U47EF Oliver Archut version

[rock soderstrom]

What also strikes me spontaneously. Is the status lamp really supplied with AC? If so, that could be problematic.

Overall, I find the basic layout of the PSU suboptimal. The AC part including the transformers should have more distance to the sensitive regions.

This also makes the required cabling unnecessarily long with all possible consequences.

 

[Spencerleehorton]

im terrible with PSU's, anymore advice to get this how it should be would be very much appreciated, i'll remove the B+ and H+ gnd to IEC and put to 7 pin socket chassis gnd

 

[Spencerleehorton]

This any better?

Pin 3 on socket I have as heater 0v, should I disconnect pin 3 and have heater 0v connected to pin 7?

 

[rock soderstrom]

This any better?

Better, but not perfect ;-) Your GND from the Heater is still coming direct from the rectifier. Take it from the end of the groundbar, see my photo.

 

[rock soderstrom]

Pin 3 on socket I have as heater 0v, should I disconnect pin 3 and have heater 0v connected to pin 7?

Pin 7 is your central GND point? If so than connect Pin 3 to it as well.

 

[Spencerleehorton]

well changing those gnd connections has done the trick!! no hum, thank you guys, told you it was a gnd problem!!!

 

[rock soderstrom]

Cool!

Here are an layout sketch as a suggestion.



I think you get the idea.

Edit: AC for the heater comes from TX1 of course. My fault..

 

[Spencerleehorton]

yes, thats great, thank you.

 

[Spencerleehorton]

Will A B the EF80 and the EF800 in both mics now, so far the EF80 in this version 2 doesn’t sound great, ringing on tube, used some tape to dull it and the mic body down.
The sound in general sounds more distant and lower in level, everything sounds less compressed compared with the EF800.
I still need to see what all the other voltages are in the mic but on night shifts so will finish them then proper testing.

 

[TLRT]

Toroid shielding and choke shielding should stand near parallel, you can verify this with better scope or audio analyzer during design your psu (check 50/100hz peaks) good design should have around 100-200uV ripple noise max on the heater line.

 

[Spencerleehorton]

here are my voltages from version 1 which i am really happy with the sound:

EF800
plate = 50.3v
kathode = 1.15v
H+ = 5.34v
B+ = 107.9v
R6/R5 = 93.3v
R8/R7 = 58.5v (pol voltage)

changing the tube doesnt make as bigger difference as i first thought, the EF80 is much more metallic sounding and is much more microphonic but voltage wise they doesnt seem to be much differnce when swapping the EF800 for the EF80.

is version 2 things are slightly different, i have tried both tubes and get the same voltages:
plate = 46.5v
kathode = 1.03v
H+ = 5.43v
B+ = 107.6v
R6/R5 = 93v
R8/R7 = 55.1v (pol voltage)

pretty sure they both have the same transformer so could be capsule which is playing the bigger part?
still need to connect the reed relay which i'll do tomorrow and go over this all again.

from what i can see i need to get the plate voltage and the pol voltage up a bit.

 

[rock soderstrom]

It's not that far away now. Are R2 and R3 (in both mics) the same size? Do you use trimmers? Can the heating voltage be trimmed to the same value?
If the resulting cathode voltage is the same, the rest of the voltages should also be more or less about right.

 

[Spencerleehorton]

Do you mean R1 and R2 which I’ve got as 200meg, in V1 they are 1G.
Only trimmers are in psu.

 

[Spencerleehorton]

Also in V1 it is still cathode bypass.
I’ll put it back to normal tomorrow and see how voltages sit and see how v1 sounds.

 

[rock soderstrom]

Do you mean R1 and R2 which I’ve got as 200meg, in V1 they are 1G.
Only trimmers are in psu.

No, I meant R2 and R3 in the microphone.

Also in V1 it is still cathode bypass.
I’ll put it back to normal tomorrow and see how voltages sit and see how v1 sounds.

Yes, comparing the voltages (and sound) makes more sense when everything is the same.

 

[Spencerleehorton]

ah ok, the labelling is a bit different on the original schematic, R2 is 120R and R3 is 30R, i'll see if i can find a 100R and a 29R

 

[Khron]

Don't sweat the 29 ohm; 100's are a standard value, on the other hand.

 

[Spencerleehorton]

ah ok, should be able to find a 100R, will check voltages once changed.

 

[Spencerleehorton]

here are the lastest voltages for Version 2 with EF80 with reed relay, omni works and sounds as it should, R3 is now 100R, R7 is 2M2 and R8 is 2M7

Plate = 47v
Kathode = 1.12v
H+ = 5.05v
B+ = 105.3v
R6/R7 = 51.4v
R4/R8 = 91.5v

 

[Spencerleehorton]

sounds wise its still way off version 1, when i plug V1 in, if i put it about a foot away pointing at my mouth and play acoustic guitar, its almost a perfect balance of voice and guitar mix wise and sounds full bodied and no weird mirophonics.
with V2 in the same position the guitar doesnt come through, is very distant the overall sound, sounds thin in comparision and metallic and ringy.
i suspect the capsule so i'll change it for another one i have and see what i get.