Hi Jens,
No, I would NEVER delete them. They are a necessary part of the stability matrix for any PP AB SS amp, and deleting them because the amp is passing only low frequencies does not preclude instability under certain high signal conditions.
HOWEVER, at low frequencies, and indeed at audio frequencies, I would defy anyone to hear a difference. They measure just 1.4uH, which is well below the 2uH thought to be of influence at frequencies beyond about 15KHz.
You mention damping factor, which is interesting. There is absolutely no point in going beyond about 100 for domestic high end. IN truth, I've found that too high a damping factor tends to reduce reverberation, leading to a very dry, uninvolving bass without the subtle loose effect that can really be very satisfying to listen to. I try for a damping factor in the 50-200 range, no higher.
Hope this helps!
Hugh
No, I would NEVER delete them. They are a necessary part of the stability matrix for any PP AB SS amp, and deleting them because the amp is passing only low frequencies does not preclude instability under certain high signal conditions.
HOWEVER, at low frequencies, and indeed at audio frequencies, I would defy anyone to hear a difference. They measure just 1.4uH, which is well below the 2uH thought to be of influence at frequencies beyond about 15KHz.
You mention damping factor, which is interesting. There is absolutely no point in going beyond about 100 for domestic high end. IN truth, I've found that too high a damping factor tends to reduce reverberation, leading to a very dry, uninvolving bass without the subtle loose effect that can really be very satisfying to listen to. I try for a damping factor in the 50-200 range, no higher.
Hope this helps!
Hugh
Hi Hugh,
I am not quite sure I agree about the reverberation part. What you are saying is actually that the speaker should get a bit out of control. I don't believe this should happen ...
When measuring dampening factor, is that done with or without the inductor for your amps?
Cheers,
Jens
Jens,
I won't get into debates here!! What I say is based entirely on empirical experience, and yours may well differ.... the old YMMV adage applies, of course.
PMA in the SS section recently did analysis on this very issue, which I suspect you've read. He measured 0.02dB increase in level at 20KHz with a simulated speaker load, using simulation certainly, but I think he corroborated his results empirically as well. I measure DF with the inductor in place, however.
This is NOT audible, Jens, and as some wag responded, it is not worth possible stability issues by omitting this component. As you can see, I'm deeply conservative in my design approach; this is because most courageous experiments end in tears, and I'm not happy about the risk of blowing up other people's speakers!!
Ciao,
Hugh
I won't get into debates here!! What I say is based entirely on empirical experience, and yours may well differ.... the old YMMV adage applies, of course.
PMA in the SS section recently did analysis on this very issue, which I suspect you've read. He measured 0.02dB increase in level at 20KHz with a simulated speaker load, using simulation certainly, but I think he corroborated his results empirically as well. I measure DF with the inductor in place, however.
This is NOT audible, Jens, and as some wag responded, it is not worth possible stability issues by omitting this component. As you can see, I'm deeply conservative in my design approach; this is because most courageous experiments end in tears, and I'm not happy about the risk of blowing up other people's speakers!!
Ciao,
Hugh
What! No debates?
I thought that was what this forum was for! However, I absolutely agree about the stability issues, and I believe the inductor is by and large inaudible. In fact, it may even make the amp sound better - exactly because it is more stable ....
One thing, though. Over the years I have tested many different types of inductors and can vouch for the fact that they do not sound the same at all. From listening tests, my preference is very tightly rolled foil inductors, as these have a much more open sound than traditional inductors. They also have considerably less resistance, although I do not think the latter is an issue in this connection.
So, I might try foil inductors instead of the standard inductors you supply with the N70 and N100 kits. What are the exact values of the inductors used?
Cheers,
Jens
Output Inductors
Hi Jens,
No problem, I do like a debate, as long as it's civil, unlike many other forums where differences of opinion all too often turn into slanging matches!
Foil is fine.....
You should wind for a value of 1.4uH, nice and small, well below the unwritten 2uH 'limit'.
You may hear a difference, but that may depend on how much work you have to put into the inductor!!
Cheers,
Hugh
Hi Jens,
No problem, I do like a debate, as long as it's civil, unlike many other forums where differences of opinion all too often turn into slanging matches!
Foil is fine.....
You should wind for a value of 1.4uH, nice and small, well below the unwritten 2uH 'limit'.
You may hear a difference, but that may depend on how much work you have to put into the inductor!!
Cheers,
Hugh
Hi Jens,
No problem, I do like a debate, as long as it's civil, unlike many other forums where differences of opinion all too often turn into slanging matches!
Foil is fine.....
You should wind for a value of 1.4uH, nice and small, well below the unwritten 2uH 'limit'.
You may hear a difference, but that may depend on how much work you have to put into the inductor!!
Cheers,
Hugh
Hi Hugh,
Hmmm - standard values for the foil inductors are 1.2 uH and 1.5 mH. If need be, could I go as low as 1.2 mH?
I have quite a few foil inductors lying around from speaker development projects, so I may even have a couple of 1.4 uHs ...
If and when I get the time to try this out, I will post my findings here
Cheers,
Jens
Remember we are talking about uH and not mH as normally used on crossovers.
1.4uH is 0.0014mH which is not standard in foils as far as I know.
Best to wind your own. Look at item 26 on this page for some winding details.
Baby AKSA contruction
1.4uH is 0.0014mH which is not standard in foils as far as I know.
Best to wind your own. Look at item 26 on this page for some winding details.
Baby AKSA contruction
Thanks, Rabbitz!
I entirely overlooked that. No, not standard on foils, but I can order the correct size
Cheers,
Jens
Hi Hugh,
Glad you safely made it back home. 475 miles non-stop is a good days work.
I usually don't have much to say concerning amp spec's but for my ears DF is a critical spec. Especially if you are using single driver speakers. The sonic difference is readily audible. Whether or not you like the difference is up to you but for me, less is more. Point is, your NAKSA could very well be the the solid state amp of choice for single driver speakers. Any customers here in Ohio or Michigan where I could put a ear on your NAKSA??
Tell me Hugh, what was the DF on your AKSA 55??
Cheers,
Brad Kizer
Brad,
Driving in Oz is very easy, almost no traffic intercity, most people sensibly travel by air!
The AKSA 55 was higher, typically around 120 or so. But the Lifeforce was much lower, around the 60 mark. The NAKSA is also low, under 100. I don't believe that high DF makes a better amp.
Of course, for a given output stage design, the DF is pretty much a function of loop gain. The lower it is, and the Lifeforce was only 16dB, the lower is the DF. The Maya, my flagship amp, has a DF even lower than the the Lifeforce, and sounds absolutely wonderful, with cavernous bass control.
I don't unfortunately have anyone in Ohio or Michigan with a NAKSA; indeed, the US has almost dropped off the radar due to the GFC and the falling dollar. It is most unfortunate, but I'm selling well in Oz for a pleasant change.
Cheers,
Hugh
Driving in Oz is very easy, almost no traffic intercity, most people sensibly travel by air!
The AKSA 55 was higher, typically around 120 or so. But the Lifeforce was much lower, around the 60 mark. The NAKSA is also low, under 100. I don't believe that high DF makes a better amp.
Of course, for a given output stage design, the DF is pretty much a function of loop gain. The lower it is, and the Lifeforce was only 16dB, the lower is the DF. The Maya, my flagship amp, has a DF even lower than the the Lifeforce, and sounds absolutely wonderful, with cavernous bass control.
I don't unfortunately have anyone in Ohio or Michigan with a NAKSA; indeed, the US has almost dropped off the radar due to the GFC and the falling dollar. It is most unfortunate, but I'm selling well in Oz for a pleasant change.
Cheers,
Hugh
Hello
About damping factor
I was doing a forums surfing and reading about thd and amps design. And I found a good explanation from Graham Maynard about damping factor, his explanation and some other posts in this thread should help to support Hugh's post about the need of a low damping factor for a better sound in a amp:
http://www.diyaudio.com/forums/solid-state/57995-many-faces-distortion-9.html#post665671
Bye
Gaetan
About damping factor
I was doing a forums surfing and reading about thd and amps design. And I found a good explanation from Graham Maynard about damping factor, his explanation and some other posts in this thread should help to support Hugh's post about the need of a low damping factor for a better sound in a amp:
http://www.diyaudio.com/forums/solid-state/57995-many-faces-distortion-9.html#post665671
Bye
Gaetan
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