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Old 24th October 2008, 03:48 PM   #801
BFNY is offline BFNY  United States
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Default Re: B1

Quote:
Originally posted by sparky6
Hi all,

I've been using a Goldpoint SA4 level control between an Aragon D2A2 and an Aragon 8008BB. I've been wondering If I'd be better off with bit of gain instead. If so, would the B1 be the way to go? What would be the advantages over passive?

Thanks...
One point related to this question is the load has an effect on the source performance. I'm referring in this case to the load as what the upstream source sees at the linestage/attenuator input.

If you use a 10K attenuator, this presents a 10K load to your CD/phono stage/tuner etc. If you use a B1 with 25K pot, the load is now about 25K. This may not seem like a lot, but I have measured a change in distortion when going from a 10K to 25K load. When playing around with circuits, I vary the load and output level while watching distortion. For sources that have tube or no feedback discreet outputs, it is something to be aware of. Most tube output stages would be happier with at least 25K, if not 50K.
Bob
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Old 24th October 2008, 04:27 PM   #802
AndrewT is offline AndrewT  Scotland
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some/many tube (valve) pre-amps do not have much in the way of output current. These usually prefer a high load impedance, anything upto 500k.
Your findings of a change from 10k to 25k load would fit with this.
Another example is the removal of the 1M0 ground reference resistor at the output of a Croft (valve) pre-amp, this is supposed to sound better due to the very slight raising of load impedance without the 1M0//load.
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Old 25th October 2008, 07:32 AM   #803
wiatrob is offline wiatrob  United States
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Default Value of R1?

From the schematic, It's 1 (R? K?) Thanks!
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Old 25th October 2008, 08:38 AM   #804
AndrewT is offline AndrewT  Scotland
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Default Re: Value of R1?

Quote:
Originally posted by wiatrob
From the schematic, It's 1 (R? K?) Thanks!
R1 from the 18V supply is 1r0 3w
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Old 25th October 2008, 05:53 PM   #805
wiatrob is offline wiatrob  United States
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Default Thanks and PCB/JFET set available

Thanks for the R1 answer.

I bought two PCBs w/JFETS (NOT to hoard, but to balance!) but plans have changed - I'd be happy to give one up for the same rate as I got them from Pass plus paypal fee if anyone is interested... CONUS is easier, but International a possibility...

-Bill
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Old 25th October 2008, 10:12 PM   #806
jims is offline jims  United States
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Hi

I'll take it. Please email me.


Thanks

JimS
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Old 26th October 2008, 01:02 AM   #807
wiatrob is offline wiatrob  United States
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I can't email because I'm under moderation Can you email me? Thnx...
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Old 26th October 2008, 11:33 AM   #808
jims is offline jims  United States
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Hi Bill

Tried to email you, but can't access your email address. I guess you have not been on the board long enough. Please post your email address.

Thanks

Jim
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Old 27th October 2008, 03:09 AM   #809
wiatrob is offline wiatrob  United States
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Jim,

wiatrob 'at' hotmail 'dot' com
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Old 27th October 2008, 04:54 AM   #810
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Quote:
Originally posted by AndrewT
some/many tube (valve) pre-amps do not have much in the way of output current. These usually prefer a high load impedance, anything upto 500k.
Arrrrr... 'Tis a pitiful preamp that a few micro-amps cannot source,
sez I.

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