Any idea?

[pyonc]

Hi guys,

While I compared the performance of two SG520 preamps, one in good condition (let me call this A) and the other in near mint condition (this one B), I've come across some interesting observation:
At the same volume level of SG520, I hear the sound from 4343 speakers a little louder with more bass from A than B.
I was a bit surprised because I expected B in near mint condition would easily beat A.
As I'm not much aware of this technical things, I just keep scratching my head.
Do you have idea about this strange outcome?
Thanks for your kind advice and feedback, as always.

[Mr. Widget]

Strange outcome? I think that is rather typical... there is a lot of vintage gear that is operational, but not necessarily working properly.

For vintage electronics you really need them to be thoroughly bench tested by a qualified tech to know what you have... it is very likely that there are multiple components in each SG-520 that are now out of spec.


Widget

[pyonc]

Strange outcome? I think that is rather typical... there is a lot of vintage gear that is operational, but not necessarily working properly.

For vintage electronics you really need them to be thoroughly bench tested by a qualified tech to know what you have... it is very likely that there are multiple components in each SG-520 that are now out of spec.


Widget

Thanks for your insight, Widget.
Fortunately, the newer SG520 has been tested by a vintage audio technician with no issues at all.
Functionally, both preamps work just fine, with all the source buttons as well as bass and treble buttons in proper working condition.
As you pointed out, these vintage gear, produced in the mid-1960s, might need a thorough check-up, just like used cars.
Still, they sound wonderful, given their production year!!!
When I got this result, I just thought to myself maybe this newer SG520 might need some more listening time for a fuller/mellow reproduction just like its older brother (their serial numbers are two hundreds apart). Just like you need to drive your new car for some time for full, efficient driving experience or if you are a runner, you need to wear your new running shoes at least a couple of weeks to break in...

[Mr. Widget]

Not to be harsh, but for any gear that is 40-50 years old the likelihood is broken not break in.


Widget

[hjames]

No offense - but ... be realistic about this.
Those amps were not built to be high end audiophile parts even then, they certainly are not today.

My brother worked with older cars - the point there is to blueprint their older systems so you can get reliable performance out of them every time.
He would go through and measure every piece of significance, match the tolerances and replace parts as needed, so they are known to be consistent
and so he got optimum, repeatable performace every time he went to the track (he ran a '64 chevelle big block in bracket racing).

if you are using the old gear without having a known skilled tech go through and completely rebuild the units with new caps that are tested to meet spec, transistors that are tested to meet spec, its a wild guess what the gear is doing inside. And if you have two of them side by side, its silly to expect whatever off the shelf parts were used during production were within a small tolerance, and now 40-50 years later, its silly to expect them to have drifted out of spec exactly the same way.

Just because it has been tested with no issues at all, does not mean it is operating in any kind of high performance mode.
It basically means its not obviously broken.

Is this the same tech that told you the other piece had no issues at all, and you found it had a bad hum or something and wound up shipping it back?

I bought a pair of speakers in Feb and decided while they worked "just fine" I didn't think their sound was at their best.
I wound up buying $120 of capacitors and replacing all 24 caps in the 2 crossovers and it made a world of difference.
And they were only from the mid 80s (30 years old) ... imagine the drift on much older components!

Thanks for your insight, Widget.
Fortunately, the newer SG520 has been tested by a vintage audio technician with no issues at all.
Functionally, both preamps work just fine, with all the source buttons as well as bass and treble buttons in proper working condition.
As you pointed out, these vintage gear, produced in the mid-1960s, might need a thorough check-up, just like used cars.
Still, they sound wonderful, given their production year!!!
When I got this result, I just thought to myself maybe this newer SG520 might need some more listening time for a fuller/mellow reproduction just like its older brother (their serial numbers are two hundreds apart). Just like you need to drive your new car for some time for full, efficient driving experience or if you are a runner, you need to wear your new running shoes at least a couple of weeks to break in...

[pyonc]

Not to be harsh, but for any gear that is 40-50 years old the likelihood is broken not break in.


Widget

Yea, I would agree.
Nonetheless, I'm just amazed at the great performance of the sold JBL vintage gear like this one.
And that's why I'm addicted to JBL vintage gear.
Thanks.

[pyonc]

No offense - but ... be realistic about this.
Those amps were not built to be high end audiophile parts even then, they certainly are not today.

My brother worked with older cars - the point there is to blueprint their older systems so you can get reliable performance out of them every time.
Go through and measure every piece of significance, match the tolerances and replace parts as needed, so they are known to be consistent and he gets optimum performace

if you are using the old gear without having a known skilled tech go through and completely rebuild the units with new caps that are tested to meet spec, transistors that are tested to meet spec, its a wild guess what the gear is doing inside. And if you have two of them side by side, its silly to expect whatever off the shelf parts were used during production were within a small tolerance, and now 40-50 years later, its silly to expect them to have drifted out of spec exactly the same way.

Just because it has been tested with no issues at all, does not mean it is operating in any kind of high performance mode.
It basically means its not obviously broken.

Is this the same tech that told you the other piece had no issues at all, and you found it had a bad hum or something and wound up shipping it back?

I bought a pair of speakers in Feb and decided while they worked "just fine" I didn't think their sound was at their best.
I wound up buying $120 of capacitors and replacing all 24 caps in the 2 crossovers and it made a world of difference.
And they were only from the mid 80s (30 years old) ... imagine the drift on much older components!

Thanks much for your sharp reminder of the importance of the need to check up old vintage gear.
Actually, I had my two woofers' voice coils burnt by a malfunctioning vintage Crown Xover, which thread I started in this forum.
As for the tech, this time a different one.
I sent back the SE400S to the ebay seller in CA, and his technician rechecked it, changed the pilot light and told me he heard no thump.
Well, I didn't want to take risk again, so I stayed away.











No different technician.