'AK Mods' SC Class A 15W Amplifier

[Deleted]

Post by jeffc on 4 minutes ago

Laugh all you like.....

Repeat "No reputation, nothing to defend...."

Hi Jeff
I was being serious about the sound absorption.
My old Oppo 981 sounded better down on the carpet, but that wasn't really practical, so it now sits on a suitably sized piece of car sound absorbing material from Jaycar.
As for the other, there are quite a few reports that RF/EMI from digital amplifiers can get back through the mains and degrade performance of CD/DVD players etc.
Some even use balanced transformers etc. on the mains to try and overcome some of these problems.
Kind Regards
Alex

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Power switching at high frequencies is efficient and compact, both for a power supply and a power amplifier. But music is rarely loud and frequently quiet.

The switchers love being run at near to full power and their efficiency reduces with lower load factors.

Thus for music , particularly good quality , high dynamic range, the efficiency argument falls close to flat, though there are the missing heat sinks and mains transformers to consider.

But then we have to consider the large levels of RFI which corrupt the audio mains , and which is coupled back, conducted and radiated to the rest of the audio system.


So far, even bringing a powered-up unit into the house degrades my system significantly and numerous countermeasures are required to even partially address the problems.

These are mainly experienced as a loss in dynamic expression and in transparency, but also in some cases as an increase in grain and sibilance in the treble.

Presumably the designers do not hear such things and remain pleased with their full power and volumetric efficiency .


Martin Colloms

[Deleted]

Well it’s funny that you should mention your experiments with wooden equipment supports because I have wooden cones under all of my equipment (not the expensive RA ones). I have those in cups also to stop the slippy slidey effect without them in place.

And yes

Under front end equipment they do have a subtle effect on SQ.

I’ve tried quite a few in my time and found they do make a small difference.

It’s actually really nice to have the discussion on caps, cones and such like so long as we stick to how things sound to us. I’m not so convinced by the idea of universal goodness which IMHO starts with the circuit. But I think that it’s right to encourage a little experimenting where people can draw their own conclusions which are all good.

Are the Silmic’s neutral? Hell no but then what cap is? I’ve tried FM in the pre and did not like em much and the FC/Suntans sounded better but neutral nope. The Silmics offer the best approximation to the SQ that I’m looking for so far but I’ll be trying others.

IMHO caps and such like should be treated like seasoning on food. We add and subtract to get the flavour balance that we like. But of course there are those who don’t think components make any difference at all and those views need to be respected and taken as honestly given.

One thing is for sure.

We all have different systems and will most likely end up with different results (one would hope).

It’s all good to have the discussion Jeff so do feel free to post some of those projects that you are working on as they may be interesting to others.

No white coats needed.

Take care

[Deleted]

May 15, 2013 9:03:34 GMT @shaun said:

Well it’s funny that you should mention your experiments with wooden equipment supports because I have wooden cones under all of my equipment

When still in the trade I used to rate the Darumas very highly, out of what was available/punted back then.

Being a tight git I made my own version using glass wine stoppers and ball bearings, which I've posted about before, somewhere...

...found my old piccy



They've evolved slightly since then but seem to do the trick pretty well.
The biggest surprise was that the Darumas worked very favourably under stand-mount 'speakers.

[Deleted]

Some gear , such as CD/DVD players MAY benefit from their internal vibration due to the motor etc. being absorbed via some means such as carpet or special acoustic insulation, rather than just being decoupled from vibration of a cabinet etc. that is energised by nearby loudspeakers, or perhaps acts as a sounding board for the player's motor.
3M 2552 aluminium tape can help reduce that too if applied to certain areas of the player's case. Unfortunately, there is no universal solution.
Some even claim that sorbothane can suck the life out of a performance.
Regards
Alex

[Deleted]

Hi Chris

Those supports look interesting and fairly inexpensive.

I use the wood cones mostly because they look nice and allow me to have a standart build from one piece of kit to another.

www.ebay.co.uk/itm/Oak-cone-vibration-isolation-feet-for-Hi-Fi-equipment-Jumbo-size-3-/171027578555?pt=UK_AudioTVElectronics_HomeAudioHiFi_CDPlayerSeparates&hash=item27d209bebb

For my hifi rack I’ve been using one of thiese for years now,

www.avforums.com/forums/av-stands-cabinets-seating-furniture/1773605-ikea-lack-rack.html

it works really well and can be endleassly configured to accommodate even the biggest of amps. When I first built Alex’s PA I just popped to Ikea and picked up another table (light oak to match my speakers) and cut it to size.

Cheap, effective, take heavy loads and build wise much like Russ Andrews stuff.

take care

[Deleted]

Modifying the LS Protector PCB to give a front panel green LED.
This will give a visible indication of start up delay time, and absence will indicate the PCB is in Protect Mode.

[Deleted]

Hi Alex

I’ve been meaning to update my board for some time now but just not got around to it.

If I have time

I’ll rip my DCPRO board out and do the above mods.

Many thanks

take care

[Deleted]

Hi All

I consider myself Rectified and errr regulated

I’ve been having a play with the rectifier diodes and tank Caps over the last few days.

I made up a few experimental bridge boards and soldered in the MUR860 T0220 that I had to hand and connected them in place of the KPPC3502 that I’ve been using for rectification up to now.

I was expecting very little change in the sound but was surprised to find an increase in clarity and speed. So one illusion shattered and one to go.

To replace the 4700uf Rubycon PET’s I had been using

Well

I’ve been wanting to try some of these for some time now and after the rectifier experiment my interest was growing about the influence that these tank caps have.

www.hificollective.co.uk/components/mundorf_mlytic_ag.html

I went for 6800uf 40V

In the past I’ve tried various caps in the PSU of my tube builds since I started into DIY and TBH never heard much difference between them.

But

I’ve had the Mundorf’s cooking now for about 20 hours or so

Well first power up was a real disappointment when I was greeted by the dry sterile sound that came from my speakers. Lovely top end bur recessed mids and Mr Bass had left town. Horribly unmusical is the best way I’d describe that sound.

After 10 hours cooking things had improved a little but things still sounded metallic and bass light to my ears.

Now after a good forming session

Well it’s hi Mr Bass long time no see.

Things have gotten a whole lot better and now I have the full audio range back the sound is ultra clear with deep bass and clear mids. The speed and attack (PRAT) seem to be much better than I had before. The soundstage has filled out really nicely compared to the original flat as a turd sound that I had on first switch on. The top end is super clear which is most noticeable on cymbals etc. with all of the shimmer and none of the spit.

They have left the Rubycon PET sounding a little flat footed and vague by comparison.

Looking promising.

So pass me a slice of that delicious humble pie

I think I may need to eat some of that.

but as i say ''here to learn''

Take care

[Deleted]

Hi Shaun
Any further improvement with the Mundorf capacitors ? I had hoped that Soundlabs would have them, but although they list Mundorf capacitors, none are presently in stock.
ebay seems to have only low capacitance ones. It could be an interesting exercise to try different value film types in parallel, under the PCB with the Rubycons ?
I also noticed an improvement went I went from 35A 400V bridge rectifiers to the MUR diodes.
Regards
Alex

[Deleted]

Hi Alex

You could try here for mundorfs

www.soundlabsgroup.com.au/

They seem to only stock the poly’s but may be able to order some M-Lytics in for you as they are listed as a Mundorf distributer.

Ok the Mundorfs in my set up are sounding pretty good ATM with the most noticeable improvement being the cleaner top and Mids with the soundstage being wider. The sound seems to extend further out from the speakers outside edge. They really do make the Rubycons sound a little over warm and dirty by comparison. The bass is a little drier than the Rubycons but more tuneful and goes a little deeper. These are one clear sounding cap and still getting better although by a smaller degree.

Yes the change in focus and clarity that I heard with the MUR surprised me a little TBH it was totally unexpected.

Now I’m thinking of trying some Quad speed Soft recovery types but trying to find some without the huge Voltage drop is proving a little difficult.

I have my eye on some of these.

www.digikey.co.uk/product-detail/en/LQA06T300/596-1362-5-ND/2522195

But I’m not sure if I have enough juice in the tank to use them.

They look quite nice and are well liked over on PFM.

Take care

[Deleted]

Hi Shaun
It may not be a good idea to go to higher voltage drop types. I think they work here because of their low voltage drop and speed.
I got the impression from the Soundlabs site where I bought my original DACT CT2, that the caps will be available.
I also suspect that we may be able to mimic the extra performance of the Mundorf caps with carefully selected parallel film types.
I have remembered that years back with a SC 100W design using 8,000uF PSU electros, that parallel 1uF250V PHE Rifa caps made a very worthwhile improvement.
( Telstra used heaps of them at the time, that became redundant with technology changes)

Kind Regards
Alex

[Deleted]

I also suspect that we may be able to mimic the extra performance of the Mundorf caps with carefully selected parallel film types.

Read more: rockgrotto.proboards.com/thread/7461/ak-mods-class-15w-amplifier?page=54##ixzz2V0Nv7nxo


Hi Alex


Could be so but with 6.800UF I’d be looking at 6.8UF and then again with 0.68UF (for the larger tank cap value) but it may be worth experimenting with a little just to know for sure.


Take care

[Deleted]

Hi Shaun
Back then we also had heaps of the Rifa 2,2uF 250V caps that were used in equipment transmission bridges.
I tried them too, but 1uF seemed to hit the sweet spot . Remember too that electrolytes and capacitor construction techniques should be better now,
so we may not need to do too much fine tuning.

Kind Regards
Alex

[Deleted]

Hi All

I think that I’ve hit a sweet spot with my tinkering with Alex’s super Class A PA.

You know what I’m talking about.

The place where you stop needing to listen to the performance of the electronics and find yourself only listening to the music.

After some sifting through data sheets for some alternative diodes to try in place of my MUR860 (not G type) I found these.

www.onsemi.com/pub/Collateral/BYW80-D.PDF

ON BYW80-200 8A 200V ultra-fast soft recovery with a low foward voltage drop

I must say that these are sounding really good and the music has taken on a nice top to bottom clarity without any emphasis on one part or other of the music. The top end seems even more extended and sweet compared to the MUR which were no slouch in that regard.

The whole thing is sounding great and just like music should sound IMHO, in my set up, to my ears.

Take care

[Deleted]

Hi Shaun
Interesting. I am about to pull the plug for the night, but I will look further into these in the morning.
Kind Regards
Alex

[Deleted]

Hi Shaun,

ON BYW80-200 8A 200V ultra-fast soft recovery with a low foward voltage drop

ON Semi show these as Fast recovery but not soft recovery?



MSR860: 600 V, 8 A Soft Recovery Rectifier is ON Semi's soft recovery diode........... codes all start with MSR for soft recovery versions.

The diodes in my PSU are 
VISHAY GENERAL SEMICONDUCTOR - SBYV28-200-E3/54 - DIODE, SOFT RECOVERY, 3.5A

they are slightly faster  at 20ns.................than the BYW80 at 35ns
Regards,
Alan

[Deleted]

Jun 4, 2013 13:24:44 GMT drymdrum said:

Hi Shaun,

ON BYW80-200 8A 200V ultra-fast soft recovery with a low foward voltage drop

ON Semi show these as Fast recovery but not soft recovery?



MSR860: 600 V, 8 A Soft Recovery Rectifier is ON Semi's soft recovery diode........... codes all start with MSR for soft recovery versions.

The diodes in my PSU are 
VISHAY GENERAL SEMICONDUCTOR - SBYV28-200-E3/54 - DIODE, SOFT RECOVERY, 3.5A

they are slightly faster  at 20ns.................than the BYW80 at 35ns
Regards,
Alan

then they must be miss-advertising them here

www.hificollective.co.uk/components/diodes.html

i'll have to write to him and complain ::)as i took his word on the matter.

speed of switching at those speeds ain't everything and these do sound better in my set up.

take care

[Deleted]

Hi Shaun,
I'm pleased that you find the diodes you have used increasing your audio pleasure.
We had a discussion about rectifier diodes way back when we were sussing out the PSU for the AK 15 Watt
and decided to use the SBYV28. The whole point about using fast soft recovery diodes is made in the 
quote below which is from...............
The Circuit Designer's Companion
By Peter Wilson.............................




With regard to  the diodes at the  link you posted...................
I had a look at the manufacturer PDF files for all diodes listed as soft recovery at that link.....................
None of the data sheets state that they are soft recovery but they do say they are very fast.
Regards,

Alan 

[PinkFloyd]

Jun 4, 2013 19:03:47 GMT drymdrum said:

Hi Shaun,
I'm pleased that you find the diodes you have used increasing your audio pleasure.
We had a discussion about rectifier diodes way back when we were sussing out the PSU for the AK 15 Watt
and decided to use the SBYV28. The whole point about using fast soft recovery diodes is made in the 
quote below which is from...............
The Circuit Designer's Companion
By Peter Wilson.............................




With regard to  the diodes at the  link you posted...................
I had a look at the manufacturer PDF files for all diodes listed as soft recovery at that link.....................
None of the data sheets state that they are soft recovery but they do say they are very fast.
Regards,

Alan 

Hi Alan,

They are supersoft if you wrap them in marshmallows.... a bit crunchy to the bite but a supersoft coating

[PinkFloyd]

Prety much "headlines" as soft recovery Alan......

www.vishay.com/docs/88737/88737.pdf

[Deleted]

Hi Mike,
those are the diodes Alex pointed us to in our  quest centred around updating the original SC 15Watt PSU.
Without looking back I think they will be a suggested part of the BOM although there were others being used at the time.
The SBYV28 is what I have used  as they are certainly SOFT RECOVERY and FAST 

Shaun is currently using ON BYW80-200 8A 200V Fast Rectifier Diodes obtained from the link he gave in his post regarding liking their sound.
Having looked at the Manu' specs nowhere do they say SOFT RECOVERY.....................nor are any of the diodes listed on that link. 

After some sifting through data sheets for some alternative diodes to try in place of my MUR860 (not G type) I found these.

www.onsemi.com/pub/Collateral/BYW80-D.PDF

ON BYW80-200 8A 200V ultra-fast soft recovery with a low foward voltage drop

I must say that these are sounding really good and the music has taken on a nice top to bottom clarity without any emphasis on one part or other of the music. The top end seems even more extended and sweet compared to the MUR which were no slouch in that regard.

Regards,
Alan

[PinkFloyd]

Can we compromise and say they are semi soft? Much like a mint humbug..... hard at first but soft once you get through the hard candy coating. If you want to go HARDCORE soft then it's marshmallow all the way..... if you like a bit of a "hard / soft" transition then look no further than an Everton Mint

[Deleted]

Everton Mints bad for the teeth...................Marshmallow for toothless gums or perhaps a little Turkish Delight. 

[Deleted]

Last night I had a look for the BYW80-200 on element 14 and they came back as MUR820G .
I had some SBYV28-10 but didn't use them as the PCB holes would have needed enlarging.
Perhaps ultra fast recovery types , although generating RF, have the resulting garbage pushed up higher into the spectrum where it has less effect on some audio devices?
With DC supplies of only + and -20V, the resulting RF generated will be much less than when these diodes are used in higher voltage supplies.
Regards
Alex

[Deleted]

au.element14.com/on-semiconductor/byw80-200g/diode-rectifier-8a-200v-to-220b/dp/2101175