Any amp modders around?

[covil]

I´ve bought this preamp just to start messing with it!! Doesn´t cost much and has three independent channels!!http://http://www.musikding.de/product_info.php/info/p2515_Anvil-Tube-Preamp-Kit.html

 

[covil]

I think Lasse also has one!!!

 

[Mago]

I´ve bought this preamp just to start messing with it!! Doesn´t cost much and has three independent channels!!http://http://www.musikding.de/product_info.php/info/p2515_Anvil-Tube-Preamp-Kit.html

yeah, awesome little thingy!
Works nice with impulses for home
http://dl.dropbox.com/u/3961577/Mixes/Mago_Preampsoundcheck_AsianHookerInstrumental.mp3


Also it works really cool with the power section of my 6505+.
Sounds tits!
I think lasse has a clip somewhere with it through the poweramp of the überschall

edit: found it
http://www.lasselammert.com/sonstiges/Anvil.mp3

 

[JakeAC5253]

I agree this design might be a bit loaded for a beginner to learn the ropes, but if you still can't get the tight sound you want, you can try removing c202 on V2A, and see if that helps clear it up a bit. You can always replace it if you don't like the sound when removed.

 

[JonWormwood]

The trick with this is to kill the low end gain in all the gain stages, remove some high end in the 2nd and/or 3rd stage (usually just the third with the SLO based amps) and get back your low end by achieving high amounts of attenuation in the tonestack. What the attenuation does is provide an apparent "boost" to the highs and lows. Generally in high gain amps, if you want more bass you can increase the value of the bass pot. Further bass boost is achieved through more attenuation in the power amp section's Global feedback circuit in Phase Inverter driven power amps.

To Jon, the Lee Jackson you posted is probably not the best amp for a beginner to learn to mod on, it strays way too much from the basic, classic and historical design. I would say you are better off building something like the gain stage of an SLO or something similar and modding things to taste. With that you could even throw a clean channel in there as you would have half a tube not being used. A switch or foot switch jack, a relay and a connection to a low voltage would be all you would need for basic channel switching.

Also Jon, the reason that you are not getting huge results with decreasing the cathode bypass caps is because you said it, you increased the gain on the stages by decreasing the cathode resistor. This mitigates the effect of the bypass capacitors. Its a long explanation with some equations, I am more than happy to explain, but simply put, when a cathode bypass cap is being used, the gain of all signals above the resonant frequency will be as if there was no cathode resistor in terms of gain. All you are doing when you mess with the gain via the cathode resistor is increasing the gain on the low end, the gain on the highs never changes. Try going back to the stock cathode resistor values, and decrease the bypass caps on V1a (C1) and V2a (C3) to 1uF.

Well I'd love to build a SLO style pre amp but these are what I have and it interests me. I'm not looking to get too in depth, I'm ordering the Merlin preamp book and I've been looking at the RCA radiotron one as well.

I went back to 1.5k and I'm starting to understanding that there's a relationship that's going on between the anode/cathode. What that it is? I'm not sure. I do enjoy the .68uf vs the 1uf that I tried as well. V2a has a 22n bypass cap...

My goals were to initially just have more gain. More distortion.

I agree this design might be a bit loaded for a beginner to learn the ropes, but if you still can't get the tight sound you want, you can try removing c202 on V2A, and see if that helps clear it up a bit. You can always replace it if you don't like the sound when removed.

Well I took out this (High freq roll off cap) and it made this awkward 'hard clipping' sort of sound on the hardest open E (tuned whole step down so D) chords.

 

[JakeAC5253]

Well I took out this (High freq roll off cap) and it made this awkward 'hard clipping' sort of sound on the hardest open E (tuned whole step down so D) chords.

That is most likely indicative of hard clipping somewhere else in the circuit. Seeing as how you increased the plate resistor on that stage to 220k, the 1nF rolloff cap across it now shunts all frequencies above ~750Hz or so. This could be the reason that you were having trouble getting a clear and tight sound, the cap could easily be made smaller for an intermediate effect.. The hard clipping could be due to the biasing changes you made.

 

[JonWormwood]

That is most likely indicative of hard clipping somewhere else in the circuit. Seeing as how you increased the plate resistor on that stage to 220k, the 1nF rolloff cap across it now shunts all frequencies above ~750Hz or so. This could be the reason that you were having trouble getting a clear and tight sound, the cap could easily be made smaller for an intermediate effect.. The hard clipping could be due to the biasing changes you made.

I figured that was the case too so I pulled all the plate resistors back to stock (100k) with the only different with the first cathode bypass cap to .68uf

I took it off again, roll down on the distortion just a hair and the problem was alleviated. I dig it.

My guitar has an active pre amp which is set VERY hot as well.