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QUDOS - the brilliant new amplifier boards from Avondale

Jonathan said:
yes - could be (the real sound) ... though this sounds quite a bit different from any of my other amplifiers ... in the bass register ... though honestly i didn't know my little audio physic tempos were CAPABLE of such bass ... I try not to turn it up too loud.

I'm not sure i understand your question about the wet tants ... how would they be 'too much capacitance' compared to any other 68µF capacitor ...? or maybe i misunderstand ... not using a cap 6 (rather four 15K µF caps at the moment) - i do have some minicap 6 boards though I will try later ...
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May be I wasn't clear in the way I wrote my reply
1. the wet tants will be fine and wont be the cause of too much bass
2. For the cap bank to the output power rails, the optimum seems to be around 18-23,000uf (3 x 6800uf per phase is good) if you go much bigger it can have the effect of sounding laden, boomy, slow.
If you are using 4x15,000 that 30,000uf for each phase so could be slowing your power supply down try a 15,000 + 6,800uf
 
thanks 337 ... yes .. well i guess it's an ongoing experiment - we will see what happens later when i try the MiniCap6 - though I'm not keen on all the rewiring needed to use the minicaps vs the 'straight' caps ... in case i had to change back ...

though ... i have to say I am a bit skeptical about the reservoir caps causing this since A. they are wired in parallel (so you're really only dealing with the 15K µF at a time) and B. at least at lower volumes one is probably only using a fraction of the stored charge which, i assume, would be 'liberated' more quickly ... maybe? I'm just guessing here though of course
 
Jonathan said:
thanks 337 ... yes .. well i guess it's an ongoing experiment - we will see what happens later when i try the MiniCap6 - though I'm not keen on all the rewiring needed to use the minicaps vs the 'straight' caps ... in case i had to change back ...

though ... i have to say I am a bit skeptical about the reservoir caps causing this since A. they are wired in parallel (so you're really only dealing with the 15K µF at a time) and B. at least at lower volumes one is probably only using a fraction of the stored charge which, i assume, would be 'liberated' more quickly ... maybe? I'm just guessing here though of course
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I would go with Alan's recommendation or maybe even further. 10,000uF per rail works for me.
I'm not a fan of CLC or CRC for power amps. So a single 10KuF cap is fine.

At any volume, you are only using a fraction of the stored energy... just think how long your amps can run after turning the power off and think about how many times the caps get recharged during that time. Any reasonable amp has decent PSRR at PS ripple frequencies. The sound quality of the transformer/rectifier/cap combination is more related to conduction angle/time and inductances than ripple IMO.
 
You're not alone with that thought, I recall a decent explanation over on diyauduo on the subject
 
though ... Les' Minicap 6 boards give me the exact same capacitance (4700µF x 6) per board on the NAP 160 - that's why i chose 15 000 µF x 2 per winding
 
Hi folks, just building my boards finally and noticed that R23 (below the bias pot if output transistors on right) on the PCB states 2K2 but on the schematic it's 1K2 - how critical is that value? I have some MFR5 2K2s but not 1K2...
 
James Evans said:
Hi folks, just building my boards finally and noticed that R23 (below the bias pot if output transistors on right) on the PCB states 2K2 but on the schematic it's 1K2 - how critical is that value? I have some MFR5 2K2s but not 1K2...
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I had to replace one 2.2k on my boards as I could not get it up to the bias recommended ,put in 1.2k and it was fine.
 
I have an ancient cb nap 250 lurking in the cupboard which needs a bit of tlc. How does a NAP 250 with QUDOS and HCR compare to a HackerNap, which is what I currently use as my power amp with a B4? Do the avondale volages really add a lot more to the sound? The 250 has a pair of Kendeil caps, which I bought from Les quite a few years ago installed at the moment, and the original Holden and Fisher transformer, although it has not been used for at least 5 years. I have a couple of higher voltage transformers that I bought at the same time as the kendeils when I had a pair of NCC boards, thinking I was going to go down that route before I got the HackerNap. So should I strip out the 250 and build a pair of monos with QUDOS and HCRs and sell all the 250 parts and HackerNap?
 
Colinb said:
I have an ancient cb nap 250 lurking in the cupboard which needs a bit of tlc. How does a NAP 250 with QUDOS and HCR compare to a HackerNap, which is what I currently use as my power amp with a B4? Do the avondale volages really add a lot more to the sound? The 250 has a pair of Kendeil caps, which I bought from Les quite a few years ago installed at the moment, and the original Holden and Fisher transformer, although it has not been used for at least 5 years. I have a couple of higher voltage transformers that I bought at the same time as the kendeils when I had a pair of NCC boards, thinking I was going to go down that route before I got the HackerNap. So should I strip out the 250 and build a pair of monos with QUDOS and HCRs and sell all the 250 parts and HackerNap?
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Les has fitted a pair of NC300 boards to a customers 250 so might be an option give him a ring.
I have a Hackernap and a voyager Qudos, the later is somewhat better.
 
James
If you match TR1 & TR2 you can get the DC offset down to a few Ma
Could also be a leaky feed back Cap

Alan
 
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