The Amp Garage

danotron wrote:He doesn't have the hands for tone.....I liked the other guys (bald guy) playing though

Indeed - it's like a saturday morning guitar center customer vs. a pro player.

That Naylor circuit has piqued my interest for quite some time.
Great fat tone there for sure. Good job!

Cheers Stephan

The X10 is a boutique build with a quite long waiting list. There are not many of these amps around, and I doubt that most of the owners would open it up to look inside. All the information in the threads you mentioned was based on some good gutshots and should be enough to build a working and good ...

Jim Kelley FACS
JTM-45/5F6A Bassman

Cheers Stephan

Bias voltage reading was also low. Maxed out only got 23 mv. Mark, what did you actually measure here - the raw bias voltage at pins 5 of the power tubes or the voltage drop across the 1 ohm cathode resistors? 23 mv as bias voltage would cause severe red plating of the power tubes. If the amp has 6...

I have the Skyliner stack in my converted Bassman which also has the 0.01uf cap and the 250k log midpot, and it's also more subtle than I expected. I tend to turn it down for cleans and up for overdriven tones.

Cheers Stephan

That should be the same effect. However I shy away from using a plate-to-grid cap on the input gain stage - if that cap shorts you have the plate voltage on the signal input.

Cheers Stephan

They were basically taking the same place as a bright cap across a gain or volume pot. Wired in that fashion they only alter the taper of the master volume pot, making it come on more quickly. In order to obtain the safety benefit they must be put between the wiper and the CCW tap (e.g. the bias con...

The tone caps may be too close to the PI input cap. Can you post a picture of your build, please?

Cheers Stephan

. Now if you reduce the signal appearing at the speaker by turning down the PPIMV, less signal is fed back into the circuit. Thanks Stephan and Colossal. I understand the concept of NFB, but where I have quoted is where I am confused...in the sense that even if you have a non-mv amp, and you are pl...

NFB works by tapping the signal at the speaker and injecting it earlier into the signal chain (i.e. into the cathode of the long tail PI) out of phase in order to reduce gain and improve linearity. Now if you reduce the signal appearing at the speaker by turning down the PPIMV, less signal is fed ba...

If the speakers were just wired together in parallel, the 5.333Ω calculation would be correct. In this case, they're connected to different secondary windings on the OT. If you look at it from the perspective of the primary, it makes more sense. Assume a 4k primary with 4,8, and 16Ω seco...

Matt OK, you were referring to the "grounded grid cap". I agree, the bigger value is better here since the long tailed pair PI is a differential amp, i.e. the more low frequencies you bleed to ground in the other side, the more they get amplified. I think the notion of making the input PI caps the s...

iknowjohnny wrote:Hey Gaz, what approximately value resistor would you use from wiper to ground with a 1M pot and a 500k pot?

I cannot speak for Gaz but I used 220k, 330k, 470k and even 1M with great success. The smaller the resistor, the stronger the effect - at the expense of a bit gain.

Cheers Stephan

El84 are sensitive so you can clip a 470k to each 100k PI plate resister to make them 82k. This would reduce gain but also raise the PI's plate voltage. Quick and easy test. Good suggestion, and easily reversed if you don't like it. I am not familiar w the spitfire pre but the first stage voltage i...