GSSL Mods. What do you think?

[Category 5]

A friend who is much more knowledgeable than I at circuit design is building a GSSL beside mine. He has proposed some mods that sound quite interesting and I was wondering if any of you had tried them, or what some of you think.

1 - Using DBX 202XL VCA's in place of 2150's - Class A biased

2 - OP275 in place of the 5532s. This guy had a hand in the design of that chip and is recommending it as a replacement.

3 - Two resistor changes on the gain of the input amps and 2 or four on the VCA input and perhaps the feedback of the next stage to lower distortion and increase headroom

4 - A really cool front panel. If it looks good it HAS to sound good :wink:

Any comments?

 

[gyraf]

The 27K- instead of 15K is an essential mod if running the unit balanced in/out, in order to keep levels straight.

And the frontpanel is the most important component of all - to perceived sound.

Don't bother with the other mods - very little (if anything) will be gained by that.

Jakob E.

 

[emtee]

[quote author="gyraf"]The 27K- instead of 15K is an essential mod if running the unit balanced in/out, in order to keep levels straight.

Jakob E.[/quote]

Did you mean UNbalanced? I thought the original values were for balanced :?

 

[gyraf]

..Yes, but there was a 6dB messup..

 

[emtee]

Aha!

 

[Category 5]

Will the DBX 202XLs and the OP275s work well in the design, even though there is little to be gained? I ask because we have some already, and at least we could save ourselves the trouble of sourcing the parts on the BOM if there's no need.

If you think the BOM is really the best way to go about things, I'll stick to it. After all, it's your project! :grin:

 

[smallbutfine]

i assume DBX 202XL will work fine as it seems to be just a later model of the originally used 202. (You don't have to use the emulation ckt components Jakob uses to make the 2150 behave like a 202)
OP275 should work, too. But i don't really know, if you get any sound quality gain from this...OK, at least the specs say it has nearly same unity gain bandwidth (i think oscillations would not be a problem) and slew rate is more than doubled...it's a fine sounding opamp however...
BTW, i know that several people here on the board tried around with different kind of opamps from AD and BurrBrown etc to 'beef' up their GSSLs, generally there's absolutely nothing to say against it...
(correct me if i'm wrong, Jakob...)

Kind regards

Martin

 

[gyraf]

I haven't tried the OP275's here, but I doubt they'll make any difference in this circuit.

The THAT2181LA is probably the best VCA, if you're going in the "clean" direction.

Remember, this is a unit with a sound - it's never ment to be neutral..!

Jakob E.

 

[peeceebee]

For me, the edgy, agressive sound quality with a tinge of distortion is what really makes these things (at least mine) shine- I wouldn't try to clean it up for anything-

 

[gyraf]

I completely agree.

I know of a manufacturer making a similar type compressor, that on purpose sets the dist. trim a bit off...

:grin:

Jakob E.

 

[Purusha]

Since you mentioned it. Than which of today's THAT VCAs is the most colored version?

I was thinking to go with 2181LBs. But would rather go to more colour option than natural, so which one gentelmen.

 

[clintrubber]

[quote author="gyraf"]I completely agree.

I know of a manufacturer making a similar type compressor, that on purpose sets the dist. trim a bit off...

:grin:

Jakob E.[/quote]

After the dust on the sidechain filtering & the Filter From T.H.R.U.S.T. has seemed to settle a bit I feel a next front panel control coming up ! :wink:

It won't be me, but could imagine people get tempted :thumb:

 

[smallbutfine]

...well, i think i'm looking for a 2 rackunit case now...this control elements got dense now. however, i'm sure that this one is a little bit fiddly and individual :grin: ...maybe "OFF, COLOUR, DRIVE, DIST" stages of effect, 2p3t rotary? :grin:

 

[bernatvm]

I completely agree.

I know of a manufacturer making a similar type compressor, that on purpose sets the dist. trim a bit off...

:grin:

Jakob E.

Old thread but I'll give it a try before starting a new one. I'm building my unit and I thought about a mod that may be nice. As you said, for more "color" it's nice to set the dist trim a bit off. Would It be useful to set the trimmer for minimum distortion and then have a switch in the front panel to engage the extra distortion?

I think It would be as easy as sending a small DC voltatge offset to the point before the 1M resistor and after the trimmer.

 

[gyraf]

You should really try it and see if the way it behaves is something that you like. If so, then yes, make it a simple FP control.

/Jakob E.