Wow, that looks like the Cohen-pre with a very fancy and powerful output.
trafoless microphone preamp wish list
- Thread starter bcarso
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bcarso
Well-known member
Hmmm. A roll-your-own trafoless "floating" output. Wonder how it does with C loading and unbalanced loads. Probably pretty well compared to the integrated version.
An odd sequence of gain resistors on the first page, but maybe the pin numbers don't map in a straightforward way to the switch contacts. Oh wait I see---it sort of wraps around.
No chances are being taken with overload, using 1N4002 diodes! The 394's have some of their own built in as well not shown on the schematic, but they won't do much to protect the op amps.
The common-mode choke at the input is a good idea. It needs to be a very tightly balanced one so that no differential current flows with signal, o/w with some, even small currents can generate significant distortion.
I guess the only thing I would consider changing would be to use a higher quality power supply, given the care taken with all of the other details.
Thanks for that Fabio!
An odd sequence of gain resistors on the first page, but maybe the pin numbers don't map in a straightforward way to the switch contacts. Oh wait I see---it sort of wraps around.
No chances are being taken with overload, using 1N4002 diodes! The 394's have some of their own built in as well not shown on the schematic, but they won't do much to protect the op amps.
The common-mode choke at the input is a good idea. It needs to be a very tightly balanced one so that no differential current flows with signal, o/w with some, even small currents can generate significant distortion.
I guess the only thing I would consider changing would be to use a higher quality power supply, given the care taken with all of the other details.
Thanks for that Fabio!
bcarso
Well-known member
I have done many discrete regulator designs, although none yet specifically addressing the needs (or desires :grin: ) of a mic preamp.
One design for a "high-end" audio electronic crossover had discrete current sources feeding discrete shunt regulators. I believe I had two floating windings on the trafo so the two regulators were identical and only tied together at their outputs. This allowed the use of N channel DMOS for heavy lifting in both the current sources and the shunt regulators. The voltage references were heavily-filtered TL431's, which do have a fair amount of 1/f noise unfortunately. I have quieter references but they are tweakier, needing some parts testing and calculations.
I like to make the regulators have really fast transient response to load changes without much ringing or overshoot. Good low ESR/ESL caps on the outputs help in that regard, but I also do step load change sims and experiments to optimize the compensation.
If there is interest and I have the time I will be happy to throw a design together and post---maybe just figure out what the desired voltages and currents are to start.
One design for a "high-end" audio electronic crossover had discrete current sources feeding discrete shunt regulators. I believe I had two floating windings on the trafo so the two regulators were identical and only tied together at their outputs. This allowed the use of N channel DMOS for heavy lifting in both the current sources and the shunt regulators. The voltage references were heavily-filtered TL431's, which do have a fair amount of 1/f noise unfortunately. I have quieter references but they are tweakier, needing some parts testing and calculations.
I like to make the regulators have really fast transient response to load changes without much ringing or overshoot. Good low ESR/ESL caps on the outputs help in that regard, but I also do step load change sims and experiments to optimize the compensation.
If there is interest and I have the time I will be happy to throw a design together and post---maybe just figure out what the desired voltages and currents are to start.
Learner
Well-known member
[quote author="bcarso"]I have done many discrete regulator designs, although none yet specifically addressing the needs (or desires :grin: ) of a mic preamp.
One design for a "high-end" audio electronic crossover had discrete current sources feeding discrete shunt regulators. I believe I had two floating windings on the trafo so the two regulators were identical and only tied together at their outputs. This allowed the use of N channel DMOS for heavy lifting in both the current sources and the shunt regulators. The voltage references were heavily-filtered TL431's, which do have a fair amount of 1/f noise unfortunately. I have quieter references but they are tweakier, needing some parts testing and calculations.
I like to make the regulators have really fast transient response to load changes without much ringing or overshoot. Good low ESR/ESL caps on the outputs help in that regard, but I also do step load change sims and experiments to optimize the compensation.
If there is interest and I have the time I will be happy to throw a design together and post---maybe just figure out what the desired voltages and currents are to start.[/quote]
Hi B,
Any chance of designing a 250V regulated power supply using discrete regulator design? Since the TL 783 is in a limbo situation at the moment....
Thanks!
One design for a "high-end" audio electronic crossover had discrete current sources feeding discrete shunt regulators. I believe I had two floating windings on the trafo so the two regulators were identical and only tied together at their outputs. This allowed the use of N channel DMOS for heavy lifting in both the current sources and the shunt regulators. The voltage references were heavily-filtered TL431's, which do have a fair amount of 1/f noise unfortunately. I have quieter references but they are tweakier, needing some parts testing and calculations.
I like to make the regulators have really fast transient response to load changes without much ringing or overshoot. Good low ESR/ESL caps on the outputs help in that regard, but I also do step load change sims and experiments to optimize the compensation.
If there is interest and I have the time I will be happy to throw a design together and post---maybe just figure out what the desired voltages and currents are to start.[/quote]
Hi B,
Any chance of designing a 250V regulated power supply using discrete regulator design? Since the TL 783 is in a limbo situation at the moment....
Thanks!
CJ
Well-known member
Tubes work great for that. Unless you don't like tubes. You do like tubes, don't you?
Please say you like tubes.
Please say you like tubes.
[quote author="Learner"]TL 783 is in a limbo situation at the moment....[/quote]
[OT]
I keep seeing people freak out about the TO-220 TL783, so FYI: They're still available online from a couple of vendors, Maxwall has some for sale in the Black Market, the SMD version is still in production, and TI has said (to me personally, as well as to others) that the TO-220 version is coming back soon. In fact, I believe our very own TI man Rochey confirmed the comeback some two days ago or so.
[/OT]
And now back to your regularly scheduled program.
Peace,
Al.
[OT]
I keep seeing people freak out about the TO-220 TL783, so FYI: They're still available online from a couple of vendors, Maxwall has some for sale in the Black Market, the SMD version is still in production, and TI has said (to me personally, as well as to others) that the TO-220 version is coming back soon. In fact, I believe our very own TI man Rochey confirmed the comeback some two days ago or so.
[/OT]
And now back to your regularly scheduled program.
Peace,
Al.
CJ
Well-known member
Al, you like tubes?
Learner
Well-known member
[quote author="CJ"]Tubes work great for that. Unless you don't like tubes. You do like tubes, don't you?
Please say you like tubes.[/quote]
I LIKE TUBES but donno much about the advantage of them ove BJTs used as a regulator, also I don't know if I will like the extra heater in the circuit not being used for audio......
Already have too many heaters in my circuit, I'll show you some tubes I've been cooking up lately in a new thread soon! :green:
Please say you like tubes.[/quote]
I LIKE TUBES but donno much about the advantage of them ove BJTs used as a regulator, also I don't know if I will like the extra heater in the circuit not being used for audio......
Already have too many heaters in my circuit, I'll show you some tubes I've been cooking up lately in a new thread soon! :green:
CJ
Well-known member
I meant these:
Learner
Well-known member
[quote author="analag"]
A good place to start.[/quote]
2250V!! :shock:
I think that's a bit much for my need....
A good place to start.[/quote]
2250V!! :shock:
I think that's a bit much for my need....
CJ
Well-known member
Actually I was talking about "The Tubes", you know, the rock band?
No man....it's 250V, I use this regulator, although I juiced it up a little. Very quiet. And you will find the discrete regulator generates less heat and you can set the current limit to your specific needs.
Another kick ass regulator, I have this one in one of my mic pres.
Analag
Analag
bcarso
Well-known member
[quote author="alk509"]I once got a caddy just like that one for about 10 bucks. Still weren't enough tubes in it to light up a room or cure a fever...
Peace,
Al.[/quote]
As they used to say, A caddy for Daddy. A thought for Father's Day.
"Don't just give him another tie. Or some more Thai. Give him the warmth of TUBES this year."
Peace,
Al.[/quote]
As they used to say, A caddy for Daddy. A thought for Father's Day.
"Don't just give him another tie. Or some more Thai. Give him the warmth of TUBES this year."
CJ
Well-known member
A car, or a guy who picks the right club?
bcarso
Well-known member
[quote author="CJ"]A car, or a guy who picks the right club?[/quote]
Hey I can hijack my own car---errr--thread.
Reminds me of Groucho saying that he would never join a club that would have him as a member.
Hey I can hijack my own car---errr--thread.
Reminds me of Groucho saying that he would never join a club that would have him as a member.
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