double vs diferential

[Praise!]

As far as my knowledge goes, symmetrical differential
(mirror image) topology cancels the second order
harmonic distortion while providing symmetrical high
slewing. A standard half symmetrical topology may
offer more open loop gain (hence less distortion)
but in practice, the inablity to slew the other way
round coupled with stray capacitance .........
I used to ponder which is better. For me, now,
I go for mirror image one.
The double differential topology is actually originated
from Hitachi.....

James
Praise! Audio 😉

 

[jewilson]

double differential topology

This topology has been around since the the 70's. Great American Sound amps or the Ampzilla.

 

[john curl]

Complementary differential or Double differential was first used by Jon Iverson of Electroresearch; and me, while I was employed by Ampex in 1968, independently of each other. Later, Southwest Technical Products published and advertised the first commercial amps using this concept. GAS came out a few years later.

 

[jewilson]

Complementary differential or Double differential

Some of the old Ampex equipment was very well built. Anyway, I new that topology had been around for some time. I though the main issue with it was matching the hfe of the pairs.

So John do you still you use Complementary differential or Double differential topology in your new designs. Of course it would be better with fet's and a couple of cascode pairs.

 

[john curl]

I have used jfets rather than bipolar transistors for the last 30 years. All the Levinson stuff was jfet input, usually complementary differential jfet.

 

[jewilson]

JC2

Many year ago I built a JC2 preamp, it must have been in 1978. The schematic was published in TAA. I was very good for the time, but no kmac. If I remember you used J110 on the inputs J175 and J212 in the outputs.

 

[Praise!]

Where do you source your devices?

I have used jfets rather than bipolar transistors for the last 30 years. All the Levinson stuff was jfet input, usually complementary differential jfet.

Hi John,

What a previliage to hear from you! My favourite
devices are JFETs as well. As anybody knows,
it is very hard to source complementary
JFETs/BJTs/MOSFETs: Where do you source them?
Where do Levinson source their JFETs?
As far as I know, these are the devices available
on the market:

2SK389 / 2SJ109 complementary monolithic low noise JFETs
2SK170/ 2SJ79 complementary high gm low noise JFETs
2SK364/2SK104 complementary very high gm JFETs
2SC3381/2SA1349 complemantary monolithic low noise BJTs

and others.

Unforunately, the 389/109 and 3381/1349 are now out
of production. Do you have any replacement you know of?

James Yung

 

[john curl]

Stick with it James. The j109/389 are still available. We use 100's of them every day. The Japanese manufacturers run out of and 'discontinue' a part, then they get so many orders that they have to make another run. Just keep your eyes open on the internet and do a periodic search for the part on Google, or another resource. Levinson (the company) went away from fets in most designs, mostly for practical reasons.

 

[Praise!]

Where exactly?

Stick with it James. The j109/389 are still available. We use 100's of them every day. The Japanese manufacturers run out of and 'discontinue' a part, then they get so many orders that they have to make another run. Just keep your eyes open on the internet and do a periodic search for the part on Google, or another resource. Levinson (the company) went away from fets in most designs, mostly for practical reasons.

Hi John,

I'm so happy to hear from you again so quickly.
May I say what a privillage!

If you don't mind, could you please tell me more on where
to source 389/109 on the internet? I've tried many times
using yahoo without much luck.

In fact, I put a purchase order to Toshiba 2 months ago
and get rejected because the factory said they cannot
"support" it. My whole business depends on it! I'm feeling
very "stuck". May be if we "join forces" to order say 100K
pieces, they will then willing to do a production run.

You said "we use 100's of them every day" where do
you work? You don't have to answer if you find it
intruding. I just knew that you designed JC-1 for
parasound home theather power amp.

James Yung
Praise! Audio
😉

 

[john curl]

We use 389/109 in all of our Parasound power amps. They are made in Taiwan, and I don't know the resource for them, but I buy them fairly often, BUT I don't go to Toshiba directly.

 

[Praise!]

Where?

We use 389/109 in all of our Parasound power amps. They are made in Taiwan, and I don't know the resource for them, but I buy them fairly often, BUT I don't go to Toshiba directly.

Hi John,

Thanks for your reply.

Could you tell me where you buy them from?

I did a search using Google instead of Yahoo and
the results are pretty good, though not good enough.

James Yung

 

[mlloyd1]

Re: Where?

This is the last place I bought some from:

MCM Electronics

You will most likely get GR grade devices.

Search this board for past threads on device discussions to find other sources for these parts.

By the way, I was curious, so I tried both google and yahoo myself. Each pointed me some possible sources. One common result was this site . I put in 2SK389 and got a number of hits for sources for this part.

Good luck,

mlloyd1

... Could you tell me where you buy them from?

I did a search using Google instead of Yahoo and
the results are pretty good, though not good enough.