Your high gain approach?

[chipaudette]

Matt,

The issue of voltages in the pre-amp has long been of interest to me. Since I was modding my DRRI, I was stuck with with the pre-amp voltages I had...basically ~260V. The Mesa Boogie pre-amp that I was emulating, though, runs at voltages up around 400V somewhere. I've always wondered how my low voltage levels affected the tone of the pre-amp relative to the real thing. Since I don't have a real boogie to compare to (and even if I did, my power amp and speaker are totally different), I can't answer that question.

It sounds like you, however, have built an amp and adjusted its pre-amp voltages. When it sounded "horrible", what was wrong with the sound? How did the sound get better when you used the right voltages?

Also, more on the theory side, I've wondered if the tone of an overdriven 12AX7 gain stage in a typical guitar amp is related directly to the supply voltage, or if the overdrive tone is more related how the tube ends up getting biased based on the supply voltage and surrounding resistors. If it is mostly a bias issue, some smart person would know how to scale the plate resistor and the cathode resistor so that my 260V supply would end up biasing the tubes to the same point as the 400V boogie pre-amp does. It gets complicated because this smart person would also have to change the coupling caps (and maybe other elements) in response to any change in plate resistor. Messy messy messy.

So, yeah, can you put any more words to your experience with the impact of pre-amp voltage supply on overdrive tone?

Thanks,

Chip

[Tubis]

I built and modified a lot of highgain and these are my points.
The more distortion the more bas and treble cut. Cut a lot of bas and a lot of low mid before the first distortion stage. Cut a lot of treble after the first distortion stage.
Go for small bypass caps on the cathodes. I?ve tried big bypasscaps and filter down more between the stages but the sound becomes more muddy and not as separated in the notes.
Go full signal into the first and second distortion stage.
Scale down the signal into the third to taste.
Lots of compression, sustain, easy shredable and all that shit if you put high signal into it.
More separated notes, dryer sounding distortion, more dynamic string respons if lower signal goes into the third stage.
If you feel the need for a fourth distortion stage, just put a dc coupled cathode follower at the end and that will cut the other half of the signal and ad more distortion.
Gridstoppers is a must if there is no other big resistors before the grids or they can load down the stage before and it sounds like shit. Remember, the gridstoppers roll of treble.
Big giant caps like sprauge orange drops can be giant antennas in the amp. Use small caps. Use shielded cables as much as possible.
Modifying an amp like the JMP with huge PCB traces could leed to squeeling. The traces act like big antennas. Avoid using those traces.

Any spelling mistakes is because i?m from sweden.

[chipaudette]

Steve,

I checked out runoffgroove.com as you suggested. Based on the text descriptions, I only saw one boogie attempt -- the "Uno", which is an attempt at a Mk I. Listening to the sound clip I wasn't that impressed. I thought that it had quite a bit of the transistor ratty-ness. The single note tone was OK (though not spongy and liquid like it should be) but the comp'd power chords sounded awful.

I also checked out the Double D. On the "bounce" setting (higher gain), he got some fun tone that enabled plenty of pinch harmonics...but again, I thought it sounded more ratty than I'd like.

Do you have any other designs that you recomend that I check out?

Chip

[booj]

Marshall MK2 for pedals. 2204 for plug in and play.

[mooreamps]

Two amps you didn't mention are disscussed in detail at:

http://ampgarage.com/forum/

You'll have to sign up to gain access to most of the good stuff but it's well worth it.

B/S. They'd just as soon nail you to a cross, and then set it on fire. Bunch of FK amatures, just all "full of themselves" with their heads stuffed up it. You won't find any real help there....

[Enzo]

Oh come on now, tell us what you really think...

[daz]

The only thing I can add is that if I'm building a high-gain amp...it MUST have an effects loop. I can get high-gain tones from a goosed Marshall...but that doesn't have any good way to put time-based effects on it. So if I'm going to all the trouble of building I really have to have a loop. That won't be the case for everybody but for me it is a must.

I used to feel the same, but there is a better alternative that affects your tone 0% and even adds a benefit. Take the direct out and go to a seperate effects amp. You get the benefit os a sort of stereo tone. At gigs it's a must for me, and going back to a single amp was horrible. It also only takes a tiny amp because unless you are a effects whore who's tone is always so wet it's drowning, you only need a very small amp just to amplify the delay repeats or the modulating part of a chorus signal etc. At home you could use a pignose or something that tiny. At a gig i use to use a classic 30, and that was way more than i needed. A blues junior would be too, but is plenty small enough. And if you use a direct out right off the speaker you get the main amp's entire signal output section and all. So any clean amp will work fine for the effects amp. in fact, the cleaner the better.

Loops are ok, but no matter how good they are they will never be as good as this method. So if you go to lengths to get great tone, why sacrifice even a drop of it when this way won't hurt it in the least and can actually improve it with the stereo effect it has.

[loudthud]

B/S. They'd just as soon nail you to a cross, and then set it on fire. Bunch of FK amatures, just all "full of themselves" with their heads stuffed up it. You won't find any real help there....

You won't get much help with that attitude. Chipaudette wasn't looking for help, just documentation on the designs and to see what other people have done. There are many posts with pictures, discussions on tweeking layouts, component selection and schematics. Certainly there is going to be disagreement, sometimes heated, among posters. And the site has it's share of back stabbing *holes. But there is good information there once you sort through it all.

You won't see the pictures or have access to the schematics unless you sign up.

[MattT]

daz,
Some amps sound better with a loop. The Soldano SLO is one example...that specific loop is part of the SLO tone. The ODS is another...that amp is usually built with a 'passive' loop (just preamp OUT and power amp IN jacks) but many players prefer the tone when the passive loop is plugged into the D'Lator (which is a buffered CF SEND and gain stage RETURN).

B/S. They'd just as soon nail you to a cross, and then set it on fire. Bunch of FK amatures, just all "full of themselves" with their heads stuffed up it. You won't find any real help there...

If you want to be hand-held/babysat...then you're right...not much help there. But if you're more self-reliant and are willing to sort through the ton of info there...it's there.