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B1 Buffer Preamp
B1 Buffer Preamp
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Old 10th November 2017, 02:18 PM   #4391
dopkomachine is offline dopkomachine  Canada
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Default Correction*

Quote:
Originally Posted by picowallspeaker View Post
It is an error using the same tube for SRPP-better using one half for the low side and one half of other tube for the upper,and also having two secondary windings of the transformer for the two heaters is quite mandatory!
I meant using a 1x 12ax7 (full bottle) for 1 channel.

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Old 11th November 2017, 05:45 PM   #4392
sarathssca is offline sarathssca  India
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Quote:
Originally Posted by Nelson Pass View Post
One of the keys to good performance with that chip is an
extremely high impedance load.
Here for chips like DS1802, it's recommended to load with high impedance.. what order impedance is recommended ? Is 10k or 20k impedance ok for this or we need even higher impedance ?
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Old 11th November 2017, 09:57 PM   #4393
Nelson Pass is offline Nelson Pass  United States
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B1 Buffer Preamp
I looked and saw that on the XP30 Wayne loaded the output of the volume
control with 1 Megohm.
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Old 14th November 2017, 12:26 PM   #4394
sarathssca is offline sarathssca  India
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Quote:
Originally Posted by Nelson Pass View Post
I looked and saw that on the XP30 Wayne loaded the output of the volume
control with 1 Megohm.
Is it that the current from the wiper pin of the digital volume controller needs to be kept at very minimum for low distortion? Is that the reason , it is being recommended to follow it up with a very high input impedance stage?

So if we would like to use this chip to replace regular potentiometers in filter or tone control circuits like (baxandall tone control ckt), do we need to use a combination of this chip and a buffer to replace a potentiometer?
ie. replace regular potentiometer with "this chip + buffer" ?

Or do we need to directly replace potentiometer with this chip and change the resisters in the tone control circuits so as to keep the wiper current less?

Last edited by sarathssca; 14th November 2017 at 12:46 PM.
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Old 14th November 2017, 04:57 PM   #4395
Nelson Pass is offline Nelson Pass  United States
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B1 Buffer Preamp
Wayne is better expert on this, but clearly the "wiper" is happier with less
current. It's not that you can't have decent function with lower impedance,
but it's worth the extra effort to not load the output of the chip.
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Old 29th December 2017, 09:27 PM   #4396
flocchini is offline flocchini  United States
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Default Original B1 with autoformer

Just watching Nelson's talk at BAF2017 with special attention to the B1-XFMR
and just have to ask:

Can a autoformer be added to the original B1? I have a pair of Jensens wired as in the attached figure. If so where would be it best be placed?

B1 original is here
http://www.firstwatt.com/pdf/art_b1_man.pdf

Thanks

Bob

Of course I would love to see B1-Korg or B1-XFMR in DIY store
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File Type: jpg jenautoformer.jpg (20.3 KB, 344 views)
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Old 29th December 2017, 10:33 PM   #4397
Zen Mod is offline Zen Mod  Serbia
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B1 Buffer Preamp
pot - buffer-autoformer

take care to short idiotproof part - series resistor on buffer output

endless talk about subject in What's wrong with the kiss...... thread
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Old 29th December 2017, 10:48 PM   #4398
flocchini is offline flocchini  United States
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Thanks ZM - I'll check the KISS thread
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Old 29th December 2017, 10:55 PM   #4399
Zen Mod is offline Zen Mod  Serbia
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B1 Buffer Preamp
good reading ...... see ya in month or two
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Old 30th December 2017, 12:48 AM   #4400
flocchini is offline flocchini  United States
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