Tube Distortion/overdrive preamp circuit needed - diyAudio
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Old 29th September 2008, 09:14 PM   #1
pjpoes is offline pjpoes  United States
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Default Tube Distortion/overdrive preamp circuit needed

I have a few tube amps, some with built in gain controls, some without. I've been wanting a true tube distortion preamp for a while with more gain than my orange amps. Something that could drive my vox AC30 or my new Blackheart. Even something with more gain than my Orange amp. Anyone know of a simple schematic for a tube preamp that could be used like this. I've avoided calling this an effect pedal (I know it really is) because I want to drive the preamp tubes at normal high voltages. I was thinking that using a single 12ax7 would be fine, the iron needed should be pretty low level. I'm assuming I would need a small preamp sized power transformer, and that would really be it. I could use a CRC filter instead of an LC or CLC to save a little money and space, and run it with a tube rectifier to give it a more vintage style of over drive, and some uniqueness over typical tube preamps and pedals. I was also thinking of using up some of my carbon comp resistors and vitamin Q capacitors.
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Old 29th September 2008, 09:58 PM   #2
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hi,

I all depends on what kind of sound you are looking for.. do you just want a boost, of a complete high-gain tube-preamp?

eg. I have build the Mesa Rectifier series preamp, and it functions very good. I can get really close to the youtube vids of the real thing, but I now realize that it is not at all the sound I was looking for.

Anyways, plenty of preamp circuits are availeble on the net, just google for Mesa, Marshall, ENGL, Ashdown, Soldano,Bogner (eg. Triple Giant), Egnater.... etc..

You might also want to consider a Power Attenuator, so you can push you amps more, without the extreme SPLs...


goodluck,
Thijs
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Old 29th September 2008, 10:28 PM   #3
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Thanks for the advice. I'm looking for something probably more along the lines of boost than pure distortion, but I have tried boost pedals, and they aren't what I want either. However, I'm not a shredder and I'm not looking for massive amounts of distortion. Creamy sustain thats very touch sensitive.

I do have a few home brew power breaks and such. Mostly made from resistors at the moment. I've considered buying a weber unit with reactive load, as I think it will sound better, but haven't wanted to spend the money.

On a completely seperate note, why do people think that Black Beauty caps in the .022uf size are worth 15 dollars a piece or more. Even remakes are getting too much. For that kind of money I could buy those jensen audiophile pieces. Even Sangamo, Pyramid, and others are going for 10-12 dollars, I mean, are you kidding me!!! I didn't want to use the Russian ones, I wanted actual NOS ones, but at these prices I'm gonna be stuck.
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Old 30th September 2008, 12:15 AM   #4
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I don't think you'll necessarily find the sound you want by employing tubes here. A lot of people find transistor pedals acceptable.

Have you tried a compressor?

How loud do you play? Do you get feedback if you crowd the stack?

There's more than just the amplification to consider. Have you tried a different gauge of strings? For example, if you were trying to sound like B.B. King he's known for using strings like piano wire.

I had a cheap strat copy once. The fingerboard varnish wore through, when I had the spare cash I traded it for a Squier. The Squier was a nice, solid predictable machine but I could only make it whistle and hiss like the other one with the greatest physical effort. I think it was the wood, but it might have been the pickups. By the time I figured it out, the shop had sold the other one. Damn.

w
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Old 30th September 2008, 03:56 AM   #5
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well.... let's see if i can find it....

i've used 2 of these cascaded with a 12V wall wart supply (rather than the 40V shown) and get a surprising amount of gain out of it. and the tubes i used weren't the 12ax7's shown, but 6BF7 submini tubes with a lot less gain than 12AX7's. it's a nice stompbox with enough boost, and tube sound.... you'll want to add 1meg level pots at the input and output
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Old 30th September 2008, 04:08 AM   #6
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thanks but I think that may not be what I'm looking for.

no I don't get feedback when I'm right up on the stack.

How loud I play is unimportant for what I'm looking for.

I don't like transistor distortion pedals and never have. The touch sensitivity of the sustain is completely different than with tubes to me, I'm not sure why, but I've never used a distortion pedal I liked, and I have plenty.

I don't like compressor pedals either, thats not the sound I'm going for, but again, thanks for the input.

B.B. King strung his lucille with .010 .013 .017p .032w .045w .054w gauge strings. My style of playing is very different from his, I prefer more sustain and bend my notes much farther, I also don't have his fat heavy fingers, and so such thick strings just aren't for me. It does make for a different sound, I'm well aware of that (My Gibson ES-165 has similar strings on it), but again, for what I'm looking for, strings will not be the answer.
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Old 30th September 2008, 04:14 AM   #7
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I should add on the string thing, 10-54, while an unusual combination, is actually more of a medium to heavy, not a true heavy combo. Heavy would be 11-50. I think the real heavy string players are the hard rockers doing drop tuning style playing.

ok I'm gonna change this a little, cuz a 54 is a pretty heavy E string, but the 10 is a medium weight higher string. I know some punk rock guys that play drop D tuning and use very heavy 6th and 7th strings in the .06-.08 range, and I've been told that some will actually put a real bass string on at .1, but I can't even imagine playing that.

Again, I'm a medium to light player, I usually play 9-42 or 9.5-45's on my tele, strat, and Phiga, while I play an 11-49 or 10-46 on my gibsons. It's just a preference for the style I play on each guitar. They are setup for those gauge strings and just seem to be a sweet spot for them.
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Old 30th September 2008, 04:17 AM   #8
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with most average-to-hot pickups, the tube pre shown above will distort if driven hard enough. gain with 6BF7 tubes is about 30, with 12AX7's probably closer to 75-100 (with 2 of the circuit shown above cascaded and running 12V plate voltage). if set right to the edge between clean and dirty, it has a real nice smooth "touch" since it doesn't go into hard clipping
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Old 30th September 2008, 04:24 AM   #9
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I just haven't been happy with the low voltage tube pedals I have used. I'm not going to argue if it works for my needs as I haven't tried, but I'm still thinking that I would prefer to build something in the higher voltage range, running full plates. While its considerably more expensive than what I want to spend, Torres offers a kit very similar to what I want.
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Old 30th September 2008, 04:35 AM   #10
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Quote:
Originally posted by pjpoes
While its considerably more expensive than what I want to spend, Torres offers a kit very similar to what I want.
So is what you really want a clone of this kit? Don't take this the wrong way as I am trying to help, but I am finding your posts very difficult to follow because you are describing the sound you want AND fixing these subjective and sometimes counter-intuitive design aspects that must be met in achieving that sound.
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