Building a symmetrical PSU B1 buffer

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#445
Hello. I have received a couple of days ago an advice from George Stantscheff with respect to using a Lightspeed attenuator in my system. Since my CDP's output Z is quite high (500R) and my poweramp's input Z is rather low (10K) it seems that I might very well need 2 buffers, one before the Lightspeed and one after it. I was already contemplating with great interest this DCB1 and building two complete DCB1s seems rather complicated. Especially considering that I'm a beginner with limited funds available.
So:
1. Is there a simpler solution than 2 B1s if I insist on trying this Lightspeed? Or at least a way to combine the two buffers to avoid building 2 symmetrical PSUs with 2 transformers? Is there any PSU design that could be shared by 2 DCB1 buffers?
2. Do you think there is a way I could use only one DCB1 between my CDP and amp, no Lightspeed but with a 50K Alps pot that I already have instead? Perhaps with a few small DCB1 modifications?
3. How important is the type and especially quality of the transformer in the current DCB1 design? I hear that very good toroids in Europe are those made by Amplimo, but a 50VA from them is 35 Euro + shipping.

Thanks.
 
#447
DQ said:
3. How important is the type and especially quality of the transformer in the current DCB1 design? I hear that very good toroids in Europe are those made by Amplimo, but a 50VA from them is 35 Euro + shipping.

Thanks.
Click to expand...

For 1,2, as Massimo said. You can even use 50K Log if you make the 220K parallel to input resistors on DCB1S 560k. Try with 20K Log though. Better for B1's sound.

3. Not that critical. I would suggest a decent EI core over a cheap toroid.
 
#448
Mouser In US is selling Hammond series 229 (flat, split bobbins, similar to R Core) 24 V CT/48 VA for 17.63 € (+ VAT), cheaper than the 24 VA model of the same series.
If you order goods for at least 75 €, shipping is free.

Moreover Selectronic in France sells nice R core 30 VA xfrms for 15.50 (vat included) and 50 VA for 23 € + shipping
 
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#458
adamus said:
finshed my b1.

sounds great. The led strings arent right yet, but i fired it up anyway and it seems fine. shall i leave as it is?
Click to expand...

How off are your Leds? Tell us about DC offset. If that is fortunately acceptable in combination with your final V+/-, then you don't really need to touch the Leds again.

What about the rest of your system, what you had before in the line control position and how it changed the sonics now?
 
#459
no offset, my multemeter reads 0v on the millivolt setting. The led strings are 5.7 for the css, and 9.1 for the vref matched very closely each side.

The preamp consists of a r2r remote vol control > DC B1

This then feeds a push pull el84 amp (baby huey). It then feeds some KEF q5's, although i am building some brines ft1600 mkII (fostex 167e).

how did it change the sonics? Deeper soundstage, slightly better seperation. Slightly (ever so slightly) cooler presentation. Clarity is the word.
 
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