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Old 22nd August 2008, 07:31 AM   #511
Salas is online now Salas  Greece
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Plain type. Not super fast.

Guys, remember:

I just devised and tested a capacitor-less B1 concept. Made in a decent way, with parts from my bin, so I can give you some report, and make a cheap portable buffered volume controller for my secondary needs. It is open for you to make it as luxurious as you like if you are going to make it for primary preamp duty in your system. Be creative, its a very simple circuit. Use Cree and BGN and golden wire and Riken, make a shunt regulated dual power supply, whatever. Just remember, no coupling caps, use good carbon series resistors, sweet spot is +/-10V PSUs. Use 10X the log pot value for a shunt resistor from wiper to ground. Its for safety and makes the pot more transparent. I will revert to glass again now. Enough with silicone.
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Old 22nd August 2008, 02:25 PM   #512
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Quote:
Originally posted by salas
I will revert to glass again now. Enough with silicone.
Silicone!? Yikes! Just what grade of 2sk170 are you using? I don't see _that one on the spec sheet. :-)

Thanks for all your work on the dual rail B1 - it was very informative to a newbie like me.

-d
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Old 22nd August 2008, 03:03 PM   #513
Salas is online now Salas  Greece
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BL that is. It reads so on the awfully hand drawn schematic somewhat above. Thank you too.

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Old 23rd August 2008, 12:31 AM   #514
Kinnja is offline Kinnja  United States
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Quote:
Originally posted by vdi_nenna
Great article! Finally get to use those surplus 1 meg resistors!


Mouser has the J113. Not seeing 2sk170, LSK170 or 2SK370.

http://www.mouser.com/Search/Refine....tt=512-J113%09

This jfet ok?

thx,

Vince

Did you get around to trying the J113?

I'm thinking about the J211, Idss 7-20mA, gfs 6-12 mmhos.
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Old 23rd August 2008, 11:03 AM   #515
Salas is online now Salas  Greece
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Hint. If you can't use an expensive pot, use a dirt cheap 22k log carbon one, shunted with 220k Dale wiper to ground. It goes well for tone with the capacitor-less B1. I wired one $1 open metallic case pot. Not bad at all.
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Old 23rd August 2008, 02:53 PM   #516
avr300 is offline avr300  Denmark
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Quote:
Originally posted by salas
Hint. If you can't use an expensive pot, use a dirt cheap 22k log carbon one, shunted with 220k Dale wiper to ground. It goes well for tone with the capacitor-less B1. I wired one $1 open metallic case pot. Not bad at all.
Pls. explain to me, why this is working.
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Old 23rd August 2008, 03:24 PM   #517
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Default Slightly OT, but...


... I've tried this with a QC24 today (basically a pot followed by a 6111WA gain stage), and it seems to work in that context, too. The slight midrange dip, that the pot introduced, went, and a touch of harshness with it. I used two 1M Dale CFM55s in parallel for each channel, the pot is a 47K black Alps (allegedly NOS, but I'm not sure about that).

Excellent hint, thanks Salas.

Best,
Oliver
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Old 23rd August 2008, 03:56 PM   #518
Salas is online now Salas  Greece
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Quote:
Originally posted by avr300


Pls. explain to me, why this is working.

See the post below yours for confirmation.

*The 10x pot value resistors are used for 2 functions in capacitor-less B1.

1. Safety. If the input loses ground reference (faulty pot with usage), I measured 4VDC at output. In a disaster scenario that a potent DC coupled amp is driven, the voice coils are going to heaven.

2. The pot track is bypassed by a much better quality resistor. It brings the tolerance between channels nearer by shunting. Averages pot quality for the better.

**Some findings are easily repeatable over systems. Officially, pots, capacitors, resistors, wires, loudspeaker drivers, tube vintage, etc are not audible and we are hallucinating here. ABX me Lord, I have sinned!
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Old 23rd August 2008, 04:11 PM   #519
avr300 is offline avr300  Denmark
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Quote:
Originally posted by salas



See the post below yours for confirmation.

*The 10x pot value resistors are used for 2 functions in capacitor-less B1.

1. Safety. If the input loses ground reference (faulty pot with usage), I measured 4VDC at output. In a disaster scenario that a potent DC coupled amp is driven, the voice coils are going to heaven.

2. The pot track is bypassed by a much better quality resistor. It brings the tolerance between channels nearer by shunting. Averages pot quality for the better.

**Some findings are easily repeatable over systems. Officially, pots, capacitors, resistors, wires, loudspeaker drivers, tube vintage, etc are not audible and we are hallucinating here. ABX me Lord, I have sinned!
I just want to know, how shunting the wiper, can bring better sonic performance. I'm well aware of the safety issue.
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Old 23rd August 2008, 04:55 PM   #520
Salas is online now Salas  Greece
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Told you. Firstly it averages better the channel balance between tracks (1% resistors VS 5-10% pots), secondly it averages the track quality characteristics for the better. Like bypassing caps.

Officially you can't ABX prove it. Only the circuit matters. A Pioneer receiver that measures good sounds as good as a Halcro amp that measures maybe a little unnecessarily better
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