Audio (Lateral) MOSFET's for Class AB - Overview, P-Spice URL's

Audio (Lateral) MOSFET's for Class AB - Overview concerning Types and some URL's (also for various P-Spice Parameter)

Not listed here are the IRF/IRFP/IRL and IRF related types, because this types actually appropriate only for class-D and pure class-A, but not for class AB push pull with 100-200 mA idle current.

1) Hitachi/Renesas vintage versions
2SK133/2SJ48 (TO3)
2SK134/2SJ49 (TO3)
2SK135/2SJ50 (TO3)
2SK226/2SJ81 (H-PAK identical to 2SK133/2SJ48)
2SK227/2SJ82 (H-PAK identical to 2SK134/2SJ49)
2SK228/2SJ83 (H-PAK identical to 2SK135/2SJ50)
2SK175/2SJ55
2SK176/2SJ56
2SK343/2SJ99 (H-PAK)
2SK344/2SJ100 (H-PAK)
2SK345/2SJ101 (TO-220)
2SK346/2SJ102 (TO-220)
Datasheets
2SK134 pdf, 2SK134 description, 2SK134 datasheets, 2SK134 view ::: ALLDATASHEET :::
2SK134 Datasheet pdf - LOW FREQUENCY POWER AMPLIFIER - Hitachi Semiconductor
2SJ48 Datasheet pdf - LOW FREQUENCY POWER AMPLIFIER - Hitachi Semiconductor
2SK226 datasheet pdf datenblatt - Hitachi Semiconductor - SILICON N-CHANNEL ENHANCEMENT MOSFET ::: ALLDATASHEET :::
2SK176 datasheet and Application Note, Data Sheet, Circuit, PDF, Pinout | Datasheet Archive
2SJ56 2SJ55
2SK343 datasheet and Application Note, Data Sheet, Circuit, PDF, Pinout | Datasheet Archive
2SK345 datasheet and Application Note, Data Sheet, Circuit, PDF, Pinout | Datasheet Archive
Replacement/Substitude advices
ECX10P20 / ECX10N20 EXICON �iƒ‚�[ƒ‹ƒhƒ^ƒCƒv�j| ƒnƒCƒGƒ“ƒhƒI�[ƒfƒBƒI
http://www.diyaudio.com/forums/solid-state/40439-new-member-replacing-2sk133-135-2sj48-50-a.html
http://www.diyaudio.com/forums/solid-state/58719-sub-2sj50-2sk135.html
http://www.diyaudio.com/forums/swap-meet/8531-i-need-2sk135-2sj50.html
http://www.diyaudio.com/forums/solid-state/47475-substitute-2sj55-2sk175-vmos-fet-s.html (Swiss Physics Model 6)
http://www.diyaudio.com/forums/swap-meet/55180-wanted-2sk176-2sj56.html
http://www.diyaudio.com/forums/solid-state/147700-substitute-2sk134-2sj49-2sk176-2sj56.html
http://www.diyaudio.com/forums/solid-state/108565-musical-fidelity-p170-blown-transistors.html
http://www.diyaudio.com/forums/solid-state/81654-vintage-mosfets.html (MF, A370)
http://www.diyaudio.com/forums/solid-state/45715-myst-tma3-transistors-hitachi-2sk226-2sj82.html (Myst TMA3)
http://www.diyaudio.com/forums/parts/121984-need-2sk225-2sj81-fets-sugden-amp-help.html
http://www.diyaudio.com/forums/parts/43030-2sj81-2sk255-help-identify.html
http://www.diyaudio.com/forums/solid-state/4094-lateral-mosfet-replacements-2sk1058-hitachi.html
http://www.diyaudio.com/forums/solid-state/37813-lateral-structure-mosfet.html (2SK1058/BUZ900)
http://www.diyaudio.com/forums/parts/99732-looking-find-2sk343-2sj99-mosfet.html
http://www.diyaudio.com/forums/solid-state/1449-mosfet-replacement.html (2SK/2SJ - ECX cross ref - post #4)
Offers (for sale)
http://www.diyaudio.com/forums/swap-meet/91344-fs-2sk133.html
http://www.diyaudio.com/forums/swap...orsetrade-my-hitachi-laterals-your-irfps.html
http://www.diyaudio.com/forums/swap-meet/158227-original-2sk343-2sj99-mosfets-140v-8a-sale.html
http://www.diyaudio.com/forums/swap-meet/100410-opa549t-2sk343-2sj99-kef.html
http://www.diyaudio.com/forums/parts/147078-2sk343-2sj99-audio-mosfets-140v-8a.html
‰�”N‚Ì‚c‚bƒAƒ“ƒvƒp�[ƒc�iƒpƒ��[�E‚e‚d‚s�j
http://www.diyaudio.com/forums/solid-state/166647-where-find-those-mosfets.html
Hitachi HMA Series, Schematics
http://www.diyaudio.com/forums/solid-state/162763-hitach-lateral-mosfets-back-march-1978-a.html
Various Schematics and replacement hints
http://www.diyaudio.com/forums/solid-state/1188-2sj49-2sk134.html
6922 driving
http://www.diyaudio.com/forums/solid-state/35848-when-6922-married-2sj49-2sk134.html
2SK135 Serial Regulator schema
http://www.diyaudio.com/forums/parts/139615-fet-help-please-2sk135.html
Hafler MOSFET checker
http://www.diyaudio.com/forums/swap-meet/58888-mosfets-xl-280-p-230-etc-natched.html#post660932
Idle current values
http://www.diyaudio.com/forums/parts/13094-2sk135-2sj50.html
Albs DacMos and schema example
http://www.diyaudio.com/forums/solid-state/19448-amp-2sj56-2sk176.html
Ampslab IM60-LM60
http://www.diyaudio.com/forums/solid-state/127297-hitachi-mosfet-power-amplifier.html
How long it survived
http://www.diyaudio.com/forums/solid-state/111116-lateral-mosfet-torture.html (2SJ50/2SJ83)

2) Hitachi/Renesas newer versions
2SK1056/2SJ160 (TOP-3)
2SK1057/2SJ161 (TOP-3)
2SK1058/2SJ162 (TOP-3, most popular)
2SK2220/2SJ351 (TOP-3)
2SK2221/2SJ352 (TOP-3)
Datasheet
http://documentation.renesas.com/eng/products/transistor/rej03g0906_2sk1056ds.pdf
http://documentation.renesas.com/eng/products/transistor/rej03g1004_2sk2220ds.pdf
http://www.datasheetcatalog.org/datasheet/HitachiSemiconductor/mXwuzrz.pdf
Power MOSFETs for General Amplifier
Power MOSFETs for General Amplifier | Renesas Electronics America
Plantefeve MOS-FET 2 x 30 W
http://www.diyaudio.com/forums/solid-state/74080-30w-mosfet-plantefeve.html
Ideal quiescent current
http://www.diyaudio.com/forums/solid-state/31420-what-quiescent-current-hitachi-2sk1058-2sj162.html
Replacement/Substitude advices
http://www.diyaudio.com/forums/solid-state/4094-lateral-mosfet-replacements-2sk1058-hitachi.html
Difference between a lateral MOSFETS and vertical MOSFETS
http://www.diyaudio.com/forums/solid-state/162453-renesas-hitachi-2sk1058-2sj162-lateral-mosfet.html
Amp Project 2SK1058
http://www.diyaudio.com/forums/solid-state/170502-2sk1058-mosfet-amp.html
http://www.diyaudio.com/forums/solid-state/65789-poweramp-2sk1058-2sj162.html
http://www.diyaudio.com/forums/solid-state/28083-holtons-lateral-amp.html (2SK1058/2SJ62)
Aussie Amplifiers
LM4702 Driving a MOSFET Output Stage /LM49830TB Ultra High Fidelity Ref Design AN1645-AN1850
http://www.diyaudio.com/forums/solid-state/140715-lateral-mosfet-thermal-vs-others.html (2SK1058)

3) Toshiba
2SK405/2SJ415 (TOP-3)
2SK1529/2SJ200
2SK1530/2SJ201 (TO-3P(L)/2-21F1B)
2SK3497/2SJ618 (2-16C1B, new type, datasheet from 2009)
Datasheets
2SK405 pdf, 2SK405 description, 2SK405 datasheets, 2SK405 view ::: ALLDATASHEET :::
http://www.audiolabga.com/pdf/2SK1529.pdf
????????????????????????????????
http://www.schuro.de/Daten/Japanhalbleiter/2SK1530.pdf
????????????????????????????????
http://www.toshiba.com/taec/components2/Datasheet_Sync//74/2868.pdf
Replacement/Substitude advices
http://www.diyaudio.com/forums/solid-state/80455-2sk405-3sk1529-2sk1530.html
http://www.diyaudio.com/forums/parts/166715-2sk1530-2sj201.html
Offers
http://www.diyaudio.com/forums/parts/134239-wanted-2sk405-2sj115.html
http://www.diyaudio.com/forums/solid-state/131646-matched-2sk1530-2sj201.html
Alaskan Audio 1R1 schematic/PCB
http://www.diyaudio.com/forums/soli...sk1530-pair-mosfet-suitable-output-stage.html
Elektuur Crescendo
http://www.diyaudio.com/forums/solid-state/23116-whats-wrong-those-mosfets.html (2SK1530/2SJ201)
http://www.diyaudio.com/forums/solid-state/73460-crescendo-amp.html
http://www.diyaudio.com/forums/solid-state/58661-help-crescendo-me.html
Reporting about sonic quality
http://www.diyaudio.com/forums/solid-state/165116-best-audio-power-mosfet.html (2SK3911)
Testing (THD curves)
http://www.diyaudio.com/forums/soli...er-mosfets-2sk3497-2sj618-little-testing.html

4) Magnatec/Semelab
BUZ901/BUZ906 (vintage type)
BUZ900/BUZ905 (vintage type)
ALF08N16V/ALF08P16V (new)
ALF08N20V/ALF08P20V (new)
Datasheets
http://www.bonavolta.ch/hobby/files/BUZ900.pdf
Magnatec. ALFET Lateral MOSFETs
http://web.archive.org/web/20030205164841/http://www.magnatec-uk.co.uk/mosdata.shtml
http://www.semelab.com/pdf/acc.pdf
http://www.semelab.com/pdf/magnatec/ALF08N16V ALF08N20V.pdf
http://www.semelab.com/pdf/magnatec/ALF08P16V ALF08P20V.pdf
Inductance Value
http://www.diyaudio.com/forums/solid-state/82122-inductance-required-buz900-23k135.html
Basic Character discuss
http://www.diyaudio.com/forums/pass-labs/24658-buz900-series-mosfets.html
Tube driving amp
http://www.diyaudio.com/forums/solid-state/154795-hybrid-buz900.html
Best Audio MOSFET
http://www.diyaudio.com/forums/solid-state/165116-best-audio-power-mosfet.html
New Magnatec Line
http://www.diyaudio.com/forums/solid-state/154482-magnatecs-new-line-alfet.html
Offers
http://www.diyaudio.com/forums/swap-meet/162884-buz900-buz905-mosfets.html
http://www.diyaudio.com/forums/swap-meet/165661-i-look-buz901-buz906.html
http://www.diyaudio.com/forums/swap-meet/86556-fs-16-pieces-buz901-buz905.html
http://www.diyaudio.com/forums/swap-meet/70452-wanted-buz901-906p-mosfets.html
http://www.diyaudio.com/forums/solid-state/70383-us-source-buz901-906-a.html
http://www.diyaudio.com/forums/swap-meet/148182-buz901dp-lateral-mosfet-wanted.html
V-GS spread
http://www.diyaudio.com/forums/solid-state/148213-genuine-buz901-906-not.html
Experiences
http://www.diyaudio.com/forums/solid-state/18796-audio-mosfet-transistor.html (BUZ900DP BUZ901DP)
Comparsion
http://www.diyaudio.com/forums/solid-state/109183-exicon-10n16-10p16-vs-magnatec-buz900-905-a.html
Replacements
http://www.diyaudio.com/forums/parts/103278-possible-replacement-buz901p-buz905-6p.html

5) Exicon vintage versions
ECX10N16/ECX10P16
ECX10N20/ECX10P20
Datasheet
ECX10N20
ECX10P20
Replacements
ECX10P20 / ECX10N20 EXICON �iƒ‚�[ƒ‹ƒhƒ^ƒCƒv�j| ƒnƒCƒGƒ“ƒhƒI�[ƒfƒBƒI
2SK/2SJ - ECX cross ref - post #4
http://www.diyaudio.com/forums/solid-state/1449-mosfet-replacement.html
Various
http://www.diyaudio.com/forums/solid-state/133560-my-exicon-amp-project.html
http://www.diyaudio.com/forums/solid-state/137674-2a-classa-using-exicon-lateral.html
http://www.diyaudio.com/forums/solid-state/476-exicon-mosfet-eval-amps.html
http://www.diyaudio.com/forums/solid-state/1238-exicon-mosfets.html

6) First Generation Power MOSFET's (V-FET's)
http://www.diyaudio.com/forums/chip-amps/157618-vfet-hitachi-2sk77-2sk76-2sj26.html
http://www.diyaudio.com/forums/solid-state/74774-2sk77.html
http://www.diyaudio.com/forums/soli...to3-like-yamaha-2sk77-nec-2d363-overview.html
http://www.diyaudio.com/forums/soli...kin-2sj28-2sj18-2sk60-2sj26-2sk76-2sk180.html
http://www.diyaudio.com/forums/swap-meet/109664-wtb-2sk60-2sj18.html

7) URL's about P-Spice Parameter
if you have good models for the 2SK1058/2SJ162, then you have good models for the 2SK135/2SJ50
http://www.diyaudio.com/forums/solid-state/31131-hafler-dh-200-220-mods-22.html ( post #217)
http://www.diyaudio.com/forums/solid-state/162763-hitach-lateral-mosfets-back-march-1978-a.html
http://www.diyaudio.com/forums/parts/3230-p-spice-models-4-2sk1058-2sj162.html#post998418 (2SK1058 and 2SJ162)
http://www.diyaudio.com/forums/solid-state/4094-lateral-mosfet-replacements-2sk1058-hitachi-2.html
‚o‚r‚�‚‰‚ƒ‚…�i•]‰¿”Å�j‚Å“d’rŽ®Š®‘S‘Î�ÌŒ^ƒpƒ��[ƒAƒ“ƒv‚ðƒVƒ~ƒ…ƒŒ�[ƒg‚·‚é�@‚»‚Ì‚Q (Curves)
http://www.diyaudio.com/forums/solid-state/2969-spice-models-2.html#post26926 (post #16 2SK1058 and 2SJ162)
http://www.diyaudio.com/forums/solid-state/31338-exicon-10p20-10n20-pspice-model.html (post #1)
http://www.diyaudio.com/forums/parts/68163-spice-model-2sk1529.html#post2254795 (2SK1529/2SK1530
Models for Multisim Stuff you won (interactice design tools)
http://www.diyaudio.com/forums/soli...0-471-472-vs-mje340-350-better.html#post34113
http://www.diyaudio.com/forums/solid-state/28633-single-ended-mosfet-amp.html#post331880 (2SK1058 and 2SJ162)
http://www.diyaudio.com/forums/solid-state/74089-spice-models-exicon-mosfets.html
http://www.diyaudio.com/forums/solid-state/22756-looking-lateral-mosfet-spice-models.html
BUZ Spice models and data
http://www.diyaudio.com/forums/solid-state/2969-spice-models-2.html#post27088

8) Various URL's
http://www.diyaudio.com/forums/solid-state/70968-replace-irf-lateral-mosfet.html
http://www.diyaudio.com/forums/pass-labs/51643-lateral-vs-vertical-p-vs-n.html
http://www.diyaudio.com/forums/solid-state/17184-lateral-mosfets-why.html
http://www.diyaudio.com/forums/solid-state/28853-sound-vmosfet.html?perpage=10&pagenumber=1

Who knows more currently produced lateral MOSFET's for replace vintage types?
 
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I have only 2 pairs of EXICON lateral in my SPICE.
ECF10N20/ECF10P20 and ECF20N20/ECF20P20

I have done some testing using ECF20N20 in SPICE.
If I am to believe the models and results
the ECF20N20 is a fantastic lateral mosfet!
The distortion is very low in compare with HEXFET.
These ones are specially made for Audio.

An externally hosted image should be here but it was not working when we last tested it.

EXICON ECF20N20 is in TO3 and takes no less than 250 Watt

Read more: ECF20N20
Datasheet: http://www.profusionplc.com/images/data sheets/ecf20n20.pdf

:)
 
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thanks for this advice. I will try to get P-spice parameter by profusion.
Here the complete type spectrum from EXICON:
Lateral Mosfet
and here the RENESAS overview URL's from not obsolete types:
Renesas Electronics
Power MOSFETs for General Amplifier | Renesas Electronics

To Mr.Tiefbassuebertr,

I have bought 16 pairs of 2SJ50/2SK135 because of the attached mosfet amp which I owned in 1982. I want to make a new mosfet 100W amp for my ineffective speakers AR3a.
Do you have a better schematic to use than the attached.

Just for the record. I have Luxman L58A which sound very good , but suffers for the lack of power ( only one pair 49/134 Hitachi per channel).

Do you know anyone who could help me on this one? Have already asked this question here without luck.

Rgds
KJ DK
 

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find a better schematic.
556a as input
corrupted Mirror in the VAS load
Mirror without cascode
VAS directly driving output FETs

All these need attention.

I agree, Andrew .. but this would work if r9 was 6.8k-10k, low voltage PS or better input trannies. Still, proper drivers and a REAL balanced VAS would be more musical and durable. Here is an example of a commercial offering that does the same "cheap tricks" (HH amplifier co.) HH Amplification - Speakers

Schema below, "dirty mosfets done dirt cheap".
OS
 

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find a better schematic.
556a as input
corrupted Mirror in the VAS load
Mirror without cascode
VAS directly driving output FETs

All these need attention.

But AndrewT - you checked the schematic and found some things to be done better - this is why I am asking? I asked if anyone has a better schematic where it is possible to built a mosfet amplifier with 2SJ50/2SK135 and proper drivers. I have tried to change the 556a with 2SA970 on the attached circuit, but just on the computer.

I know that the schematic has some difficulties. - Could you or anyone else come up with a usefull and well sounding amplifier - a amplifier to be built by a not educated audio engineer??? as optician I have made several DC amplifiers with bipolar power transistors - and with luck.

I have tried with one Borberly mosfet amp, many components, may be too complicated that we looses the the clean sound??

A simple good circuit for double pair of 2SJ50/2SK135 is what I am asking for.
 
But AndrewT - you checked the schematic and found some things to be done better - this is why I am asking? I asked if anyone has a better schematic where it is possible to built a mosfet amplifier with 2SJ50/2SK135 and proper drivers. I have tried to change the 556a with 2SA970 on the attached circuit, but just on the computer.

I know that the schematic has some difficulties. - Could you or anyone else come up with a usefull and well sounding amplifier - a amplifier to be built by a not educated audio engineer??? as optician I have made several DC amplifiers with bipolar power transistors - and with luck.

I have tried with one Borberly mosfet amp, many components, may be too complicated that we looses the the clean sound??

A simple good circuit for double pair of 2SJ50/2SK135 is what I am asking for.

With the 2SJ50/2SK135 ANY BJT forum amp will work with a few mods. I happen to have a whole pile of lateral projects here: HFS /WEBSITE/PDF1/Electronics/Projects/Audio_amp/Mosfet_25-1kw/

In fact , download the "subzero" amp (similar to yours) by Dr. jagodic .. he is a college professor and all his designs are soundly based and tested. Most are very well received by the European DIY'ers.
OS
 
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With the 2SJ50/2SK135 ANY BJT forum amp will work with a few mods. I happen to have a whole pile of lateral projects here: HFS /WEBSITE/PDF1/Electronics/Projects/Audio_amp/Mosfet_25-1kw/

In fact , download the "subzero" amp (similar to yours) by Dr. jagodic .. he is a college professor and all his designs are soundly based and tested. Most are very well received by the European DIY'ers.
OS

Thank you - amplifiers designed like the "subzero" could be the one I was looking for. Have you tried the circuit? I assume that the "zero" could be built with two pairs instead of three ( power fets)?

It is quite some collection of power fet amplifiers you got there -

I have a very well sounding bipolar amp without global feedback - the amp "The End MKII" has in comparison with other amps "beaten" most of the so called "high end" amplifiers, exept some very expensive amps from Audio Research. The controll of the woofer from bipolar outputs seems better than from power fets, but the mid- and high midrange and frequences above 8-10kHz sounds better from power fets (I think) - I would like to try and add 2 or 3 pair of the Hitachi's in a good circuit, just to "see" if I can get almost the same woofer control from the fet's.

It is difficult to achieve everything within one amplifier!
 
Not listed here are the IRF/IRFP/IRL and IRF related types, because this types actually appropriate only for class-D and pure class-A, but not for class AB push pull with 100-200 mA idle current.
?

I find the IRFP240/9240 work well with low bias currents as low as 7mA.
Despite the irfp's being switching transistors they all sound very good in class AB amps.
 
I find the IRFP240/9240 work well with low bias currents as low as 7mA.
Despite the irfp's being switching transistors they all sound very good in class AB amps.
What? 7 mA idle current by this MOSFET's?
Interesting to know, how looks the input signal gate current of the IRFP240/9240 just below the clipping aera by complex usual load at the output (min. 2 ohms).
 
What? 7 mA idle current by this MOSFET's?
Interesting to know, how looks the input signal gate current of the IRFP240/9240 just below the clipping aera by complex usual load at the output (min. 2 ohms).

The input signal isnt important, its what is at the speaker and that looks great, no distortion into 4 ohms.

Peavey also have a low bias current approach and it works well for them too.
 
Audio (Lateral) MOSFET's for Class AB - Overview concerning Types and some URL's (also for various P-Spice Parameter)

Not listed here are the IRF/IRFP/IRL and IRF related types, because this types actually appropriate only for class-D and pure class-A, but not for class AB push pull with 100-200 mA idle current.

Who knows more currently produced lateral MOSFET's for replace vintage types?

Hi tiefbassuebertr,

Thanks for posting all of this very useful information about MOSFETs.

However, you are unfortunately repeating a common misconception that IRFP vertical MOSFETs are not suitable for class AB amplifiers. This is completely untrue and many people have built the amplifiers to prove it. They work perfectly well with 150mA bias per pair. There are pros and cons when comparing vertical to lateral MOSFETs, but in many ways the verticals are even better. This is all explained in Chapter 11 of my book, "Designing Audio Power Amplifiers".

I prefer vertical MOSFETs over laterals and among verticals I prefer the Toshiba parts, but they have been discontinued.

The MOSFET power amplifier with error correction that I published in 1983 used IRF HEXFETs and produced lass than 0.001% THD at full power at 20 kHz. Moreover, it had substantially better thermal stability than BJT amplifiers.

Although you may be misled by thinking that they were designed for switching applications, when properly applied they are every bit as linear as laterals (and far faster and capable of much higher current).

Cheers,
Bob
 
Hi tiefbassuebertr,
Thanks for posting all of this very useful information about MOSFETs.
However, you are unfortunately repeating a common misconception that IRFP vertical MOSFETs are not suitable for class AB amplifiers. This is completely untrue and many people have built the amplifiers to prove it. They work perfectly well with 150mA bias per pair. There are pros and cons when comparing vertical to lateral MOSFETs, but in many ways the verticals are even better. This is all explained in Chapter 11 of my book, "Designing Audio Power Amplifiers".
I prefer vertical MOSFETs over laterals and among verticals I prefer the Toshiba parts, but they have been discontinued.
The MOSFET power amplifier with error correction that I published in 1983 used IRF HEXFETs and produced lass than 0.001% THD at full power at 20 kHz.
http://www.cordellaudio.com/papers/MOSFET_Power_Amp.pdf
Moreover, it had substantially better thermal stability than BJT amplifiers.
Although you may be misled by thinking that they were designed for switching applications, when properly applied they are every bit as linear as laterals (and far faster and capable of much higher current).
Cheers,
Bob
I have heard and perform repair services of variuos of such amps, e. g. from the french brand "Cairn EZO". From the view of THD values you are right. Even by the use of only 5-10 mA the measuring results not really bad. But from the view of listening tests the difference between 100-150mA idle current to 500 mA idle current (like pure class A by medium levels) is much more larger than one might suspect the differences in the THD measurement, especially in the upper midrange/high frequency aera (voices e. g.).
And additional also larger than by the use of audio MOSFETs like Hitachi/Semelab and BjTs by compare of similar values for idle current.
From my audible experience IRFs in PP power follower output stages need at least 300-350mA idle current, if the amp was provided for full range applications (and not only for the lower frequency aera in bi-/multiamping systems).

My first assumption, the problem could be the absence of an additional driver stage for driving of the internal MOSFET gate caps has not been confirmed - unfortunately.
Perhaps the error correction by fig. 12 about
http://www.cordellaudio.com/papers/MOSFET_Power_Amp.pdf
could help to remove the observed audible effects, this I haven't check out until now.
 

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I have heard and perform repair services of variuos of such amps, e. g. from the french brand "Cairn EZO". From the view of THD values you are right. Even by the use of only 5-10 mA the measuring results not really bad. But from the view of listening tests the difference between 100-150mA idle current to 500 mA idle current (like pure class A by medium levels) is much more larger than one might suspect the differences in the THD measurement, especially in the upper midrange/high frequency aera (voices e. g.).
And additional also larger than by the use of audio MOSFETs like Hitachi/Semelab and BjTs by compare of similar values for idle current.
From my audible experience IRFs in PP power follower output stages need at least 300-350mA idle current, if the amp was provided for full range applications (and not only for the lower frequency aera in bi-/multiamping systems).

My first assumption, the problem could be the absence of an additional driver stage for driving of the internal MOSFET gate caps has not been confirmed - unfortunately.
Perhaps the error correction by fig. 12 about
http://www.cordellaudio.com/papers/MOSFET_Power_Amp.pdf
could help to remove the observed audible effects, this I haven't check out until now.

In every type of amplifier, be it vertical MOSFET, lateral MOSFET or BJT, one will always have bad examples of performance and sound that may tempt one to make generalizations about that technology, and this we have to be careful of. The amplifier for which you provided a circuit is a poor example of a MOSFET amplifier, and your speculation about the problem being a lack of a driver is probably right.

It is also true that MOSFETs like higher quiescent current, and this goes for both vertical and lateral MOSFETs, and is a result of transconductance droop.

With a single pair of IRFP240/9240 biased at 150mA without any special measures like EC, I regularly achieve less than 0.03% THD at 20 kHz at any power level and they sound marvelous.

Cheers,
Bob
 
Thanks for the great list of lateral Mosfets and links!

I was wondering has anybody experimented with higher voltage Mosfets that can handle 180V drain source voltage, such as, 2SK2221/2SJ352, ALF08N20V/ALF08P20V, the double die versions ALF16N20V/ALF16P20V, or BUZ series?

How do they compare in terms of parasitic oscillations, cross-over distortion and matching between the N and P pairs?

The 2SK2221/2SJ352 have internal protection zener diodes, which is a bonus.

Thank you,
Alexandru
 
I am still looking to Peavey's approach "low bias currents"
I have found this patent:
Smart voltage rail reduction audio amplifier - Patent # 6975172 - PatentGenius
http://www.pat2pdf.org/patents/pat6975172.pdf
but Peavey has earned more than 180 patents.

The patent mentioned looks somewhat like a class H or class G design. I did not see any reference to "low bias currents". It is always interesting to see approaches to achieving low distortion with low quiescent bias currents in class AB designs, if that is what you are referring to. Particularly with MOSFETs, transconductance droop at lower bias currents can be a source of distortion. That was the main reason that I introduced Error Correction to vertical MOSFET power amplifiers.

Cheers,
Bob