Heatsinks for Bosoz?

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#822
PSU corrections

It was pointed out that the diode indicators on the positive rail should be reversed. Would I be correct in assuming that refers to the axial style rectifier diodes only? If one is using, eg, MUR820's, they would be installed as per indicated on the board.

Thanks,
SteveA
 
#825
BobEllis said:
the TO-220 diode silk screen is reversed, too. Use the negative side as a guide.
Click to expand...


Hi Bob,
That's what I thought. Got them (the MUR820's) with their backs to the big caps. I want to check things out (for the trsanformer I bought one of the PE $29 specials).

I am a little unsure of the hookup for this thing. The orange-black-orange (55-0-55) secondaries go to the 60V in (orange/orange). Black to ground. The yellow (14V) secondaries go to the negative input. Would this be correct?

Kari indicated D8-10 sum to about 14V. I used three 1N5230's which is 14.1V; I would assume this is okay also.


Thanks,
SteveA
 
#827
BobEllis said:
Steve,

that's certainly close enough, as long as your negative rail is at least -7 volts you'll do fine.

Just to make sure, you caught the glitch with D9, D10 right?
Click to expand...


Yes, I did. I installed them on the underside of the board as per Kari's post.

I thought about the hookup of the transformer to the supply board and was wondering if this would be better:
1) one of the 55V leads to +rail and the center tap to the ground tab on the positive rail.
2) use the 16-0-16 in a similar fashion for the negative rail.
3) tie up and insulate the other unused leads (ie, both 14V secondaries and the unused 55V and 16V leads).

I'll take some pictures of the supply board and post them (just to make sure I implemented the corrections properly.

SteveA
 
#828
SteveA said:



Yes, I did. I installed them on the underside of the board as per Kari's post.

I thought about the hookup of the transformer to the supply board and was wondering if this would be better:
1) one of the 55V leads to +rail and the center tap to the ground tab on the positive rail.
2) use the 16-0-16 in a similar fashion for the negative rail.
3) tie up and insulate the other unused leads (ie, both 14V secondaries and the unused 55V and 16V leads).

I'll take some pictures of the supply board and post them (just to make sure I implemented the corrections properly.

SteveA
Click to expand...


For the PE transformer the above hookup gives +59.7V/-10.8V.

SteveA
 
#829
My XBosoz is done!
It works perfect. It was straight job after assembly, I just hooked it up and there it is!
Sounds great. I have been listening whole afternoon and I like it a lot. System config:
Moded DCX2496 - signal direct from DAC - to Lundahls 1674 - to Apex 6 ballanced channels relay volume control - Bosoz - Aleph 30. Awsome.
I use two transformers - one is 2x55V and second one is 2x18V. I am getting 60 and -10.5V. Kari's boards and parts from Columb. Everything was right on, I just had to enlarge holes for 1000uF/100V caps and for 3w resistors on the Bososz boards. Not a big deal. Now I have to mount boards in the case. Most likely I will do separate case for PS since it is very bussy in the case that I originally planed for. Apox controls and Lundahls are already in, and I still have to add 6 Bosoz channels.
Thank you Kari, Colomb and Mr. Pass for Class A enjoyment.



🙂 🙂 🙂 🙂 🙂 🙂
 
#830
AR2 said:
My XBosoz is done!
It works perfect. It was straight job after assembly, I just hooked it up and there it is!
Sounds great. I have been listening whole afternoon and I like it a lot. System config:
Moded DCX2496 - signal direct from DAC - to Lundahls 1674 - to Apex 6 ballanced channels relay volume control - Bosoz - Aleph 30. Awsome.
I use two transformers - one is 2x55V and second one is 2x18V. I am getting 60 and -10.5V. Kari's boards and parts from Columb. Everything was right on, I just had to enlarge holes for 1000uF/100V caps and for 3w resistors on the Bososz boards. Not a big deal. Now I have to mount boards in the case. Most likely I will do separate case for PS since it is very bussy in the case that I originally planed for. Apox controls and Lundahls are already in, and I still have to add 6 Bosoz channels.
Thank you Kari, Colomb and Mr. Pass for Class A enjoyment.


🙂 🙂 🙂 🙂 🙂 🙂
Click to expand...

Pictures ?

I'm Looking forward tobuilding Briangt's and mine for all 4 of my Mini A's. How did the part's work that i sent you ?
 
#832
AR2 said:
My XBosoz is done!
It works perfect. It was straight job after assembly, I just hooked it up and there it is!
Sounds great. I have been listening whole afternoon and I like it a lot. System config:
Moded DCX2496 - signal direct from DAC - to Lundahls 1674 - to Apex 6 ballanced channels relay volume control - Bosoz - Aleph 30. Awsome.
🙂 🙂 🙂 🙂 🙂 🙂
Click to expand...

Hi AR,
I have a M-audio Superdac, which has the same DAC-chip as you have. I did a lot of mods on it, and one of the succesfull ones was changing the output to a Lundahl 1527XL. Although it sounded great, the music was a bit mellow. I used the Kari boards as a new output stage. No low-pass or high-pass, just two resistors to get the signal down in the optimal range.

Also sounds great! I had some more trouble getting the boards together. I used Elma Silmic II capacitors, which are too large. I had to drill new holes, and mount the capacitors on wood to get above the other parts :happy2:

Greetings, Harry
 

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#833
harryeng said:


Hi AR,
I have a M-audio Superdac, which has the same DAC-chip as you have. I did a lot of mods on it, and one of the succesfull ones was changing the output to a Lundahl 1527XL. Although it sounded great, the music was a bit mellow. I used the Kari boards as a new output stage. No low-pass or high-pass, just two resistors to get the signal down in the optimal range.
Greetings, Harry
Click to expand...

Great - looks good. Yes, you do not need any filtering since Lundahls takes care of it, as well as they stop DC. I use Solen caps on the boards and they fitted well. It will be interesting to have someone run cap competition in order to find out what are the best ones.
I was listening with just Lundahls before the amp and it all depends what amp and speakers are driven. I acctually prefer less electronics in the signal path, and for my mids I have 2A3 amps that have quite enough gain to drive the speaker without any preamplifiication. In Aleph case I definitevly needed some preamplification. I made temporary preamp with Burr Brown opa627 and BUF634 but my first impression is that XBososz is much better.
I had GC in place of Aleph and that amp had enough gain so I didn't need any preamp there, but the sound is not even close to Aleph in my opinion. Detail and imaging in the top end is just to cry for. Mids are really tube like. My ribons are singin'

🙂
 
#835
finally

After a couple of years I am finally building this pre with Kari´s boards.

I will do the cascoded version and what I want to know is which mosfets need to be mached. I know q2 and q3 but I am not sure about q4 and q5.

Also I will be using a stepped atenuator for volume control. What would be a good summed impedance for Rx plus Ry?

thanks.
 
#840
Kari said:
Hi,
i matched 4 fets as i'm using the cascode feature. The ccs fet does not need to be matched with the others but of course you can match all 5 of them. If you opted for not using the cascode then you need to match 2 fets.

My 2 cents...

/Kari
Click to expand...


simple;

two lower mosfets matched;
two upper mosfets (both cascodes) matched;
ccs mosfet - use most different valued one from matching process.....that's good place for specimens like this
 
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