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Topic: More Standel |
David Ball
From:
North Carolina High Country
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Posted 8 Mar 2019 1:01 pm |
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I have been following the Standel rebuild thread with interest, and came across a good deal on one of the all solid state models from the mid 60's. Its an Artist Super X--I got just the head. It had just been re-capped and cleaned. Everrything except the electrolytics appears to be original and it's in very nice shape.
Dang this thing sounds great, and it's loud. It's one of the models with two separate power amps. Both power amps are driven by both channels' preamps, so it's not a stereo rig. It has the big old Germanium transistors, which sound a whole lot like tubes.
In hifi, I'm a big direct heated triode amp fan. I have a friend who used to build single ended hi fi amps using "Germs" and it was hard to distinguish the direct heated triodes from the Germs.
This is a bass amp, so no trem or reverb (which I wouldn't use anyway), and no "accent" switch. I'm running a Black Box and a Demeter spring reverb into it and playing through a JBL D140 and a Double T 12. One of the best sounding amps I've ever had.
Anyway, I'm a happy camper and got into it cheap.
Quick question for someone knowledgeable about Standels--this amp has two blue modules, which I take it are the preamp/tone modules; one green module which seems to be a summing amp or something like it. But it also has a black module, which from the schematics on line looks like some kind of opto-isolator. I've seen them at the input of the Standel powered speakers, but I can't really tell what its purpose in this amp might be. I haven't traced the wiring out yet, but the two blue modules go into the green module and the black module appears to be kind of sitting out there. Any clues? The model number on the amp is SA10B.
Dave |
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Jack Stoner
From:
Kansas City, MO
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Posted 8 Mar 2019 2:06 pm
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I did amp repair, in Nashviile, in the early 70's. A comment on those old transistor amps. If something goes out in the output it takes the power transistors and the driver transistors. I worked on a Standel powered column speaker and one of the output transistors shorted and both power transistors and the driver transistors had to be replaced.
I worked on others, Kustom and early Fender attempt at transistor and it was the same way.
One model of the Emmons amps was made by Standel. That would be a nice amp if you come across one of those. |
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David Ball
From:
North Carolina High Country
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Posted 8 Mar 2019 2:21 pm
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Yeah, from what I've seen on other transistor amps of the day, the output sections do tend to go out all as a package This particular Standel uses a transformer as the phase inverter like you'd see in a lot of hi fi amps (also the Fender Musicmaster Bass amp), so there's only one driver transistor per power amp. Guess that would just be one fewer transistors to replace if anything blows! I guess it might serve as some isolation between the driver and the output transistors. The date codes on all of the transistors is 1965, so they're pretty tough I guess!
I'm generally an all tube guy--I've built and repaired tube amps for decades--never really done anything much with solid state amps, but this Standel really stands out from what I've heard so far.
Dave |
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Michael Brebes
From:
Northridge CA
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Posted 8 Mar 2019 3:40 pm
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All the full solid state bass amps I've seen only have two blue modules and one green. No black. That is what I would expect.
_________________
Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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David Ball
From:
North Carolina High Country
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Posted 8 Mar 2019 3:55 pm
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Here's what it looks like underneath--I guess Standel was constantly changing things along the line!
Dave |
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Michael Brebes
From:
Northridge CA
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Posted 8 Mar 2019 7:06 pm
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That is not a standard module. All standard modules are the same size as the blue and green modules. Unfortunately the resolution is so small that I can't see what is there and how it is hooked up to everything else. I tried zooming in and it just blurs to nothing recognizable.
_________________
Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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David Ball
From:
North Carolina High Country
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Posted 9 Mar 2019 3:07 am
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Yeah, that was a crappy picture--sorry about that. Here's some more:
It appears to be some kind of negative feedback device. One wire goes to a resistor leading to the hot side of one of the speaker outputs as can be seen in the third picture. The other goes to the green wire on the green module. There is a pair of twisted wires--the green and black leads off of the green module--that jumpers the whole thing over to the second channel. The whole thing looks like it might somehow replace the choke and cap to ground shown in the schematics. Or probably it IS the choke and cap, but with a feedback resistor thrown into the mix.
Dave |
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Michael Brebes
From:
Northridge CA
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Posted 9 Mar 2019 8:06 am
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Yes, Standel was notorious for having schematics continually changing. Later schematics show the feedback loop going from the output into the phase inverter circuit. Later schematics show high frequency shunting at the summing point of the Green module. I think that capacitor and inductor are in that black module and incorporated in the feedback loop. That's one of the things that make the amps so hard to work on.
_________________
Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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