JE EL34 Build

[colin.hepburn]

Originally Posted by Richard

Hi Colin, GZ34 1.9A, indirect too so it would turn on more slowly

Yep Maybe i should get a couple

[colin.hepburn]

i have now switched of the soldering iron in disgust as i have just noticed pin four is missing from one of the 6SL7 socket's and i don't have a spare and double

[colin.hepburn]

Originally Posted by colin.hepburn

i have now switched of the soldering iron in disgust as i have just noticed pin four is missing from one of the 6SL7 socket's and i don't have a spare and double

No spare valve bases well how lucky can you be I just got back from walking the dog and making a coffee I saw what I thought was solider splatter a closer look blimey it’s the pin so happy day again and it just clipped back in the socket and a little twist on the bottom solider tag it’s not coming out

[bob orbell]

Well done Colin, that makes up for all the times you got wet while walking the dog. BOB

[colin.hepburn]

Originally Posted by bob orbell

Well done Colin, that makes up for all the times you got wet while walking the dog. BOB

Hi Bob
Raining again up here BOB one day I will get the whole way round with the mutt and get back still dry

[colin.hepburn]

Well the heater's work any way




And a bit more
progress today Coffee Break and Dog Walking Time I Have to say it’s not my most tidy work if this amp works out to be any good it will be rebuilt into a smaller case what I didn’t take in to account was the foot print on the case I made to big

[colin.hepburn]

Well this JE EL34 SE Amp Must Hold the Record for the How Long Did It Take to Build
YEP it is now finely Build and Working Playing Dana Krell Girl in the room CD into an Old pair of Wharfedale Delta 30.2s which are 8 ohms @89db have to say it sounds good and ha yes there’s on Humm honestly with ear right up to the speaker now that did surprise me
SO advice pleas I AM running the EL34s in to a 5K load so into 89db the amp is at full volume this would be ok for late night so would changing the load give any more power and if so which would be best 2.5k or 3.5k

[Richard]

Nice one Colin How did the HT voltage work out, did it come down much with the load?

Re power, I did wonder about the current and voltage when I looked at the circuit,
28V over 880R cathode resistor is 32mA
HT at the anode is given as 375V so that's just 11W plate disippation. You could run them harder.

I can't see an OPTX load shown but seem to remember triode EL34 ra is about 900R so 2.5K should be ok.

Maybe look at other designs to get an idea what to try if anything. Perhaps 560R cathode resistors and recheck the current, HT, and plate disippation. Assuming the OPTXs are good for a bit more power of course. I can't see it making more than about 3W at the moment.

[colin.hepburn]

Hi Richard
First Slaps wrist I was a bit two edger and it was 3AM so I just fired it up not recommended I know
I will check all current and voltage today before I go any further I am not happy with psu caps at volts so will have to double them up
AS the 880R is non standard mike H over at audio talk recommendation was to used 680R so fitted the 680Rs 28/680=41mA the James OPTX are 90mA@20 Watts I was thinking maybe trying PSE but as it stands it would be a bit close for comfort 6SL7/EL34 84.5 mA

[colin.hepburn]

OK I have had a Listen to the Amp on my main speakers Sand filled Wharfedale 8.3s 6 ohms @ 89 db again volume pot at maxi but a much more solid and very good sound but not a enough volume but not to bad for late night listening ??
So Some Voltages
First the psu small change added R1 150R
B+ is a 415 Volts
EL34 Anode pin 3 404 volts on both valves
Pin 8 Cathode 32 volts left 31 volts right note cathode resistor changed to 680R

6SL7 Anode Pin 2/5 167 volts left 170 volts right
Pin 3/4 1.8 volts left/right