How to improve the sound of my G-Pultec?

[living sounds]

Finished half of my new Calrec a few days ago and I have to say this sounds a lot more like what I had expected from the Pultec.

The latter one sounds sort of cloudy in the low end (though it can do a deep low end boost the Calrec can't) and less refined, pleasant in the high end in comparison. The Pultec is more neutral, but it has an edge to it in the high/midrange that keeps me from using it most of the time. It also seems to take away some detail, but not in the good way.

How to address this best? I used Edcor XS1100 (LL5402 'clone') on the in- and output, matched Electro-Harmonix tubes, solen fast capacitors for the bass and the filtering cap after the gain stage, polystyrene for the high boost and polyester for the high cut (which I never use). I think I also wired the connections from the switches and back with a non-copper cable (iron), of which the width is however quite strong.
I also used the cheap Toko inductors and some standard pots.


So, what to do? Better inductors? Get rid of the input transformer? Change the output transformer? Change the high cut caps to polypropylene (although I never use the high cut)? Use copper wire (that would be very tedious work indeed? Change some of the other caps? Bypass some of the caps with smaller, better types? Change the tubes? Even change the pots?

I tried to put more resistance on the high boost to make it wider, but this decreases the actual boost, it doesn't work.

Thanks!
Gregor

 

[okgb]

I have one built to the gyraf specs that has never sounded right either
sort of a dullness riding over everything , using the same setup
but subbing my Tube Tech eq in , no problems .
It's not unusable but uninspiring , i don't use it

 

[ioaudio]

try listening to the unbalanced signal before the output transformer (after the output cap!).
something rings my bell when i read srpp output stage (G9 / Pultec) combined with the Edcor XS1100. for the input it could be ok.

meanwhile i prefer transformerless output from srpp stages, just unbalanced to converter seems to reveal the better qualities of this toplogy.

if you have problems with the high/mid boost a better sounding inductor will help. though toko´s have been ok for some manufacturers in the past, most of the newer designs i see popping up on gearslutz use costum made coils.

 

[living sounds]

Thanks guys!
I rewired the Pultec without the transformers (unbalanced) and added a bypass cap to the output capacitor and added a 22k resistor to the output for unity gain and like the sound much better now. A much clearer, better defined punch (especially with a lot of low end dialed in) and more transparency in the highs. I don't miss any color. There's even a lower noise floor now since the transformers were picking up some hum.

Now I'm still wondering about the inductors. Is there really anything audibly different besides DC resistance (and thus Q with) between - say - the Toko inductors, a Carnhill product or one of ioaudio's?

 

[khstudio]

After hearing SEVERAL different inductors I would have to say that the cheap plastic ones are my LEAST favorite... not even favorites, I don't care for them.

Do yourself a favor & get some nice "Quality" inductors, like Cinemag, IOAudio, Sowter, etc...
or wind some yourself if you can.

You can use this online calculator to figure out which cap values to use (with whatever inductor you get) to get the frequencies you want... even extras or even changing the ones you don't like.

"Capacitance-Frequency-Inductance" by OPAMP Labs, Inc.
http://www.elec-toolbox.com/calculators/cfl.htm

Your choices are:
Cap.(uF) Freq.(Hz) Ind.(Henrys)

So for mH values (like the Pultec)
50mH would have to be typed in = .050

You have to move the decimal to the correct position... same goes for the caps.

10k = 10000 for FRQ

You should get the idea.

DIY is why we're here... if you do all that work & don't like something you've built then start changing stuff... at least you'll learn, just like you did with the TX's.
You may want to try some different iron, tubes or caps too... but the inductors would definitely be one of the first things I get rid of.

It's hard to mess up a Passive EQ (or the Pultec circuit)
& if it doesn't sound good in BYPASS - it IS NOT going to sound good engaged!!!

Kevin

 

[living sounds]

Thanks Kevin!

So what are the sonic differences between these brands? Have you tried them? I'd love to experiment myself, but buying them and trying them all out is simply cost- and time-prohibitive at the moment here....

Gregor

 

[khstudio]

[quote author="living sounds"]Thanks Kevin!

So what are the sonic differences between these brands? Have you tried them? I'd love to experiment myself, but buying them and trying them all out is simply cost- and time-prohibitive at the moment here....

Gregor[/quote]

All the ones I named should sound similar & be an improvement over the ones you have.

 

[living sounds]

Yea, but in what way? A wider Q would be beneficial I think, but what else would change?

 

[khstudio]

[quote author="living sounds"]Yea, but in what way? A wider Q would be beneficial I think, but what else would change?[/quote]

Wider Q? :roll:

There's a Q control already on the Pultec that gets plenty wide... unless yours is built wrong or broken... or maybe those inductors just don't sound good...hmmmm.

I don't know what other advise I could give you. Try it and see. I'd also recommend some searching, research & reading. But NOTHING will help you more than trying it for yourself. :wink:

Good luck.

 

[Janalex]

Thanks guys!
I rewired the Pultec without the transformers (unbalanced) and added a bypass cap to the output capacitor and added a 22k resistor to the output for unity gain and like the sound much better now. A much clearer, better defined punch (especially with a lot of low end dialed in) and more transparency in the highs. I don't miss any color. There's even a lower noise floor now since the transformers were picking up some hum.

Now I'm still wondering about the inductors. Is there really anything audibly different besides DC resistance (and thus Q with) between - say - the Toko inductors, a Carnhill product or one of ioaudio's?

Sorry to revive this old thread. Was gonna try this. The 22k resistor is in series with output between output and pin2? What is the value of the bypass cap and it goes across the output cap under the pcb?

 

[living sounds]

That was 15 years ago, can't remember any of it, sorry. I did take out the tube stages completely and replaced them with Enhanced Pultec 5532 based ones. Those didn't work so well either. I ultimately ended up with misapropriating a CAPI 2-ACA board as balanced input and gain make up stage. Now it's a very nice sounding EQ with no hum at all.