The Amp Garage

Well you've got at least one dud there. Have you considered using thermistors for a soft start instead of a standby switch? not really , because you need to hold high voltage at least 20-30 seconds and if not.. all of the Ub line caps will be on max voltage .. You need something like 500k. So or Au...

Stephen1966 wrote: ↑Fri May 10, 2024 10:07 am
The ticking is some kind of internal arcing?

Yes, and the voltage drops are there too in the same time.. on variac if i lower the input voltage, then in one moment is ok situation, but on nominal looks like is going to the white smoke.

Chasing the ghost

faulty caps video:
https://drive.google.com/file/d/18ELqsP ... sp=sharing

Here is something what happened after in the amp.. failure on 450V elcos in the preamp section (they were new Kemet - Long life - ex Rifa) ? Very strange, i didnt measure wall voltage before.. maybe little bit over 230? Looks like caps took surge voltage during cold start (power and standby switch p...

For the past weekend we had some festival dedicated to vinyl and tubes, where was amp played.. i took nude and rude version without box.. Very nice experience.. maybe little bit too fatty/creamy sound with 1x12" Alnico Cream.. room and people damped the heights so better in the start to have more mi...

I wonder if anyone can actually call out a tube by hearing it. not possible.. also there is wide range of manufacturing types and shapes..but you can hear the differences.. and NOS are at least 30% better than modern tubes.. Altough i have good luck with 12AX7 JJ, often they are good enough-till-gr...

ECC81 most probably , need to put tube on the tester to see the currents

about tube preamps.. they are here all the time, real built and durable.. not those pcb+processors garbage types.. they have 0 value it is actually a shooting in his own legs to go this route, but they will realise after some years what a fail this is..IMO

Hey Bepone, Thanks for the clarification. My plan is not to drive the amp with a multi effect, but rather to have a lot of flexibility between preamps and power amps coupling. I have a musicman PT and OT that I would like to couple them with any preamp to get the feel of those 700V without building...

if there is a scope, then is easy..

1. remove NFB wire
2. put 100mV signal on the input
3. trace to the output tubes pin 5

blind shot..i suspect there is no gnd wire on some tubes, missing

So my questions are: That original wiring of the speaker jack, grounded with the bias pot, is that correct, or is it a design flaw from the manufacturer?? yes If so, this makes me question the rest of the grounding scheme in this amp, so I'll then have to take a deeper look at the rest. Could you p...

last 2 days update on the OD sound and tweaks..while clean is correct, OD wasnt so.. i have found OD sound too fuzzy for my taste, not amusing in any way... on the lower register.. tweak to cure that - both OD potentiometers changed from 100k to 250k..(actually they are like that in 183 schematic, n...

i have put mixed NOS and modern , for output Philips Miniwatt brown base EL34

Amp tested clean very very nice, drive under testing, tranformers are good! Nothing too much, normal attack, normal bass , normal treble

mounted transformers on experimental chassis..