Tube driver mod plz?

[JimRayden]

I don't know if anyone has pulled it off but I'm searching for a certain mod for the AMZ Tube Driver. I've read the Tube Driver has an SS section to create distortion and the tube section after it to smooth it off.

I want to mod the SS-part to give me a clean boost, so the tube would be the one that saturates. Would that sound too ugly as being a starved-plate setting?

I can't redesign it myself, so any help on what to replace would be great.
Here's the schem: http://www.muzique.com/schem/tubedrvr.gif

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Jimbo

[JimRayden]

Anyone?


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Jimbo

[Gringo]

I'd lower the value of the 500k pot in the op amp loop (100k or lower), and go with a better opamp than the 4558, say a tl072.

You should build the op amp part of the circuit and listen to it on its own until you are confident that it does not clip. Then add the following tube stages.

HIH

[JimRayden]

Would it be possible to have only the tube section? Or maybe replacing the SS-part with adding a tube?

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Jimbo

[JimRayden]

Pumpedy bump.

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Jimbo

[jrc4558]

No, but you may get away with using j-fets.
Go to runoffgroove.com and lok at their emulations.

[george]

Hi

Why don't you actually build one to see if you like the sound or not?

I used to own one, I thought it sounded pretty tubey, although a bit too high gain for my tastes (I like my shaka tube better).  If the opamp was distorting , it didn't sound like it was.

You would probably get more desirable variations by trying different brands of valve.

hth

[JimRayden]

Hi

Why don't you actually build one to see if you like the sound or not?

I used to own one, I thought it sounded pretty tubey, although a bit too high gain for my tastes (I like my shaka tube better).  If the opamp was distorting , it didn't sound like it was.

You would probably get more desirable variations by trying different brands of valve.

hth

1. I HAVE built one. I want to mod it.
2. I do think it is too much gain.
3. I'm not noticing too much variation in sound when I'm changing the valves. I'm guessing that's because valve's the one that only smooths it off, not the one that distorts. I want only the valve to saturate, so I could then try different brands.

No, but you may get away with using j-fets.
Go to runoffgroove.com and lok at their emulations.

I don't see any connection between this and j-fets.

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Jimbo

[mojotron]

I have tried a lot of tubes in the Tube Driver (the 4 knob version), and noticed good deal of variations in tone/gain. The differences between JJ 12AX7 and Sovtek 12AX7WXT is pretty significant (both sound great though).

As well as putting in a really good opamp, decreasing the size of the gain pot (as mentioned before) as well as increasing the source voltage on the opamp circuit, you could bleed off some of the high frequencies in the feedback loop by putting a .1uF cap and a 12k resistor between the wiper on the gain pot and ground... stuff along those lines... would work for getting a clean boost to the tubes w/out too much redesign.

My guess is that, in a closed loop like tha on the 2nd stage, tthe opamp is doing some distorting.

[george]

2. I do think it is too much gain.

hmm think you need to build a Shaka Tube. NICE low gain sounds.

Although it might be worth trying a 12AT7 (slightly lower gain version of 12AX7), I recall this gave me a bit nicer low gain sound when I had my 9V tube driver ...

[Doug_H]

If you don't want the op amp to distort, you have 2 cards to play with: gain & headroom.  Either lower the gain of the op amp circuit, raise the voltage supply to it, or do a combination of both.

Here is a good tutorial on op amps:

http://sound.westhost.com/amp-basics4.htm

Look at the diagram of the non-inverting and inverting amplifiers and determine which one is yours. The article tells how to determine gain so you can figure out how to lower the gain from there.

Everybody wants "tube sound" but that always means different things to different people. I have not built this particular tube driver but it looks like it has the potential of being a real fizz-bomb to me. My intuition tells me the stage gains are too high and voltage supply too low, but I could be wrong, I haven't heard it.  And some people like what sounds fizzy to me.

But IMO, like others have mentioned, you would be better off with a BK Butler derived tube driver circuit like the Shaka Tube or the GGG Tube Driver. That circuit has more adequate headroom and the gains of ea stage are better balanced. And yes the op amp does distort but it sounds good so who cares?

Doug

[cd]

You know, the best thing I ever did to my starved plate/Tube Driver type pedal was to add clipping diodes (LEDs to ground) before the tube.  Improved the tone 100%, before that it was simply harsh, noisy, and amusical like a fuzz.  Even when I set the opamp stage for max headroom, it still sounded lousy IMHO.  Nothing like whacking the front end of a high headroom/voltage tube stage.

[JimRayden]

Doug, actually, I've already bought the stuff to build a GGG TD. Does that sound lower gain than the one I posted?

Also, I've already tried several tubes in my tube driver. And they didn't sound too different to me. So I thought it was because they didn't need to distort.

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Jimbo

[Doug_H]

Doug, actually, I've already bought the stuff to build a GGG TD. Does that sound lower gain than the one I posted?

Probably.

Doug

[JimRayden]

w00t

lol
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Jimbo

[nero1985]

cant u add a cap to ground on the tube's cath? like on the FET sourse,,, a .68uf film to distort the tube??

[JimRayden]

Can anyone comment on this? I'm not too good at designing. I'm good at soldering and schematic reading.  

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Jimbo

[george]

check out the Shaka tube, it has exactly this arrangement on both 12AX7 stages.

I didn't like how it made mine sound though - too bassy

[JimRayden]

Thanks, I'll try it out.

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Jimbo

[Ardric]

It looks to me like the GGG Tube Driver has an error.  C3's positive side should be connected to the other end of R3, at the junction of R3, D1 and IC1's pin 8.  Is this correct?