The Amp Garage

I got a few today and will do tests. They may be the same, jelle

Yea, simply use 20uF caps for each preamp node. My guess was that the dual 10uF cap was available, and Dumble used it. It works, but a single 20uF works and is what one would normally see. Other amps had dual 40uF for clean and OD. Maybe that's what he had available that day. 20uF works well. have f...

3 preamp tubes: this means either no: Cleans, OD, PI or loop. Take your pick, lol

The 100W ODS documented here (102, 124, and 183) all use 4k7 and 390 from the 4 ohm tap. A 50W adaptation would reduce the 4k7 to 3k3, or move the FB source the to the 8 ohm tap. Either way you will get the same level of NFB as the 100W. The resistor change results from using the calculation I post...

So if I’m following this correctly for the sake of understanding the math; the presence cap would go from 2.2uf to 1.5uf? Also, what I’m gathering is that using what I already have - all I’d need to do is run the wire from the 4k7 off the board to the 8ohm tab on the impedance switch rather than th...

The 100W ODS documented here (102, 124, and 183) all use 4k7 and 390 from the 4 ohm tap. A 50W adaptation would reduce the 4k7 to 3k3, or move the FB source the to the 8 ohm tap. Either way you will get the same level of NFB as the 100W. The resistor change results from using the calculation I post...

I would run 330r and 4.7k off the 8 Ohms tab. Have fun

Thanks for the input Jelle! Not sure if I have the 102 resistors. When I purchased the set - I wasn’t certain which circuit I was using so I just asked you for a 4th gen resistor set. I can list out the values to determine which I have if that helps? if you have 330r and 4.7k....use the 4 Ohms tab ...

The one thing I would be worried about is the amount of global negative feedback. If you have my 100W SN#102 resistor set, I'd run it off the 8 Ohm tab to compensate for the reduction of negative feedback from going from 100W to 50W.

Have fun!

Quick build summary: - 50 watt 102 build using black panel Bassman iron all around -->Nice, that works well - added external bias points -->I am not a fan, for the simple reason that when tubes go bad, its wise to check if all is still OK inside the amp. - eliminated half-power switch - made all my...

Yes, those Dralorics sounds better than most resistors out there.

jelle

Glad you found it!!!

I cannot wait for the requests to tune those as well to make them sound right. :roll: People also forget how many differences there are between the different serial # amps. People will see a 'SSS' and immediately think "Oh Stevie Ray Vaughn!!" meanwhile, it'll be a clone of Kaiser's or Jackson Brow...

Jelle, A very sexy build...I love the combination of the uber-rare NOS parts you are using. The 121K Plates coupled with the 1.69K Cathode resistors a good strategy given the scarceness of the usual suspect values here. For me, I'd run 1.82K on the Cathodes but 1.69K is surely close enough and you ...