G-PULTEC problems, please help!
- Thread starter daveee
- Start date
Help Support GroupDIY Audio Forum:
...just use some low-power resistors in parallel - e.g. 100K or 220K.
In general, there's rarely any need for more than 2W resistor total - we're only drawing some 5-6mA.
(to calculate dissipated power in W, multiply voltage drop in V x 0.005A )
Aim at ca. ½W per 100V drop in voltage across resistor.
Jakob E.
In general, there's rarely any need for more than 2W resistor total - we're only drawing some 5-6mA.
(to calculate dissipated power in W, multiply voltage drop in V x 0.005A )
Aim at ca. ½W per 100V drop in voltage across resistor.
Jakob E.
6.0V is plenty fine for heating.
Read tube data sheets, says +/-10%, you do the math...
Jakob E.
Read tube data sheets, says +/-10%, you do the math...
Jakob E.
Hi
I did my first listening test today with different transformers from OEP(Not the best, but good for test)
A262A7E ratio: 1+1:1+1
a262a2e ratio: 1+1:2+2
My 1st try with
Input with 2:2 A262a2e
output with 2:1 A262A7E
2nd try With Input A262A7E 1:1
output With Input A262A7E 2:1
I'm loosing 3 DB compare to the signal coming.
It's a little bad
I've read Pultec is really low impedance
So should i decrease the impedance of my transformers?
Oep A262A7E is 600ohm
Maybe a 150ohm will be better?
Another idea i had is increase voltage of tube to 220V i'm at 217V but i'm not sure.
Otherwise my EQ sound very good.
Free Hum Free noise.
I try to ear any noise or hum but No.
What a fuckin warm low and tasty high.
I did my first listening test today with different transformers from OEP(Not the best, but good for test)
A262A7E ratio: 1+1:1+1
a262a2e ratio: 1+1:2+2
My 1st try with
Input with 2:2 A262a2e
output with 2:1 A262A7E
2nd try With Input A262A7E 1:1
output With Input A262A7E 2:1
I'm loosing 3 DB compare to the signal coming.
It's a little bad
I've read Pultec is really low impedance
So should i decrease the impedance of my transformers?
Oep A262A7E is 600ohm
Maybe a 150ohm will be better?
Another idea i had is increase voltage of tube to 220V i'm at 217V but i'm not sure.
Otherwise my EQ sound very good.
Free Hum Free noise.
I try to ear any noise or hum but No.
What a fuckin warm low and tasty high.
spase
Well-known member
anyone can tell me how to wire the edcor sx1100 on input...
i tryed to go unbalanced everything its fine,but want to have a balanced connection and dont know how to wire the input tranie.
i tryed to go unbalanced everything its fine,but want to have a balanced connection and dont know how to wire the input tranie.
spase
Well-known member
i tryed with this pcb, everything its working unbalanced , thats only with the output transformer, but when i add input nothing happens i dont have any signal.I think its the problem with the wiring on that input transformers becouse unbalanced everything its working.
spase
Well-known member
i connected everything , when i try to connect from my main output from the soundcard i have great signal, but when i try from my other outputs i have very low level signal.Anyone know something about this?
p.s everything its working on the filter board.
p.s everything its working on the filter board.
If unbalanced source, make sure to de-balance (xlr pins 1+3 shorted)
Jakob E.
Jakob E.
Audioman
Well-known member
Hi Guys,
I have a problem with one of my two G-Pultec,
I used JJ E88CC gold pin tubes but one of the two tubes after a few hours of activity is dead
if apply 0 dbu to the input the output read -35 dbu ...
in the other unit instead if apply 0 dbu on the input i read -5,41 dbu at the output , is it all normal ?
P.S. where i can download the high resolution schematics ?
I have a problem with one of my two G-Pultec,
I used JJ E88CC gold pin tubes but one of the two tubes after a few hours of activity is dead
if apply 0 dbu to the input the output read -35 dbu ...
in the other unit instead if apply 0 dbu on the input i read -5,41 dbu at the output , is it all normal ?
P.S. where i can download the high resolution schematics ?
Attachments
frazzman
Well-known member
Hi all,
Does anyone know if a 4db drop in level is "normal" when the EQ is engaged (even in bypass, but same with circuit "in" but no boost or attenuation).
No input transformer and EDCOR Xs1100 on the output.
Everything else seems to function ok but HT voltage is way too high at 324V. Need to replace 3K3 resistor with 18K perhaps?
Does anyone know if a 4db drop in level is "normal" when the EQ is engaged (even in bypass, but same with circuit "in" but no boost or attenuation).
No input transformer and EDCOR Xs1100 on the output.
Everything else seems to function ok but HT voltage is way too high at 324V. Need to replace 3K3 resistor with 18K perhaps?
Fabio (Audioman) and frazzman,
We've been through this a couple of times before:
Gain through the GPultec depends on two things:
1 - The actual raw gain of the tube used - this varies some +/- 2½dB on NOS tubes, probably more on new-production ones. You could use Russian 6N23P for slightly more gain in average (if you can find those).
2 - The ratio of the values of hi-boost potentiometer (10KA) and the hi-cut potentiometer (1KA) - this is where we do the actual -20dB no-eq-attenuation (Schematic - http://www.gyraf.dk/gy_pd/pultec/gy_pd_sch.gif )
For adjusting to unity gain, you could probably put a 1K Ohm trimmer potentiometer at the TOP (clockwise end) of the hi-cut pot and adjust for unity at no-hicut-setting. Only side-effect of this will be slightly less available maximum-hi-cut at pot extreme setting.
If you do this, let us know how/if it works - would be nice to have in this thread
EDIT: Confirmed working -
Please also note that this circuit was made for LL5402's in and out - other brands of transformers or no-input-transformer may very well give varying results.
Jakob E.
ps: I've had quite a few JJ tubes fail me after short time. Maybe it's poor production standards, maybe they are specified slightly different than real E88CC's, and don't like us going to extremes of cathode/heater potential differences. I use Philips 6922, and like them a lot.
DO NOT run this circuit above +250V HT - the tubes don't like this. Raise series resistor value until you have some 200-250V HT under load (tube heated, ca. 30sec.). A standard 0.6W type resistor will nearly always do fine - you do the math of power dissipated at given resistor and given voltage drop....
We've been through this a couple of times before:
Gain through the GPultec depends on two things:
1 - The actual raw gain of the tube used - this varies some +/- 2½dB on NOS tubes, probably more on new-production ones. You could use Russian 6N23P for slightly more gain in average (if you can find those).
2 - The ratio of the values of hi-boost potentiometer (10KA) and the hi-cut potentiometer (1KA) - this is where we do the actual -20dB no-eq-attenuation (Schematic - http://www.gyraf.dk/gy_pd/pultec/gy_pd_sch.gif )
For adjusting to unity gain, you could probably put a 1K Ohm trimmer potentiometer at the TOP (clockwise end) of the hi-cut pot and adjust for unity at no-hicut-setting. Only side-effect of this will be slightly less available maximum-hi-cut at pot extreme setting.
If you do this, let us know how/if it works - would be nice to have in this thread
EDIT: Confirmed working -
frazzman said:
Please also note that this circuit was made for LL5402's in and out - other brands of transformers or no-input-transformer may very well give varying results.
Jakob E.
ps: I've had quite a few JJ tubes fail me after short time. Maybe it's poor production standards, maybe they are specified slightly different than real E88CC's, and don't like us going to extremes of cathode/heater potential differences. I use Philips 6922, and like them a lot.
DO NOT run this circuit above +250V HT - the tubes don't like this. Raise series resistor value until you have some 200-250V HT under load (tube heated, ca. 30sec.). A standard 0.6W type resistor will nearly always do fine - you do the math of power dissipated at given resistor and given voltage drop....
Audioman
Well-known member
@ Gyraf i had mount the trimmer as you suggest but doesn't work , i measured a gain loss of 3 dbu .
i have also tested the amplifier section with a physical bypass in/out , and the amplifier gains 18 dbu in full bandwith
i also verify the 10k resistor on the control pcb and all is correct.
now with the tube very hot and the signal generato at 0 dbu in bypass mode i have a loss of 2,3 dbu
let me know how can i do to solve the problem
Thank you in advance
i have also tested the amplifier section with a physical bypass in/out , and the amplifier gains 18 dbu in full bandwith
i also verify the 10k resistor on the control pcb and all is correct.
now with the tube very hot and the signal generato at 0 dbu in bypass mode i have a loss of 2,3 dbu
let me know how can i do to solve the problem
Thank you in advance
how much gain variation do you get with a 1K trimmer?
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