Perreaux SM2 & 2150B...

[Michael Chua]

Hi zeoN_Rider

I absolutely agree.
Correct TONE = real sound = magic

That's why the 2SK1058/2SJ162 are still my favorite OP.

Regards
Mike

 

[nickds1]

I now have the full schematics and service notes from Perreaux - for the SM2 - I'll post updates if anyone is interested.

 

[Luke]

The output stage on Perreaux amps is based on Hitachi app notes. The Driver is definitely proprietry. I remember one of the engineers telling me that the amps sampled the rail voltage flucuations and fed it back into the input out of phase to reduce distortion. Does any oen know if Ive got this right or if its possible?

BTW in its day the SM3 was the flagship. PMF5550 was a behemoth, it took two people to lift safely and I think could deliver 2kw/ch into 2 ohm. It went 1850, 3150 and 5550, sm2, sm3.

 

[fredex]

........I remember one of the engineers telling me that the amps sampled the rail voltage flucuations and fed it back into the input out of phase to reduce distortion. Does any oen know if Ive got this right or if its possible?...........

Yes this correct there was a pot inside which was adjusted at the factory. Also the PCBs were symetrical and the power +/- cables feeding the boards were dressed whilst looking at a scope to achieve cancellation of any loop effects. There was a lot of attention paid to details.

 

[nickds1]

Re: Hi nickds1!

I have PMF 1850 & SM3.

Have full service manuals.

Any chance of a look at the SM3 docs? I have the schematic from Perreaux, but not the service manuals...

Thanks

 

[Luke]

Fredex, did you work at Perreaux or know them?

BTW attention to detail is very true. Look at the finish and layout of the SM3, pretty respectable for a 20 year old preamp.

 

[fredex]

@ Luke Yes I worked there during SM2 days.

 

[nickds1]

@ Luke Yes I worked there during SM2 days.

I'm just looking at the SM2 schematics and there is no DC rail sampling there - there is just one pot used to adjust the bias for each FET class A output stage.

There is a DC bias taken from the -45VDC rail (divided down to below -2.8V) applied to each long tailed pair, but nothing else.

Visually, its a very appealing preamp - nice PCB layout.

 

[fredex]

Luke. No that technique was only for power amps from memory 1050 2150 etc. You could measure the effects, hear them?

 

[Luke]

@ Luke Yes I worked there during SM2 days.

I worked there during the sm3 days Think I was only there for 6 months or so. So are you from Napier?

I realise the distortion cancellation was for power amps. I actually bought the 3350 reference when they closed shop.

 

[fredex]

Luke drop me an email we may know the same people, does Patterson ring a bell?

 

[nickds1]

What's the difference between the SM2 & SM3?

 

[stoN_Cold]

Hi nickds1!

Put sch. for SM2 I'll put sch. for SM3 & we'll see!

Regards zeoN_Rider

 

[nickds1]

For a short time only!

SM2 part 1
SM2 part 2

 

[brianco]

Nickds1

Very many thanks!

All I need now is the 2150!

 

[nickds1]

All I need now is the 2150!

Drop me a PM with your email...

 

[stoN_Cold]

Hi!

Here is SM3

http://rapidshare.com/files/257916588/SM_3_sch..pdf.html

Regards zeoN_Rider

 

[brianco]

Many thanks -

The site does not seem to host PMs however my mail is closed. I will now open it for a few hours on the off chance. Click on my name!

Brian

 

[stoN_Cold]

Hi brianco!

Put on like Reply your E mail .

Regards zeoN_Rider

 

[nickds1]

What's the difference between the SM2 & SM3?

Now I've looked at the schematics, pretty much nothing at all - mostly changes to the input switching and sensitivity...

I'll stick with the SM2 then!