B1 preamp build thread

6L6

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You will need to connect the circuit ground to chassis or it will hum. Are you using the PassDIY pcb? The mounting holes all have connection to ground, use one metal standoff and the rest nylon, and make sure the metal standoff touches the metal of the chassis. (Remove any paint or anodization) Also make sure every panel of the chassis is electrically conductive to each other.

I would then insulate every connection, RCA, barrel, switch, etc… but the potentiometer body must touch chassis.
 
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Looks beautiful @DuncanF ! Nice work. Do you also have shots of the font and rear panels?
BTW, What relays are you using? I am surprised that the PIC can drive a relay coil directly. That is a beautiful thing. Cheers!
Hi. Sorry. I've not been around for a while. I'll try to post some pictures in the next few days. The Omron G6K 5V relays are controlled from the PIC with a standard transitor switch/flyback diode arrangment.
 
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Looks great @DuncanF ! Where did you get that PCB, it looks like having both preamp and psu on a single board. Is this the one sold through Pass' website?
Hi. Sorry. I've not been around for a while. PCB is my own design taking the B1 schematic and adding a PIC microcontroller to drive the input switching relays under the control of a tactile switch on the front panel. PSU for B1 and PIC (5V) is located near the front panel. The PIC is tucked up near the transformer. The back half of the board is the B1.

I used Kicad to work it up and had the PCBs made by Seeed Studio.
 
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You will need to connect the circuit ground to chassis or it will hum. Are you using the PassDIY pcb? The mounting holes all have connection to ground, use one metal standoff and the rest nylon, and make sure the metal standoff touches the metal of the chassis. (Remove any paint or anodization) Also make sure every panel of the chassis is electrically conductive to each other.

I would then insulate every connection, RCA, barrel, switch, etc… but the potentiometer body must touch chassis.
Thank You
Yes, I’m using the orig Pass PCBs
 
Hello again.

Almost all of the parts for my B1 are here.
I’m not happy with one component though and I hope someone can help…

Ideally I’m looking at a design almost like in the first post. Just two round knobs. But I couldn’t find a two position rotary selector. Instead I got a rather big switch which I, now that I have it here, don’t like at all….and it is not black nor could I find a nice black one.
I’d rather have two black knobs, one for input and one for volume.

For volume I got the EIZZ 24 pos. step attenuator.

Does anyone know of a nice two position rotary switch OR is it possible to block one position from the 3-pos rotary switch from EIZZ???

Please, I do not want more than two positions!!

Thank you
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Hello!!
One knob is still missing and I’m thinking about making some kind of description on the panels, but other than that I’m quite happy.😊

The RCA are sh*t and the log pot is not ideal at the top end but very nice at my usual listening volumes.
One one side there is a phono tube pre from project, on the oder side a digital streamer. Output into active transmission line speakers.
What I find especially pleasing is, if I switch from analog to digital, the volume level is exactly the same. But I guess that’s not the achievement of the buffer.
Thanks for your help in the process
 

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Me again,
I do experience a little but annoying humm sound, what I think is the 50Hz from mains.
Anyone any advice on how to find that and how to get rid of?
On the audiofile attached you can hear when I remove or replug the DC Plug. It is enough to just hold the "-" from the plug to the socket and the hum is there...
Oh, I can't attach an audio file...
 
Yes, every panel and the housing of the pot is connected to „-„ of the power supply.

The noise gets introduced when I connect the „-„ pole with the power supply and stays after pushing the plug in completely.

Are there any requirements to the power supply? Reading Mr. Pass file on the B1 almost anything should go, right?
 
UPDATE:
I connected my adjustable power supply from my workstation @ 24V and … no hum…

guess I have to update my wall adapter…can someone recommend a decent one? But not the overpriced ifi please.
i do own some of the Peter Daniels PCB‘s but I really want to avoid implementing that kind of power supply for this as I don’t want 230V inside the housing. (Everything except my power speakers is low voltage)