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JBL SA600 Vintage Amplifier Review

mhardy6647

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Some also had Tape, and sometimes even Line. As I recall, they were all just line-level inputs.
Personal fave was the (in)famous Dynaco PAT-4, with an input labeled SPARE. :)

blog-stereonomono-Dynaco%2BPAT-4%2BStereo%2BPreamp2.jpg


I... I actually have one of these. Don't judge me, OK?! ;)





Little Dynaco-snippets from Stereophile magazine, albeit removed from their original contexts. :)
 

EJ3

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The eagle has landed.

I was seven years old and probably in second grade when they landed on the moon. I asked my mom to buy me the vinyl record of the moon mission communication between NASA and Apollo. I lost it over the years, but I found one on eBay not long ago.
I have an unopened copy on reel to reel. I am a few years older, as I am a 57 Variety.
 

Xyrium

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Speaking of restoration: One might be tempted to build a contemporary amp in the cabinet of such a "dinosaur".
Yes, the retro freaks would consider it a sin, but still...
Look at Teac kickin' it in class D with some nice meters on the front:
 

EJ3

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Look at Teac kickin' it in class D with some nice meters on the front:
I like it! Would be interesting on Amirm's bench. I also like the

AD-850-SE (It needs something like Dolby-S), though.​

 

AndreaT

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Pics or it never happened! Just kidding, I think it looks and sounds wonderful.
Yes…until you take advantage of the first octave with subwoofers and flat source/DAC/pre/amp response to 20 (or 16) Hz and the symphonic orchestra comes alive, and of the very low noise and you appreciate the ppp in Beethoven or Mahler…
 

AndreaT

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If I am not mistaken, the Spare input was there to allow user configuration for those who had two record players, or two tape recorders…it could be made into a RIAA input or a Tape Head…
 

EJ3

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70 Watts? That's like an NC122MP module in a box for $2,000? I think Teac is a bit past their heyday.
In Japan (were I spent a large part of every year from 2003-2018) you would find most things overpriced by our standards. But they seem to be well paid, so...
 

Sal1950

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amirm

amirm

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GXAlan

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solderdude

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@amirm Some pics of the inside can reveal what parts were changed during the restoration and can shed some light on the measured performance.
Headphone out is 160Ω for those that wonder.
 
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Sound86

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Ive had many many vintage amplifiers over the years and even if their measurements dont compete with modern designs they are by no means doorstops. Many are beautifully built with high class materials and enhance every home they are in. And they are part of Hifi history. I can only applaud the effort to restore such a nice unit and actually keep it in working order for coming generations :)
 

pma

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I was really curious how this amp should perform and how it could have performed when it was new. As the circuit is simple, I have put it into MicroCap, trying to keep parts as close as they were.

This is the schematics
Locanthi_scheme.png

and it was designed by a competent circuit designer. R4+C2, R27+C9 and C6 make very interesting and perfectly working frequency compensation. Small signal frequency response looks like this
Locanthi_freq.png

It is wide and flat. Remember I speak about the power amp section only, without bass/treble eq.

The idle current is quite low, due to simple bias circuit with 5 diodes in series. This is the point that might have been grossly improved. Because of the low idle current, distortion is rising at low power. However, the value of distortion above 100mW is fully acceptable.
Locanthi_thdpow8R.png

In this distortion/power simulation, please take into account that ideal voltage sources are used to supply the amp.

I will investigate the PSRR as well, and I expect it will not be as good as these basic parameters.

I am pretty sure I would be able to re-create this power amp section of the Locanthi amplifier, with new PCB design and parameters close to the original.
--------------

EDIT: PSR below. It is good at middle and high audio frequencies, but deteriorates at low frequencies.

Locanthi_psr+.png
 
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