Wayne's BA 2018 linestage

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#2,123
I’m thinking of taking my Balanced Zen Line Stage and converting it to the BA2018 Line stage when the PCBs are back in stock. My existing chassis has plenty of room, inputs, pots, and outputs. I would build it balanced. The power supply is the big change needed. My power supply is the spec’d one for the BZLS — 60v regulated that uses two 30v+30v toroids. Can I substitute smaller transformer(s) to make it suitable for the BA2018? I assume I’ll need to make some downstream changes in the zeners, but beyond that I’m very inexperienced departing from an existing design. Anybody point me to a resource maybe? It could be a learning experience! Thanks.
 
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#2,126
6L6 said:
Just use a lower voltage transformer and make the Zener strings 24ish volts instead of 60.

Zen Variations 3 discusses this style of PSU - Zen Variations 3 | Pass DIY
Click to expand...

So i keep three zeners per side, that’s a little over 27v at 9.1v per zener. Or replace the third one with a smaller zener to get closer to 24v? And buy two small (30VA maybe) 12+12v transformers. Or just one 20+20v transformer feeding both sides? This is all new to me.

Then, do I just bridge each of the other zeners with wire, or bypass them all at once with just one wire per side? I don’t think I fully understand zeners’ two-way flow.
 
#2,128
Two stereo pots gives you Balanced volume and balance control. I was reluctant to have two volume knobs until I actually tried it, and to my surprise it's not at all fiddily as I expected and it works quite nicely. :yes: It's also a realistic solution as finding a 4-gang pot is getting to be a serious pain in the last few years...

As for switch, you want a 4-pole, 3-position, shorting rotary. Like so -
https://docs.rs-online.com/6e81/0900766b81531898.pdf

https://www.mouser.com/ProductDetail/Alps-Alpine/SRRM433700/?qs=4QwOlnKYOEsVs7%2B5af2rdg==
 
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#2,129
Awesome. Thanks 6L6! You are always quick with the right answers.

What would work best 25k log or 50k log for this line stage input? I am primarily using digital sources with balanced outputs, but might get a balanced phono stage at some point.
 
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#2,131
The last board I sent to the fab house was absolute garbage. Can someone please look over these to make sure I didn't mess anything up?
 

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#2,132
Wow, that's a crazy impressive board! Any problem having the transformer so close by or is it not so much of an issue at these levels?

I notice you use copper pour to fill in the empty space between tracks. Any pros or cons on doing this as a general practice?

:cheers:
 
#2,133
twitchie said:
Wow, that's a crazy impressive board! Any problem having the transformer so close by or is it not so much of an issue at these levels?

I notice you use copper pour to fill in the empty space between tracks. Any pros or cons on doing this as a general practice?

:cheers:
Click to expand...

I designed it in such a way that if I am getting noise from the transformer, I can just break it off at the V-cut and relocate the power supply.

I have no idea about the copper pours, top is +18v and bottom is -18v. After thinking about it, I just might have to go change it......
 
#2,136
lay out like this?

Hi friends

I'm in the midst of the build... Will have a BA-18 with a Toroid 18-18 50VA, VRDN-PSU, i-select, either a 20K Precision Electronic Pot or a Elma Relay-attenuator, and a pair of output-transformers for the oomph...

It will all end in a 1U chassis, so space is a bit scarce. The Capacitor on the i-select is just that tiny bit too high, so I'll mount it vertical...

Does anyone spot any flaws in this layout? (Don't think there are until now, but you see and know more than I...

Thank you!
😀
 

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#2,139
„Not needing _smaller_ donut“?
Oh mighty zm, I hope you’re fine? [emoji83]
(I don‘t 100% recall the value of it, but it is a working one—has been confirmed many times already...)

It‘s the CineMag CMOQ-4HPC. I got them in a wave of absolute greed (and anxiousness the Linestage wouldn't be sufficient to drive F4. Which will not be the case I am convinced by now 😉 ). Just copied the work of william2001
 
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