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QUDOS - the brilliant new amplifier boards from Avondale

A couple of better but still not good photos....

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As you can see, I still need to do a bit of tidying up..but its now been pressed into TV service for the Christmas period so nothing further will happen to it till the new year.
 
Getting some bits up together for the second amp. I have found a few PSU boards from a group buy some/many years ago, miniCAP style but with the facility to drop a snubber on the AC 'in' and L or R after rectification then L and or R between the caps...is there preference for CLCLC, CLCRC or CRCRC. I know there was a thread running but buggered if I can find it.
Any preferred 100V caps for the HCR200 regs?

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I have L's and make my own when needed. The R's I was thinking 5.1R 3watt ish. Anyone use the snubber and what values used.

TIA

Graham
 
If you're doing the snubber right then it should be a modest C-RC between each secondary and the snubbers. 15n and a 10n plus 10-100r will get you in the ballpark.

10n -15n/22r for my 300 VA 24v airlinks. The difference in getting the resistor value spot on is significant. Time for a scope...
 
Have now split my boards into a 2 box dual mono configuration. Have got the front ends powered by R-Core/PFM CAP/ Avondale VBE combo @ 51.5V output. I've initially set the bias current for the NCCs at 55mA. Has anyone experimented with different values and noticed a difference?
 
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The front end draws about 22ma IIRC. You add this the the NCC bias to get the overall current draw. I run my NCC's at 150ma (172ma in total) at which the amps run slightly warm. It adds a warmth and clarity to the musical presentation, which I like. Its not black and white but its there.
 
I run another pair of entry level QUDOS amps at 100ma in a shoe box size case. Now these do get quite warm at 100ma. They seem to be liking it so far as their powered 24/7.

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Thanks for replies. So with 22mA drawn by the front ends, mine are at 77mA total. I’ll try taking the current up to 130mA = 152 mA equivalent for un-split power rail bias.
 
Jo Sharp said:
Thanks for replies. So with 22mA drawn by the front ends, mine are at 77mA total. I’ll try taking the current up to 130mA = 152 mA equivalent for un-split power rail bias.
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Yes...The issue is that at 'idle' current is flowing and heat is generated this then needs to be removed through the case work/heat sink. When you start driving speakers even more heat is generated, this additional heat is also removed through the same case/heat sink. I can't (don't want too) run my little amps at more than 100ma as it seams 'feels right' temp wise, 'touchy and feely'. At 120ma it feels too warn..I should invest in a thermal camera...and monitor/record more scientifically.....

I said warmth in the earlier post, another word would be sweeter..
 
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Some cheap DVMs have an input for a (cheap, usu. supplied) 'K' type thermocouple; I have one - it's very useful for this kind of thing :)

(eg my latest-iteration of a >>decade-old headphone amp project runs c. 130mA/rail/channel on +/-28v... what felt 'hot' locally is only, actually, 50deg/C at the output device..which is fine by me, and works v.well in bias stability terms.)

tl;dr: metering for this is cheap!
 
I'll keep a look out Martin. I built some Pass Class A's I used an old garden thermometer stuck to the sinks with a big blob of blue-tack. 55deg/C after some hours running. The sinks felt hot (uncomfortable) after a min or so but I could keep a finger on the mosfets indefinitely. :)
 
Be handy for testing the accuracy of the central heating thermostat that. Another weapon in the battle against excessive usage. Can you get a holster for it?
 
James Evans said:
Be handy for testing the accuracy of the central heating thermostat that. Another weapon in the battle against excessive usage. Can you get a holster for it?
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As a competent DIY'er it shouldn't be too difficult to rotate the temperature dial relative to the control - about 6C difference should do the trick.
Don't tell the other half about expectation bias though :)
 
S-Man said:
As a competent DIY'er it shouldn't be too difficult to rotate the temperature dial relative to the control - about 6C difference should do the trick.
Don't tell the other half about expectation bias though :)
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If only it was so simple, we've gone all Hive now - different skill set. Having said that, I can now switch it off from the other side of the world if I want :)
 
(Professionally speaking - I've seen dummy wall thermostats installed, purely to give the illusion of local control... it does keep people happy! )
 
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