B1 Buffer Preamp - Page 93 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th November 2008, 04:41 AM   #921
diyAudio Member
 
Join Date: Apr 2008
DAMMIT I hate not being able to edit stuff... I know it doesn't HAVE to be regulated, but will I be able to hear a difference with a gainclone and Insignia bookshelfs? Also should it go

source -> attenuator -> B1 -> gainclone
source -> B1 -> attenuator -> gainclone

For the attenuator I'll prob wire up a quick n dirty linear pot (50k) w/shunt resistor (7.5k)...but I'll eventually be using an Optivol which has an input impedance of 27k and likes a high load impedance (100k+). I don't really understand the whole input/output impedance issue tho, which is why I was wondering about how to configure the chain

Oh and I measured 330kohms from output ground to L+ and output ground to R+ on my source...is that something important in such a discussion?
  Reply With Quote
Old 14th November 2008, 09:20 AM   #922
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
The B1 after the attenuator is the correct arrangement.
You are using the B1 to lower the output impedance of the pot BEFORE sending the signal down the interconnect.

The 330k are output resistors that take any leakage current from the source to ground. A similar resistor fitted to the input of much equipment does the same thing. Although bad practice to hot plug interconnects we (all) do it occasionally and having zero DC at the ends of the RCAs before plugging helps prevent the big bang at the speakers. Once the interconnect is established the two high resistances have almost zero effect on transferring the signal.

Your source will see a load impedance of ~50k at very low volumes, 50k//7k5 at maximum volume and a range of impedances between these limits at intermediate volumes.
The B1 will see 12k5//7k5 as the maximum source impedance down to near zero ohms at minimum volume. The B1 should easily tolerate this.
However, the source might not like 50k//7k5 (~6k5) as a load.
Another B1 installed in the source equipment would be a solution. But it might not need this drastic action.

Your last post confirms you have advanced to "edit" status.
__________________
regards Andrew T.
  Reply With Quote
Old 14th November 2008, 02:59 PM   #923
diyAudio Member
 
maxlorenz's Avatar
 
Join Date: Oct 2003
Location: osorno , Chile
Hi Pink,

Quote:
ahh the B1 can handle more than 24V? Cause I'm building a gainclone (i know wrong thread) which will have about a 30V supply...does it have to be regulated?
Being an eternal beginner myself, I strongly recommend you to study the datasheets of the active parts of every project you embrace.

OT, but not too OT:

I have built this gainclone with regulated supplies (+/-29V) and it does not sound too bad at all

http://www.pinkfishmedia.net/forum/s...light=powerreg

(it has the link to the Teddyreg included)

I later took the (+) output of the PowerReg to feed another single ended class A preamp (which will be changed to a B1), through a (+) TeddyReg. A regulated integrated chipamp. Something to consider...

I like things complicated...

Cheers,
M
  Reply With Quote
Old 19th November 2008, 02:41 PM   #924
Gooch is offline Gooch  United States
diyAudio Member
 
Gooch's Avatar
 
Join Date: Aug 2005
Location: West Coast of Florida
Hello Everyone

I finished assembling my B1 PCB last night many thanks to Nelson Pass for the simple lay out and great pcb's. I put the pcb into a old Dynaco pass preamp chassis to get it working. Later on I will build something better for it along with the shuntreg that is in the NS10 thread. Well it sounds GREAT for something that has really no burn in time it not a s forward sounding as my tube preamp I will compare the two over the next few nights also the Dell laptop power supply works like a charm.


Cheers
Dave
  Reply With Quote
Old 19th November 2008, 03:31 PM   #925
diyAudio Member
 
merlin2069er's Avatar
 
Join Date: Sep 2008
Location: Toronto
Blog Entries: 1
Send a message via MSN to merlin2069er
I got my b1 boards in and am looking for a few more parts to complete the b1 buffer preamp.

Where can I find a decent case?

I found the knobs (226-2030-ND) KNOB CLR GLOSS.75"DIA .125"SHAFT
and the pots (KA2531S28-ND) POT 25K OHM 2W LOG TAPER on digikey.
(hope they'll do)

I'm still looking for c101, c201 - I've got 2uf auri caps but I guess I shouldn't sub those in for the 10uf Axon.

I'm also looking for power adapter (18v - 24) and the power input jack.

Any help is greatly appreciated.

Thanks,
JG
  Reply With Quote
Old 19th November 2008, 04:33 PM   #926
diyAudio Member
 
Join Date: Jul 2004
Location: Toronto, Canada
Default Axon=Solen

I think Axon are the same as Solen fast caps (read something to this effect on the internet).

You can get Solen from them in Montreal or from PCX (partsconnexion) in Toronto. PCX is having a sale right now.

Sayal in north Scarboro has walwarts or you can just order one from digikey. Read back in the recent pages for an example

Happy Hunting!
  Reply With Quote
Old 19th November 2008, 08:03 PM   #927
diyAudio Member
 
Join Date: Apr 2008
Quote:
Originally posted by merlin2069er
I'm still looking for c101, c201 - I've got 2uf auri caps but I guess I shouldn't sub those in for the 10uf Axon.
I was wondering the same thing...can smaller caps be used for c101/201 or will that cause audible low freq cutoff?
  Reply With Quote
Old 19th November 2008, 08:55 PM   #928
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
There was a guy a while back that made one without capacitors. I dont know what sticking a smaller cap in would do, but seems it can be done without caps if the power supply is dead quiet.
URiah
  Reply With Quote
Old 19th November 2008, 09:25 PM   #929
Gooch is offline Gooch  United States
diyAudio Member
 
Gooch's Avatar
 
Join Date: Aug 2005
Location: West Coast of Florida
Solen will work fine if you can't fine Axon I bought mine years ago at Parts Express but they don't carry then anymore. Michael Percy has both types. http://www.percyaudio.com/
  Reply With Quote
Old 19th November 2008, 09:26 PM   #930
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
I got some nice clarity caps at Madisound for about $6 each.
Uriah
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
buffer/preamp? TheDriver41 Chip Amps 2 3rd October 2004 08:40 AM


New To Site? Need Help?

All times are GMT. The time now is 03:20 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2