B1 preamp build thread

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Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
value of volume pot is having all with Rout of sources upstream, B1 buffer itself not caring at all about vol pot value

Log is what you need for volume, that's physiology related; you can use linear pot shunted to result in log law; search on Rod Eliot's web for "better volume control"

After dealing with AVC, I'm not looking back at resistive attenuators, when max sound quality is of interest
 
G

glennjarrett

Member
Joined 2010
marec said:
Hi All
I wanted a simple, low component preamp and decided on the B1.
I bought a board and FETs from PassDIY. I already had some components ( capacitors, resistors) from building loudspeakers years ago. Of course, when the boards arrived, none of these would fit! So, I decided to build it point-to-point. It was my first electronics project, so it was educational (to say the least!) trying to build it from the circuit diagram. Anyway, after a little trouble shooting, I have a preamp that seems invisible to me, so I am delighted.
However, an enclosure has now arrived from China and I'd like to rebuild the amplifier using components bought to fit the board. I really don't want to cannibalise the original to recover the FETs, so am asking about available substitutes. I know the established opinion is to buy another board and bits from Pass, but the original board and semiconductors cost £85 delivered to the UK. I can probably match FETs from a group, but don't know what to order...
Any help would be greatly appreciated..
Click to expand...
have a read of the last few pages
its not 100% confirmed as i have no means of testing distortion but it looks good on the graph and sounds good to my ears
Mezmerize B1 Buffer Preamp
 
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Indigent Audio

Indigent Audio

Member
Joined 2020
So I am almost done with my B1 (Jfets and board from PassDIY). This is going to be the buffer/switch for a tube amp which already has a pot. I am planning on a bypass switch on the b1 for the volume control, any issue doing this?

Also I am considering transformers on the B1, I read ZM somewhere talking about jfet gender and needing to be careful? Was this wit or wisdom? both or nether? I had no idea I thought most electronics where non-binary. Can someone clarify?
 
S

srian

Member
Joined 2011
Indigent Audio
My advise, use a 20 to 25k log as the input pot to B1.
If not at least connect a 25k resistor to ground and feed the 1k gate resistor on top of it so that you maintain a 25k input impedance.
The jfets you got will be in Idss matchedpairs. If so do try not to separate them
 
ItsAllInMyHead

ItsAllInMyHead

Member
Joined 2019
Paid Member
That is the post I said was nice. I am not disagreeing, but looking for further context from your point of view. Perhaps explain why 20k is optimum for the B1 vs. 10k if you are only taking into consideration the sentence quoted above re: the low pass filtering. 10k would be better, yes?
 
M

marec

Member
Joined 2006
Hi All
Thanks for the helpful replies. Especially the reference to the Korg thread. I've read the first 40 or so pages and developed square eyes AND a major headache! LOL. What I need from the thread is a practical description of how to select the J112 s and associated resistor. Is this information amongst the 500+ pages? If so, I'll keep myself busy over Xmas. If not, I think my best solution may well be a second board and FETs from PASSdiy...
Rgds
 
Soundhappy

Soundhappy

Member
Joined 2012
6L6 said:
Three more stores? I suspect that would increase overhead by 3x, and so the retail prices would have to be increased by 3x. :D :D :D

Postage (Something out of the control of the store) is almost assuredly cheaper... :yes:
Click to expand...

Yes 3 more stores = good for DiyAudio business.
Easy buy for much more Diyers , incrase dynamic speed of sales,
less taxes and lower shipping costs. All Winners
DiyAudio shop division by Italian ModuShop for Europe ?
What think the Big Bosses Team Direction ? :)
 
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