Pultec EQP source impedance

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clintrubber

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Jun 3, 2004
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Excuse me for a separate thread:

Since the Pultec-EQP-filter-circuitry is directly connected to the input (ignoring any 1:1 TX-influence), I was wondering to which extend the source impedance has influence on the filter-curves.
I should try/sim etc, but was wondering: should it be 600 Ohms ? Or just low ?

Also: when putting buffer (with about zero Zsource) in front of it, it should have a series resistance then.

I got triggered by a remark of NYD on CJs simulations:

[quote author="NewYorkDave"]It looks like you're doing you simulations with a "perfect" zero impedance signal source.

Add a suitable series resistance to the signal generator output to see what your curves will really look like.

By the way, you can get similar curves with much fewer components and less insertion loss by using a certain "original design" EQ circuit that was posted a while back... :wink:[/quote]

Thanks,

Peter
 
Source impedance is very important for the eqp-filter, as it will be loaded down to 75R at max.boost&highQ at the frequency selected. Higher source resistance simply limits the amount of high boost available..

Jakob E.
 
Thanks for the reply.

I was 'afraid' (big word) of tilting or otherwise disturbing the EQ-curves by providing the incorrect Zsource, so was wondering whether the unit was perhaps meant to be used with say a 600 Ohms source-impedance.

But I now understand a lowZ-source will be fine, so sounds like it'd be good to put a low-Zout buffer in front of it. Main purpose to properly drive that eventual 75 Ohm load and it makes the complete unit insensitive to whatever kind of source happens to drive the box.

(Maybe inserting a small R (say 15 Ohms) in series with that ~ 0 Ohms Zout-buffer.)

Thanks,

Peter
 
[quote author="RogerFoote"][quote author="clintrubber"]<snip>so sounds like it'd be good to put a low-Zout buffer in front of it. Main purpose to properly drive that eventual 75 Ohm load and it makes the complete unit insensitive to whatever kind of source happens to drive the box.<snip>
Peter[/quote]

I am very interested in this... Thanks Peter[/quote]

Hi Roger,

Have a look here:

http://www.groupdiy.com/index.php?topic=1435

How much overengineering is going on I don't know, but better safe than sorry.
PRRs Tori-amp seems also suited.
But OK, let's combine this buffer-stuff in the other thread.

Bye,

Peter
 
The Lang PEQ was essentially a solid state Pultec, but with Freed transformers. And I still have your transistor package sitting here. Let me know if there is a better address to send it to. Sorry for the public PM, Just trying to keep my PM box a little cleaner.

:oops:

cj
 
[quote author="CJ"]The Lang PEQ was essentially a solid state Pultec, but with Freed transformers. And I still have your transistor package sitting here. Let me know if there is a better address to send it to. Sorry for the public PM, Just trying to keep my PM box a little cleaner.

:oops:

cj[/quote]

Hi CJ,
I saw the Lang makeup-schematic at the Dan Alexander site, but hadn't ever heard of Freed.

About those Darlingtons & PM, all fine. PM indeed full to soon.
I can email you on the address that contains ...@nk...., OK ?

Bye,

Peter
 
Freed was an American manufacturer of high-quality signal and power transformers. Their factory was located on Weirfield St. and Cypress Ave. in Ridgewood, NY, on the Brooklyn/Queens border. I was born around there and lived only a few blocks away :grin:. CJ has a few pages of Freed info on his site.
 
[quote author="NewYorkDave"]Freed was an American manufacturer of high-quality signal and power transformers. Their factory was located on Weirfield St. and Cypress Ave. in Ridgewood, NY, on the Brooklyn/Queens border. I was born around there and lived only a few blocks away :grin:. CJ has a few pages of Freed info on his site.[/quote]
Thanks Dave for the link, nice info. It'll be fun to use parts that were made nearby i.s.o. just from somewhere unknown.

Bye,

Peter
 
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