Wayne's BA 2018 linestage

[JPS64]

@6L6


PDF documents statues only for DIY!


JP

 

[wayne]

People are free to use this for DIY since it was put in the public domain.

 

[zman01]

Wayne,

Thanks to you and all others who contribute generously for the building and listening pleasure of the DIY crowd.

Hope the new PCB iterations will lead to more builds! 🙂

 

[JPS64]

Merci Wayne.


JP

 

[xrk971]

People are free to use this for DIY since it was put in the public domain.

Thank you, Wayne. It’s definitely for DIY only.

 

[6L6]

😎

 

[Russellc]

As a bit of data, here is the interest list for JPS64's design:



There are many ways to start projects in the commercial world. Often feasibility studies, list of willing customers, completed initial designs are often submitted as part of a proposal to show how ready a project is to proceed to the next level. Those are usually the ones selected because they show a thoughtful state of the art design, a solid well-prepared team that can execute, plus a list of willing and ready customers. Granted, this is DIY and not commercial, but the process can be similar in many ways. We are very lucky in DIYA to have someone with JPS64's experience providing us with these nice designs.

I have sent you a PM about being added to list, thanks.

Russellc

 

[JPS64]

Hello future builders,


here the last datas for production (small modification for better output level adjustment).


JP

 

[6L6]

Good timing for this, I am out out the purple PCBs. (packing up the last pair right now)

 

[zman01]

6L6,

Understand that a PSU with output within +/- 15W-22V will work. With reference to your build where you used the Broskie PSU kit, what is the voltage rating and VA of the toroidal transformer and how many volts are you getting at output?

https://www.diyaudio.com/forums/pass-labs/329240-waynes-ba-2018-linestage-4.html#post5651378

Thanks in advance.

 

[Mod Man]

A 25-30 VA transformer with two 18 vac secondaries is plenty. The Broskie power supply set up for 18 volts dc works great. Can’t recall how much voltage swing the output has but should go close to the rail voltage.

 

[PJN]

Well I finally started my build of the purple boards that Jim was so gracious to make available. Had a rainy day this weekend so I was able to populate both boards, and what busy little boards they are. I haven't finished hooking them up yet though, hopefully later this week. I made up a case out of some left over 1/4" plywood and scrounged around in my parts bin for the other stuff I needed. Here are a few pics of where things stand so far. The mouser BOM was perfect, many thanks to Jim and Wayne for everything they do for the community. The only thing that I'm nervous about is the PSU voltage, it's 29 vdc instead of 24 vdc, I think I'll contact Peranders to see why this build is higher than the BOM for the 24 vdc build should make it. Hopefully I'll get is singing soon.

 

[xrk971]

I love the wooden box look, PJN. Nice!

Btw, I just got my verification build PCBs for the WBA18 in Yarra/M2X format yesterday (the ones on the left). Will be populating soon and hope to have first sound by this weekend. If successful, will order production boards with ENIG.

 

[PJN]

Hi X,

The Yarra is on my build list. I want to build it as a gift for my son, he needs an upgrade to the mediocre pre he's using now.

 

[xrk971]

Hi PJN,
The Yarra GB2 is now starting up again and pre-orders are now being taken.

You can use the Yarra to run the WBA18 amp core modules. I just tested them last night for bias current and DC offset. I was getting 13mA bias and the revised pot is given g pretty good adjustment range and resolution to get circa 10mV output offset. The temperature sensitivity of the offset is rather high. Just breathing on the circuit makes it drift by tens of mV. I wonder if the transistor pairs should be thermally bonded and covered with a shrink tube?

I am testing them at +/-15v rails. Does anyone know if this preamp can safely run from +/-30v rails? I have an extra high rail voltage on my Yarra in order to drive a 50w 0dB gain Class A power amp.

 

[6L6]

+/-24v is as much as I've used on the circuit, and it works fine.

The KSA1845 and KSA992 are 120v parts, and the TTA004 outputs are 160v, I can't imagine there would be much issue with 30v unless one is carrying too much bias and dissipation becomes the limit...

 

[xrk971]

I’m actually using 2SA1837 and 2SC4795 (flipped around). They don’t feel too warm. At 30v and 0.013A each they will be 400mW - well within their operating safe limit. Might need a small flag heatsink? Will give it a try quickly and hope magic smoke doesn’t fly out.

 

[PJN]

Thank Jim, that make me feel better.


Hi X, I'll check out the GB

 

[Centurion53]

Volume attenuator

I'm finishing up my line stage and want to add a volume control. Was thinking of using an Alps R27. I have never used one before so was wondering if anyone could recommend a particular one for this application or other viable options.
Thanks

 

[6L6]

25 or 50k