Which Hi-pass filter for G-SSL ???

Hello everybody,

I have a dilemma, which Hi-pass filter to put in my G-SSL circuit. The one Greg is selling PCB's for or the THRUST version based on API. Is there any other option available? (just asking) Can someone explain a little what is the difference between these two and which one is most versatile and has more adjustable options for drums and mix buss.

I plan to put also a button in the front panel for trimming the THAT2181LB's distortion. Has anyone tried this one yet?

Plus a red led inside the meter for the overloaded signal, like in the Drawmer 1968 ME. :idea:

I'm not sure what the trust filter does, but I'll tell you exactly what Steffen's high pass does (ie. the one I'm selling). It's simply a buffered high pass filter that's inserted into the sidechain to roll off low end, which makes the compressor "trigger" less on the low frequencies. That's it. It doesn't change the "sound" of the compressor in any way. On some material, I bypass the filter, on other, mostly bass heavy material, it helps so you don't get that pumping.

Regarding the button for trimming the VCA. I don't know why this is necessary. There's already a pot on the board for trimming. Set it and forget it. :thumb:

I'm sure someone else will comment on what the trust does, but I remember there being a big thread about it, so maybe the info is in there.

[quote author="Purusha"]Hello everybody,

I have a dilemma, which Hi-pass filter to put in my G-SSL circuit. The one Greg is selling PCB's for or the THRUST version based on API. Is there any other option available? (just asking) Can someone explain a little what is the difference between these two and which one is most versatile and has more adjustable options for drums and mix buss.[/quote]

I was wondering the same - so to avoid picking my brain too long about this I went ahead to simply implement them all.
As Greg said, find the thread & locate the additional schematic I added with even two flavours of Thr*st for more overkill-options. :thumb:

FWIW, here are direct links to the schematics:

http://home.hetnet.nl/~chickennerdpig/FILES/API/sc-circ_thrst_01.jpg
http://home.hetnet.nl/~chickennerdpig/FILES/API/API-Thrust-circuit_20060112.pdf

Hi Greg,
thanks for your replay. Regarding Stephen's high pass I understand it's function. It's similar to Drawmer's big switch. It's a must option for such a compressor. I will check out the posts about Thrust hi-pass. Then I will decide. If I decide to go with Stephen's than I will order from you 12 PCB's very soon. I'll let you know.

Regarding the VCA's trimmer I will just put the same value potentiometer on the front panel instead the one on the PCB. Why not, it's more fun mixing with more options. :thumb:

Sounds good, just let me know about the PCBs. I received my 2nd batch today.

For the trimming vs. pots:
I would use BOTH!!!
Say, you wanna change the vcas (due to failure or newer/better version), you can trim the vca's independent from the frontpanel to the exact clean(est) signal, then use the frontpanel pot/rotary/switch to bring in the offset for "color" (a great idea for you since your 2181 can be very clean and undistorted but at will be driven into distortion.)
Why do you want it?
For what the dual pot / rotary / switch should be labeled : "COLOR"
At least (as gyraf stated many times) some manufacturers and users of these machines *insist* in an offset to get the well sounding distortion of the dbx'x / THAT's as an artistic expression possibility :grin: ...

@thrust...
it's a while ago but i think Steffens circuit is a well done and super functional hi-pass filter with a selection to exclude low signals from influencing the amount of compression with well stepped cap values, the thrust filter works different and puts a characteristic across the whole audioband.
There is nothing against using BOTH. Give a step more to the rotary of steffen's hi-pass and switch the sidechain filter over to the thrust circuit. mount both filter circuits at the place for the transformer and above, they have nearly same parts count, use mounting bolts! Or offboard in case you can't mount this way (1 height unit etc).
I will do this! (my ssl in the last stages, exchanging some resistors to pots, frontpanel pcb as breadboard etc...)

[quote author="Purusha"]... and has more adjustable options ...[/quote]

Stephen's (Greg's PCB) filter has more options than the thrust (mine is just on/off).
if you want a load of options use clintrubber's version.

I wouldn't mount the THD trim as a pot to the front. you won't hear it much, and it would be hard to find the cleanest position. implement two trims, make them switchable. one for the best setting, one for more THD. I would do it like that, but that's just me ...

I wouldn't mount the THD trim as a pot to the front. you won't hear it much, and it would be hard to find the cleanest position. implement two trims, make them switchable. one for the best setting, one for more THD. I would do it like that, but that's just me ...

Click to expand...

Thanks, this sounds as a very good idea.

Why do you want it?

Click to expand...

To have more clean option on the mix buss and more dist. on dums.

@thrust...
it's a while ago but i think Steffens circuit is a well done and super functional hi-pass filter with a selection to exclude low signals from influencing the amount of compression with well stepped cap values, the thrust filter works different and puts a characteristic across the whole audioband.
There is nothing against using BOTH. Give a step more to the rotary of steffen's hi-pass and switch the sidechain filter over to the thrust circuit. mount both filter circuits at the place for the transformer and above, they have nearly same parts count, use mounting bolts! Or offboard in case you can't mount this way (1 height unit etc).
I will do this! (my ssl in the last stages, exchanging some resistors to pots, frontpanel pcb as breadboard etc...)

Click to expand...

Please confirm if I understood this right. I build the Thrust and Stephen's hi pass and make both part of one rotary pot? I didn't had the chance to study any of them yet. How much steps does each of them have, just OFF/ON or more options?

[quote author="clintrubber"][quote author="Purusha"]Hello everybody,

I have a dilemma, which Hi-pass filter to put in my G-SSL circuit. The one Greg is selling PCB's for or the THRUST version based on API. Is there any other option available? (just asking) Can someone explain a little what is the difference between these two and which one is most versatile and has more adjustable options for drums and mix buss.[/quote]

I was wondering the same - so to avoid picking my brain too long about this I went ahead to simply implement them all.
As Greg said, find the thread & locate the additional schematic I added with even two flavours of Thr*st for more overkill-options. :thumb:

FWIW, here are direct links to the schematics:

http://home.hetnet.nl/~chickennerdpig/FILES/API/sc-circ_thrst_01.jpg
http://home.hetnet.nl/~chickennerdpig/FILES/API/API-Thrust-circuit_20060112.pdf[/quote]

Hi,

I was just reading your post where you described the idea. When will you built this so we can hear your comments?

ok my f*kin internet explorer kicked me while posting :evil: , so the answer ini short:

HOW TO USE ONLY ONE ROTARY:
HP filter schematic from steffen in gregs layout like here
http://members.cox.net/capstanrecording/Sidechain_Sch.pdf
If thrust original (like silent:art, only in an out)...

use 2 pole 7 pos switch for simple bypass, 3 pole for full hard bypass.

simple bypass (2 pole) :

Wire up pole 1 like for the HP from steffen, but begin with pos 2. short pos1 to pos2 (HP OFF in pos 1+2)

connect the sidechain in-signal (mono) to pole 2.
position 1 to thrust in.
position 2-7 to HP steffen in.

full hard bypass (3-pole):
like above...
connect the sidechain out to pole 3.
position 1 to thrust out
position 2-7 to HP steffen out.
-
Makes one panelswitch
THRUST,OFF, 60Hz, 90Hz, 130Hz, 200Hz, EXTERNAL

Full hard bypass with both output options on thrust from clintrubber (http://home.hetnet.nl/~chickennerdpig/FILES/API/sc-circ_thrst_01.jpg):
Requires 3 pole 8 pos rotary.

Wire up pole 1 like for the HP from steffen, but begin with pos 3. short pos1 to pos2 to pos3(HP OFF in pos 1+2+3)

connect the sidechain in-signal (mono) to pole 2.
position 1+2 to thrust in.
position 3-8 to HP steffen in.

connect the sidechain out to pole 3.
position 1 to thrust loud out
position 2 to thrust medium out
position 3-7 to HP steffen out.

Makes one panelswitch
THRUST LOUD, THRUST MEDIUM, OFF, 60Hz, 90Hz, 130Hz, 200Hz, EXTERNAL

Hope i got it all now :grin:

Kind regards and happy DIY

Martin

Wau... :thumb:

What is the difference between the normal THRUST and other two LOUD and MEDIUM THRUST?

BTW thanks for the info. Great job.

In mine, I just put a .02 cap in the circuit after the 47k sidechain summing resistors, parallelled by a 200k pot. Very simple, does the trick very nicely.

Obviously a one trick pony, but being able to dial in the amount of hi pass to the sidechain works very nicely...

Sorry, I am too much of a newbie still to grasp your version of Hi-pass. Can you make some more easy explanation for me. I got the point what it does but I need also to undestand how to build it. :grin:

Thanks.

This one:


:green:

If you just want a HPF, this one works fine. I use mine all the time.

Beautiful ASCII art design! :grin:

[quote author="Purusha"]Wau... :thumb:

What is the difference between the normal THRUST and other two LOUD and MEDIUM THRUST?

BTW thanks for the info. Great job.[/quote]

Have a look at the curves in the A*P*I 2500 manual:
http://www.apiaudio.com/man2500.pdf

Two different slopes.


BTW, I'm mounting Gregs HPF-PCB on a larger veroboard (of matching green colour :wink: ) that both serves as a motherboard and contains the thristy-circuitry as in my posted schematics. Dunno yet whether I'll be adding all those additional HPF-frequencies to fill up that 12-position rotary - might be more elegant to add just two additional thr-positions and limit travel to 6+2 positions.

Bye,

Peter

:grin: 24 positions and use like detented pot :grin:

[quote author="smallbutfine"]:grin: 24 positions and use like detented pot :grin:[/quote]
You're not ridiculing my 12-position-filter, are you ? :wink:

*not*at*all*