The Amp Garage

Nothing really, just wondered if there are "better".

Talking about the big dielectric can type ones. Is there a brand or spec anyone would recommend, at a reasonable cost, as an upgrade to the ones Mojotone supplies? Will changing them actually make any difference? The spec as supplied with the kit is: - 1 x 32/32 uF dual - 1 x 50/50 uF dual - 3 x 220...

Finished!

1. Will it work? 2. Will it sound okay? Okay is good enough, I'm not looking for nuances or perfection. 3. Do I need to put a coil (inductance) in there? If so what value and where? I presume in series on the input side to mimic a speaker coil, just don't know how many (milli)henries. Thanks in adva...

The problem came back so I went ahead and fitted a new socket, which turned out to be much "tighter" than the old one.

I found a similar issue on one of the EL34 sockets so now I've ordered a replacement one of those too.

Thanks everybody.

When you buy a set of balanced tubes, what exactly are they balancing?

What do numbers like "34" or "41" written on the boxes actually mean?

Are higher or lower numbers better or doesn't it matter?

Turned out I had a bad 1 meg resistor I hadn't checked before. I swapped that out and Hey Presto! everything was on the money. Voltages are down a bit because our mains voltage is too, I expect - 100+ deg. F. outside, Sunday afternoon, everyone at home, with their ACs going full tilt. Thanks for all...

Corrections:

P1 = 276.0 V
P2 = 82.9 V
P3 = 86.4 V
P4 = 6.6 VAC
P5 = 6.6 VAC
P6 = 277.2 V
P7 = 75.6 V
P8 = 86.8 V
P9 = 6.6 VAC

I think I've fixed it!

BTW my paternal grandfather was the BBC's Chief Engineer when he retired, still in the tube era, in 1968. Some things just rub off on you, like not relying on wiggling things to make them work. It's not to make it work, it's to find the source of the problem. Wiggling and poking things with a stick...

sluckey wrote: ↑Sun Aug 06, 2023 2:45 pm What voltage do you measure on pin 2 and pin 7 of V4?

P1 = 164.4 V
P2 = 3 mV
P3 = 87.5 V
P4 = 6.6 VAC
P5 = 6.6 VAC
P6 = 455.6 V
P7 = 3 mV
P8 = 87.5 V
P9 = 6.6 VAC

That's without power tubes fitted.

BTW my paternal grandfather was the BBC's Chief Engineer when he retired, still in the tube era, in 1968. Some things just rub off on you, like not relying on wiggling things to make them work.

I haven't tried "prodding" the receiving end of the socket, and I'm worried that if I do I'll end up making the sockets bigger, causing more problems. The sockets themselves, with the cover bases I've fitted, don't allow much "wiggle", unfortunately, and in any case this old engineer doesn't like st...

cdemike wrote: ↑Sun Aug 06, 2023 12:33 pm I like the bias pot bracket

Sheet (or should that be sh#t) metalwork at its finest, right?

I always thought balanced out put was the important thing, not necessarily in put - you want your "push" and "pull" phases to be more or less equal on the out put side. Once I get the voltages about right I can experiment a little, say upping the 91k to 100k or dropping to to 92k, and / or putting a...

A few photos. Bear in mind I'm not a pro with a workshop, and that this is my first build, so be kind :-) I fitted a 5k pot so I could adjust the power tube bias without swapping out resistors. I also fitted 1 ohm resistors as the ground wires for the power tubes, so I can measure plate currents by ...