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QUDOS - the brilliant new amplifier boards from Avondale

Hi Stack, I don't know about cooling off under load, but I've also noted that the HCR200 modules run fairly warm.

I'm rebuilding my Avondale'd 250 with CAP6's in place of the regulator modules. The NCC220s should be fine unregulated. We'll see.
 
Hey Flash. It's been awhile. Hope you are doing well. My 250 is really old (circa 1982). So it has these old funky rectifiers in it, so that was my first concern. But Les basically said they're fine and told me not to worry about them (that was before I got the boards). Anyway, it just seems unusual behavior to me. But maybe it is normal. Not hearing anything that would suggest there's an issue.
 
flashgo said:
Hi Stack, I don't know about cooling off under load, but I've also noted that the HCR200 modules run fairly warm.

I'm rebuilding my Avondale'd 250 with CAP6's in place of the regulator modules. The NCC220s should be fine unregulated. We'll see.
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That's essentially the amp that I'm building for a friend now (except it's dual mono: 330VA transformer, HackerCAP, and QUDOS). I'm wondering how that will compare to the Voyagers you finished for me (with the VBE powering the front-end of the QUDOS).
 
Hi Mike! You've prompted an interesting idea. The FE regulation is really beneficial. By replacing the regulator boards in the 250 with HackerCAP's fit where the reg boards were, there could be a way to use the space where the original caps were for FE regulators. The Avondale CAP6's are too big for this scheme in a 250 box.
 
flashgo said:
Hi Mike! You've prompted an interesting idea. The FE regulation is really beneficial. By replacing the regulator boards in the 250 with HackerCAP's fit where the reg boards were, there could be a way to use the space where the original caps were for FE regulators. The Avondale CAP6's are too big for this scheme in a 250 box.
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Trying to make it fit is a constant problem. ;)
 
Know I'm quite 'late' to this, but considering modifying my NCC200 amp boards to QUDOS spec. I see from skimming through this (long thread) that everyone seems quite pleased with the results of going to QUDOS and that altering existing NCC200 boards is not difficult. Thanks to James Evans for the link to the pages on modifying this earlier in this thread, taken from https://pinkfishmedia.net/forum/threads/can-you-see-a-problem-with-this-set-up.252587/)
What I'd like to ask is are there any down-sides to this? Don't want to loose that big, bouncy reproduction you get with the NCC200, but feel that there is a slight loss of detail or slight lack of definition in the mids that could be improved upon. Is this basically what you get going by to QUDOS please?
Thanks,
Andy P
Also, it seems that replacing the resistor // with resistor + cap feeding the bases of the driver transistors with just a 10R seems to be the latest revision. Can anyone confirm this please?
 
glenn jarrett said:
you could have asked Les to sell you the ncc220 qudos bare boards
and used most of the components off you ncc200 only a few differences
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Given how arduous transplanting components can be, my personal preference would be to order the new QUDOS boards, and use the spare NCC200 in another amp. ;)
 
Less risk also. New parts, a proper board and a professional job. Looking at what I got, it's better than what I would have produced by far.
 
I have a 250 with Avondale regulator boards and self built 220s.
I have the bias set to 100ma at present and it sounds excellent.
I have used it at this setting for several years and it gets warm but not hot.
Could any of you more knowledgeable chaps comment on the advantages/disadvantages of higher and lower bias settings.
 
muchtoofast said:
NCC220 snipped transistor TR5 by muchtoofast, on Flickr

NCC220 Qudos by muchtoofast, on Flickr
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I'm finally pulling together all the spare bits and bobs I have here from previous builds to start on another one. I notice from the above board photo that R4/C9 and R27/C10 are not fitted, but on the Avondale website they are still shown on the board photos. R5 looks to be 10R above

Does anyone have details of the latest and greatest circuit diagram for the Qudos? The one I have here has 27R/100n and 15R for R4/C9 and R5. The photos on the Avondale site appear to show R4 61R and R5 27R, if I'm reading the colour codes correctly!

Cheers
 
James Evans said:
I'm finally pulling together all the spare bits and bobs I have here from previous builds to start on another one. I notice from the above board photo that R4/C9 and R27/C10 are not fitted, but on the Avondale website they are still shown on the board photos. R5 looks to be 10R above

Does anyone have details of the latest and greatest circuit diagram for the Qudos? The one I have here has 27R/100n and 15R for R4/C9 and R5. The photos on the Avondale site appear to show R4 61R and R5 27R, if I'm reading the colour codes correctly!

Cheers
Click to expand...
FWIW The pair of beautifully built boards I bought from Avondale 2 years ago did not have the 27R and 100nF fitted.
 
bravem01 said:
FWIW The pair of beautifully built boards I bought from Avondale 2 years ago did not have the 27R and 100nF fitted.
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Thanks. Thinking about it, I suppose I'd need to know if there are any value changes elsewhere in the circuit as well in order to leave them out, so I may well just go with the circuit diagram I have.
 
Bill Colledge said:
I have a 250 with Avondale regulator boards and self built 220s.
I have the bias set to 100ma at present and it sounds excellent.
I have used it at this setting for several years and it gets warm but not hot.
Could any of you more knowledgeable chaps comment on the advantages/disadvantages of higher and lower bias settings.
Click to expand...

There is no sonic benefit IMO for driving the bias outside the 100mA other than waist energy as unwanted heat. The 100-120mA does seem to be the sweet spot. Leave as is and enjoy.
 
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