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QUDOS - the brilliant new amplifier boards from Avondale

Thanks Malcolm.

Another question re drop in replacement suitability - are these new boards still happy with the vbe front end supply as used in voyager/clones?

I can think of no reason why not. The stability of the amp
lies in the preceding stages.
 
(Snipped) ..... you lose a 1N4148 and 100R resistor from the output stage and TR10 changes from an MJ15003 to an MJ15004.

You've perhaps hit the nail with this Malcolm and highlighted the source
of the characteristic 'rip' in NAPA circuits. The use of the Baxendall diode
to simulate a complimentary device may result in a non-linear transfer
of signal into the output pair but there will be more technically able
members than I who may care to comment.

An amplifier I once designed for Sugden, used a diode chain to achieve
output bias but produced the same kind of 'rip' I outlined above. Only
when I modified the circuit to a more conventional resistor network,
did the rip disappear.
 
I have no idea what you gents are talking about. It's a bit like the Japanese poetry we were taught at school- inherently beautiful but way beyond my faculties of understanding. I am embarrassed to ask such a trog question amidst such elevated discussion but are/will these boards be 'fittable' to a NAP180?
 
I have no idea what you gents are talking about. It's a bit like the Japanese poetry we were taught at school- inherently beautiful but way beyond my faculties of understanding. I am embarrassed to ask such a trog question amidst such elevated discussion but are/will these boards be 'fittable' to a NAP180?

Yes, they can.
 
I have no idea what you gents are talking about. It's a bit like the Japanese poetry we were taught at school- inherently beautiful but way beyond my faculties of understanding. I am embarrassed to ask such a trog question amidst such elevated discussion but are/will these boards be 'fittable' to a NAP180?

Yes, they can. They are the same size as the NAPA boards fitted in NAPs 110, 140, 160 (CB), 180 and 250. You can see one fitted in the same place as the original NAPA board in the photo in the OP.
 
Actually, after I posted the above, I was thinking; you already do your own reservoir cap board (very highly regarded), your own amp boards (similarly popular) and you have just started doing the 500VA transformers and you either already make or are working on regulator boards (sorry, I'm out of date and not sure which) - as such, one could easily build ones own Avondale 135's from scratch.
 
I thought this board is a replacement for the NCC200 and the replacement for the NAP135 boards is the NCC300.

Matt
That is what Les has written on the Avondale web site and I believe that design is in the final stages.
http://avondaleaudio.com/naim-audio-upgrades/
However right now you could still use the NCC-200 Amplifier with the HCR-200 Reg.
The Voyager Amplifier uses the NCC-200 with the VBE filter to the front end supply only.
http://avondaleaudio.com/audiophile-regulator-modules/
Alan
 
I thought this board is a replacement for the NCC200 and the replacement for the NAP135 boards is the NCC300.

Matt

There are several levels of 135 system in use today beginning with a standard
duo of 135s driving a pair of Briks, next a foursome driving for example a pair
of SBLs in either passive or active form and then, the ultimate, a six pack used
actively with Briks.

Active systems:

Sharing advice with a specialist in active Briks, it seems that the way forward is to
produce different configurations of converted 135s with the NCC300s looking after
bass driving duties where the B139s present a current-hungry load. Then, either
the NCC300s or Qudos conversion to the 135s on midrange duty (yet to be finalised
after listening tests) finally, treble driving may be looked after by HCR200 regulated
supplies feeding Qudos modules biased heavily into Class A mode to complete the
six-pack lineup.

Passive systems:

Using a simple duo of 135s, the NCC300s appear to hold the key to current delivery
so this will be the staple diet for passively driven Briks etc.

We're still working on this project and will be for some time but after the initial reports,
I'm beginning to alter my cold attitude towards Briks - it seems that there has been a
deficit in the amplifier department for many years and it's this I'm looking to address for
135 owners.

More later......
 
I have several times extolled the wonders of 'briks on this august forum. ;)

Having been through many configurations, I agree with Les and his friend that, when it comes to 'briks, the more power the better. After that, an active configuration allows for tuning the amps to the drivers. Interestingly, I've come to much the same configuration:
  • Bass – NAP135 x 2 (better than NAP250 x 2 with separate channels for each of the four B139s)
  • Mid – NAP180 converted to almost dual mono with a CAP-6 on each NAPA board
  • HF – NAP250
I will be working towards the NCC300 + Qudos configuration.

For my part, I've played with different feedback caps for the different drivers. While the mil-spec tants are excellent everywhere, here are some options:
  • Bass – MMK 47uF x 2
  • Mid – mil-spec tant 47+uF
  • HF – AVX polypro 47-68uF

Cheers to Les for advancing the state of the art!
Flash
 
Personally my 135's only drive the mid and tweeters in my Yammies with the bass handled actively by another amp (with much more power), so the Qudos may be the way to go - let's see how Les' thoughts pan out.
 
There will be another pair of 110 monos with "qudos" boards soon. Had a quick chat with Les today, and ordered the amp boards and 2x psu boards. Lovely chap, cant wait. Now lets see how the ES14's like them!
 
Personally my 135's only drive the mid and tweeters in my Yammies with the bass handled actively by another amp (with much more power), so the Qudos may be the way to go - let's see how Les' thoughts pan out.
Anecdotally, when I had a 135 4-pack hooked up to my Epos ES30s, I found the best result for me was a pair of 135s for the tweeters, and the other pair for the mids and woofers. I tried both ways round, dedicated woofer amp vs dedicated tweeter amp, and preferred the latter.
 
In my case the dedicated bass amp also applies some DSP to overcome the predominant room modes and, being active as opposed to bi-amped, is connected directly to the drivers without a passive crossover.
 


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