AWA BAR2

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AWA BAR2

Postby chrisp » Tue Mar 08, 2016 9:31 am

Hi, my name is Chris and I am a germanium addict.

Well not really, but I am looking to do the AWA BAR2 thing that Rob and Alastair know well.

Current plans are -

(a) direct XLR outs on each channel with transformer outs
(b) 0db, 10db, 20db pad on each output
(c) JLM GoBetween on each input
(d) DI on each input (probably a Bo Hansen design rather than the JLM)
(e) ditch the mix section
(f) replace the power/battery test switch with a metering select switch
(g) maybe find room to add in my AWA BAP2 pre to make in a 5 pre box, but this is simply an idea to use the 5th front panel knob

What else works? What is needed? Recapping? Anyone have a trio of the huge AWA output can transformers?
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Re: AWA BAR2

Postby Chris H » Tue Mar 15, 2016 8:34 pm

......................Anyone have a trio of the huge AWA output can transformers? :))
Those around here who have them usually don't want to get rid of them. Best place to look is following "leads" on gumtree.......finding an ad for some old electronic gear, asking questions like, you dont have any old AWA transformers. That's the most likely way of finding them.
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Re: AWA BAR2

Postby chrisp » Wed Mar 16, 2016 8:40 am

Thanks Chris for the suggestion.

I've opened up the case now - all looks in reasonable nick. I'm tracing the wiring around to get in my head the topology. Looks like input -> transformer -> volume -> amp card / mixer so far.

A schematic would be great - christopherpreston at iinet net au if anyone feels generous.

But here is a more general question. I could stuff all this into a 2U rack and it would still be a BAR2, and that was my original thought. But I have the original case - its just larger and more cumbersome. When you think of channel strips, they tend to be re-cased, but this to me seems a bit different. I am tending towards changing my mind and restoring the beast in its original case, even though some of my proposed mods are tricker that way. What are you thoughts?
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Re: AWA BAR2

Postby Chris H » Wed Mar 16, 2016 2:18 pm

i've kept mine in the original case and added "rack ears". I think its also worth keeping the mix for times when you need to blend a mic and di. I do this with bass often when recording to my otari 1/2 inch 8 track. I also use inline pads on the output so i can gain the thing up a bit and not be too hot to tape. I have 10 and 20 dB pads for this. The Bar 2 is +8 on the output not plus 4 and if you dont pad them down you often cant drive the germanium transistors into furry land without clipping what you are going into, tape or converters.
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Re: AWA BAR2

Postby rob » Thu Mar 17, 2016 5:32 pm

I could help with a schematic when I'm back in the workshop next week.

the topology is input - transformer - preamp - vol pot.
from memory the pot is dual gang and tweaks gain and level to mixing amp.

these unit's preamps don't have a lot of headroom and maximum level out of the preamp is only around +10dB.

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Re: AWA BAR2

Postby chrisp » Tue Mar 29, 2016 6:10 pm

Thanks Rob, a schematic would be great to understand what is going on.

What's the go with recapping vintage gear like this - In the past I have just assumed the electros are all dry and replaced them. Wisdom of the ages?

I know the GroupDIY and GearSlutz people get very hot under the collar (that's a pun) about capacitors, but really? They are mostly +/- 20% so I'm guessing the voltage (at or above spec) and the temp tolerance are where the money should go, but any wisdom appreciated.
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Re: AWA BAR2

Postby rob » Tue Mar 29, 2016 6:46 pm

shoot me an email and i'll dig out the schematic

modern capacitors generally are very good
you can increase the voltage rating within reason without a problem
keep the uF the same or if you know what's what these values can be rounded up to the nearest standard value
high temp, low ESR caps are worthwhile
The capacitors that WES components sell are good and cheap
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