Poor Man's Pultec EQP1-A

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Andreas Pfeiffer said:
How much is one board?
How big are they?
I am sure the info is somewhere, but a quick answer - please :)

Check black market for Ian's poor mans pultec boards. Above for Pier's boards for make up gain.
Ian is also curently designing a valve make up gain board. Check in the 'drawing board'.
 
Just wanted to say, looks like a great project, I wonder why nobody came up with this before?
Great work Ian, and thanks for sharing!
...Not to mention that this is yet another great project for strictly p2p club!  8)
 
Andreas Pfeiffer said:
How much is one board?
How big are they?
I am sure the info is somewhere, but a quick answer - please :)

regarding my IO board, it is 12 euros each one if bought in the group buy
one board is mono and also two layers (double face),

it is 173x105 mm



 
Hi Ian,

I paid mine as well and made it 24 GBP to cover the transfer fees because of the missing 'gift' option here.
Thank you so much for this great project and your efforts in making the pcbs available!

Michael
 
Andreas Pfeiffer said:
How much is one board?
How big are they?
I am sure the info is somewhere, but a quick answer - please :)

Andreaas, I have you down for two sets of the EQ PCBs (that's four in total) for a total of 12gbp including shipping. See page 9 of this thread for the complete list.

Cheers

Ian
 
Hi Ian and everybody,
I have question about the PM EQ.
I like to build this pair in a 500 format.
I like to make a 600 ohms version with the PPA boards as amp.
I have two 1:1 600/600 ohms (neve VT24499) and four edcor XSM600/10K(1:4.1) in stock

What's the mods to do?
Does it need to change some res or pot values?

Best,
Cyril

 
creal said:
Hi Ian and everybody,
I have question about the PM EQ.
I like to build this pair in a 500 format.

The PCB is 1.5 inches wide by 2.1 inches high and you need two for each EQ. I don't know if you will get two PCBS and the four pots that go with them into a 500 format.

I like to make a 600 ohms version with the PPA boards as amp.
I have two 1:1 600/600 ohms (neve VT24499) and four edcor XSM600/10K(1:4.1) in stock

What's the mods to do?
Does it need to change some res or pot values?

Basically you need to divide the pot values by 4.7, so the 4K7 becomes 1K, the 47K becomes 10K and the 470K becomes 100K just like the original Pultec.

Then you need to multiply all the capacitor values by 4.7

Cheers

Ian
 
ruffrecords said:
The PCB is 1.5 inches wide by 2.1 inches high and you need two for each EQ. I don't know if you will get two PCBS and the four pots that go with them into a 500 format.

I've been thinking about it for a while and I decided to go 2U in 500 format. Lot's of space on the front panel to put all the knobs and enough current to supply tube makeup stage. Hope to finish it soon :)
 
Here are a couple of design updates. I have redrawn the EQ schematic to show just the EQ alone and I have included the calculated values for a recommended set of frequencies for both the hi and lo boost/cut. I have also changed the value of the series resistor in the hi cut. The new value (430 ohms)  gives a broad bell response with simultaneous max cut and boost followed by a flat response. If you want the same bell followed by a cutting response use 100 ohms instead.

I have also attached tables of the calculated values for all the hi and lo boost/cut capacitances at the recommended frequencies plus a recommended combo of capacitors to get as close as practical to the stated frequency plus a 'cheapskate' capacitor (single) value where possible for those who want to reduce cost as much as possible.

Lastly I have drawn and EQ system schematic which shows the input and output transformers, the EQ, the gain make up amp and the EQ in/out switch so you know how it is all meant to go together.

Cheers

Ian

http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png
http://www.ianbell.ukfsn.org/pics/CapValues.pdf
http://www.ianbell.ukfsn.org/pics/EQSystem.png

Edit: corrected resistor value.
 
Ian, you still have the lin/logs a bit messed up, if your going by what you said about the original pultec over in the make-up thread.

Cheers
 
ej_whyte said:
Ian, you still have the lin/logs a bit messed up, if your going by what you said about the original pultec over in the make-up thread.

Cheers

I think it is right, LOL. Both the hi pots are lin and both the log pots are log. That's what I said on the other thread too.

Cheers

Ian
 
ruffrecords said:
Both the hi pots are lin and both the log pots are log.

The pic shows hi cut as log, and low cut as lin, unless I am mistaken somehow?

Cheers
 

Attachments

  • PMEQP1-AMKII Rings.png
    PMEQP1-AMKII Rings.png
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ej_whyte said:
ruffrecords said:
Both the hi pots are lin and both the log pots are log.

The pic shows hi cut as log, and low cut as lin, unless I am mistaken somehow?

Cheers

No, that's right, but that is the old schematic. The new one was referenced above:

http://www.ianbell.ukfsn.org/pics/PMEQP1-AMKII.png

If you get the old schematic when you click this link it is probably because your browser has it in its cache so you need to refresh your browser. The new one is version 1.1 dated 30 th April.

Cheers

Ian
 
ruffrecords said:
If you get the old schematic when you click this link it is probably because your browser has it in its cache so you need to refresh your browser. The new one is version 1.1 dated 30 th April.

Cheers

Ian

Aah thanks, got it now, sorry for the confusion  :-[

Cheers
 
ej_whyte said:
ruffrecords said:
If you get the old schematic when you click this link it is probably because your browser has it in its cache so you need to refresh your browser. The new one is version 1.1 dated 30 th April.

Cheers

Ian

Aah thanks, got it now, sorry for the confusion  :-[

Cheers

No problem, it is easily done.

Cheers

Ian
 
ruffrecords said:
creal said:
Hi Ian and everybody,
I have question about the PM EQ.
I like to build this pair in a 500 format.

The PCB is 1.5 inches wide by 2.1 inches high and you need two for each EQ. I don't know if you will get two PCBS and the four pots that go with them into a 500 format.

I like to make a 600 ohms version with the PPA boards as amp.
I have two 1:1 600/600 ohms (neve VT24499) and four edcor XSM600/10K(1:4.1) in stock

What's the mods to do?
Does it need to change some res or pot values?

Basically you need to divide the pot values by 4.7, so the 4K7 becomes 1K, the 47K becomes 10K and the 470K becomes 100K just like the original Pultec.

Then you need to multiply all the capacitor values by 4.7

Cheers

Ian

Many thanks Ian for advices.
I will be little busy this week little, but i'll post the BOM for the 600ohm version and the front panel for the 500 format.

Best
Cyril
 

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