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Old 5th February 2013, 10:19 AM   #1031
mikelm is offline mikelm  England
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Quote:
Originally Posted by RKH View Post

a. Is there a need to be concerned about the 38 mV channel?
No

Quote:
b. I neglected (forgot) to ground the inputs when I set the bias. Should I go back and redo it?
Should not make much / any difference with an FET i/p
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Old 5th February 2013, 01:02 PM   #1032
RKH is offline RKH  United States
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Thanks Guys for the replies.

I will button it up and have a go ASAP. I have a little bit of tidying up to do with wiring and the chassis assembly.

More to come ...

Cheers,
Ryan
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Old 5th February 2013, 08:38 PM   #1033
AKSA is offline AKSA  Australia
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Hi Ryan,

37mV, 38mV, not a problem!

Being unable to set it higher is just fine. That is a design limit to prevent excessive quiescent at switch on. Never much of a problem of latfets, but a high issue with mosfets, and dangerous, explosive settings for bipolar output stages.

We look forward to your listening test!

Cheers,

Hugh
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Old 6th February 2013, 04:53 AM   #1034
RKH is offline RKH  United States
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Default It lives !!

Just a quick update. Where to begin? How about the eye candy first:

Here is my version residing in the DIYAudio Standard 4U Chassis. 2 Antek 25 x 2 @ 400VA transformers. I was too anxious to get it going to bother with any fancy lights on that gorgeous front panel. On-off switch resides on the IEC inlet on back.

Post 1 of 2 or so ....
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Old 6th February 2013, 05:41 AM   #1035
RKH is offline RKH  United States
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Default Continued ...

Dang, just lost my post due to a touchy mouse.

When I put everything in the chassis, I rechecked the bias and offset. Now both sitting nicely at 37 (and change) mV. I had to re-zero the offset a bit. I'm running 1uF Mundorf MKP in the input spot. The recommended Auricaps were out of stock when I was collecting parts.

Current set up:

SB Touch serving flac -> CA Dac Magic -> DCB1 (Mesmerize) -> Fetzilla -> MJK Open Baffles (~93 dB/watt efficient)

Initial impressions ...
A wee bit of turn on thump. Background noise is black as night. I couldn't hear a thing. Playing Krauss/Plant at very low levels (the family is in bed). Sound stage is noticeably better than the amp it replaced (for this set up). Detail is extraordinary. Did I say the detail is extraordinary?

I don't write/haven't written much about listening impressions on any of my diy Amps. I lack the words and experience. I'm not here to pit one of my projects against another. My basic 'call' is do I like it or not. I really like what I hear in the Fetzilla. Definitely a keeper

This was really a fun build. For me, it's the journey, not just the destination The board layout is great. The parts count is relatively low. Construction was quick. Dialing in the bias etc. was a snap. The availability of the awesome diyAudio chassis was fortuitous timing. I really like it when a plan comes together.

I cannot wait to put the amp through its paces when I can turn it up a bit and listen with more intention. But... after all of 25 minutes powered up, it is great. Really great.

Cheers to Hugh for making the boards available and the support of this thread! As I wrap this up... currently playing Anne Akiko Meyer's Air, (violin conerto) just lovely.

Ryan
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Old 6th February 2013, 06:11 AM   #1036
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Very nice build,I was very shure you liked this amp.
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Old 6th February 2013, 08:19 AM   #1037
mikelm is offline mikelm  England
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Nice build
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Old 6th February 2013, 10:22 AM   #1038
AKSA is offline AKSA  Australia
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Hi Ryan,

You know, since my daughter is living in NYC, when I get well I'm hoping to go to the US again. I would like to visit you in CO, I love that state passionately.

Your build is wonderful, very elegantly and carefully assembled. No wonder it makes no noise! I'm delighted it sounds good, Kudos to Greg, Mike, and Paul - and yeah, I liked the pcb layout too!

Cheers,

Hugh
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Old 6th February 2013, 01:26 PM   #1039
RKH is offline RKH  United States
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Default Speedy recovery

Hugh et al.,

Thank you all for the compliments on the build. I neglected to thank the others: Greg, Mike, and Paul. Well done fellows. After I signed off last night, I continued to listen for another hour. The amp continued to surprise me and I caught myself smiling, even giggling out loud. It is really that good.

Hugh, I wish you a speedy recovery and will welcome you to Colorado when you are able. We have a lot to show you and plenty of local brew that is well worth tasting if you are inclined and able.

Too bad I have to go to work today ... I can think of another, far better way to spend my day.

Cheers,
Ryan
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Old 6th February 2013, 07:39 PM   #1040
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Quote:
Originally Posted by AKSA View Post

You know, since my daughter is living in NYC, when I get well I'm hoping to go to the US again. I would like to visit you in CO, I love that state passionately.

Cheers,

Hugh
Hello Hugh

If you go to NYC one day, I could try to meet you there if it's possible for me.

Bye

Gaetan
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