Poor Man's Pultec EQP1-A Build Support Thread

[ruffrecords]

Thanks for the description Ian. I've sent .775V 1k signal in, that measures .680V at bypass switch and on CCW of High boost pot/switch. At CW pin of High boost switch (the divider between the High boost and cut that should be -20db lower) my signal is 26mv. Am I correct that this isn't what I should be seeing? I apologize, I'm a horrible trouble shooter.

You are correct, that is not the right level. You should see something in the region of 75mV at that point but make sure you have the high cut turned fully off as well. I suspect there is something funny happening with you extra mid sections which are also connected between this point and ground. I would advise disconnecting the mid completely and just concentrate initially on the hi and lo boost/cut. Get that working first and then add in the mid circuits one at a time. it's a bit laborious but it is the only sure where to eliminate things.

Cheers

Ian

 

[duantro]

Yes Ian, I have my mids disconnected as per your suggestion earlier. The center pole/wiper of the boost cut pots on mids are unhooked.

 

[ruffrecords]

Yes Ian, I have my mids disconnected as per your suggestion earlier. The center pole/wiper of the boost cut pots on mids are unhooked.

OK then you need to trace and  check the circuit you have in detail. Try disconnecting the gain make up and the EQ bypass circuit and measure again. Something somewhere is pulling down that signal.

Cheers

Ian

 

[JohnWatkins]

Am I correct in assuming that the DPDT switch for the EQ bypass switch should be ON-ON, not ON-OFF-ON?  Sorry if this has been covered.

 

[ruffrecords]

Am I correct in assuming that the DPDT switch for the EQ bypass switch should be ON-ON, not ON-OFF-ON?  Sorry if this has been covered.

That is correct. Also, if you are using the mid section add on, the SPDT switch to select mid boost/off/cut should be an 0n-off-0n type.

Cheers

ian

 

[JohnWatkins]

Thank you!

 

[pacorro]

Ian... I need to know the input impedance of the Poor man's Pultec for calculating one cap in the unbalancing stage. Can you tell me what impedance is at the input of the circuit?
Thanks

 

[pacorro]

I measured the impedance in my unit.
Input impedance is over 50k in both channels. Output impedance is also over 50k, though I expected over 10k as you told me, Ian.
Is this normal?  ???

 

[ruffrecords]

I measured the impedance in my unit.
Input impedance is over 50k in both channels. Output impedance is also over 50k, though I expected over 10k as you told me, Ian.
Is this normal?  ???

How did younmeasure the input and output impedance?

Cheers

Ian

 

[pacorro]

With a multimeter, red on hot at T2 and black at the ground in pin 3 for the input.
At the output with red on xlr pin 2 and black on ground at xlr pin 3.
One channel is 49,4 k input and 51,6 k output. The other is similar, 50k input and 51k output.

 

[kante1603]

That is dcr,not the impedance.

Udo

 

[pacorro]

Sorry, but... What is dcr?

 

[kante1603]

Sorry, but... What is dcr?

DCR=Direct Current Resistance.

 

[pacorro]

Thanks. How can I measure the input impedance in my device?

 

[ruffrecords]

With a multimeter, red on hot at T2 and black at the ground in pin 3 for the input.
At the output with red on xlr pin 2 and black on ground at xlr pin 3.
One channel is 49,4 k input and 51,6 k output. The other is similar, 50k input and 51k output.

I am confused about the putput XLR - is this directly out of the EQ or after a gain make up amp? What positions were the pots when you made this measurement?

Cheers

Ian

 

[duantro]

Yes Ian, I have my mids disconnected as per your suggestion earlier. The center pole/wiper of the boost cut pots on mids are unhooked.

OK then you need to trace and  check the circuit you have in detail. Try disconnecting the gain make up and the EQ bypass circuit and measure again. Something somewhere is pulling down that signal.

Cheers

Ian

Upon disconnecting the output amp at the center pin of the bypass switch, I go from 12v to 58v, at this connection.

 

[ruffrecords]

Yes Ian, I have my mids disconnected as per your suggestion earlier. The center pole/wiper of the boost cut pots on mids are unhooked.

OK then you need to trace and  check the circuit you have in detail. Try disconnecting the gain make up and the EQ bypass circuit and measure again. Something somewhere is pulling down that signal.

Cheers

Ian

Upon disconnecting the output amp at the center pin of the bypass switch, I go from 12v to 58v, at this connection.

Is that dc volts or signal?

Cheers

Ian

 

[duantro]

Yes Ian, I have my mids disconnected as per your suggestion earlier. The center pole/wiper of the boost cut pots on mids are unhooked.

OK then you need to trace and  check the circuit you have in detail. Try disconnecting the gain make up and the EQ bypass circuit and measure again. Something somewhere is pulling down that signal.

Cheers

Ian

Upon disconnecting the output amp at the center pin of the bypass switch, I go from 12v to 58v, at this connection.

Is that dc volts or signal?

Cheers

Ian

AC signal from 775mv input signal generator

 

[ruffrecords]

Yes Ian, I have my mids disconnected as per your suggestion earlier. The center pole/wiper of the boost cut pots on mids are unhooked.

OK then you need to trace and  check the circuit you have in detail. Try disconnecting the gain make up and the EQ bypass circuit and measure again. Something somewhere is pulling down that signal.

Cheers

Ian

Upon disconnecting the output amp at the center pin of the bypass switch, I go from 12v to 58v, at this connection.

Is that dc volts or signal?

Cheers

Ian

AC signal from 775mv input signal generator

I don't understand this. With less than one volt input and no gain make up amp, how can you get a gibber output than the input. Or did you mean 'goes from 12mV to 58mV which would be about right.

Cheers

Ian

 

[duantro]

Sorry Ian. Yes I meant 12mv when output is connected and 58mv when disconnected.