought it from said it came from a church, where they
had upgraded to stereo. Sure enough, the inputs were marked with
"podium" and "alter" and the levels were marked also. It has 6L6
output tubes and puts out 20 watts of power. Going into the thing,
I stripped out 4 nice cannon connectors and 4 low to hi Z impedance
transformers, which will be used for another project. There are
4 12AX7 input stages, each feeding into a volume control, with the
wiper connecting to a mixer bus through a 47K ohm resistor. So,
what do ya do? Well, ya cut the first three 47Ks from that mixer
bus and feed each of those into the next stage so as to cascade
all 4 12AX7 input stages. Now, we have a 1/4' guitar jack into the
1st stage of 12AX7 amplification, out through the 1st volume control
and into the second stage... - ...out of the 4th volume control
and into that mixer bus, which was shortened a bit to avoid hum.
That's 4 pre volumes and one master, bass and treble on what I call
THE PREACHER. It screams...
Joe Jas
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 557.1 | Wow | CSC32::G_HOUSE | Greg House - CSC/CS | Tue Mar 29 1988 14:27 | 5 |
Great idea! Sounds like it would really have a lot of flexability
in the max distortion dept. Bet it's a blast! Where can I get
one?
Greg
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| 557.2 | For that Van Halen sound | MARKER::BUCKLEY | Rocker Built for Speed! | Tue Mar 29 1988 14:38 | 10 |
Joe,
from there you need to wire a load box to it, and put a line out
after the master volume to allow this unit to be plugged into
power amps. You know, like a (bridged) CS800 or something.
That would be rock n roll!
wjb
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| 557.3 | question | RICKS::CALCAGNI | Tue Mar 29 1988 15:16 | 6 | |
Where do the bass and treble pots fit in? I've got this idea
(unsubstantiated) that the best place is after the final pre-amp
stage. Some of the old Fender tweeds do it this way, as opposed
to newer designs which have tone controls early in the signal chain.
/rick
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| 557.4 | Just Kidding! | VIDEO::BUSENBARK | Tue Mar 29 1988 16:42 | 6 | |
And just think you didn't have to spend $1k to $2k for it and
didn't wait for months for delivery......
So when are you going to hook up a PDP8 to it?
:^)
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| 557.5 | Re-re-re-re-re - I feel like the Supremes! | FLOWER::JASNIEWSKI | Tue Mar 29 1988 17:30 | 11 | |
Re .1 - I dont know - stumbled on this one!
Re .2 - Or, I can drive that 350 watter I'm try'in to sell
Re .3 - Although I dont know, dont have a schematic, I suspect
the tone controls do reside "downstream" from the preamp section.
Re .4 - Not a PDP-8, but those 4 octal sockets which held the
impedance changing transformers would make a fine relay socket,
for channel switching.
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| 557.6 | Preacher => FDA | ELESYS::JASNIEWSKI | This is the story so far! | Mon Dec 19 1988 12:00 | 35 |
The Preacher got a drastic transformation this past week. It's
now a Full Differential Amplifier, and, I needed a place to document
the event. This one seems obscure enough...
I completely rewired the thing. WJB hinted at master volumes
after the phase splitter sound better, so I... Hmmmmm, maybe better
not give out the unique circuit topology in a public forum just
yet! As far as I know, no one has built such a unique circuit with
the intent of rendering the "Metal" sound. There is a feature, which
falls out of the design *structure*, that generates "the sound"
I believe...
:')
Right now, it's a true HM amp. It's got pre and master volume
- that's it. For reasons unbeknownst to me, it doesnt seem to *need*
any tonal compensation, which I hope is another natural "flaw" due to
it's structure :'). It's very powerful, seemingly pumping more than
20 watts! I can literally shake the house with it. It's the highest
gain thing I've ever built, that remains stable...I'll definately
need a "Mesa/Boogie" 12AX7 to help fight the microphonics in that
first tube though!
It's got a very full, wholesome tone - perhaps about as "fat"
as you can get. It's got a good crunch all on it's own and will
sing (of course) something for ya for nearly every bar chord. It
seems to have a great high end and loves those "little harmonic
things" that the HM players do which I guess is really "chicken
picken" or "fleshing" the string. I believe that any tonal compensation
needed could be rendered by a graphic eq after the guitar or by
choice of speaker system. I'm using a 100 Watt Yamaha 12" mounted
in a EV monitor style cab, which seems to work fine.
Joe Jas
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