preamps and tone stack hope this dont sound to stupid

[dixiedevil1369]

ok i'm no math wiz nor have i ever built an amp but i am getting ready to give it a go with the help of my amp tech guiding me thru so to get on with it from my understanding the more preamp tubes you have the more gain you could achieve if i do a 6550 or a 6L6 based power supply could i or would it help my gain stage if instead or the same ole 3 to 4 preamp tube setup most commonly used today if i was to use 8 preamp tubes in my gain stage would this work? would i have to have more than 4 power tubes?

like i said this probably sounds really stupid but it was a idea i had any imput would be great.

[Wilder Amplification]

You would have to most likely throw away most of the gain via the interstage coupling components to keep from slamming the grids of the downstream stages too hard and prevent blocking distortion if you planned on cascading every stage. Or you can set a few of them up as DC coupled cathode followers, common cathode triode stages w/local NFB or paralleled stages w/split cathodes, etc etc. You can even do a cathodyne+ phase inverter circuit w/buffered outputs with two of the preamp tubes. But the amount of preamp tubes/gain stages you have in the preamp has nothing to do with how many power tubes you have in the power amp. That all has to do with the OT primary impedance you run vs B+ voltage vs rated plate dissipation, power output, power supply current source, etc etc.

My only question is...why?

[dixiedevil1369]

i'm on a tone quest to get all the distortion i can from a amp head instead of pedals pedals are great but i when it comes to my overdrive and distortion i want the tubes to bring it home or what ever else in there brings it in i guess i should have asked this diffenerent now that i look at it so to put it to point i want to get more gain and distortion without haveing to use pedals i have 2 amp heads now and i know the 1 with the 6550 power is bringing in the distortion and gain and i know that the 2nd amp i have that runs 4 12AX7's is bringing it in i just need more so in my mind i was thinking more tubes more gain.

what you discribed sounded like i wouldnt be doing anything other than adding more weight to my amp is i added more tubes instead of getting more gain so that tells me i need to figure out how to get my gain from another component that s in the amp

[Wilder Amplification]

You seriously don't need that many tubes to get the gain you're seeking. I've done it with 4 preamp tubes (one of them being the phase inverter) as well as with the stock 3 that you find in a Marshall.

Here's an open source mod I came up with that I've done to a couple of 2203/2204 preamps. The only other thing that this scheme doesn't show is the 0.01uF cap I place in series with the NFB resistor in the output section to beef up the low end since the front end is treble peaked. I use a 100K NFB resistor in series with the 0.01uF cap with the NFB taken from the 16 ohm tap.



Awesome sounding high gain preamp that you won't need an external boost with. It's all in where in the audio pass band you add the gain...not just "add gain in general".

[defaced]

if i do a 6550 or a 6L6 based power supply could i or would it help my gain stage if instead or the same ole 3 to 4 preamp tube setup most commonly used today if i was to use 8 preamp tubes in my gain stage would this work? would i have to have more than 4 power tubes?

No, you don't need more power tubes for more preamp tubes. Think of an amp as two parts, a preamp and a power amp. For this discussion they're basically work independently. The preamp shapes the tone, the power amp makes the signal bigger to drive the speaker. So if you have more tone shaping preamp tubes, it doesn't really mean too much to the power tubes provided you don't slam them with too large of a signal.

I agree with Jon though, 8 preamp tubes is very excessive. If I were you, I'd start with 4 gain stages (2 tubes) which is pretty common (Recto, SLO, VHT Deliverance, etc), and go from there. More is almost positively not better in this case, unless you like unstable amps with lots of noise (Peavey 5150 for example has lots of preamp stages and also a lot of noise).

[dixiedevil1369]

thanx for the info guys this will help alot and since where on the subject here i have been thinking of doing a amp with instead of a normal gain(distortion) i always wondered what it would sound like if i could put fuzz in instead of gain(distortion)

[Wilder Amplification]

First off...gain is NOT distortion. Too much gain is what causes overdrive...meaning that you're amplifying the signal more than what you need to be to drive the next stage to full output swing, which creates "distortion" (or you're attempting to add more gain than what the amplifying stage itself can supply cleanly, which allows the input signal to push the stage into overdrive).

Some people get "gain" and "headroom" confused and think they're co-related. Headroom is gain that you're not using and when you increase gain you use up headroom. Headroom has more to do with how high the signal can swing and is determined via the B+ voltage and the plate resistor value (some understanding of load lines and grid curves will reveal why the plate resistor comes into play on it). The plate resistor also affects gain as well. Increasing gain just increases the input sensitivity of the stage so that a smaller signal is needed to push the output signal swing to maximum.

That being said, fuzz and distortion both involve overdriving a gain stage. However, fuzz involves overdriving the snot out of a stage more than regular "distortion" would. Due to the way the grid limits the input signal on a tube stage when the grid is pushed beyond zero volts I don't think tubes are very well suited to a "fuzz" type overdrive without some sort of clipper diode circuit. But since I'm not a fuzz fan I've never attempted to do a fuzz circuit with tubes so I could be way off base here.