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In Reply to: RE: more on Hk W-5m restoration, passive preamp? posted by PeterI on June 19, 2012 at 13:41:25
If you use a 100k pot it's output impedance will be 25k when adjusted to -6db.
If you have 200pf of cable + Miller capacitance the -3db point will be 32kHz. The phase will be off all the way down to 3.2kHz.
Get a autoformer volume control from Dave.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
for an autoformer. Have you used these?
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
No I haven't but Dave knows his stuff on magnetics. I bet they sound great.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
it is an interesting implementation.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
Mine has 24, 2db steps. Feeds straight to the SET 5687/6b4g power amp.
An AVC is great in that it's output impedance is the same as the source when turned all the way up and the output impedance goes down as you turn it down.
At -6db you're at 1/2 the winding so the impedance ratio is 4:1
If your source is 1k ohm, the output impedance of the AVC is 250 ohms.
If the input impedance of the power amp is 100k ohms, the source "sees" 400k ohms.
It's a win, win.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
the supplies.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
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