Arny Krueger wrote:

"Eeyore" wrote

In my case my I was comparing the H-H TPA 50 amplifier (
a fairly classic A/B design of its era and quite widely
used in pro-audio - including the BBC ) with ~ 0.1% THD
on the spec sheet with a friend's recently assembled kit
ampliifer using Crimson Elektrik modules. These used a
rather more 'state of the art' design with the then new
high speed Japanese output devices ( the H-H used
Motorola darlingtons ).

Lets just say the difference wasn't subtle !

The H-H sounded gritty by comparison to the much smoother
Crimson.

I had to search high and low to find much out about H-H brand equipment.
Apparently they were popular in the late 70s.

Before that in pro-audio.


I wouldn't try to generalize
very much related to just one sample of such an ancient obscure piece.

I had several. It was a classic textbook design btw. They certainly weren't
obscure over here. Everyday wokhorses in fact.

Graham

"Sander deWaal"

If you're referring to Hitachi 2SK135/2SJ50s, they are *vertical*
MOSFETs.


** ******** !!

They are LATERAL mosfets.

I have a nice stash of 2SK176 /2SJ56 son hand, plus some of the newer ones
by Semelab with numbers like BUZ901 and BUZ 906.




........ Phil

In article , Eeyore rabbitsfriendsandrel
writes


tony sayer wrote:

Arny Krueger writes
"Eeyore" wrote in

In my case my I was comparing the H-H TPA 50 amplifier (
a fairly classic A/B design of its era and quite widely
used in pro-audio - including the BBC ) with ~ 0.1% THD
on the spec sheet with a friend's recently assembled kit
ampliifer using Crimson Elektrik modules. These used a
rather more 'state of the art' design with the then new
high speed Japanese output devices ( the H-H used
Motorola darlingtons ).

Lets just say the difference wasn't subtle !

The H-H sounded gritty by comparison to the much smoother
Crimson.

I had to search high and low to find much out about H-H brand equipment.
Apparently they were popular in the late 70s. I wouldn't try to generalize
very much related to just one sample of such an ancient obscure piece.


I recall them and they did sound very rough. But they were mainly used
for PA and such applications......

Many were indeed used in rock PAs simply because they were few British high
power amplifiers of that era but far from exclusively. There was even a special
BBC version of the TPA25.

" There's also a photo of one of the many AIR studio consoles, in their Oxford
Street control rooms. I was interested in the rack of power amplifiers that you
can see to the right of the console. These silver faced units were HH
Electronic TPA100 power amps and what looks like three smaller TPA25 amps at
the bottom of the rack. "

http://www.auroraaudio.net/cgi-bin/d...format&om=348&
forum=DCForumID1

Graham


Amazing to see just how much vintage Neve gear is around these days and
still in service
--
Tony Sayer

On Tue, 17 Oct 2006 18:29:05 +0200, Sander deWaal
wrote:

Eeyore said:


What do you know about previous examples of this. I've just generally heard
that they hadn't been brilliantly succesful.


Technics used something like that, named class AA or somesuch.

Initially "New Class A". Later (90s) "Class AA".

Even after hours of operation, they were useful as champagne coolers.

The one I had didn't get hot, even though it was fitted with a
temperature sensitive fan (I could never imagine it being activated).
However, by their own figures Technics amps drew enormous current---up
to 330w for quite low power output,. Which means they only sound nice
until the power bill comes in!

In any case mine didn't sound as nice as most of the Marantz amps and
receivers I've had.

"Eeyore" wrote in
message
Scott Dorsey wrote:

tony sayer wrote:

Anyone ever made a good commercially viable class D
amp?...

Everyone and his brother has. A huge number of portable
devices, from iPods to laptops, are using class D stages
because of the low power consumption. You're also
starting to see them inside a lot of powered speakers.
Tripath and TI are some of the popular manufacturers.

I keep hearing good things about Hypex btw.

The big problem sonic with switchmode amps is excessive output impedance
within the audio range.

Hypex gets points for putting output impedance at 20 KHz on their spec
sheets, but I notice big "TBD" entries on the spec sheet for their
latest-greatest:

http://www.hypex.nl/newweb/docs/UcD700_datasheet.pdf

Doesn't seem to stop them from trying to sell them, though!

http://www.hypex.nl/classd/classd.pdf

gives about 0.1 ohm at 20 KHz, which corresponds to a damping factor of
about 80. This compares to 0.4 or so ohms for a typical traditional power
amp with output choke, so the Hypex is very good.

In article ,
Eeyore wrote:
In my case my I was comparing the H-H TPA 50 amplifier ( a fairly
classic A/B design of its era and quite widely used in pro-audio -
including the BBC ) with ~ 0.1% THD on the spec sheet with a friend's
recently assembled kit ampliifer using Crimson Elektrik modules. These
used a rather more 'state of the art' design with the then new high
speed Japanese output devices ( the H-H used Motorola darlingtons ).

Lets just say the difference wasn't subtle !

The H-H sounded gritty by comparison to the much smoother Crimson.

Agreed - they were never much good. The later MOSFET sounded better.

--
*Why don't sheep shrink when it rains?

Dave Plowman London SW
To e-mail, change noise into sound.

tony sayer wrote:

Eeyore writes
tony sayer wrote:
Arny Krueger writes
"Eeyore" wrote in

In my case my I was comparing the H-H TPA 50 amplifier (
a fairly classic A/B design of its era and quite widely
used in pro-audio - including the BBC ) with ~ 0.1% THD
on the spec sheet with a friend's recently assembled kit
ampliifer using Crimson Elektrik modules. These used a
rather more 'state of the art' design with the then new
high speed Japanese output devices ( the H-H used
Motorola darlingtons ).

Lets just say the difference wasn't subtle !

The H-H sounded gritty by comparison to the much smoother
Crimson.

I had to search high and low to find much out about H-H brand equipment.
Apparently they were popular in the late 70s. I wouldn't try to generalize
very much related to just one sample of such an ancient obscure piece.


I recall them and they did sound very rough. But they were mainly used
for PA and such applications......

Many were indeed used in rock PAs simply because they were few British high
power amplifiers of that era but far from exclusively. There was even a special
BBC version of the TPA25.

" There's also a photo of one of the many AIR studio consoles, in their Oxford
Street control rooms. I was interested in the rack of power amplifiers that you
can see to the right of the console. These silver faced units were HH
Electronic TPA100 power amps and what looks like three smaller TPA25 amps at
the bottom of the rack. "

http://www.auroraaudio.net/cgi-bin/d...format&om=348&
forum=DCForumID1

Graham


Amazing to see just how much vintage Neve gear is around these days and
still in service

There's an outfit dedicated to keeping them in service. I've heard they'll even build
new new old pcbs on request.

Graham

"Dave Plowman (News)" wrote:

In article ,
Eeyore wrote:
In my case my I was comparing the H-H TPA 50 amplifier ( a fairly
classic A/B design of its era and quite widely used in pro-audio -
including the BBC ) with ~ 0.1% THD on the spec sheet with a friend's
recently assembled kit ampliifer using Crimson Elektrik modules. These
used a rather more 'state of the art' design with the then new high
speed Japanese output devices ( the H-H used Motorola darlingtons ).

Lets just say the difference wasn't subtle !

The H-H sounded gritty by comparison to the much smoother Crimson.

Agreed - they were never much good. The later MOSFET sounded better.

Unquestionably so but it's tricky to make a truly bad amp with those Hitachi
devices. I have seen it done though. A piece of disco **** going by the
brand name of Lyonforge.

Graham

"Phil Allison" said:

"Sander deWaal"

If you're referring to Hitachi 2SK135/2SJ50s, they are *vertical*
MOSFETs.


** ******** !!

They are LATERAL mosfets.


You and Graham are correct, they are laterals.

My apologies.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

Dopey Plowborg said:

*Why don't sheep shrink when it rains?

How many hits did you do to come up with that one, Plowie?




--

"Christians have to ... work to make the world as loving, just, and supportive as is possible."
A. Krooger, Aug. 2006