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Chip Amps Amplifiers based on integrated circuits

Doug Selfs NE5532 Power Amp. Thoughts anyone !
Doug Selfs NE5532 Power Amp. Thoughts anyone !
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Old 1st October 2010, 01:11 PM   #31
steph_tsf is offline steph_tsf  Belgium
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Quote:
Originally Posted by Mooly View Post
And just going "subjective" for a moment... it would be interesting to compare an inverting configuration to eliminate common-mode issues.
At the moment I'm in a big doubt about this. Maybe we need to distinguish between the subjective results and between the 1ppm THD goal. It could be that the inverting version, not subjected to common-mode voltage, hence possibly delivering less than 1ppm distorsion, sounds ugly in comparison with a non-inverting version delivering around 4ppm THD. And we now have the Jan Meier design, featuring a middleman approach with a global feedback enduring moderate common-mode (the moderate gain differential amp) encompassing non-inverting buffers seeing a strong common-mode. On top of this, the Jan Meier distributed class A symmetric extension needs to be carefully assessed. Regarding the power supply, Douglas Self seems to be using a 300 VA transformer for two channels, hence 150 VA per channel. Isn't this overkill ? Say there are 64 opamps per channel, each eating a 5 mA quiescient current. This is only 320 mA in total hence 12 watt on a 36 V supply. Where do the remaining 120 watt go ? Step to 256 opamps per channel, and you get a 1.28 amp quiescent current. On a 36 V supply, this means 46 watt waste. That's not horrific. Consider each opamp being able to deliver 25mA current. With 256 opamps in parallel, you get 6.4 amps. This is decent. A class A design would sink alot more quiescent current.

Last edited by steph_tsf; 1st October 2010 at 01:22 PM.
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Old 1st October 2010, 01:16 PM   #32
Merlinb is offline Merlinb  United Kingdom
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In the Elektor article they said that the original design contained two electrolytic capacitors that were removed due to "issues". I couldn't work out whether the Elektor team had changed the design, or whether Self did it himself.

In the later article where they tested electrolytics for distortion they came to the same conclusions as Self; they don't cause distortion as long as you make them 'big' enough. But, that being the case, they still didn't say why the original circuit was changed! Did Elektor change it for no good reason, and prove itself guilty of audiophoolery?
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Old 1st October 2010, 01:18 PM   #33
Juergen Knoop is offline Juergen Knoop  Germany
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one difference is striving for efficiency...no waste of materials, labor, cost, energy etc.
The Self design features:
-high parts count
-high parts cost
-costly and space wasting PCB
-high quiescent power consumption
-low output power

it seems like being a nice case study or gimmick for a magazine like Elektor, no complains from me...yet I wouldn't expect it coming from Mr. Self
regards
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Old 1st October 2010, 01:24 PM   #34
AndrewT is offline AndrewT  Scotland
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Originally Posted by Juergen Knoop View Post
an amateur than from a professional or engineer.
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Can you explain ? What are the fundamental distinctions or criterions between professional, engineer and amateur ?
An Amateur is someone who is following a topic from which he/she does not earn a significant income and who may or may not have a great knowledge of the Topic.

A professional is one who earns a substantial proportion of his income from working with the Topic. He may know much or nothing or anywhere in between about the Topic.

An Engineer is qualified in the Topic or a branch of that same topic and has proved to his/her institution that they are competent in the topic and/or branch. The Engineer must also prove that he/she is following a course of continuous self development in the topic they are currently involved with.
These qualifications and self development demand that the Engineer knows what he/she is commenting on and that they will never deliberately mislead/defraud any one studying the topic and work for the good of the community they serve.
It is for these reasons that EUR ING and similar are held in some esteem in many countries, except the UK, where everyone that dabbles with a screwdriver can call themselves an "engineer" due to the lack of protected status for the "Engineer" title. c.f. "Doctor", "Architect", "Accountant" etc which are protected in the UK.
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Old 1st October 2010, 01:38 PM   #35
steph_tsf is offline steph_tsf  Belgium
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Quote:
Originally Posted by Merlinb View Post
In the Elektor article they said that the original design contained two electrolytic capacitors that were removed due to "issues". (...) Did Elektor change it for no good reason, and prove itself guilty of audiophoolery?
I have noted the strange local supply decoupling scheme, each NE5532 being decoupled with one capacitor connected between V+ and V- without touching the ground. However, in the Elektor article I can't find any info about two electrolytic capacitors needing to be removed. Can you provide a web link ?

Last edited by steph_tsf; 1st October 2010 at 01:40 PM.
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Old 1st October 2010, 01:46 PM   #36
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally Posted by steph_tsf View Post
I have noted the strange local supply decoupling scheme, each NE5532 being decoupled with one capacitor connected between V+ and V- without touching the ground.
That's standard practice.

Quote:
However, in the Elektor article I can't find any info about two electrolytic capacitors needing to be removed. Can you provide a web link ?
It was in the paper edition (I don't have a copy, I read it at the library). Somebody here will have a copy though, I expect.

Last edited by Merlinb; 1st October 2010 at 01:52 PM.
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Old 1st October 2010, 01:47 PM   #37
Joachim Gerhard is online now Joachim Gerhard  Germany
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I do that all the time and it works just fine. I use only one 0.1uF cap and add sometimes Elcaps of around 100uF from each supply to ground. Even very fast chips like the AD797 or the AD8065 worked well done that way.
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Old 1st October 2010, 01:53 PM   #38
steph_tsf is offline steph_tsf  Belgium
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Quote:
Originally Posted by Juergen Knoop View Post
The Self design features high parts count, high parts cost, costly and space wasting PCB, high quiescent power consumption, low output power. It seems like being a nice case study or gimmick for a magazine like Elektor, no complains from me...yet I wouldn't expect it coming from Mr. Self. Regards
Dead right ! Would be interesting to know the inside story, and why and how Elektor got involved in this NE5532 project knowing there is already a company specializing in the Blameless PCBs, connecting to Douglas Self. The Signal Transfer Company: Compact Blameless Power Amplifier
Over there, they feature the Compact Blameless amplifier, conservatively specified at 6ppm THD 1kHz 25 watt into 8 ohm, and measured using an Audio-Precision SYS-2702 at 4ppm THD 1kHz 25 watt into 8 ohm. Measurement bandwidth is 80 kHz. A 22 kHz BW would deliver a lower THD figure. This, using +24V and -24V supplies. They don't say if they need to be regulated for getting such low THD figure.

Last edited by steph_tsf; 1st October 2010 at 01:59 PM.
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Old 1st October 2010, 02:01 PM   #39
Merlinb is offline Merlinb  United Kingdom
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Quote:
Quote:
It seems like being a nice case study or gimmick for a magazine like Elektor, no complains from me...yet I wouldn't expect it coming from Mr. Self. Regards
Dead right !
Woah, chill out! It's just a novelty power amp project, not a conspiracy. Even Self has his fun side!
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Old 1st October 2010, 02:03 PM   #40
SY is offline SY  United States
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Doug Selfs NE5532 Power Amp. Thoughts anyone !
Quote:
Originally Posted by Juergen Knoop View Post
The Self design features:
-high parts count
-high parts cost
-costly and space wasting PCB
-high quiescent power consumption
-low output power
You've described 99% of high end audio.
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