JE EL34 Build

[colin.hepburn]

Originally Posted by Richard

That'd be ok to try, short term at least, will make 11K paralleled with the 27K, current is 8mA so 0.7W for the whole dropper.

AH right thanks Richard I tend to forget you can use resistors in parallel to get other values

[Richard]

Originally Posted by colin.hepburn

AH right thanks Richard I tend to forget you can use resistors in parallel to get other values

Yes, or use another 27K in parallel as Philip was getting at. The voltages will see-saw with the current/load changes and often the only way is to blob them in and check the result before doing something more permanent

[pre65]

Colin, there is a series and parallel resistor calculator on this web site if you are not sure how to do it.

It's a goldmine for those lacking in mathematical skills, I use it a lot.

http://www.electronics2000.co.uk/

[colin.hepburn]

Well I know have a working Amp I don’t believe I missed this but without going in to detail I neglected to wire up the 6SL7 Drive Valve to the EL34 Output Valve what a prate so I was just hearing the EL34s
Here’s a pic of the working amp note the uncased WAD Phono Two in the back ground

[colin.hepburn]

Quick update
OK I have now got the shunted Alps 100k pot in now with 92k audio note tants so now WAD phono stage and CD players all sound very good feeding in to the shunted alps no pre amp i have a nice stead gain up to where I like it at about 10 o’clock All other components are Elna Silmic and Nichicon Takman Carbon And Orange Drop Cap
Latest Voltages
PSU B+415 volts
EL34 pin 3 Anode 404 volts both
EL34 pin 8 Cathode 28.5 volts both
6SL7 Anode pin2/5 Left channel 168 volts right channel 171 volts
6SL7 Cathode pin 3/4 1.8 volts both
400Hz single Test DMM set volts AC
Input 1.6 volts both
EL34 pin 5 Grid 2.6 volts Left 4.5 volts Right Why the Difference between channels
Speaker left 1.1 volts Right 1.2 volts

[Richard]

Originally Posted by colin.hepburn

Quick update
400Hz single Test DMM set volts AC
Input 1.6 volts both
EL34 pin 5 Grid 2.6 volts Left 4.5 volts Right Why the Difference between channels
Speaker left 1.1 volts Right 1.2 volts

Hi Colin,

The rest looks good but not sure what test you've done or are asking here, is that an AC or DC voltage on pin5?

If it is a DC voltage on EL34 pin5 it shouldn't be there, cathode bias so should be 0V on grid, suspect the 0.22uF coupling caps leaking if they are paper.

If it's an AC voltage tell us more about the test.

[colin.hepburn]

Hi Richard
This test is playing a 400Hz test tone CD through the amp checking AC voltage from input to output Which Mike H and nick asked me to do with my DMM set to its lowest AC range which is 200volts AC this gave a reading of 1.6 volts AC at the input Phono for both channels
EL34 Pin 5 Grid Left 2.6 volts 4.5volts Right
Speaker outs 1.1 Left 1.2 Right Nick said he would have expected them to be the same and suggested swapping the 6SL7 around and sees if the low voltage follows the valve

[colin.hepburn]

OK I Re tested the 400Hz tone test with the Alps pot full open
EL34 Pin5 Grid Left 18.4 Volts AC Right 14.4 Volts AC
Swapping the 6SL7s over just gave small change to Left 18.2 volts AC 14.1 Volts Right
Could the lower voltage differences be the Orange Drop Cap on the right channel?

[Richard]

Hi Colin,

I thought that's what the test might have been but couldn't reconcile 1.6V input with only 2.6V and 4.5V on the EL34 grids.

Now I understand, you were putting that voltage into the pot at usual listening position so it was being attenuated many dB.

Swaping the 6SL7s was a good move and showed they are fine.

I feel the reason will be the pot tracks. They are always different. Swap the inputs to the amp after the pot over and see if the EL34 grid voltages follow.

[colin.hepburn]

Hi Richard
Thank for your reply
So nothing wrong really then other than an uneven pot perhaps then
forgot to say I added the 3.3k resistor the EL34s 680 ohm Cathode resistor giving me 560 ohms and dropped the 27k to an 11k this amp has lots of grip and pace running into 89db speakers