Transformerless Varimu Compressor

[clintrubber]

Magic eye spotted ! :thumb:

 

[solder_city]

that circuit will thump like a son of a bitch.

there are some cheap single ended tube agc's but to do it with any kind of quality its got to be a balanced circuit.

 

[Rob Flinn]

[quote author="solder_city"]that circuit will thump like a son of a bitch.

there are some cheap single ended tube agc's but to do it with any kind of quality its got to be a balanced circuit.[/quote]

DId you read PRR's analysis of the same circuit on the previous page ??

 

[Guest]

[quote author="solder_city"]that circuit will thump like a son of a bitch.

there are some cheap single ended tube agc's but to do it with any kind of quality its got to be a balanced circuit.[/quote]

Or a good HPF after it.

"Balanced for less distortions" is a noncense. Balanced for less control signal in output - it is the purpose.

You may load both tubes in balanced varimy compressors by my CCS-es similar to this one, you will get variable anode current with nearly constant anode voltages, however time constants should be selected accordingly.
However, I did not try it in varimu VCAs, but I believe it will work much better than a dumb resistive load.

 

[NewYorkDave]

 

[chrissugar]

Woohoo,
Dave is back! :grin:

chrissugar

 

[clintrubber]

[quote author="NewYorkDave"]
Less talk, more action.
[/quote]

:thumb:

 

[emrr]

RCA BA-25 uses transformers, but the input transformer is set up single-ended for simple carbon pot volume control and follows it with an interesting phase inverter circuit I've not seen in anything else.

I've heard a fully single-ended type before, and it worked far better than I'd have imagined. It was still more of an effect box than a useful clean tool. there were many many single-ended types used in PA applications.

 

[Schmilsson]

> it's all in polish but the diagrams are pretty clear.

Ah, good old single-ended vari-gain. It works. It thumps, and violently at short attack times. It has large 2nd harmonic; or rather, THD becomes "high" about 20-30dB before a push-pull vari-gain stage's THD would get high. It may actually be "musical", but for wide dynamic range material it won't be clean.

Sorry to dig this old thread up. I'd really like to check a single ended vari mu schematic out. That polish link is dead though. Anyone got that one or something similar in their stash?

 

[Piedwagtail]

Eskimo,

I built a single-ended Federal.OEP 1:1 input transformer to 6sk7 grid,put the bottom to the timing circuit.
Guerilla tactic output straight off the plate via a big fat capacitor.
No 6sn7 at all,no output transformer.
200V HT,6.3V AC heaters.

On a mix, with beats it is plain ridiculous.
On voice,solo legato line eg.monosynth it's a flippin marvel.

Here's the etch note from my library.
Draw with an inedible inkpen,lines and dots,not the curving links or marked components.
Octal sockets sit in holesawed holes and hardwire into etched board.
Transformer off board,filament wiring twisted direct to sockets.

I later replaced the 47k and resistor across the timing cap with pots for attack and release controls, but my notes are incomplete on that.


Robert

 

[michal_k]

> it's all in polish but the diagrams are pretty clear.

Ah, good old single-ended vari-gain. It works. It thumps, and violently at short attack times. It has large 2nd harmonic; or rather, THD becomes "high" about 20-30dB before a push-pull vari-gain stage's THD would get high. It may actually be "musical", but for wide dynamic range material it won't be clean.

Sorry to dig this old thread up. I'd really like to check a single ended vari mu schematic out. That polish link is dead though. Anyone got that one or something similar in their stash?

here you are:
http://www.edw.com.pl/ea/kompresor.html

 

[Schmilsson]

Piedwagtail: haha, awesome! I'd love to hear that!

Thanks michal_k!

I'll be making a 438, so it's push pull for now, but I'd love to try that out later on.

 

[PRR]

> Rezystor R23, potencjometr P3 i kondensator C14 stanowia obwód calkujacy.
> Resistor R23, potentiometer P3 and the capacitor C14 form a circuit integrator.
> Stala czasowa tego obwodu zawiera sie od 0,220s do 1,22s.
> Time constant of this circuit is between 0.220s to 1.22 s.

zero point two seconds attack time?

This is one of the hard-to-eliminate limitations of one-hand-clapping or/and transformerless audio limiters. There is a compromise between audio coupling cap bass response and attack time; also no thump-cancellation so you must keep limiting-action very much slower than the lowest audio frequency you will pass.

Jest to jedno z trudnych do zniesienia ograniczeń jednej strony-oklaski i / lub transformerless audio ograniczników. Nie ma kompromisu pomiędzy audio sprzęgu cap basów i czas ataku, a także nie-pobrząkać anulowania dlatego należy zachować ograniczenie działania znacznie wolniej niż najniższe częstotliwości dźwięku Zdasz.  ??? ;D ??? ;D

 

[opacheco]

How about  a compressor based on EF89 pentode ?

http://www.elektronika.qs.pl/kompresor.html

Unfortunately it's all in polish but the diagrams are pretty clear.

the link is dead???....do you have a the active url addres??

Thanks a lot,
Opacheco.

 

[michal_k]

> it's all in polish but the diagrams are pretty clear.

Ah, good old single-ended vari-gain. It works. It thumps, and violently at short attack times. It has large 2nd harmonic; or rather, THD becomes "high" about 20-30dB before a push-pull vari-gain stage's THD would get high. It may actually be "musical", but for wide dynamic range material it won't be clean.

Sorry to dig this old thread up. I'd really like to check a single ended vari mu schematic out. That polish link is dead though. Anyone got that one or something similar in their stash?

here you are:
http://www.edw.com.pl/ea/kompresor.html

 

[abbey road d enfer]

[quote author= link=topic=5255.msg241701#msg241701 date=1169843327]
You may load both tubes in balanced varimy compressors by my CCS-es similar to this one, you will get variable anode current with nearly constant anode voltages, however time constants should be selected accordingly.
However, I did not try it in varimu VCAs, but I believe it will work much better than a dumb resistive load.

[/quote]This will obviously be better than a "dumb resistor", since it is a simulated inductance (choke), so it will have the property of reducing slow variations and still passing audio, but will not have the inherent capacity of a balanced circuit to eliminate control voltage bledd.

 

[Blue Jinn]

I realize the limitations of my knowledge, but what exactly does the Nixie tube do in this?

 

[gemini86]

It's just a meter... For visual aid.

 

[Blue Jinn]

OK, is it mechanically connected in some way to P2? I don't read Polish, but I'm guessing that  W-2 is simply a 2 pole 12 position switch and it looks like that is all that is controlling the numerical display...

I have a tube like this, not a nixie, but a 7 segment tube, and its associated bcd converter chip. I think I may even have the circruit in the 1971 RCA hobby book somewhere... Seems you'd need more to get it to register what is going on?

http://www.decodesystems.com/nixie.html

 

[Schmilsson]

I'm gonna dig this one up again simply because I like the prospect of an SE vari-mu so much.

there were many many single-ended types used in PA applications.

Examples? I'd love to eye a few schems.