EL34 power amp project

[bikerhifinut]

Thanks Richard.
It may look a bit "rustic" but it works "reet nice" as they say round here.
I have been tweaking it a bit with revised earthing runs and also lifting the heater reference above ground by 40V to give the ECC81 LTP phase inverter an easier life as the cathodes sit at around 70V.
Theres a bit to go in terms of tidying up, by eck those close ups make my soldering look tatty, probably cos it is.
I will be going back to the feedback calcs with a view to reducing the amount by say 3 to 6dB as the Leak design runs close to the limits in terms of HF stability, although on the Scope there were no signs of HF or RF oscillations that I could see.
As well as a slight reduction on the global Feedback I am looking at reducing the gain of the input stage a little bit more, as a volt is plenty sensitive with my preamps and sources and I am hoping that will push the noise floor right down.
Those danbury output transformers must be well executed I think, even though running at about half rated power flat out which gives them a head start, there's no apparent or perceived reduction in bass "slam" etc on loud transients and kick drums etc.
I have a bit of wriggle room on the input stage gain by reducing anode resistor value etc. I don't want to dispense with the cathode bypass cap as that could affect LF response adversely. However I have thought about a potential divider tap on the first valve anode resistor if I can't get the gain down by conventional methods which includes the use of a different input valve. Theres room to open the bases out for Octals which could be handy for say a 6J5 ( half a 6SN7) in the input. I guess I could just parallel connect an ECC82 or even use a 12B4 if I stayed with B9 valves.
But what isn't broke I am reluctant to fix.

Andy.

[bob orbell]

Looks nice Andy, but tidy the books up, there's a good lad, . Bob

[bikerhifinut]

Now that wouldn't be me Bob!
As it happens the whole lots going elsewhere temporarily, that rooms been painted out now and its reassigned as the new main bedroom in the house.
next month we start a major upstairs renovation involving tearing down the old dormer and rebuilding it a bit larger and to a better standard of construction and finish to hopefully see us out.
The hopeful gain is we get a bigger room upstairs and we felt it was wasted as a bedroom so its planned for a lower window to get the best of our Cumbrian Mountain view and I'll put the A/V gear in that room as its going to be the biggest we have, if a bit awkward in shape as the sloping roff will still be at one end. Which will pose some interesting accoustics i am sure but won't know until its done. And I also get an accessible clean dry and warm work area to play with my old radios and amps.
I'm discovering just how much odd bits and pieces and lengths of wire I have stuffed into storage boxes, some will keep but I suspect the tip is getting a fair bit.

Andy.