When I finally made the breakthrough with the Grateful Dead, I designed a line amp with 20K open loop bandwidth. That became the Levinson JC-2 line amp, because Mark Levinson evaluated it as well. Why?
Why, what?
Is this a quiz?
The JC means John Curl, the number 2 indicates that it the second line amp.
You are also using the same number now on the Parasound JC-2
Is this a quiz?
The JC means John Curl, the number 2 indicates that it the second line amp.
You are also using the same number now on the Parasound JC-2
I should be more clear. The original Levinson JC-2 and the Parasound JC-2 share one quality approach: Fets where possible, class A operation, balanced topology, high open loop bandwith. This works for me, but it is not shared by many quality IC designs.
The JC-2 always follows the JC-1. It is an interesting parallel that Parasound called the preamp the JC-2, when Levinson did the same thing 35 years before, or in 1973. In Levinson's case the preamp followed the JC-1 pre-preamp, and in Parasound's case the preamp followed the JC-1 power amp. I allowed this to happen, but I did not initiate it.
The JC-2 always follows the JC-1. It is an interesting parallel that Parasound called the preamp the JC-2, when Levinson did the same thing 35 years before, or in 1973. In Levinson's case the preamp followed the JC-1 pre-preamp, and in Parasound's case the preamp followed the JC-1 power amp. I allowed this to happen, but I did not initiate it.
PMA said:
PMA,
Variable 1st stage degeneration??
On a fully balanced, open loop design why would you do it any other
way?
cheers
Terry
John
Thank you for being clearer.
I do agree in what you are writing, but must admit that I’m not using many Fet’s.
I use BJT’s with cascode and of course CCS and current mirror.
Maybe I should try to use some more fet’s.
What did happen with the Vendetta Company and products?
Wouldn’t there be a market for the active x-over now that more and more people are looking for an active solution instead of putting a lot of C’s L’s and so on between the amp and the loudspeaker?
And it is good to know that you didn’t initiate the use of the same name on the products.
Stinius
Thank you for being clearer.
I do agree in what you are writing, but must admit that I’m not using many Fet’s.
I use BJT’s with cascode and of course CCS and current mirror.
Maybe I should try to use some more fet’s.
What did happen with the Vendetta Company and products?
Wouldn’t there be a market for the active x-over now that more and more people are looking for an active solution instead of putting a lot of C’s L’s and so on between the amp and the loudspeaker?
And it is good to know that you didn’t initiate the use of the same name on the products.
Stinius
The use of first stage degeneration SHOWS that Charles is OK with local source degeneration or local feedback.
Terry Demol said:
I don’t think he is talking about degeneration, but about the volume control.
Stinius
terry:
that makes sense to me, too.
i was worried that changing the degeneration could change the spectral balance of the distortion, which doesn't sound like something you'd want to do when changing volume. however, (apologies to john) i have to admit i haven't thought it through.
i need my wife to go on a shopping trip so i can have time to play with some ideas ...
maybe justcallmedad will pop over soon and talk about his experiments ...
that makes sense to me, too.
i was worried that changing the degeneration could change the spectral balance of the distortion, which doesn't sound like something you'd want to do when changing volume. however, (apologies to john) i have to admit i haven't thought it through.
i need my wife to go on a shopping trip so i can have time to play with some ideas ...
maybe justcallmedad will pop over soon and talk about his experiments ...
Terry Demol said:
We have used variable source degeneration in mike input amps in the past. It is Charles' way to be ahead of the pack, so to speak. So far it has worked for him.
John,
'....because it usually has a time constant included in it that is called the 'dominant pole' that is often in the audio range, and sometimes below 10Hz.'
One way around this is to use a CFA topology - its then very easy to put the dominant pole way above the audio band. I think its easier in CFA's (discrete) to tailor the open loop gain as well. My next pre-amp will do this with, I am planning, switchable loop gain from the front panel via some small signal relays. Should be interesting to compare how the sound is affected, but first I will complete my 4562 based design in the next 4 weeks.
'....because it usually has a time constant included in it that is called the 'dominant pole' that is often in the audio range, and sometimes below 10Hz.'
One way around this is to use a CFA topology - its then very easy to put the dominant pole way above the audio band. I think its easier in CFA's (discrete) to tailor the open loop gain as well. My next pre-amp will do this with, I am planning, switchable loop gain from the front panel via some small signal relays. Should be interesting to compare how the sound is affected, but first I will complete my 4562 based design in the next 4 weeks.
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