Some Q about BSOZ Powersupply - diyAudio
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Old 8th November 2001, 05:51 PM   #1
hifi is offline hifi  Sweden
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just to be on the safe side i would like to ask some questions about that preamp.

1, would it benefit from a couple of extra RC stages after the rectier and after the voltage stabb. ?

2, would the relay ladder circuit from P1.0 work well on the output of the BSOZ or must i recalculate the resistor values....?

3, How big a transformer will suffice? 100VA 200VA?...

4, how much the output mosfets disipate?...

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Old 8th November 2001, 06:32 PM   #2
grataku is offline grataku  United States
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Interesting questions since I am building that circuit myself. Hopefully Nelson will stop by here later. This is what I gathered in my preliminary survey of other people experiences with this design:

1) I am sure that RC filters would improve the PS noise figure at least until the noise reaches a low plateau. Recently someone reported hum problems so additional filtering maybe worthwhile.

3) I have just ordered an 80VA 60+60 V toroidal from Plitron so that better be enough!
Nelson is using two 30VA trafos.

4) The two channels should absorb a total of 160 mA. With this current figure each mosfet in the power supply section should dissipate 20 x 0.16 = 3.2 W. The actual amplifing devices should absorb considerably less.
I hear that the cooling sinks suggested by Nelson are a tad too small for comfort and that the resistor 3 W rating is also rather bold as these res. get very very hot. I don't remember for sure but 1W dissipation seems about right for each resistor.



[Edited by grataku on 11-08-2001 at 12:36 PM]
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Old 8th November 2001, 08:39 PM   #3
hifi is offline hifi  Sweden
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i have redrawn the layout a bit. to cater for "standing" heatsinks for all mosfets. and totaly separated pcbs for both channel aswell as made it possibly to use separate diodes for rectifying.

i think the heatsinks i thaought of using had an 5-9W rating.



/micke
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Old 9th November 2001, 06:48 AM   #4
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I am using two 160VA, 30-0-30 transformers with a 16,000uf capacitor bank which I am sure is overkill but my BOSOZ sounds absolutely effortless and it stomps some other expensive pre-amps. I have compared it to.

Tony D.
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Old 9th November 2001, 08:12 AM   #5
hifi is offline hifi  Sweden
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hmm the price difference in 100VA vs. 200Va is only 10$ ...
but then again the original only uses 2pc of 30VA

btw did u add extra capacitanc on the "main" boards after the rectyfier/voltage reference circuit?.....i mean dosnt the irfp9610/irfp610 mind highly capacitive loads or?

/micke
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Old 9th November 2001, 10:34 PM   #6
grataku is offline grataku  United States
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Tony,
320 VA and 16000uF for the preamp: what do you use for your power amp??!!
Are these types of over contruction really required here? I mean I like preamps to look like preamps, kind of slim and cute.
Was there any particular reason (ie high ripple noise) to go to such extremes in filtering caps? Did you actually compared your version to the original Pass version?
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Old 9th November 2001, 11:52 PM   #7
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Default Dual Split Bobbins

I'm only using 24 VA for each 2 channels of my 4 channel BLS pre-amp

If N. Pass doesn't get hum from using his original design and you do - try looking over what you've done again.

Don't forget the power supply board ALONE is regulated, thus even more reducing more noise (hence, no need for out of this world large uF caps).
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Old 11th November 2001, 07:16 AM   #8
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Default Hi Grataku

I had the transformers and caps. kicking around and after posting here regarding the positive aspects of oversize power supplies I replaced the stock BOSOZ power supply with the Godzilla one and everything was just more "there".

Absolutely effortless and huge soundstage and probably a bit of placebo effect as well, you know, it's big so it's got to be good.


Tony D.
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Old 23rd December 2001, 09:57 AM   #9
Variac is offline Variac  United States
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Default Will my 1010VA Transformer work?

I ordered 2 of the
1010VA 37.5V transformer from Apex jr

The nice guy there said that he measured the output of
the 4 taps at 37.5 volts under NO load.
My dream SOZ would be about 25 watts/ch, which
would use a transformer rated at 32 volts
My thought was that the output voltage would sag down to about that much if rated as manufacturers rate them (under load-right?

Also, the outputs aren't necessarily center tapped.
But- couldn't I just parallel 2 to get more amps, the connect the black wires to create a common. Then wouldn't the remaining wires be plus and minus supplys? I should wait for their arrival, but I need to know if I've screwed up ordering them.


I'm pretty ignorant obviously, but I've gotten responses from
Nelson Pass the various times I've written him. This time I'm trying to avoid bothering him again!

One more vote for Nelson being a great guy!!!

I hope useful info for other SOZ builders:

Apex jr has a bunch of 8 ohm 50 watt alu power resistors
at $2 ea
I ordered 32!
also 6 1 ohm 50 watters

Maybe not non-inductive-but what can you do?
I can't afford to pay $6 apiece for them!

I got six pretty huge heatsinks per channel from B.G. Micro:

http://bgm.bgmicro.com/prodinfo.asp?...t+sink&stype=3

They are each 4" x 10.5" x 1" and only 3.95 ea.

I got a bunch of power supply caps from these guys:
http://hometown.aol.com/brigar2/capa...apacitors.html

30,000 mfd at 63 volts
If this doesn't take you to the right place, just select computer grade capacitors. These say McIntosh on them-At least they were designed for power amps!

I have no connection to these guys but I've searched the web pretty hard and these seem to be the best deals.

Any help on the transformers?

Mark Cronander
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Old 23rd December 2001, 01:09 PM   #10
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I think your post is for SoZ (not related to Bride of SOZ pre-amp).

Anyways, if you're looking 25 watt SoZ - 6 of those heatsinks you've ordered is quite a bit on the lean side. Imagine that almost all 1000 watts (1 channel) is being dissipated into 6 of those heatsinks.

I'm building up a collection of heatsinks myself below:

http://www.geocities.com/super_bq/Heatsinks.html

Getting a transformer that is center-tapped or not is based upon the type of power supply configuration you plan to use. You don't have to do "dual-complimentary" that uses the center-tap (like I did on my SoZ). Full-wave rectification should do the job - only disadvantage is the possibility of more mechanical hum from the transformer.
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