Pass B1 Buffer Preamp help

[marsupialx]

So did correcting the pot fix things?

 

[muhy3]

So did correcting the pot fix things?

I haven't been home yet to play around with it, but as soon as I can confirm I'll let everyone know. I'll even phone up my mum.

 

[muhy3]

So did correcting the pot fix things?

Ok, so tried the pot thing, the result being the volume control up/down in the correct direction cw/ccw. I went over some of the dodgy solder spots, and voila! It works a charm, and omg what a difference it makes when you can control volume yayyyy!!!

 

[muhy3]

Well, I've been tempted to try a Salas SSLV shunt regulator in my B1 since they work so well in my BA3-FE, but I'll probably never get around to it. I have extra boards, you're welcome to them if you like.

Hey, I've sent you a PM thanks

 

[albertNL]

I now feed my 24V smps into a Salas shunt and send it's output to the B1 (replaced power supply caps on the B1 board by 1000uF Silmic II). It was definitely worth it!

 

[KevinHeem]

I now feed my 24V smps into a Salas shunt and send it's output to the B1 (replaced power supply caps on the B1 board by 1000uF Silmic II). It was definitely worth it!

OK, you've got my attention. So you're bypassing the diodes and connecting the smps power supply where? What values are you using for C101/C102 and C103/C104? What did you use for combination of R105/R103. Do you need the 1000uf capacitors on the B1 board (what do they do)? Last question (for now) what did you use for R101.

 

[KevinHeem]

Vlad,
I have an extra mini kit for the SSLV as well, it has most of the parts needed for the build.
I'll send you a PM.

 

[albertNL]

OK, you've got my attention. So you're bypassing the diodes and connecting the smps power supply where? What values are you using for C101/C102 and C103/C104? What did you use for combination of R105/R103. Do you need the 1000uf capacitors on the B1 board (what do they do)? Last question (for now) what did you use for R101.

Yes I bypassed the diodes. Check the schematic: Connect your DC input to holes of the D121 and D124 closest to C105.

I used kits from Tea Bag for a number of builds. I think it was 2 red leds for D105 and D106 (jumper in D101) and 3 green leds in D102-4 (jumper the last one).
I would have to open the case to make sure what else I used, but my notes (but these were not specific to the B but were written for the other builds, although most parts will be the same) say:

C101 220uF Elna Silmic II
C102 nothing
C102 nothing
C104 6.8uF Wima MKP10 100V
C105 1000uF Elna Silmic II

R101 I am not sure. My notes say 10R 3W? I think it was closer to 4R than 10R. I did not solder R101 in when I first assembled the board. I connected different values with aligator clips first to check which value would give the amperage I wanted. I just hooked the output of the Salas shunt psu to a dummy load and powered it from a bench psu to determine which value to use for R101.

R103 3k6
R105 5k variable

Hope this helps.

 

[erik777]

Is the Pass B1 Buffer able to handle a 2k2 impedance load from the amp ?

 

[AndrewT]

2.2Vac from a CDP, or similar, will pass ~1mAac into a 2k2 load impedance.
That leaves ~ 4mApk to drive all the capacitances likely to be on the output of the B1.

 

[pqls]

Similar experience here, only on channel,of one outpu working- bought the PCB and fets from Pass Diy, orientation of fets is correct

 

[alvinlim]

I have two sets of 'matched' jfets = 4 matched 2SK370s from Passdiy (idss matched) and 4 matched 2SK170s (using Vgs) from a diyaudio member. Two questions:

1. Which is the preferred Jfets? the 170s or the 370s?
2. Would Vgs be a proxy for matching using IDSS?

Thanks!

 

[liubincalvin]

I have two sets of 'matched' jfets = 4 matched 2SK370s from Passdiy (idss matched) and 4 matched 2SK170s (using Vgs) from a diyaudio member. Two questions:

1. Which is the preferred Jfets? the 170s or the 370s?
2. Would Vgs be a proxy for matching using IDSS?

Thanks!

Hi Alvin, those k170 are idss matched at Vgs=0V.

 

[alvinlim]

Calvin, Thanks! my mistake.

So, only question 1 left - which is the 'preferred' JFET for B1?

 

[6L6]

K170

Match for Idss, use a 9v battery for the 12v shown in the diagram -

An externally hosted image should be here but it was not working when we last tested it.

 

[alvinlim]

K170

Match for Idss, use a 9v battery for the 12v shown in the diagram -

An externally hosted image should be here but it was not working when we last tested it.

Thanks! Can I understand the reasoning behind choice of k170?

The specs of both jfets are exactly the same except for one parameter - drain power dissipation

 

[6L6]

The silicon inside the 170 and 370 is absolutely identical in every way.

The outside black plastic package is different - the K170 is TO-92, the K370 is in a Toshiba proprietary package with the wonderfully boring name 2-4E1C

K170 are difficult, but not impossible to get. The Linear System LSK170 are available in the diyAudio store. K370 are borderline unobtanium at this point, being discontinued many years ago. It is a safe assumption that any and all on ebay are fake.

 

[alvinlim]

Ah. Am I correct in my understanding that k170 is recommended cos it is still 'obtainable'? I asked the question cos I have both - k170 and k370. The k370 was from passdiy many years ago - so 8 assume that they are 'ok'

No difference then in using either of them if I understand correctly.

 

[6L6]

The silicon inside the 170 and 370 is absolutely identical in every way.

No difference then in using either of them if I understand correctly.

Correct.