looking for a discrete transistor parametric circuit diagram

[clintrubber]

I sit corrected!

Not quite - you're right, that circuit section isn't the param; file-A is as indicated the low filter section.
Hmm, I just posted it (at a time I should have been horizontal) so didn't notice it was defin. from that unit, but just not the relevant section ! :?

So yes, it looks like there are indeed a discr. params in existence, and one of them might be this Trident, but we don't have the relevant sections here. I assume at least that for it's param-sections this unit doesn't switch to uA741's on 45V ! :wink:

BTW, how they realize a presumably 2nd order filter with a single freq-pot deserves some further attention - but later :wink:

 

[Bo Hansen]

Hi guys,

Yes I have the complete schematic, but it is not usable in this condition it is in just now, because it is a very old one square metre xerox copy, and after all years it is also very, very dark, so it is hard to see the drawings, even in the orginal size.

So I´m sorry to say, this I have scan for you before, it is the only I have for the moment.
Maybe later on, after the summer, I can redrawn the schematic, but it take a lot of time, so this must wait for a while.

Yes, the schematic show one of the three filter sections, and they are "full parametric" with sweep, Q and gain controls, and the filter topologies are a R and C "twin T-net" and the mostly of the amps are simple two transistor "inverted" amp with a gain transistor and a emitter follower, and there are also some "serial feedback" two/four transistor amp, with and without complementary output pair.
(besides the "twin T-net" it is same building bricks as i Triad A or B-range consoles)

--Bo

 

[Bo Hansen]

I have clean up the old scan of the Trident CB9066 schematic, and I also take a look on the big orginal (one square metre sheet) but for the moment it is impossible to get something out of this dark orginal.

http://web.telia.com/~u31641623/Trident CB9066 eq, a.jpg

http://web.telia.com/~u31641623/Trident CB9066 eq, b.jpg

--Bo

 

[jhaible]

Here's an idea.
Not related to the Trident stuff, but (hopefully) to the original question.

You can build a para EQ around a state variable filter.

You can build a very nice sounding (except for one thing, see later ...) state variable filter from unbuffered CMOS inverter gates. This has been used in music synthesizers, probably for the first time in the EDP Wasp.
The benefit of this filter is ist very smooth overdrive character.

The drawback is that the CMOS gates are quite noisy. Ok for synthesizers, but hardly for studio gear.

But wait. Inside an unbuffered CMOS inverter there are just two complementary MOSFETs. So that's where I start to think "discrete". Why not just use two discrete MOSFETs (hopefully less noisy than cheap CD4000A series gates), and build your SVF (or parametric EQ) from that?

I haven't found the time to do this yet (involves transistor selection, I fear), but it's in my head for some years now. Somebody should try this. What I expect is a EQ with "character", not a very clean one.

Just an idea.

JH.

 

[clintrubber]

Sounds like an interesting approach !

Just wondering (but not wanting to spoil the fun !) how the character & EQ work co-operate - I mean, the character gets somewhat shaped by the chosen EQ-curve right away and not added later in say the DC-biased output-TX.

Regards,

Peter