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QUDOS - the brilliant new amplifier boards from Avondale

337alant said:
Steve,
Les is very helpful and you will get plenty of support from here as well , just ask;)
Post pictures as you go before switching anything on

Alan
Click to expand...
I will, amp in the foreground, a scared looking me out of focus on the background, hair on end all Einstein style..
 
nn_in said:
Whats the difference between 821 and 821A .
Iam assuming 821A is a stepup from 821
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The 821A is a step up from the standard 821. The 'A' stands for audiophile if I remember correctly. There are three main areas of difference between the two, the 821A has better capacitors, better resistors and the components are selected and matched. The 821A is now known as the 821 AR. That said, the standard 821 performs very well.

You need to be aware that the boards need to be fitted either in a Naim NAC preamplifier (up to the NAC72 but not the later models) or in Avondale's own 821 preamplifier and that you will need a separate dual 24v power supply if using a Qudos power amplifier. A Naim preamplifier gives the option of including a phono (MM or MC) board in addition to its line-level inputs whilst the 821 preamplifier has only three line-level inputs.

IMG_0673 by Malcolm Connah, on Flickr
 
That makes it clear now.I dont have a Naim amp so considering only for qudos
However on Avondale website only the vertical board is shown .The horizontal board is not shown ? Do both the boards come or only vertical board will be shipped?
Iam assuming the dual power supply is fed from a separate DC PS box to 821 box.So can the DC PS that powers the Qudos be used for 821 ?Which Avondale regulators can i use or can i use any suitable dual dc power supply?

Apologies for the number of questions.

A table on Avondale's website would be valuable.One table for Avondale and another one for Naim users
 
You need to phone Les at Avondale.

I don’t know if he’s currently making the preamplifier itself which is the horizontal board in the case with all the sockets and controls. The vertical boards are shown on the site mainly for people wanting to fit them in Naim preamplifiers. If you order them what you see is what you will get.

If you are not experienced with DIY electronics construction I wouldn’t recommend starting with a power supply because of the dangers of mains electricity. Neither would I recommend using the power supply in your Qudos amplifier. A suitable power supply would require a relatively low power transformer, a bridge rectifier, a reservoir capacitor and a dual regulator. I can definitely recommend the Avondale TPR4 for the regulator.
 
misterc6 said:
You need to phone Les at Avondale.

I don’t know if he’s currently making the preamplifier itself which is the horizontal board in the case with all the sockets and controls. The vertical boards are shown on the site mainly for people wanting to fit them in Naim preamplifiers. If you order them what you see is what you will get.

If you are not experienced with DIY electronics construction I wouldn’t recommend starting with a power supply because of the dangers of mains electricity. Neither would I recommend using the power supply in your Qudos amplifier. A suitable power supply would require a relatively low power transformer, a bridge rectifier, a reservoir capacitor and a dual regulator. I can definitely recommend the Avondale TPR4 for the regulator.
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Yes good advice Malcolm I was meaning the 821A's to be used in one of LesW horizontal boards its a neat solution if you only have a few inputs
The 821 boards need a 2 x 0-24V supply and as you stated the TPR4 makes the ideal reg.
I am using the 821A's myself but I needed 5 inputs so I built my own

IMG_2036 by Alan Towell, on Flickr

Alan
 
I'm using a UPC1237 Speaker Protection Board in a couple of builds. They have two grounds in and out (for L+R). In contrast, the standard Avondale way to wire the speaker ground is to come from the centre tap connection on the CAP6 directly to the ground speaker posts. I'm not sure if actually need to go through that protection board.

I don't know whether this UPC1237 shuts off only the (+) line, or whether it does the ground as well.

Should I continue to do it the Avondale way (going directly from the CAP6 CT to the negative speaker posts), and also add a line to the negative input on the protection board? Or do I actually need to go through the board?
 
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misterc6 said:
You need to phone Les at Avondale.

I don’t know if he’s currently making the preamplifier itself which is the horizontal board in the case with all the sockets and controls. The vertical boards are shown on the site mainly for people wanting to fit them in Naim preamplifiers. If you order them what you see is what you will get.

If you are not experienced with DIY electronics construction I wouldn’t recommend starting with a power supply because of the dangers of mains electricity. Neither would I recommend using the power supply in your Qudos amplifier. A suitable power supply would require a relatively low power transformer, a bridge rectifier, a reservoir capacitor and a dual regulator. I can definitely recommend the Avondale TPR4 for the regulator.
Click to expand...
I have done a few DIY stereo builds.
Thank you for the responses.Highly appreciated.
1. If i choose to go only for qudos module w/o the 862 preamp.
a)Analog o/p of BT connected to qudos i/p.( BT box like arcam miniblink connected to a ipad and volume is controlled via ipad) .Will it work ? I do understand that BT is limited in audio quality but i dont spin vinyl or CDs
b)If i plan to use a passive pot with qudos which alps pot do you recommend.
Note that I do recognize that using the 862+TPR4 (preamp+ regulator combo) extracts the best out of the qudos
 
I have been reading one of Doug Self’s book recently and looking at my Qudos boards.
I am not sure that the output transistor end of the feedback resistor is in the ideal place.
Clearly this verges on heretical and I am sure there must be a reason for the way the board is laid out the way it is.
It would not be difficult to do it Doug’s way.
Am I missing something?
And whilst I am doubting the way things are done.... Why do all earth returns go back to a good solid earth one end of the rectifier/capacitor/resistor/inductor board or the other but signal earth goes to the amplifier?
Cheers Andy.
 
andrewsutton said:
I have been reading one of Doug Self’s book recently and looking at my Qudos boards.
I am not sure that the output transistor end of the feedback resistor is in the ideal place.
Clearly this verges on heretical and I am sure there must be a reason for the way the board is laid out the way it is.
It would not be difficult to do it Doug’s way.
Am I missing something?
Cheers Andy.
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I suspect that Les W is the only one who can answer this, and he no longer posts on PFM.
 
Jonathan said:
Just curious what people are thinking of their qudos builds ... it certainly takes a little while to burn in ... I’m finding mine surprisingly bass heavy ... which is kind of neat as my speakers are doing things they never did before but I’m finding the general balance so far from other amplifiers I’ve had a BIT disconcerting. Maybe it’s the wet tantalums I used ... just curious what others are finding.
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Installed my boards this time last year. Took a while to burn in. HIFI was then boxed up from February until late this August. It sound amazing now. I'm thinking of the 300 boards next.
 
andrewsutton said:
I have been reading one of Doug Self’s book recently and looking at my Qudos boards.
I am not sure that the output transistor end of the feedback resistor is in the ideal place.
Clearly this verges on heretical and I am sure there must be a reason for the way the board is laid out the way it is.

Cheers Andy.
Click to expand...

Looks fine to me (3rd pic):
https://avondaleaudio.com/audiophil...-Power-Amplifier-Modules-per-pair/p/105991264

The feedback is taken "down stream" of where the emitter resistors join.
 
I've just deleted a post I made an hour or so ago in which I asked a couple of questions as a few minutes of Les W's time had me sorted, and all I can say is that I now have a couple of Qudos boards running in my amp.
Many have said they take a while to burn in so I'll leave them playing quietly for a couple of days, but even for a TOTAL beginner like me they are very easy to install.
I expect I'll be putting a couple of NAPA4 boards up for sale soon, so if anyone wants any, or can give me an idea of what they may be worth then please let me know!
 
steveinspain said:
I've just deleted a post I made an hour or so ago in which I asked a couple of questions as a few minutes of Les W's time had me sorted, and all I can say is that I now have a couple of Qudos boards running in my amp.
Many have said they take a while to burn in so I'll leave them playing quietly for a couple of days, but even for a TOTAL beginner like me they are very easy to install.
I expect I'll be putting a couple of NAPA4 boards up for sale soon, so if anyone wants any, or can give me an idea of what they may be worth then please let me know!
Click to expand...
Next step is the power boards!
 
Can anyone help or maybe just reassure me on this?
https://www.dropbox.com/s/49y5kurk5e29ge6/P1000697.JPG?dl=0
I finally got around to using HCR200s (thanks Graham). I left them set as they were with 44v output (52v input).
I took so long because I needed to change the QUDOS boards (Avondale built summer 2018) from T section heatsink to U section to fit. Desoldering always worries me because I have made a hash of it before. This time was better though, using a sucker and braid, practice I suppose. The promlem came screwing the bd237s back onto the heatsink, it was 3mm or so too high because the U section was thinner. It would have been easy if I had removed bd237 before remounting the output transistors. I ended up fiddling around and exposed the bd237s to more heat and mechanical stress than I would have liked. I didn't realise they were cheap and fairly standard, so I should just have got a new pair.
I wired up to test expecting problems, but now playing nicely with stunt speakers. The black U section heatsinks are only warm to touch.

My questions are:-
Testing the boards they seemed to want to run at about 100mA, increasing to 110-120mA only lasted for 5 minutes before drifting back to 100mA. DC offsets flickered around 2-3 mV. Although when I really cranked the current up the offset started to run away above 50mv on one occasion so I didn't try that again. Does that sound OK? Is bd237 responding to the heat and regulating the current? Real plug and play?
The other minor thing is. Have I taken the QUDOS 0v s far enough back?

Thanks in advance
 
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chrisn said:
Can anyone help or maybe just reassure me on this?
https://www.dropbox.com/s/49y5kurk5e29ge6/P1000697.JPG?dl=0
I finally got around to using HCR200s (thanks Graham). I left them set as they were with 44v output (52v input).
I took so long because I needed to change the QUDOS boards (Avondale built summer 2018) from T section heatsink to U section to fit. Desoldering always worries me because I have made a hash of it before. This time was better though, using a sucker and braid, practice I suppose. The promlem came screwing the bd237s back onto the heatsink, it was 3mm or so too high because the U section was thinner. It would have been easy if I had removed bd237 before remounting the output transistors. I ended up fiddling around and exposed the bd237s to more heat and mechanical stress than I would have liked. I didn't realise they were cheap and fairly standard, so I should just have got a new pair.
I wired up to test expecting problems, but now playing nicely with stunt speakers. The black U section heatsinks are only warm to touch.

My questions are:-
Testing the boards they seemed to want to run at about 100mA, increasing to 110-120mA only lasted for 5 minutes before drifting back to 100mA. DC offsets flickered around 2-3 mV. Although when I really cranked the current up the offset started to run away above 50mv on one occasion so I didn't try that again. Does that sound OK? Is bd237 responding to the heat and regulating the current? Real plug and play?
The other minor thing is. Have I taken the QUDOS 0v s far enough back?

Thanks in advance
Click to expand...

How long did you wait between 100mA and 120mA,? it takes some time for the 237 to 'catch up' and stabilize. Set to 100mA and leave for an hour (lid on) we know that's OK!)) but check every now and again that all is well. Then start upping the bias bit by bit say every 15mins. So try again but take some time and smaller increment to hit 120mA. It takes a while for the heat to saturate through the spreader.
 
Haven't posted on PFM for several years (under a new username now) but after a recent renewed interest in all things hi-fi I stumbled across these Qudos modules. Having a now 10 year old Avondale S100 amp with NCC200s I couldn't resist giving these a try...
Ordered a pair last Tuesday night, got an email Wednesday saying they were shipped and arrived Thursday - better than service from Amazon!
Fitted them on Saturday and now running in nicely. Initially I've set them to 100mA bias to confirm temperature is OK (and it is!) so will try tweaking them up after xmas.
But I can say already these are a great step up. Much cleaner, more natural presentation, effortless flow and more detail. Bass in particular is more detailed and defined and soundstage is deeper and more realistic. Bass guitars or double bass are a particular joy and easier to follow through complex passages as are voices which sound very natural now.
Really pleased with the improvement for relatively small outlay, which along with another value for money upgrade to source has really transformed my system.

I should add I did manage to blow the 5A fuse on the amp mains input during the setup for some reason, which gave me a scare, but everything seems ok now with bias and offset values all as expected. I did read on another thread about the recommendation to fit a speaker protection circuit to this amp which I think I will look into now!
 
I too had a 5A fuse blow in the extension lead I was using to test my amp. The 2.5 T fuse in the amp was fine, so reassured.
My latest is, the HCRs and Qudos heat spreaders and devices are idling at about 50 deg C (Pitking pyrometer). They are heat sinked internally in a vented case with the Qudos boards running at 120mA. So I think this is OK now.
Sound good, but just running in.
Probably do need to fit DC protection although not done so yet. I would need to mount the velleman on the back of the case with a separate cover as there is no space.
Thanks for the help
 
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