The Amp Garage

… I have changed about everythin partwise, filtercaps, rectifiers etc. Only visible sign in the amp iyself was a burnt grid resistor. For a 6L6 to cause a 470R 5W screen grid resistor to become damaged, the valve in the socket must either have shorted badly, or have lost bias. HT fuses are a really...

As the input stage anode is fed via 100k, the voltage / current at the input if the screened cable shorted is rather limited.

Have you checked the high frequency to ultrasonic frequency and phase response of your’s? Mine has a weird resonant peak and phase shift around 40kHz. I didn't I don't have balanced signal generator, maybe runing the secondary with SG and solid state amp will work, but never tried. I think the only...

The issue with a valve rectifier and the standby switch depends on whether it’s a hot switching arrangement, ie the switch, when open, it interrupts the reservoir cap’s charging current. If it does then it’s hot switching and will probably result in the peak anode current limit of ghe rectifier bein...

... Too tired of replacing bad rectos! At least when they fail they make a cool light show. 8) That’s nuts, it’s the simplest thing to eliminate that failure mode. Just re-arrange hot switching standby switches (or just leave them permanently closed), most importantly fit back up silicon diodes and...

The slow ramp up of HT voltage, the elimination of HT surge voltage / current, provided by a GZ34 is a wondrous thing. Obviously some people don’t appreciate it, or at least don’t think it’s worth the additional infrastructure etc required to support it. That’s fine, suitable solid state diodes are ...

Adding a 2nd tonestack to the DCCF has an obvious, significant effect on its large signal waveform.
The difference may not be particularly audible though, it’s apparent but certainly it doesn’t change the tonal character.
I decided not to follow that option though.

neskor wrote: ↑Fri Oct 13, 2023 8:34 pm I have one right know.
Impedance is around 6.5K

Have you checked the high frequency to ultrasonic frequency and phase response of your’s?
Mine has a weird resonant peak and phase shift around 40kHz.

The first year or 2’s production mostly used the RSDeluxe, hard wired for 6k6 primary and 15 ohm secondary. https://i.ibb.co/pPwMwm5/66-RSOT-4.jpg https://i.ibb.co/xFLykLV/RS-Page-1.gif https://i.ibb.co/59PP9vH/RS-Page-2.gif Subsequently the Drake 784-103 was mostly used, 8k primary to 8, 16 & 100V ...

R.G. wrote: ↑Wed Oct 04, 2023 3:15 pm … I can't remember from the curves whether the second or third harmonic predominates as loading changes …

Me either!
I was just working on the basis of low order harmonics predominating and it being push pull, so there should be a fair degree of cancellation of even harmonics

All of the OTs mentioned are kinda lofi, low spec type. Perhaps not quite as low spec as those in equivalent Gibson models of the same era.

All else being equal, 6k6 would probably have a lower clean power output and higher level of 3rd harmonic at high power output.
For better bandwidth, a beefy lamination stack and interleaved windings are beneficial. So heavier and more expensive.

It really is comically ridiculous stuff to use for a highish voltage circuit board substrate.

Was an input trimmer fitted?
If the supply voltage is too low and input signal too high, that or any circuit will clip.
Or the send signal may have been too high for some pedals to cope with.

… I thought that using a separate 50V tap would be more stable … What’s your rationale for thinking that, what do you mean by ‘stable’ here? The rectifier for the 12V supply is weird, looks like a voltage doubler; why do it like that if you’re using a custom transformer? As a few general points, I ...