EQP1A with cascode amp circuit

[Deepdark]

quick one. i want to replace the 7 position highs with a 6 positions. with a inductor of 269/169/69/22, and a 2k2(2k5??) high Q pot, is there something else i should change,or the filter section remain the same?

The inductor has a wider range than the original so you will need to alter the frequencies if you want the same Q curves as the original but otherwise there are no changes to make.

looking at individuals inductors, mouser stock a lot of them. is there some manufacturer they are Worth looking for? API Delevan, Hammond, Fastron, Murata, etc. I looked at Cinemag and Carnhill to know if they have/could make them. I know Sowter stock them, by the way.

Sorry, no experience of inductors for original design.

Cheers

Ian

Individualy, the inductors values are 100mh, 100mh, 47mh, 22mh. So in series it gives the values i wrote. What do you say by i need to alterate the frequency to get the same curve as originaly? Do you mean replacing certain cap values? There is a couple of caps values who changed, probably to keep the curve as close as possible to the original filter curve. I follow the gpultec filter schematic to do that mod.

 

[ruffrecords]

I don't understand. The Gyraf inductor taps are at 22mH, 50mH, 100mH, 175mH.

The original EQ1A has individual inductors of 22mH, 33mH, 47mH, 68mH, 82mH and 150mH.

Cheers

Ian

 

[Deepdark]

Weird, I'm looking at the schematic right now and it's 22 47 100 100. Maybe he changed that later. Anyway, there is too much changes in the filter.

 

[ruffrecords]

Here's the Gyraf one I looked at:

http://www.gyraf.dk/gy_pd/pultec/pultech.gif

Cheers

Ian

 

[Deepdark]

Ah i understand. This is the reverse eng. He did of the original eqp. I think the filter schematic wasn't available at the time. The one i spoke about was the srpp version with his modified filter section. After looking at it, i found a couple more modifications.

Looking at the original filter section, is it possible to just letting go the 16k freq, to make a 6 positions instead of a 7? What would be the consequences in the overall filter? Does it need more change or We can just not put the 3n3 caps and wire the hf boost from the 5n6  cap? I know the total inductance Will not be the same so it Led me to think if this Will result in a different overall filter response.

 

[Deepdark]

Is anybody know who sells the RA series from lorlin (double desk rotary switch). Newark and mouser don't stock them.

 

[ruffrecords]

There will be no problem if you simply drop one frequency and do not use that inductor tap.

Cheers

Ian