EMT 261 Compressor/Limiter Circuit Analysis (never seen THIS chip used in a compressor before)

[@jandobbelsteen8953]

I don't have a reference to any compressor design, but I do know of at least two Eurorack modules that use the AD633 multiplier chip. The Northcoast Synthesis Middlepath VCO uses two AD633 chips for linearization of the exponential converter, resulting in good temperature stabilization. And the Befaco A*B+C dual ring modulator uses two AD633 chips for, well, A*B+C.

[@Lantertronics]

The AD633 is very expensive but very very very good -- it doesn't need trimming the way the 1496 does.

[@taloowa5800]

The Neuman BSB-74 is a high-frequency acceleration limiter (sort of like a D-Esser) used in their SAL-74 cutting amplifier racks. It is really fantastic... one of the best modules that does that job. A 4 quadrant multiplier was state of the art when it was designed into these units but subsequently, there became better ways for audio gain or filter control, at least in the dynamic range department. The BSB was not built as a stand-alone set. It was only available as part of the record-cutting system.

[@Lantertronics]

Oh wow! (As an aside: I really don't get how anyone could think vinyl is the be-all-end-all of music reproduction technology. There's so many compromises you need to make in getting the music on the vinyl... I didn't even know about this high-frequency acceleration limiter thing you're talking about.)

[@campbellmorrison8540]

I actually dont know what an audio compressor is so thank you for introducing me to a new area, I'll check out your page. I have used the AD633 for a multiplier in an analogue computer but thats my total experience in this area

[@wsc112782]

It would be interesting to see your analysis of the diode bridge config used as a gain control element in the Neve compressors :)

[@toy_electronics1464]

Would love to see a deep dive into some of the few diode bridge compression approaches

[@mysneekers5862]

Oh, I did make a Compandor from a article using the NE570 chip. That chip is a Compandor

[@harlanfalejczyk2478]

that would fit with it being used to make an analytical signal

[@duffharris9295]

It would be cool to see you explain how the memory module for an original tube CBS Audimax works

[@Lantertronics]

I hadn't heard of the CBS Audimax. It looks interesting, I will need to check it out! :)

[@CharlesTsaiE]

Little Labs LL2A, its functioning by using analog multiplier(ADI's IC), pretty rare and i wonder is there any drawback or cons in this topology compressor?

[@Lantertronics]

I will need to check that out!

[@misterhat5823]

That's a 1495, but you say and show the 1496 datasheet. They are similar, but not the same.

[@Lantertronics]

Good catch!

[@mysneekers5862]

I think I remember my teacher using the MC-1495 in a circuit to demonstrate AM modulation.

[@harlanfalejczyk2478]

is there one signal or two going into the envelope detection stage? the multiplier could be used to make a quadrature signal for reducing distortion at the peak detector

[@Lantertronics]

I don't think it's doing anything that complicated, but the schematic is hard to follow.

[@hithereitsme7090]

Siemens U73 (tube) or U273 (transistor) compressor

[@christopherventer6391]

I would love to see your analysis of a PWM compressor like the Pye or Great River. They're pretty uncommon but a very interesting method of doing compression (and sound awesome imo).

[@danielsanichiban]

Also Cranesong STC-8 uses PWM attenuation

[@johnmusgrave7062]

Little Labs makes a 4 quadrant compressor.

[@Lantertronics]

I will need to check that out!

[@synthnerd4539]

Don't think I've seen this in a compressor either, but I've seen them in ring modulators, which is basically just amplitude modulation, so I guess it makes sense?

[@Lantertronics]

Yup!

[@gwalla]

Those transformer symbols on the schematic look weird. I assume the black rectangles are taking the place of the row of half-circles to indicate the coils, but why are there two on one side?

[@sauerdrops484]

Yes, the black rectangles are the transformer windings and each of the transformers has 3 windings. Thats how they did professional/industrial schematics in Germany at the time.

[@Lantertronics]

Yeah I think I've seen similar things in Neumann schematics.

[@frankjamesbonarrigo7162]

No audio?

[@Lantertronics]

Oh, I don't actually own one! I was just looking at the schematic. (For that matter I don't actually most of the gear I analyze on this channel).

[@0e0]

do diode bridge compressors do anything similar?

[@Lantertronics]

They're kind of doing their own thing, exploring dynamic properties of diodes. They're kind of spiritually close to a FET compressor like the 1176 although the implementation details are quite different.

[@Scrogan]

From what I remember, those mixer chips are a pain to work with in their voltage ranges.

[@Lantertronics]

Yeah the 1496 is cheap but kind of challenging, it needs lots of trimmers.