Doug Selfs NE5532 Power Amp. Thoughts anyone !

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
While browsing the bookstands yesterday I saw this in Elektor,
The 5532 OpAmplifier, part 1 - ELEKTOR.com | Electronics: Microcontrollers Embedded Audio Digital Analogue Test Measurement

All the specs are in the link. Doug mentioned this amp in his new book but it was a surprise to see a "real developed version"

300ma quiescent... so how much output is available in class A I wonder when each individual device is a class ab stage.

Wonder how it sounds... this could be an opamp tweakers ultimate challenge, never mind using different devices, how about "mix and match".

I'd love to know how it sounds compared to say Dougs blameless amp.
 
My first question about this is - is it designed to run from a regulated supply? The specifications for the rails (+/-18.3V) look especially tight if not. Next would be - how did he manage to degrade the slew rate for the 5532 which is typically 9V/uS? Given the relatively modest output power, I think a bridged version using 128 chips is going to be a reasonable upgrade.:D
 
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steph_tsf

Member
2008-03-27 12:21 pm
I think Douglas Self started a quiet revolution with this seminal design. Seeing something like this from the "Blameless" creator caused a shock in my mind. Now, after one week or so, I'm realizing that Elektor made it available to the masses, for evaluation purposes.
As said above, this is a quiet revolution.
Imagine a small PCB having the same footprint as an Intel CPU. Using SMT quad-opamps. You then can apply an inexpensive CPU cooler. Imagine regulated switched-mode power supplies, kind of laptop power supplies. Imagine a bridged amp using a single 36V regulated switched-mode power supply. Imagine a 1ppm THD figure. Could it be we just entred the 1ppm Blameless gridAmp era ? More about this here : http://www.diyaudio.com/forums/chip-amps/174405-1ppm-gridamp.html#post2318498
 

wakibaki

Banned
2008-01-08 11:51 pm
My first question about this is - is it designed to run from a regulated supply?

The answer to this is yes, there's a circuit for a power supply in the .pdf article.

I wouldn't put too much reliance in the slew rate figure, the article may not have been very well proof-read, a little thing like that can easily slip through.

I'm delighted with the concept itself, it's novel and unconventional, it always pleases me when someone departs from the expected, and this is certainly not something I expected, or I would have tried it myself.

It's tempting to try building one, if there weren't plenty of amps around here already I'd be giving it a go. In fact it's likely I'll try some variation on this at some stage.

w
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
The slew rate puzzled me too... must have another gander at the circuit details.

This is one of those projects "where you just know you want too"... very intriguing.

The cost of using other opamps could be prohibitive though, 5532's are around £0.27 inc VAT for 50+ other devices around the £2 to £3 mark in similar quantities.
 

jcx

Member
2003-02-17 7:38 pm
..
Get a better op amp? apply heat sink, use multiloop topology...

...
Imagine a small PCB having the same footprint as an Intel CPU. Using SMT quad-opamps. You then can apply an inexpensive CPU cooler...
Imagine a 1 ppm THD figure...

6x TPA6120 dual op amps, rated 400 mA each op amp - parallel pairs biased against each other for Class A push-pull output (a little over 200 mA Class A bias for the headphone amp)

this is sized as a headphone amp so the outputs are cascaded for higher drive V (600 Ohm cans or the insanely low sensitivity AKG K1000)

TPA has exposed Cu power pad meant to be soldered to board for several W dissipation, by soldering "belly up" I contact them to the Cu slug of a pc cooler - running ~ 30 W quiescent total without fan

re arranging the I,V by flat paralleling you could get 2.4A, 15 V peak each channel for ~ 14 Wrms into 8 Ohms Class AB stereo

all up, both channels paralleled as a monoblock the shown components, heatsink should drive down to ~3 Ohms
 

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The answer to this is yes, there's a circuit for a power supply in the .pdf article.

I wouldn't put too much reliance in the slew rate figure, the article may not have been very well proof-read, a little thing like that can easily slip through.

I'm delighted with the concept itself, it's novel and unconventional, it always pleases me when someone departs from the expected, and this is certainly not something I expected, or I would have tried it myself.

It's tempting to try building one, if there weren't plenty of amps around here already I'd be giving it a go. In fact it's likely I'll try some variation on this at some stage.

w

I will be bringing the Elektor prototype to BAF. Hear for yourself!

As to proofreading, this unit has been extensively tested in the Elektor lab. Those specs are real-world measurements.

jan didden
 
Have you had chance to listen to it at home ? or at least in known surroundings where you could get a true impression of it's performance.

I had a short casual listening in the Elektor lab, but will do more testing before coming to BAF.
But it is interesting to hear what sounds like a good poweramp knowing that its just a bunch of opamps ;-)

jan didden