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Old 21st May 2007, 07:07 PM   #1
lineup is offline lineup  Sweden
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Thumbs up 10 Watt Single End, JFET input - Lateral N-MOSFET output

hi

Daniel Petrov from Sofia part of Bulgaria
is know at this forum widowmaker - profile
for his Death of Gainclone - DoGC amplifier
DoGC uses a clever and unusual output idea.
See separate topic, with discussion to try figure out how that one works ...


Today, I found another of his creations.
In a Bulgarian forum Daniel started a topic 2007-03-27 ( 27th of March )
Link:
Еднотактен клас А с полеваци

It is a 10 Watt Single End, JFET input - Lateral N-MOSFET output amplifier.
As can be seen in my attached schematic
it features very good, but still not hard-to-find transistors:

- 2SK389BL .... hifi low noise jfet for input - paralleled for 12 mA in first stage

- TL431, BC550C, BC639 for good Output Class A bias control and PSRR (supply insensitivity)

- Two 2SK1529 Lateral MOSFET for Output Stage

- No global feedback from output to input stage

-------------------------------------------------------------------------------------

2SK1529 is a Toshiba Lateral MOS of same series as 2SK1058.
But with a bit higher power:
- 2SK1058, rated 07A, 100Watt
- 2SK1529, rated 10A, 120 Watt
See amplabs.com POWER MOSFET data: http://ampslab.com/components_powermos.htm


Here below is is the attachment of this nice
- True Class A
- Single END
- ZERO global Feedback
- Toshiba Lateral MOSFET output
- 10 Watt
- Easy to build Power Amplifier
- Separated input-output power supply
- CLC filtered supply, a la Nelson Pass



Regards
lineup


-------------------------------------------------------------------------
PS. widowmaker, hope you do not mind I post this
and copy your schematic into www.diyaudio.com forum here
... Me and many other have to brush up our bulgarian language .. a bit
Attached Images
File Type: gif widowmaker_se-10w-classa-no-feedback-lateral-mosfet.gif (40.0 KB, 6247 views)
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Old 22nd May 2007, 01:13 AM   #2
Leolabs is offline Leolabs  Malaysia
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Why still output coupling caps????
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Old 22nd May 2007, 04:23 AM   #3
Minion is offline Minion  Canada
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And why only 10w outout but a 250vA Transformer, seems like a Big waste of power even for Class A....Seems like it might be a good space heater......

I"m no expert but it seems a few Changes to the design would probably greatly increase the output power, Like a Bipolar Medpower stage before the Output stage would actually give the Mosfets a good signal to drive the output stage, which is Probably why it is only 10w output and such a big Xformer......

I just finnished building a 30w Guitar amp (into 4 ohm or 18w into 8 ohms) and it uses a simple Opamp to drive a complemtry Pair of Small signal devices (BC550C/560C) which drive a Tip41/42 Pair of 6A devices and only uses a 50vA Transformer, and NO Output Caps, There shouldn"t be any output caps if useing a Dual Polarity PSU, Unless there is a Huge DC Offset, In which case the design should be looked at again as to eliminate any DC offset....

it seems Like a Pretty flawed design even for a space heater...But what the hell do I know.....


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Old 22nd May 2007, 06:09 AM   #4
AKSA is offline AKSA  Australia
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Lineup is absolutely right. This Daniel Petrov is very clever.

The answer to the criticisms lies in the fundamental law of physics; loosely explained, more of this means less of that.

If you want highest possible sound quality, Class A is generally the way to go. There are exceptions, but it sounds pretty damn good. Petrov's design is economical, but looks old fashioned, and is inefficient electrically. But before commenting on these all too obvious flaws, it's a great idea to build it - there is sufficient information there although the choke size is not specified - try 1H for the jfet supply and 25mH for the output supply.

I think once you have heard this, even with a dc blocking cap on the output, you will smile, click your fingers and wonder why you'd not given it a try years before.....

How do I know? I built something very like this (my own design, also with an electro at the output) about 12 years ago and it remains my benchmark. Nothing I've done since manages quite to pip it.

Cheers,

Hugh
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Old 22nd May 2007, 08:27 AM   #5
lineup is offline lineup  Sweden
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Quote:
Originally posted by Leolabs
Why still output coupling caps????
Quote:
Originally posted by AKSA

Lineup is absolutely right. This Daniel Petrov is very clever.

--------

How do I know? I built something very like this (my own design, also with an electro at the output) about 12 years ago and it remains my benchmark. Nothing I've done since manages quite to pip it.

Cheers,

Hugh

Thanks Leolabs Minion & AKSA.

1. Leolabs:

if you have only single supply 25V and output is at 12.5V something
I would NOT recommend attach speaker direct. ( will give 12.5 VDc across terminals )
If you mean, 'why doesn't he use dual supply?'
Well, that wouldn't make sense if you are after SE, Single END performance, 'sound'.

We can experiment with different quality and values OUTPUT CAPS.
I might try, for 6 Ohm LSP-ers
2x2.200uF in parallell or parallell two 4.700uF.

It should be noted, that Good Standard Electrolyts ( for example low impedance version )
of today,
are very superior in quality, than what was available at the time back
when these SE Amplifiers, Class A or Not, were the main stream.


-------------

2. Minion:

You are not sure you understand or know why to 'use only 10 Watt max output'.

True, it is not impressive in compare to 50-100 Watt rated.
For a young DiscJockey to use at his Disco-club, 10 watt no.

But here is more about not overdo, do more than we actually really NEED.
Class A can get TOO HOT


For a small to normal livingroom and non-disco, non-rave, non-techno music,
Maybe even Jazz, Blues, Soul or why not some interesting Classical pieces.
YES !!!
10 Watt into a normal LOUDspeaker ... is almost too much.
Even in the peaks of songs.


About Nelson Pass,
an old designer, his 'kitchen-table' effort and his 'First Watt' project:
He is using lower powers, 10 Watt and less and often in Class A output.
Info:
http://www.firstwatt.com/



--------------------------------

3. AKSA
.... Quote: .................................................. .................
Nothing I've done since manages quite to pip it.
Cheers,
Hugh

.................................................. ..................................

AKSA. Thanks for popping in to my new topic.
I know you know, so no need to inform you about this amp.

Your words are for others to think a bit about.

To Try to disagree with
.. or try validity of them by a real life setup, maybe
.. and so maybe have to agree!

Because you have long time experience.
Much longer than I have, eventhough we are same old age.

Regarding The designer of this amplifier, widowmaker - Petrov,
and the amplifier it self:
.... it takes one, to know one


-----------------------------------------------------------------------------------

This means,
.. in order to make a fair judge in a subject
.. you should at least have good knowledge in this field, subject
.. otherwise, you would need to ask some questions
... to get to know more, before making statements and be sure of things

---------------------
Example:
if a Priest in some Church, without any special knowledge,
is asked about what he thinks of Farmer John Smith, his breed of PIGS
and if they would be good to buy, if going into Pigs- farming,
this Priest should NOT try to say anything else
than ( what is not said often enough, by supposed experts ):
- I really do not know.
- You have to ask somebody better informed!


A priest is an authority, like doctor.
But their expertise are very much restricted to the field of their profession.

A farmer would know farming better,
although he is not, in our society, regarded authority
.. still in his profession, farming .. He Is The Real Autority to ASK


Regards
lineup
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Old 22nd May 2007, 08:33 AM   #6
Nordic is offline Nordic  South Africa
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Yep, Hugh, I also burried the "electrolytics on the output sounds bad" myth with some simple mosfet hybrid heaphone amps... I am yet to match that quality of SOUND in a loudspeaker driving amp...


If memory serves right, then the lower the impendance of the load, the larger the cap's value needs to get, in order not to form a knee in the audiable range...

being a perpetual beginner it took me while to figure out that there can be DC (silent) as well as AC (audiable) on the same signal wire... once that much is known the remedies are multiple... but, I for one will not have a problem with a good cap on the output.


I am not saying go and put them where there is no need... but don't expect them to suck the same way they did in the seventies....
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Old 22nd May 2007, 08:38 AM   #7
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Mmm,

me no likey the iron core coils at 2.8 amps bias level and the SK389 in parallel mode currently looks like a bit of a waste.
(Minion's post made a jolly moment)

2SK1529 no same series as 2SK1058 !
Both have gate, drain and source in the horizontal plane but the
Hitachi 2SK1058 is grandchild of 2SK135 and Toshiba 2SK1529 is afterbirth of 2SK405.
Rds-on of the Toshiba is somewhat lower, 0.83 ohm, 1 Ohm for the Hitachi's.
Not exactly sure about my memory database, but there's an image inside of the Aurex 2SK405(+2SJ) in the 100 watt Bower &Wilkins MPA-1 monaurals.

Nice MOSFET pictures
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Old 22nd May 2007, 12:01 PM   #8
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i like the design very much.....very nice indeed
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Old 22nd May 2007, 10:43 PM   #9
AKSA is offline AKSA  Australia
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Hi Lineup, Nordic,

This output coupling cap is interesting. What is often not realised is that speaker earth return current passes through filter caps on direct coupled amps with bipolar supplies, and that in this instance such currents must compete head on with charge pulses coming off the power supply rectifiers. This causes intermodulation, and particularly damages very low level signals which give the necessary spatial cues for good imaging.

A coupler does not suffer charge spikes, and if the supply is unipolar, the power supply caps pass earth return currents on one half cycle only. This does not completely eliminate the problem, but it does ameliorate it.

Another advantage of these coupling caps is the opportunity afforded to hot bias the tweeter/midrange cap on the crossover. You can connect these drivers direct to the output rail at a potential around half Vcc, and thus get the benefit of better, more linear operation for the mid and high frequencies. This is a huge advantage. Then the electrolytic coupler has only bass duties; and a quality electrolytic, with a polarising voltage across it, is actually extremely good sonically.

Cheers,

Hugh
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Old 9th June 2007, 06:54 AM   #10
lineup is offline lineup  Sweden
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Quote:
Originally posted by AKSA
Hi Lineup, Nordic,

This output coupling cap is interesting. What is often not realised is that speaker earth return current passes through filter caps on direct coupled amps with bipolar supplies, and that in this instance such currents must compete head on with charge pulses coming off the power supply rectifiers. This causes intermodulation, and particularly damages very low level signals which give the necessary spatial cues for good imaging.

A coupler does not suffer charge spikes, and if the supply is unipolar, the power supply caps pass earth return currents on one half cycle only. This does not completely eliminate the problem, but it does ameliorate it.

Another advantage of these coupling caps is the opportunity afforded to hot bias the tweeter/midrange cap on the crossover. You can connect these drivers direct to the output rail at a potential around half Vcc, and thus get the benefit of better, more linear operation for the mid and high frequencies. This is a huge advantage. Then the electrolytic coupler has only bass duties; and a quality electrolytic, with a polarising voltage across it, is actually extremely good sonically.

Cheers,

Hugh

Yeah, hugh.
you added some more benefits to using output caps

.. and in fact most any sound system uses 'Output Caps'
.. the difference is that
they are normally not called 'output caps'

They are loudspeakers crossover input caps.
Especially for higher frequency speaker drivers.
To block unwanted frequencies, to enter wrong element, woofers/tweeters,
and to keep things as constant as possible, as seen from amplifier out


I repeat:
Modern capacitors, has got SUCH high quality, we should use them more often.
I mean electrolytics are not like them used to be, back in the 60-ies / 70-ies.
Big Caps are a very simple & REALLY GOOD solution, many times.

An easy alternative to complicated 'stired up' jumbo mumbo to try to keep DC-levels in control.
And after all this DC-Coupling-Phreak-Show, a real show off in Volt DC 0.001, millivolts,
they would use a Crossover full of capacitance... anyway
Thinking they are smart

Some things are stupid and has not much of logic in it,
but some things are more Twisted & more Stupid than other things....


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