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Old 18th April 2005, 02:56 AM   #1
Will is offline Will  Malaysia
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Default Is it possible - 6922 Active X-over running with ~ +/- 40V ?

I have plans to build an active 2 way speaker design using a Jordan JX92s (already have them) and mating with another 10 incher, and tubes are high on my list.

It seems whatever 6922 tube active x-over circuit design available at the moment (that I know of) runs with high voltage (above 100v). I'm not sure bout Marchand though.

Is it possible to run the 6922 at lower voltage (below 50v) which then allows large capacitance PSU to be used ?

Anyone with such a circuit ?

regards,
Will.
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Old 18th April 2005, 03:03 AM   #2
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Default Re: Is it possible - 6922 Active X-over running with ~ +/- 40V ?

Quote:
Originally posted by Will
Is it possible to run the 6922 at lower voltage (below 50v) which then allows large capacitance PSU to be used ?
You've lost me, why is that specifically necessary?

I don't know what kind of active circuit you intend on using, but chances are it needs to be at least partially direct coupled for stability, and that demands voltage. Even tubes in general do not like <50V.

Tim
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Old 18th April 2005, 03:07 AM   #3
Will is offline Will  Malaysia
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Based on the fact that 6922s are widely used as buffer circuits, running them with low voltages (below +/- 50v) allows a large PSU capacitance to reduce noise/hum without having to resort to chokes.
The active x-over circuit I'm referring to is a 4th order L/Riley.


regards,
Will.
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Old 18th April 2005, 06:14 AM   #4
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Quote:
Originally posted by Will
without having to resort to chokes.
Execute this person. Right now. He thinks chokes are bad somehow...

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Old 18th April 2005, 07:03 AM   #5
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Quote:
allows a large PSU capacitance to reduce noise/hum without having to resort to chokes.
What are you talking about? 99% of commercial equipment using 6922 does not use chokes. Active regulation is one option but RC filtering may also be effective and easy. A single large filtering cap is probably the worst sounding solution.
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Old 18th April 2005, 07:14 AM   #6
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You can run 6922s on that low a voltage (Joe R uses +/- 35 V on his buffer in the TBIGC), but they work better with higher voltages.

Remember that the power supply is critical to the sonics of the amp and caps are probably the most colorful of all passive components -- no electrolytics is a good goal, and those get really big & really expensive if you want to use lots of C.

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Old 18th April 2005, 07:35 AM   #7
Will is offline Will  Malaysia
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Quote:
Originally posted by planet10
You can run 6922s on that low a voltage (Joe R uses +/- 35 V on his buffer in the TBIGC), but they work better with higher voltages.

dave


That's exactly my point Dave...
I agree running with higher voltages will sound better, and it's easy to get away with +/- 40 volts, which requires 50v rated cap to do the job.

Come on, do you really think I'm going to use one single large cap for the job ? Simple solution - just parallel multiple 1000uF caps (probably 20 of them)

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Will
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Old 18th April 2005, 07:42 AM   #8
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Default Re: Is it possible - 6922 Active X-over running with ~ +/- 40V ?

Konnichiwa,

Quote:
Originally posted by Will
Is it possible to run the 6922 at lower voltage (below 50v) which then allows large capacitance PSU to be used ?
It is POSSIBLE, but why bother?

The cost for making the PSU something like +/-160V and thus the more linear is quite notional.

Instead of 20 pcs 1,000u/50V, buy a simple pair of
115+115V: 9V+9V mains transformer, operate one "reverse" and use a pack of 6pcs 100uF/250V capacitors with a set of 1K resistors (final values of R & C would depend on exact current drawn) and you get a well filtered +/-160V for no more money than your "big cap" supply and things will sound better too.

Sayonara
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Old 18th April 2005, 08:09 AM   #9
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Default Re: Re: Is it possible - 6922 Active X-over running with ~ +/- 40V ?

Quote:
Originally posted by Kuei Yang Wang
115+115V: 9V+9V mains transformer, operate one "reverse" and use a pack of 6pcs 100uF/250V capacitors with a set of 1K resistors (final values of R & C would depend on exact current drawn) and you get a well filtered +/-160V for no more money than your "big cap" supply and things will sound better too.
What Thorsten said... this is how the P/S looks on one of his RIAAs....

Me i'd grab a pair of the 115-->115 V 170mA isolation transformers that are surplus from old-style razor plugs.... quite a few in my stash

dave
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Old 18th April 2005, 08:15 AM   #10
Will is offline Will  Malaysia
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Okay, lets not go off topic shall we ?

Anybody with a 2 way L/R 4th order active cross over circuit using 6922 running off at +/- 40volts ?
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