Pioneer SM-700 - Quite impressive little thing!

[QSilver]

Picked one of these up a while ago just as a curiosity. I got round to re-capping it today seeing as it days from 1970 I figured it would be best.

Most caps measured 70% over what they should. Only strange thing was how they had used one capacitors terminals to bridge two sections of circuitry together. I replaced this with a small wire bridge.

Fitted it with some Nichicon PW's and some Panasonics for output capacitors with fairly low leakage, checked the centre point and idle current and hooked it up.

I thought it best to go to the top and just hooked it into my SPEC-3 and wow...

For a little old capacitor output amp, it sounds brilliant! Has a great deep sound stage. Eagles are sounding good along with a few others.

Anyone else come across one of these - I like it for the tiny dimension and now the sound.

 

[larryderouin]

I've got a few small cap coupled Sansui's and Fisher S.S. 1st Gen receivers. I get the same response. Deep sound stage, very nice mids, bass is a bit sloppy, like it's hunting for it's sweet spot but never hits the mark, and nice highs. The bass response is pretty much normal for all of them, you can tone it down with the Bass knob and it'll settle down some. Surprisingly my Pioneer stuff isn't cap coupled, not even the SX-434. Guess they got the circuits for OCL straightened out by 1974.

 

[QSilver]

Yes, very clear highs a little over bright at the moment and the bass seems to be improving the more its left on.

 

[Noodle]

Anyone else come across one of these - I like it for the tiny dimension and now the sound.

Yep, got three of them with matching SC-700 pre-amp and SF-700 crossover, along with CS-A700 speakers which can be run as full range or separated for each amp.
Did a test run once with a single SM-700 on some CS-88A's and was surprised at how it sounded.

 

[MPXNL]

It's actually a SA-700 without the preamplifier etc.

 

[QSilver]

Nice! Figures about the SA-700.

I'd love to get hold of a SC-700... SF-700 would be interesting too...

 

[Oldsansui441]

For a little old capacitor output amp, it sounds brilliant! Has a great deep sound stage. Eagles are sounding good along with a few others.

Anyone else come across one of these - I like it for the tiny dimension and now the sound.

What a nice little amp, can't be too many around, l just had to look it up as l had no idea they existed, makes sense from what MPXNL said about it being the amp section from a SA-700.

 

[MPXNL]

There are 2 parallel added output caps.
Remove them and do a little rewire there.
Replace the 2 original output caps on the amp board with > 2200/35 Panasonic FC or something like that.
Put in 4 new rectifier diodes and a bigger smoothing capacitor will do the rest.

 

[QSilver]

There are 2 parallel added output caps.
Remove them and do a little rewire there.
Replace the 2 original output caps on the amp board with > 2200/35 Panasonic FC or something like that.
Put in 4 new rectifier diodes and a bigger smoothing capacitor will do the rest.

A closer look at the schematic would have told me that..... I should have checked. I've just replaced them all yesterday. I used 1000uF 35V Panasonics in both places. A 2200uF in one place would have been neater but nevermind. It still sounds very good. Only capacitor I haven't changed yet is the filter cap. Was considering up rating it a little seeing as there is a lot of space for a capacitor there.