B1 Buffer Preamp

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#1,901
woodturner-fran said:
So I'm wondering if theres anything I should go back over on my build?
Click to expand...

I wasn't finding the B1 to be lean, however I don't have an Aikido to compare it to. I did see a boost in bass and clarity (and so on) when I replaced R102/R202/R104/R204 with 221 ohm resistors. At the same time as replacing the resistors, I made a connection from the board ground to the chassis, and I'm told this also can help.

-j
 
#1,905
B1 is being fed from Peter Daniels audiosector DAC, twisted pear opus DAC, pass pearl with step up tx from zyx MC cart, phonoclone 3. B1 is feeding into a pass F5 amp.

zen mod: I'll have a look at that but...

diomedian: I think I'll try changing those resistors first, just because its easier to do right now.

I'll try this and report back.

I'm thinking this is something with my build because no-one reports any lack of bass, and none of the pass gear I have would by bass shy, in fact its something that they excell in.


Fran
 
#1,907
woodturner-fran said:
B1 is being fed from Peter Daniels audiosector DAC, twisted pear opus DAC, pass pearl with step up tx from zyx MC cart, phonoclone 3. B1 is feeding into a pass F5 amp.

zen mod: I'll have a look at that but...

diomedian: I think I'll try changing those resistors first, just because its easier to do right now.

I'll try this and report back.

I'm thinking this is something with my build because no-one reports any lack of bass, and none of the pass gear I have would by bass shy, in fact its something that they excell in.


Fran
Click to expand...

Mine was built per original parts spec and sounds fantastic. I'm still curious about peoples opinion on replacing the 1k resisters for R102/202 and R104/204 with lower values. Earlier someone replaced them with 330k and here just recently I see 221k replacement.
 
#1,909
AndrewT: taking one at a time:

say output of buffalo DAC.... cap is 1.2uF, facing into impedance of B1 buffer (which has a lightspeed which I can't tell you exactly the impedance of cos it varies a bit, but a good estimate is 10k) and then into the F5 which has no caps at all (DC amp as I understand it). As I said, 10uF output caps on the B1.


But: I swapped the 1k resistors for 221R and on initial listening, the bass is definitely up a bit compared to before. So, until I listen more I think this might be sorted.


Fran
 
#1,911
mmm thats interesting. The other preamp that I'm comparing against uses the older version of the lightpseed and its min impedance is 27k IIRC. That would fit with your theory. I need to look into this further I think.

In the B1 itself there is the pot (supposedly 25K but as I mentioned mine is a lightspeed which is a bit different) with a 1uF cap in series. So say from buffalo I have 1.2uf>>approx 10K>>1uF>>> B1 circuit>>>10uf>>221R and then to F5.

I need to confirm my findings too with reducing R102/202/104/204 as well. I just didn;t get long enough tonight.

Fran
 
#1,913
woodturner-fran said:
AndrewT: taking one at a time:

say output of buffalo DAC.... cap is 1.2uF, facing into impedance of B1 buffer (which has a lightspeed which I can't tell you exactly the impedance of cos it varies a bit, but a good estimate is 10k) and then into the F5 which has no caps at all (DC amp as I understand it). As I said, 10uF output caps on the B1.


But: I swapped the 1k resistors for 221R and on initial listening, the bass is definitely up a bit compared to before. So, until I listen more I think this might be sorted.


Fran
Click to expand...


LIghtspeed is nowhere near 10K input impedance

better make that buffalo output cap 10 times bigger , and you'll have bass .
 
#1,916
OK:

theres 1.2uf on the output of buffalo.

B1 is built as per stock, but with lightspeed for attenuator. Now, I'm saying this is an average of 10K.... maybe I'm wrong. But IIRC a good estimate was 10k.

Then in the B1 theres a 1uf input cap followed by 1K then//2sk170s// and that 10uF output cap followed by a 1k again.

Those 1K are the ones I changed to 221R (R102/202/104/204 in pass sch)

Then signal leaves B1 and goes to F5 amp where theres no caps and its a DC amp AFAIK.

Is that any clearer? Apologies for confusion caused and thanks for the help.

Fran
 
#1,917
AndrewT said:
are you sure?
when at minimum volume the series LDR will be many tens of kohms.
when at maximum volume the grounding LDR will be many tens of kohms.
when in between the sum of both LDRs will be the Rin value.
Click to expand...

range of that sum really depends which LDRs are used ; *2 or *3 ;

I'm using *3's , so maybe I'm just carried away .....

in any case - re-read few first posts in George's thread , regarding output impedance of source
 
#1,918
Wanted to pop in and say that I finished my prototype b1 pre yesterday. I really liked it when I plugged it in and it worked.

It's nothing special partswise: koa speer (kiwame) resistors, vishay/axon/panasonic/pas caps, PEC pot, 18v wall wart, neutrik rca's. I like the rca's.

I compared it to the other preamps I had one hand which were an Experience Music TVC based DHT unit and a Transcendent Sound Grounded Grid. Even with no play in time it was better than the GG. The DHT TVC unit was MUCH better. I did the comparison for my wife who was shocked to say the least.

Thank you Nelson, Colin, and everyone else here that makes this one of the coolest virtual realms on the net,

Chris
 
#1,919
Congratulations chrismercurio,

I just hope mine comes out as well as yours. I will get going on building mine once I get done painting the house or it gets too cold to continue with that seemingly endless venture.

Enjoy your colaborituve creation that makes music! You are right this is the coolest audio forum on the net. Many thanks to Nelson.

Keith

"Sam with the showing scalp flat top, perticular about the point it made"

F.Z.
 
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