The Amp Garage

You’re on it!!

My first thought when I saw those specs was a cathode biased push-pull El34 amp, but that would really be testing the max (or very close) of the claimed specifications

Also printer2 your amp looks great too and is only increasing my curiosity with these things

ax84ch - this project is fascinating. I somehow stumbled across your Facebook post about the amp while researching the RCA BA-2C (go figure) and it really has been repeating on me. I know you say specs are scarce, but have you seen the bigger 300V 300mA version listed on Amazon associated with this ...

Guys! I have been home for a few days but just got a chance to get back to the amp. Colossal, the wire you spotted - I snipped it late last night but only this afternoon got a chance to give it a go. I think that was it!! I played the amp for 10 mins straight, cranked, 5AR4 rectifier, hottest it cou...

Hi Colossal - thanks and good eye there! I believe the pots are 1M. The tone cap probably snuck its way into my little drawer labeled “.01 uf” and I must have just grabbed it without looking closely when getting all the parts together. Once a build gets going I start to chuck along at a pretty good ...

https://youtu.be/QVxM1BWDXLM?si=IIqi4BNjH4tgs6uX

Here it is

Hi guys, Thanks for all your help, questions and suggestions! LOUDthud - good eye catching the missing wire in the drawing. IRL there is indeed a wire grounding the volume / tone setup. See attached photo where red arrow indicates ground wire and blue arrow shows grounding point. TUBEDUDE - the gree...

Tubedude - you mean the zip tied leads that aren’t in use?

Hi guys! As noted I don’t get as many opportunities as I would like for loud testing, etc. I understand and generally agree with the basic principle of most issues being a cold solder joint or bad tube. However, I have run into some weird ones over the years. One amp that really gave me a hard time ...

Anything helps, thanks Tim!

Here’s the layout drawing

Hi guys, I haven’t been here in a while. Admittedly, I have come here most often looking for help to diagnose and address unusual issues incurred in my builds. And you guys always deliver. If my numbers ever come in, you’re all getting Ferraris! But anyway, I’m a busy guy with a job and a family. As...

Martin, you said: “Fooling around with the 6F6 data sheet and scaling things (data sheet is at 250V Vg2, where you are at 232) I believe your 9k2 load line is crossing the Vg1=0 grid curve at around 100V, and you are only getting around 6.5W output power. In theory, at the same voltages, a 12k load ...

I have been infinitely curious about these 7pin beauties - 6005 is synonymous with 6AQ5 if I’m not mistaken. There’s enough testimony out there stating how glorious these sound for me to have bought some 7 pin sockets and a pair of 6AQ5s but the train always stops there as I have had difficulty find...

Using the formula Martin suggested from Merlin’s website, I got this: with 5AR4 & 6F6s Plate voltage measured 331 from plate to ground. Plate to cathode is 313 2 x (331 - 50)^2 = 78,961% 9200 = 17 watts OR 2 x (313 - 50)^2 = 69,169 % 9200 = 15 watts with 5U4GB & 6F6s Plate voltage 311 Plate to catho...

Thx Martin!

I’m going to take some more readings tonight. Will report back soon