Searching for a Pulptec EQP1A schematic

[analag]

I have ran out of what to build so I have decided to build the ubiquituos Pultec EQP1A. Apart from Gyraf and a few other sites there seem to be a blackout of useful info. Pictures and junk but not real useful stuff.

Analag

 

[chrissugar]

Hey Analag

CJ is just kidding. You can find the schem of the original Pultec at many places (even at his place). In this thread there are some links to various schematics and also a discussion about diferences:
http://www.groupdiy.com/index.php?topic=6850&postdays=0&postorder=asc&start=15

The Pultec sound comes from the interaction of all the elements: input, interstage , output transformers, the filter circuit and the push pull tube amp. Unfortunately you can't build the exact original because there is at least one element you will not find anywhere, for example the Peerless217 transformer.
Although you can build an equaliser that has the caracter of the Pultec filter circuit but with a modern gain circuit, like Jakobs SRPP or maybe a discrete opamp based one. It will be more hi-fi.
Hope it helps.

chrissugar

 

[gyraf]

I don't think that there is a schematic of the actual potted eq circuit "out there" - it was kept secret, and never revealed even in the service manuals (that showed amplifier only). I ended up reverse-engineering the circuit for the gyraf pultec - but I believe it to be fairly correct...

It is supposed to be a Bell labs patent from the 30'es - but I haven't had luck with a patent search either.

Jakob E.

 

[SSLtech]

I believe that (Wo)M*a*N*l*E*y use the correct circuit, with the permission of the original designer.

I have a Manley 2-channel Pultec on my bench at the moment...

Keef

 

[chrissugar]

Jakob,
in the manual there is not only the amp circuit but also the filter:
http://www.purpleaudio.com/pdflib/PultecEQP.pdf

chrissugar

 

[electronaut]

[quote author="SSLtech"]I have a Man ley 2-channel Pultec on my bench at the moment...[/quote]

Is the filter section potted in their version?

E.

 

[CJ]

Hold on, I am opening Adobe Illustrator so I can export a jpg. So I should be done in three days if I don't crash. :twisted: :twisted: :twisted:

The heck with Illustrator.
Here, print this:

http://vacuumbrain.com/The_Lab/TA/Pultec/eqp_filter.pdf

Your getting some extra bands. Take any complaints to the front desk.

 

[analag]

Downloaded and saved, much appreciation. Work will begin as soon as I source the parts. Thanks for all the help.

Analag