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-   -   Power supply for power amp. (http://www.diyaudio.com/forums/solid-state/253917-power-supply-power-amp.html)

Alan0354 1st April 2014 07:05 AM

Power supply for power amp.
 
Hi

I am new here and I am interested in building a SS power amp. I have been an EE for a long time and designed guitar electronics before, but I absolutely know nothing about audiophile electronics. My first question is about power supply.

1) What is the requirement of the power supply other than the obvious reason to supply power?

2) Is regulated power supply good for audiophile amp or you want to add some sag like in guitar amps?

I know this is kind of stupid question, in guitar amps, people don't like stiff supply, they want sag. So I don't want to take for granted one way or the other.

Thanks

bimo 1st April 2014 08:33 AM

Quote:

Originally Posted by Alan0354 (Post 3876036)
Hi

I am new here and I am interested in building a SS power amp. I have been an EE for a long time and designed guitar electronics before, but I absolutely know nothing about audiophile electronics. My first question is about power supply.

1) What is the requirement of the power supply other than the obvious reason to supply power?

2) Is regulated power supply good for audiophile amp or you want to add some sag like in guitar amps?

I know this is kind of stupid question, in guitar amps, people don't like stiff supply, they want sag. So I don't want to take for granted one way or the other.

Thanks

I believe there are no audiophile amplifier. Sometime amp with 0,1% THD called udiophile amp, but amp with 0,01% THD called hi-fi amp. Even, amp with 1% THD using exotic components can called audiophile.
I know THD is not only a parameter that determine the quality of an amplifier.
1) Use regular power supply for class AB. Use capacintance multiplier for class A. You should consider using cap multiplier on amp that using CFA topology.
2) No need using regulated power amp, it is not efficient. Better using capacitance multiplier.

Alan0354 1st April 2014 08:43 AM

Quote:

Originally Posted by bimo (Post 3876110)
I believe there are no audiophile amplifier. Sometime amp with 0,1% THD called udiophile amp, but amp with 0,01% THD called hi-fi amp. Even, amp with 1% THD using exotic components can called audiophile.
I know THD is not only a parameter that determine the quality of an amplifier.
1) Use regular power supply for class AB. Use capacintance multiplier for class A. You should consider using cap multiplier on amp that using CFA topology.
2) No need using regulated power amp, it is not efficient. Better using capacitance multiplier.

Thanks for the reply. What is CFA means?

Is capacitance multiplier using a pass transistor to buffer a filtered voltage using some resistor divider? It's is half way of a regulated supply and it's without negative feedback?

rephil 1st April 2014 10:26 AM

Quote:

Originally Posted by Alan0354 (Post 3876036)
Hi

I am new here and I am interested in building a SS power amp. I have been an EE for a long time and designed guitar electronics before, but I absolutely know nothing about audiophile electronics. My first question is about power supply.

1) What is the requirement of the power supply other than the obvious reason to supply power?

2) Is regulated power supply good for audiophile amp or you want to add some sag like in guitar amps?

I know this is kind of stupid question, in guitar amps, people don't like stiff supply, they want sag. So I don't want to take for granted one way or the other.

Thanks

Hi Alan 0354,

you could get many answers in getting and reading the following books :

Bob Cordell : Designing Audio Power Amplifiers, copyright 2011
Douglas Self : Audio Power Amplifier Design, sixth edition
Randy Slone : High-Power Audio Amplifier Construction Manual

IMHO this last one is the good one for somebody that wants to build his first amp without getting too much problems. The others are more advanced and also very, very precious books :wiz:, very well written, with plenty of informations !

Welcome here, don't forget to look at some of the best diy amp that have been proposed, like the SymAsym from Michael Bittner, or the SymAsym TO3 from Rudi Ratlos. There are many other very good amps you might build here, look around ...

I wish you to have great success :up: in your builds.

Best regards

rephil

Ian Finch 1st April 2014 10:40 AM

"Audiophile" describes the category of listener - a discerning type who strives for the impression of high quality - i.e. everything that sounds rich, engaging and detailed in the music programme. Despite protest from engineering and professional audio circles, this is a higher listening priority to them, than relying on faithfulness to the original signal input to be the the judge and jury of the most entertaining listening experience.

Put another way, it's subjectivism V precision as design goals.

If you design and build for either camp, you'll wind up with quite a different set of parts, construction priorities, materials and costs. In commercial products, the price differential can be staggering with the normal priorities of $/watt and least distortion often being totally reversed and clients comparing the component quality, fittings and feel of controls etc. This is a different world.

BTW, you are right about capacitance multipliers, often used to improve the PSRR of the front end of all types of linear amplifier.

CFA (we have lots of acronyms) means Current Feedback Amplifier as opposed to the regular designs which are Voltage feedback types, though this is a misnomer in the traditional distinction since the meaning of CFA now applied, derives from the IC Opamp terminology.
An example is the VSSA amplifier by Lazy Cat
http://obrazki.elektroda.pl/1401721700_1369759564.png

Alan0354 2nd April 2014 01:07 AM

Quote:

Originally Posted by Ian Finch (Post 3876207)
"Audiophile" describes the category of listener - a discerning type who strives for the impression of high quality - i.e. everything that sounds rich, engaging and detailed in the music programme. Despite protest from engineering and professional audio circles, this is a higher listening priority to them, than relying on faithfulness to the original signal input to be the the judge and jury of the most entertaining listening experience.

Put another way, it's subjectivism V precision as design goals.

If you design and build for either camp, you'll wind up with quite a different set of parts, construction priorities, materials and costs. In commercial products, the price differential can be staggering with the normal priorities of $/watt and least distortion often being totally reversed and clients comparing the component quality, fittings and feel of controls etc. This is a different world.

BTW, you are right about capacitance multipliers, often used to improve the PSRR of the front end of all types of linear amplifier.

CFA (we have lots of acronyms) means Current Feedback Amplifier as opposed to the regular designs which are Voltage feedback types, though this is a misnomer in the traditional distinction since the meaning of CFA now applied, derives from the IC Opamp terminology.
An example is the VSSA amplifier by Lazy Cat

Thanks
I guess I said audiophile to mean I am looking for higher quality than the normal quality. So far, I have an Acurus 200W per channel power amp and I consider it is the very low end of the audiophile. I really like the YBL amp that was over US $4000 back in 1998. I have a pair JM LAB top of the line Focal floor speaker, which I consider middle of the road audiophile speaker, no where close to the Utopia line. This is how I call it. I bought the Acurus amp when I had a pair of Kef that was about US $1000 at the time, so it is not matching to the JM Lab and it really showed when I A/B the YBL amp. So my goal is to build an amp that match the JM Lab, BUT not over the quality because it is only middle of the road. I don't want to build any exotic amp that I will run into the speaker not matching up to the amp.

As for the CFA amp you show, is the feedback is from the 1K to 47ohm from the output to the two emitter of the two input transistors?

Thanks

Alan0354 2nd April 2014 04:18 AM

I forgot, what is the advantage of using CFA vs VFA? I used a lot of CFA opamp for high speed signal, it definitely have advantage in high speed wide band application. Also the bandwidth is much less closed loop gain dependent. But for audio that is only to 20KHz, what is the advantage?

Ian Finch 2nd April 2014 05:40 AM

Quote:

Originally Posted by Alan0354 (Post 3877180)
....As for the CFA amp you show, is the feedback is from the 1K to 47ohm from the output to the two emitter of the two input transistors?...

Yes, that's correct, for both polarities.

CFA designs have speed advantages as you suggest but the interest is for subjective reasons. Many have believed for decades that incredible bandwidth leads to great improvements in subjective audio performance. Several postulations linking this to low IMD and TIM have been floating around just as long. There are massive threads and long, bitter professional exchanges over the subjects.

There is another view that the higher level of distortion in simple practical amplifiers like this one is "nicer" sounding than a similar performing VFA design typically produces. This can be measured and appreciated, as we read the enthusiastic comments in the construction threads. I can much more easily accept this reason, given the wide support of the DIYs themselves, over some years now.

Alan0354 2nd April 2014 05:47 AM

Quote:

Originally Posted by Ian Finch (Post 3877338)
Yes, that's correct, for both polarities.

CFA designs have speed advantages as you suggest but the interest is for subjective reasons. Many have believed for decades that incredible bandwidth leads to great improvements in subjective audio performance. Several postulations linking this to low IMD and TIM have been floating around just as long. There are massive threads and long, bitter professional exchanges over the subjects.

There is another view that the higher level of distortion in simple practical amplifiers like this one is "nicer" sounding than a similar performing VFA design typically produces. This can be measured and appreciated, as we read the enthusiastic comments in the construction threads. I can much more easily accept this reason, given the wide support of the DIYs themselves, over some years now.

Thanks, you lead me into another question: Do you need some amount of distortion for the amp to sound good? An amp that has no distortion sounds clinical?

Is IMD = intermodulation distortion? What is TIM?

ivanlukic 2nd April 2014 06:07 AM

Alan,

There is no need to design amp from scratch. There is some very nice amps that will cover your needs (JM Lab speakers) in the kit form like VFA LJM L12, or as ready-made CFA pcbs like Jason's version of VSSA.


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