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JBL SA600 Vintage Amplifier Review

Cars-N-Cans

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It was actually one of the first silicon amplifiers. Solid state amplifiers before this were using Germanium!
It is impressive performance for the time and its a shame they could not get the PSU noise down. They did add UFR diodes presumably to eliminate some of the spikes from the reverse recovery time of slower diodes with the transformer's leakage inductance. I would assume that the noise was there from the start when it was first made, and probably due to the fields coupling into the audio circuits and/or maybe poor PSRR, but not a EE so cant say for sure what the true culprit may be.
 

tktran303

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Well you can see now why early SS amplifiers had a bad reputation...

Kinda like the first class-D amplifiers...

Or the first computers...

Or first internet enabled mobile phones...

First color TVs

Even when you take out the power supply PS noise it meets the spec of 0.1% distortion (SINAD 60dB down)

... yum or yuck depends on the partnering equipment of the time.

Anyone got speakers from the 1920-1940's to send to Amir?
 
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pma

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There is no attack, just reality.

This "reality" might be questionable. Nobody knows, including the owner, what were the original transistors and how the replacement parts fit to the original circuit. A quick search through internet shows that people put anything inside during "refurbishment".

2n2637_2536.jpg


2n3298.jpg
 
OP
amirm

amirm

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@amirm, what does the “test” mode do?
From the manual, it seems to invert one channel and sum with the other. Then you listen to see if you get anything but silence. At least this was my quick read of it.
 

fordiebianco

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As a collector of vintage Rotel and JVC receivers I am not surprised, but I appreciate the review and the measurements, so thank you to the trio of @amirm , the donor and the restorer. I have all my old amps regularly serviced, but I am aware that if I listen to a Rotel RX 150 my enjoyment of its looks will likely bolster the psychoacoustic effect. If there's music I want to listen to with particular attention to production I switch the chain to a modern class-d amp. Nevertheless, the visceral enjoyment that a nice early seventies receiver can give me is not matched by my little black boxes.
 
D

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I guess it would be sacrilege to swap out the power supply for an SMPS :eek:

@amirm, what does the “test” mode do?
Maybe an outboard power supply so things don’t get butchered up inside?

I do you love the mid 60s look, and they took that early solid state look a step further, trying to differentiate themselves from the tube amp look
just a couple of years earlier.
 
D

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Maybe one of the first early amplifiers that I can actually see today’s JBL reflecting this early design, with that two-tone look of the face plate, it just reminded me of some of their AVR’s of today. Just a beautiful piece of history, and I would sure hate to drop that on my toe lol.
 

DanielT

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I guess it would be sacrilege to swap out the power supply for an SMPS :eek:
Probably yes. Like putting a new engine in an otherwise fully renovated old vintage car. But okay just to test it would be interesting in itself.:)

Wondering if that amplifier is used daily by the owner or if like a vintage car it is only taken out occasionally and driven a bit?

With vintage cars, it is also the case that many people find the renovation itself to be the most enjoyable part of the whole thing;) :)
 
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