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Bruno Putzeys Balanced Preamp - Group Buy Part 2

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#262
Thanks chaps. 🙂

OK, those that didn't reply to my chaser email and my PM have now been removed. I've started emailing those on the waiting list to see if they're still interested.

Algar_emi, I've emailed you a proforma directly as I know you're going away. 🙂
 
#263
drpro said:
Ordered parts from Mouser, hopefully got everything right. Finding nice caps that are small enough took a bit. Any rate I have attached a Word .doc with Mouser part numbers. Please feel free to add to or modify.

No case, switch, transformer, knob in this list.
Click to expand...

Thank you for the BOM from Mouser. I have decided to order the same parts with one exception. The relay you suggest TE connectivity is asking for 550mW. It seems to be too much for me. So I decided to order Omron relay with number
653-G6K-2P-DC12
It is asking just for 100 mW.

Ladislav
 
#268
That's very kind of you drpro.

Gents, is there anyone here has also participated in Enrico's 6 input board? I shall be quite grateful if you could upload the combined BOM. It is rather expensive for us (@India) get stuff from Mouser. It would greatly help to know that I got the BOM right.
 
#271
drpro,
Your relays are not the proper pitch.

tfboy,
For the potentiometer, on Bruno's tech sheet, at the bottom, the part number is for logarithmic... Why is Excel document original BoM stating linear? Which one to use?

Also why do we need electrolytics of 50V and 63V when the power supply is bipolar 12Vdc? We should be able to safely use 35Vdc caps no? This would give more choices. The caps suggested on the BoM are too big to fit the board anyways... Unless you solder some on top and some on bottom, they just won't fit the board.
C10, C16, C26, C27, C28, C29 = 5mm with 2mm lead pitch
C4, C7, C8, C9, C21, C23, C24, C25 = 6.3mm with 2.5mm lead pitch
C12, C13, C14, C15 = 10mm with 5mm lead pitch

I have some Digikey alternative parts for those interested

Thanks
Do
 
#272
You are so right, Do. I didn't check the Omron spec sheet, just went with the suggestion. My bad. I have identified another TE relay at Mouser that has the same pitch and only draws 150mw 655-V23105A5003A201. So please check me, I have updated the BOM to reflect this relay.

I would love to have a Digikey choice also, Do.

Thanks
David
 
#273
If we can safely use 35Vdc caps (this has to be confirmed), then my suggestions for Digikey are the following:

C10, C16, C26, C27, C28, C29 = 5mm with 2mm lead pitch = 565-1703-ND
C4, C7, C8, C9, C21, C23, C24, C25 = 6.3mm with 2.5mm lead pitch = UES1V100MEM-ND
C12, C13, C14, C15 = 10mm with 5mm lead pitch = 565-3571-ND

I do not use audio caps for the power supply section, I prefer higher reliability and lower ESR which audio caps usually are not.

For power header, here are the parts:
1x WM5225-ND CONN HEADER 3POS .156 VERT GOLD
1x WM2112-ND CONN HOUSING 3POS .156 W/POLAR
3x 08-56-0106 CONN TERM FEMALE 18-24AWG GOLD

Relays
3x PB1125-ND RELAY TELECOM DPDT 2A 12V

Switch SPDT
1x 450-2108-ND SWITCH TOGGLE SPDT 0.4VA 20V

I'm not going to solder XLR designed to fit this board specifically but rather use different ones with silver cable extension, so I have no parts to suggest... Anyways, Mouser has a much better selection for XLR jacks...

Again, please double check the parts above for errors before ordering and wait for an answer for the 35Vdc caps (personally I'm ordering mine).

Thanks
Do
 
#275
drpro said:
Ok, I am confused. I am looking at the board in hand along with the schematic and don't see any open slots for opamps.

Am I missing something?
Click to expand...

See pic attached.
 

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#277
pinnocchio said:
drpro,
Your relays are not the proper pitch.

tfboy,
For the potentiometer, on Bruno's tech sheet, at the bottom, the part number is for logarithmic... Why is Excel document original BoM stating linear? Which one to use?

Also why do we need electrolytics of 50V and 63V when the power supply is bipolar 12Vdc? We should be able to safely use 35Vdc caps no? This would give more choices. The caps suggested on the BoM are too big to fit the board anyways... Unless you solder some on top and some on bottom, they just won't fit the board.
C10, C16, C26, C27, C28, C29 = 5mm with 2mm lead pitch
C4, C7, C8, C9, C21, C23, C24, C25 = 6.3mm with 2.5mm lead pitch
C12, C13, C14, C15 = 10mm with 5mm lead pitch

I have some Digikey alternative parts for those interested

Thanks
Do
Click to expand...
Hi Do,

Bruno recommends using a linear pot.

The initial BOM had the log one - Bourns ptd902-2015f-a103 The G word: Demo project - A balanced volume controller | EDN
When he did the tests, he "accidentally" used a log pot.

From the comments on the article:
It does. Carbon ink is notably nonlinear for instance. Other types may be better. At low frequencies the temperature dependence of the resistive material becomes noticeable. This circuit arrangement helps minimize the impact on distortion of these problems.

After publishing the graphs I found that I'd inadvertently stuffed a logarithmic pot on the board (quite something after all that pontificating about it needing to be linear). Indeed, after I'd fixed that the distortion at LF went away too. Score for theory. I might put up the new measurement one day. It looks a sight better than the one in the article.

The funny thing about ohm's law is that there are no resistors that follow it exactly. Every resistor data sheet gives an indication of the extent in which it deviates. If this info is not stated it just means that it's missing 🙂
Click to expand...

Regarding the caps, which BOM are you looking at?

For C10 - C29 - 5mm diam, 2mm pitch caps, I'm using the Panasonic EEUEB1H220S.

For C4 - C25 - 6.3mm diam, 2.5mm pitch, there are the Panasonic Bipolar ECEA1HN100U.

And the Panasonic EEUFC1E102L for the 10mm / 5mm pitch.
 
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