I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos fets from the
'80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r and ipl
acoustics tl4 speakers at the front and Ariston ( small black tubular things
that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound between
them ?

Pete

In article , Pete
wrote:
I am looking to build an amp for home theatre/hifi use. currently have
an amp using Hitachi's default design for mos fets from the '80's (
2sk49 2sj50 I think ). It is used with a tagmclaren av32r and ipl
acoustics tl4 speakers at the front and Ariston ( small black tubular
things that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar SAP15P and SAP15N 2SA1943 and 2SC5200 mosfet 2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound
between them ?

No need for WW3 since no meaningful answer is possible without knowing the
actual details of the designs which use them, and more info on the use. :-)

The main thing you could tell from the above is the max power / current /
voltage you might be able to drive. But if that is 'sufficient' for your
speakers and listening level that becomes irrelevant to the choice.

If the SAP devices are of the type that are darlingtons with the internal
thermal compensation diodes, then they may make thermal stability easier.
But I personally never liked darlingtons or power fets as I found they
tended to be prone to ultrasonic hooting. But YMMV. The SAP and mosfets can
make driving and biassing easier. That said I am old fashioned so am most
comfortable with using simple bipolar output devices.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Pete" wrote in message
...
I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos
fets from the '80's ( 2sk49 2sj50 I think ). It is used with a
tagmclaren av32r and ipl acoustics tl4 speakers at the front
and Ariston ( small black tubular things that sound quite
good ) at the back.

I plan using LM4702 but have three options for the output
stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in
sound between them ?

Pete





Why bother? The basic Hitachi design is as good as it gets. You
can improve things by building aproper regulated power supply for
it.

Mine, on Ambit boards, was dual mono with regulated PSUs designed
by John Lindsey Hood would do about 112W at the onset of limiting
into 8R and 224W at the onset of limiting into 4R. In 'normal'
use it barely got warm. It was as flat as a pancake (OK +/-
0.2dB) from about 12Hz to well over 100KHz, with maximum phase
error of about 2 deg at 12Hz and about 80KHz. Surely that's good
enough for anybody?


--
Woody

harrogate three at ntlworld dot com

"Pete" wrote in message
...
I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos fets from the
'80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r and ipl
acoustics tl4 speakers at the front and Ariston ( small black tubular
things that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound between
them ?

**Depends on implementation. The MOSFETs, of course, will always sound like
MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
devices are amongst the most advanced, lowest distortion output devices
developed. The SAP15s are easy and convenient to implement, but you run the
risk of using a device unique to a single manufacturer. Once that
manufacturer deletes them from the product line-up, you'll be screwed for
spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
Collectors coupled to the load.


--
Trevor Wilson
www.rageaudio.com.au

On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
wrote:


"Pete" wrote in message
...
I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos fets from the
'80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r and ipl
acoustics tl4 speakers at the front and Ariston ( small black tubular
things that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound between
them ?

**Depends on implementation. The MOSFETs, of course, will always sound like
MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
devices are amongst the most advanced, lowest distortion output devices
developed. The SAP15s are easy and convenient to implement, but you run the
risk of using a device unique to a single manufacturer. Once that
manufacturer deletes them from the product line-up, you'll be screwed for
spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
Collectors coupled to the load.

Compressed? You can of course produce a transfer characteristic to
back this up? As far as I am aware it is perfectly possible to produce
a MOSFET design without a trace of compression - which would of course
show up as an unimaginably huge distortion figure.

d

"Don Pearce" wrote in message
...
On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
wrote:


"Pete" wrote in message
.. .
I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos fets from
the
'80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r and
ipl
acoustics tl4 speakers at the front and Ariston ( small black tubular
things that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound
between
them ?

**Depends on implementation. The MOSFETs, of course, will always sound
like
MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
devices are amongst the most advanced, lowest distortion output devices
developed. The SAP15s are easy and convenient to implement, but you run
the
risk of using a device unique to a single manufacturer. Once that
manufacturer deletes them from the product line-up, you'll be screwed for
spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
Collectors coupled to the load.

Compressed?

**Yep.

You can of course produce a transfer characteristic to
back this up?

**Negative Tempco of gm.

As far as I am aware it is perfectly possible to produce
a MOSFET design without a trace of compression - which would of course
show up as an unimaginably huge distortion figure.

**What can I say? It what they sound like, when operating in low bias Class
A/B. When operating in high bias Class A/B or Class A, they show no signs of
compression. At low currents, they suck. Ask anyone who has taken the time
to do a double blind listen. I have. Many times. Shockers.


--
Trevor Wilson
www.rageaudio.com.au

On Wed, 4 Nov 2009 07:52:21 +1100, "Trevor Wilson"
wrote:


"Don Pearce" wrote in message
...
On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
wrote:


"Pete" wrote in message
. ..
I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos fets from
the
'80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r and
ipl
acoustics tl4 speakers at the front and Ariston ( small black tubular
things that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound
between
them ?

**Depends on implementation. The MOSFETs, of course, will always sound
like
MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
devices are amongst the most advanced, lowest distortion output devices
developed. The SAP15s are easy and convenient to implement, but you run
the
risk of using a device unique to a single manufacturer. Once that
manufacturer deletes them from the product line-up, you'll be screwed for
spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
Collectors coupled to the load.

Compressed?

**Yep.

You can of course produce a transfer characteristic to
back this up?

**Negative Tempco of gm.

As far as I am aware it is perfectly possible to produce
a MOSFET design without a trace of compression - which would of course
show up as an unimaginably huge distortion figure.

**What can I say? It what they sound like, when operating in low bias Class
A/B. When operating in high bias Class A/B or Class A, they show no signs of
compression. At low currents, they suck. Ask anyone who has taken the time
to do a double blind listen. I have. Many times. Shockers.

Negative tempco makes no difference. The gain of a power amplifier is
set by a pair of feedback resistors. Provided there is sufficient open
loop gain available (and we must assume there is) there can be no
compression. The system will perform at constant gain up to the
clipping point just like any amplifier.

I presume you are treating this as an interview for a job reviewing in
Stereophile?

d

"Don Pearce" wrote in message
...
On Wed, 4 Nov 2009 07:52:21 +1100, "Trevor Wilson"
wrote:


"Don Pearce" wrote in message
...
On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
wrote:


"Pete" wrote in message
.. .
I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos fets from
the
'80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r and
ipl
acoustics tl4 speakers at the front and Ariston ( small black tubular
things that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound
between
them ?

**Depends on implementation. The MOSFETs, of course, will always sound
like
MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
devices are amongst the most advanced, lowest distortion output devices
developed. The SAP15s are easy and convenient to implement, but you run
the
risk of using a device unique to a single manufacturer. Once that
manufacturer deletes them from the product line-up, you'll be screwed
for
spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
Collectors coupled to the load.

Compressed?

**Yep.

You can of course produce a transfer characteristic to
back this up?

**Negative Tempco of gm.

As far as I am aware it is perfectly possible to produce
a MOSFET design without a trace of compression - which would of course
show up as an unimaginably huge distortion figure.

**What can I say? It what they sound like, when operating in low bias
Class
A/B. When operating in high bias Class A/B or Class A, they show no signs
of
compression. At low currents, they suck. Ask anyone who has taken the time
to do a double blind listen. I have. Many times. Shockers.

Negative tempco makes no difference. The gain of a power amplifier is
set by a pair of feedback resistors. Provided there is sufficient open
loop gain available (and we must assume there is) there can be no
compression. The system will perform at constant gain up to the
clipping point just like any amplifier.

I presume you are treating this as an interview for a job reviewing in
Stereophile?

**I doubt that. I have been critical of Stereophile many times. I have also
performed several DBTs involving MOSFET amps and BJT amps. The first was way
back when Perreaux first burst onto the scene with their MOSFET amps. I
wondered at what I was hearing, so I set up a Phase Linear 400 amp for
comparison. The Phase Linear was determined (not just by me) to be much more
dynamic sounding. The only MOSFET amps I've heard which do not suffer this
problem are those manufactured by Pass Labs.

Tell me about your blind listening experiences with MOSFET amps and BJT
amps.


--
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson" wrote in
message


**Depends on implementation. The MOSFETs, of course, will
always sound like MOSFETs - dull, boring, undynamic and
compressed.

Sounds like more of the same "every amplifier sounds different religion that
Trevor has been entertaining many of with for years and years.

It wasn't that long ago that Trevor was making similar claims about power
amps with that well-known circuit design *failing* known as loop feedback.

So Trevor, which is worse, MOSFETs with or without loop feedback, versus
bipolars with or without loop feedback?

"Arny Krueger" wrote in message
...
"Trevor Wilson" wrote in
message


**Depends on implementation. The MOSFETs, of course, will
always sound like MOSFETs - dull, boring, undynamic and
compressed.

Sounds like more of the same "every amplifier sounds different religion
that Trevor has been entertaining many of with for years and years.

**I'll make it easy for you. Locate an old Phase Linear 400(b) and an early
Perreaux amp. Set up a DBT between the two and ask the listeners what
differences they feel they can hear (if any). Let me know what results you
find. Both amps are plentiful and cheap, so the test should be an easy one.
Both amps use ****-loads of global NFB, minimal bias current and primitive
topology so the only major differences are related to the output devices
used.

Take the time to listen for yourself. You might be surprised. I was.


--
Trevor Wilson
www.rageaudio.com.au