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B1 preamp build thread
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Old 7th August 2018, 02:46 PM   #551
Zen Mod is online now Zen Mod  Serbia
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B1 preamp build thread
right now I can't understand what's wrong - PSU or whatever you connect to it

anyway - if PSU isn't having intended voltages at outputs, just replace LM regs where voltage isn't ok

simple as that
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Old 7th August 2018, 02:53 PM   #552
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the issue was that by accident i attached the power supply to my b1 with reversed polarity (that was 2 month ago). you helped me troubleshoot the b1 and it seemed not to have taken any damage.

then you gave me advice on how to check if the psu survived the reverse polarity. to do so you advised me to attach 1r resistors in line with the rails and measure voltage across them. this is what i just did and the voltage is exactly the same as without resistors. now i was wondering
1) what the purpose of the measurement with the resistors in line is?
2) if that tells me that the psu is fine?

the voltage between +/- is 30v. 15v if i measure across "+" and ground or " - " and ground. that's the way its supposed to be i guess.

sorry for the confusion
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Old 7th August 2018, 03:23 PM   #553
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in line resistors where there to measure voltage sag across them , and reflect is there any malfunction

it was supposed that you do that and write back your findings , so we can proceed further if needed , or declare it OK

this way , asking zillion years later , you're just adding confusion to already confused ZM

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Old 7th August 2018, 03:26 PM   #554
Mixi is offline Mixi  Europe
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i understand that my reply comes a little late - sorry for the confusion!

seems that there is no voltage sag across the resistors, does that mean the PSU can be declared ok?
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Old 7th August 2018, 03:43 PM   #555
Nisbeth is offline Nisbeth  Denmark
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B1 preamp build thread
If you measure +/-15V on the output of that PSU it's probably fine. However, what isn't fine is that you seem to have a dual-rail PSU supplying a single-rail amplifier. Can you draw how the two boards are connected together? From an earlier picture it looks like you have previously run the B1 on two 9V-batteries in series - did it hum then?
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Old 8th August 2018, 02:41 PM   #556
Mixi is offline Mixi  Europe
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Quote:
Originally Posted by Nisbeth View Post
If you measure +/-15V on the output of that PSU it's probably fine. However, what isn't fine is that you seem to have a dual-rail PSU supplying a single-rail amplifier. Can you draw how the two boards are connected together? From an earlier picture it looks like you have previously run the B1 on two 9V-batteries in series - did it hum then?
i'm afraid you're quite right. i did use the dual power supply for the (single rail) b1. i have to admit that i really only used it for maybe 5 seconds - with reverse polarity as mentioned before. after that i only used the two 9V batteries. and yes, there was some hum - how did you know?

unfortunately i don't remember how i connected the together. i believe +15v to '-' on the B1 and -15v to '+' on the B1. Wrong obviously.

Would it be possible to use a dual supply for a single rail amp at all?
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Old 8th August 2018, 03:03 PM   #557
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quite possible
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Old 25th October 2018, 10:48 PM   #558
Neel007 is offline Neel007  Netherlands
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I would like to build a B1 to connect to my Amp Camp Amplifiers, I am building two, with both the switch for bridged mode and the XLR input (for balanced input).
Would the B1 be a good preamp for that setup?
Could I build the B1 with balanced outputs (and RCA input)?
Will the power supply I added work properly with the B1?PSU Preamp.jpeg

Sorry for soooo many questions..

Cheers,
Neel
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Old 1st November 2018, 07:42 PM   #559
freespace377 is offline freespace377
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Default So many grounds

I'm building the B1 and my Pass Lab board has each of four standoff holes grounded. My experience in tube amps makes me reluctant to do more than one ground connection to the case. Anybody had ground loop problems?

The board only switches the hots of the two inputs while their grounds are all commoned. In stomp boxes the sound is better with grounds switched too. Anyone have experience on isolating and switching the signal source grounds?

Thanks

Dan
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Old 10th November 2018, 05:06 AM   #560
freejazz00 is offline freejazz00  United States
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I'm posting my build, below, just to share with others on the thread...

But first I'd like to thank Jim (6L6) and Gianluca (HiFi2000). Jim answered, very patiently, LOTS of questions, and Gianluca made sure the chassis fit all of the parts properly. My build and understanding certainly would have been lesser without their assistance. Their time and contribution to the threads (in Jim's case) and customer service (in Gianluca's case) certainly make the DIY experience of many folks much better. Many thanks to you both.

I built my B1 to match the ACA amps I built concurrently. The only modification I made from the stock form was to add a power switch to the front panel.My big parts splurge were the Goldpoint attenuators, which are fantastically cool. Everything inside is from the recommended parts on the BOM with exception of the Mundorf caps I purchased at a stellar discount, and then only because I couldn't find the ones NP used.The hookup wire is Kimber, the RCAs are Cardas and the switches are NKK. These aren't the cheapest parts, but are far from the most expensive. I'm not sure the unit would sound much different if I used more or less expensive parts. In fact, I'm a little amazed at how little sound signature the B1 has. NP noted that some folks find passive pre's lifeless in sound quality, but I don't find that in this case.

The B1 and the ACAs were my first builds. I think the jump in the learning curve from the ACAs to the B1, which is very easy, had more to do with learning how to pick parts from Mouser, follow a BOM and other minor skills not needed with a project like the ACAs.

I'm very happy with my little DIY system. Now I"m off to try a few more complex projects like the Pearl 2 and the AJ. I've caught the DIY bug and really enjoying learning about how the electronics "work" and the simple pleasure of putting something together with my own hands.

Thanks again to Jim and Gianluca!
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