B1 Buffer Preamp

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D

dviswa

Member
Joined 2004
Dear Mr. Pass, ZM,

I know B4 is coming, but I have a Full range OB with Woofer assist project going, so perhaps with a little help from you I can do a P-P protoboard version. Here are a couple of questions:

In post #161 ZM posted one of your drawings. That drawing did not identify the 3 Rs and 3 Cs, but ZM did in his hand drawn picture in post #153, so I will use the same. What is the formula for computing R1, R2, R3 and C1, C2, C3 in ZM's HP filter. I am assuming the same formula can be used to compute the values for the LP filter as well. ZM presented some values which are good for crossing over into a tweeter not into a full range.

What is the insertion loss of this configuration? that might determine if I will need a gain stage.

What is the slope of this filter?

ZM, I did not understand why you tied the outputs of the 2 filters together with 10K at point 6. Please explain.

Thanks a lot,
Dinesh
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
dviswa said:
.......

ZM, I did not understand why you tied the outputs of the 2 filters together with 10K at point 6. Please explain.

Thanks a lot,
Dinesh
Click to expand...


ZM is , as usual , not responsible for anything :clown:

I just digged old Papa's drawings , saved on my PC form old Pass site - previous to hacking several months ago ;

I hope that Papa will answer you ; if not - I'll try later ( tonight)
 
V

vonfilm

Member
Joined 2006
B1 Digi-Key Order

I am getting ready to order parts from Digi-Key for my B1. I would appreciate recommendations if there are better choices.

R1 1Ohm 3W P1.0W-3BK-ND 5% Metal Film
R2 10K 1/4W P10.0KCACT-ND 1% Metal Film
R3 "" "
R4 15K 1/4W CMF15.0KQFCT-ND 1% Metal Film
R100 1M 1/4W P1.00MCACT-ND 1% Metal Film
R200 " "
R101 " "
R201 " "
R103 " "
R203 " "
R102 1K 1/4W P1.00KCACT-ND 1% Metal Film
R104 " "
R204 " "
R105 221K CMF221KQFCT-ND 1% Metal Film
R205 " "
C100 1uF BC2076-ND Metallized Polypropylene Film
C200 " "
C3 " "
C101 10uF EF2106-ND Metal Poly Cap
C201 " "
C1 15,000uF P6890-ND Electrolytic
C2 " "
D1 Diode 1N914BCT-ND
D2 ??? Not sure what Digi-Key part would be appropriate

Matching JFETS from Pass Labs -DIY

P100 25 K Mono Stepped Attenuators form 8Audio.com on Ebay
P200 " "
4 way switch GH7102-ND Grayhill Rotary Switch

C101, C102 Also ordered Axon 10uF Metallized Polypropylene from Zalytron

I am ordering enough parts for 2 B1's. One will be with the Pass Labs-DIY board and the other will be Zen Mods 9volt version built point to point or dead bug style.

I am sure that you can tell I am new at this. Any thoughts or recomendations will be appreciated.
 
D

dviswa

Member
Joined 2004
Zen Mod said:

ZM is , as usual , not responsible for anything :clown:
Click to expand...
Sneaky you... :D
But, papa did not do it...

Zen Mod said:

I just digged old Papa's drawings , saved on my PC form old Pass site - previous to hacking several months ago ;
Click to expand...
Aha... the secret comes out. I was totally impressed that you had all that stuff stashed away since 80s. ;) Not so, huh...

Zen Mod said:

I hope that Papa will answer you ; if not - I'll try later ( tonight)
Click to expand...

I hope papa answers....
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
dviswa said:
ZM,

Looks like Papa is too busy with the B3 or he does not want to spill the secrets, yet.

Basically, I want to knwo how to calculate the RC values for the cross over frequencies needed in my setup.

TIA,
Dinesh
Click to expand...


seems that we - here at Paforum have new search engine - Papaoogle

:rofl:

I think that even dreky wikipedia have one or tttttwo pages regarding Active Filters ........

bang , think , then ask ...... it's funnier that way ...... ya see that ( at least ) I'm the one who's always asking dumb questions ...... so don't be shy :clown:
 
B

BFNY

Member
Joined 2004
Zen Mod said:



seems that we - here at Paforum have new search engine - Papaoogle

:rofl:
Click to expand...


uh huh, for filter coefficients try the links on this page for starters - you want to use a Sallen-Key filter topology for the referenced schematic. :idea:

http://www.sherlab.com/index.htm?/filter/filter.html

There are many web pages and free downloads that perform the calculations. My favorite active filter program was a free program from TI, not sure they still have it available for download.
Bob
 
vitalstates

vitalstates

Member
Joined 2006
vitalstates.org
I don't normally use a pre as all my sources are digital...but curiosity got the better of me and I couldn't resist so...matrix board out again....
 

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vitalstates

vitalstates

Member
Joined 2006
vitalstates.org
I felt pushed to post this now as the B1 looks like being buried alive in all the replacements and proposed newer versions...so before it becomes complete history I'd like to say its brill...and certainly works for me without gain......

here it is with jurassic cd player, F4 and ariels...enough wizz-bang for me and sounds totally transparent....

It will come in very handy for taking amps to meets...
 

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M

Mihan

Member
Joined 2008
B1 for subwoofer?

I am operating a CD player into a tube power amp and an active subwoofer (with inbuilt attenuation). I intend constructing a B1 Buffer to drive the power amp.
Can I drive the sub direct from the CD player (with or without a resistive splitter) or do I need to build a second B1 buffer for this?

Thanks
Mihan
 
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