Anyone know history of Sound Amps ? - Warning Amp porn

[FUCHSAUDIO]

Thanks for the reply Andy !

I thought that my Plush connection to NY was valid. This amp was made cheaply, but so were a lot of good sounding pawnshop prizes like Silvertone, Harmony and later Magnavox / Gibsons. It just seems that nothing was much more robust that it had to be. Isn't that what product engineering is all about - make everything fail at the same time.
Just don't take it on the road.

PS That's tone wood under the circuit board.

The "connection" could have been employees, technicians, or buying parts on Canal Street. It's tough to say. Plushes were the worst: They bought surplus caps, extended resistor leads off used parts, pots and caps were often from different suppliers in the same amp. They did not scrimp on transformers and tubes, but they sure did in other places...

The wood under tag board is clearly Ampeg Gemini style stuff. Jess (moreorless) spitting on the ground when I asked about John and Sound amps, made me think perhaps there was bad blood. Jess built things for Sam Ash, Guild and a few other companies as an OEM, maybe John stole customers..we may really never know the whole story. Same kinda thing with Ampeg and Sano. Spoke with people involved with both companies, and since they were within miles of one another, surely they shared suppliers, employees etc, but they were not made by the same companies, as was sometimes alluded to.

Heck, I have an ex Tech-21 employee working at my shop now...lol. They are literally 2 miles away. I almost rented space in their building ! I knew guys at Plush who ended up at Earth. Earth guys who went to Marlboro, or repair shops in the NYC area. Ken Fisher leaving Ampeg to do Trainwreck. Paul Rivera worked at Plush in NYC for a lunchtime.....and Mesa, and Yamaha... Kager was at Ampeg, started his own thing wtih Sundown...and consults to other companies like Yamaha, Naylor, Pignose, Electroplex. I'm now doing design and building stuff for others, this is a smaller business than ya think some days.

In any case, Sound amps were pretty cool. Not sure how many were made. The business was literally a storefront the last time I drove past the address I had for it in Mineola .

[chopstuck]

Again Andy, thanks for the info.

This is exactly what I wanted to know.

Twenty years ago when I was younger and dumber, I would picture these factories as unrealistic happy places where everyone involved was a musician and they loved their part of the making of music "history". Growing up in Mesa AZ I was a stones throw from where all the big power car audio amplifiers were made in Tempe. Precision Power (PPI), also made Sedona, Orion and Hafler were just a few miles apart. I would visit them from time to time and gradually as the sheen wore off the visit you could sense the tension between the parties.

I believe Bogner and Hafler stuff was made in Tempe because when business shifted and shops closed, hi-fi stuff and guitar preamps kept showing up at pawnshops shrinkwraped like new.

Employees went from one company to another, allegations were made about this and that. As a 20 year old kid no one would tell me the specifics back then.
I left there 15 years ago and can only imagine like all of the made in USA gear it has gone overseas or Mexico. My only reminder is a prototype Hafler bass preamp called the T-1 I scored. Just Vol ,MV 4 or 5 band EQ.
It's hand lettered and signed on the inside. It too sounds great but never made it into production AFAIK.

Sounds like Sound as well as the other companies knew where the cheapest parts were, where the trained staff were and what circuits sounded good.

And no I'm not meaning to write a book.

Andy I have to thank you again for your insights.

Like you said some of these thing we will never know.
It's nice just to get a feeling of what the situation was like.

Marc

[FUCHSAUDIO]

Chop: The hard reality at Plush was: Let's see how fast you build something, how well (or if) it works, and you can come to work tomorrow. People actually got incentives for doing things quicker than others.

The wiring usually reflects this attitude and is usually pretty sloppy and inconsistent from unit to unit.

After all the "fun" of being the in music business wears down a little, meeting rock stars or people you idolized, it all comes down being more realistic and paying attention to to profit margins, actually making a living and staying alive against the other competitors. The sheen can and does wear off...to some extent. Especially true when you learn who gets paid how much to play junk (not here folks), or who expects more free product than whom (not here neither).

[chopstuck]

From my experience with Plush, the number one question was always:

Why hasn't this thing burned up yet ?

The upholstery was poorly finished and there was a lot of it. Lots of petroleum based foam, vinyl close to lots of really hot tubes and the wiring all just improvised.

I mean "FOOM !" ya know ?

My Plush transformers went into my first big amp build....
a Fender high power tweed Twin. (sans tube recto).

It sounded pretty good as I recall.

[M Fowler]

I blew up my Plush 100 blue metal-flake head with 3-15 inch speaker cab in 2002 and sold it on an auction sale.

Can't say I miss the big ole piggyback rig.

[FUCHSAUDIO]

It escapes me at the moment, but the Plush iron was made (maybe in Michigan ?), and was reputedly optimized by Saul Marantz and Sid Smith his Chief Engineer. I have the maker's name someplace.

Saul claimed, in an issue of The Absolute Sound magazine, that Plush was trying to clone Fender transformers and had trouble getting them to sound right. "Sid and I rewound them to make them better than the originals". Both companies were in NYC and it sounds like a reasonable claim.

I have a 6 X 6L6 Plush with a OA2 screen regulator tube that is in Marshall territory volume and sheer brute force in "cajones".

[lumox0013]

andy if you could find the name of that manufacture I would love to know the plush 1060s is my main amp and nothing else Ive tryed in the last 15 years sounds quite like it,i think alot of the magic in that amp is in the transformers.thanxx for the insight as well

[FUCHSAUDIO]

Northlake Engineering

[KT66]

I drew up a schem for the Sound amp, but there were a few things that I had to guess at or had trouble determining from the drawing, so you may want to verify it and get back to me so I can complete it.

There is no grid load resistor shown at the input so I assumed it is 1 Meg. I was confused about the first filter cap(s) - it shows 80, but is it 2 in parallel that total 80 ? There was no value shown for the resistor that connects the PS diodes to the 1st cap/screens/plates. Seems like that's a sag resistor to simulate a tube rec - haven't seen that before in an amp of this vintage. It looks like the OT CT connects to the screen supply at the tube socket. I'm not sure that the tone stack is correct, I had trouble differentiating some of the connections in the layout.

Does the trem work with no pedal plugged in ? If so then the jack for it must be a shorting one and it would make me think that there is a switch built into one of the trem pots to turn it on and off. It looks like the trem connects from the depth pot to the 470K grid load resistors of the power tubes in the pics, but the drawing omits this. It seems like there might be something more going on at the Depth pot but I can't tell from the pics or drawing.

Anyway, I'd be happy to finish it if you come up with the info.

[Cliff Schecht]

The resistor in the PSU is probably just to drop the B+ a bit. Makes life on the tubes easier. I use this "trick" often. If you know the current draw of everything on the B+ lines and what voltage you want to drop, the formula is (V1-V2)/I=R to choose an appropriate R value. Think of it as a cheap replacement for a choke, kinda the opposite of a sag resistor.

[KT66]

Maybe they used a resistor there to lower the B+ as you suggest, but as a manufacturer I would think that they could just get a PT with the correct voltages. Anyway, with a resistance in the power rail in that position in a class A/B circuit there is going to be a sag effect for the same reason that you get one with a tube rec due to it's internal resistance : when more current is drawn by the output tubes, the voltage drops in the whole power supply a bit because of the relationship between voltage, current and resistance that is described by Ohms law. Also, for the same reason, there is no sag effect possible in an amp that is true class A because the current draw is constant.

Btw, I dig your hi-fi build with those cool lookin 807s.

[FUCHSAUDIO]

I think of those as surge resistors...maybe minimizes the initial bang into the caps....I doubt it's to lower voltages...

[Cliff Schecht]

Maybe they used a resistor there to lower the B+ as you suggest, but as a manufacturer I would think that they could just get a PT with the correct voltages. Anyway, with a resistance in the power rail in that position in a class A/B circuit there is going to be a sag effect for the same reason that you get one with a tube rec due to it's internal resistance : when more current is drawn by the output tubes, the voltage drops in the whole power supply a bit because of the relationship between voltage, current and resistance that is described by Ohms law. Also, for the same reason, there is no sag effect possible in an amp that is true class A because the current draw is constant.

Btw, I dig your hi-fi build with those cool lookin 807s.

Werd. I am about to put the hi-fi rig to the test again now that the girlfriend is off at work. I love how 807's look too, very tube-like!

Also I stand corrected. I tend to think in class A because that's mostly what I build and really study. When the push-pull pair is initially pushed hard it empties the reservoir caps and is suddenly not able to push as much current through continuously. This does happen in class A amps as well but to a lesser degree because the difference between instantaneous current and quiescent current draw is much less.

With that said, I think the function of that resistor is really dependent on the value (that isn't posted). If it's a few Ohms to ~50 Ohms then I will believe that it is an inrush current limiter for the 80uF caps. The only reason I could think that they would be using it to drop voltage is if they went with a "standard" transformer that was cheaper than a custom unit (as it usually is, even back then). A simple resistor can drop the voltage to safe levels and perhaps extend the tube life as well. That sounds a bit ambitious for a simple tube amp design from the 70's though, I too think it's inrush current limiting.

[Hellhammer]

There was no value shown for the resistor that connects the PS diodes to the 1st cap/screens/plates. Seems like that's a sag resistor to simulate a tube rec - haven't seen that before in an amp of this vintage.

According to Valve Wizard a small resistor between the rectifying diodes and the reservoir cap helps smear out diode switching noise.

Whenever the diodes switch on and off, as they deliver large pulses of current to the reservoir capacitor, they tend to produce a voltage spike known as a 'switching transient'. This can introduce high-frequency 'hash' noise into the power supply. This can be alleviated to some extent by placing a small resistor in series with the rectifier before the reservoir capacitor. This effectively 'slows down' the rate at whch the diodes switch on and off, smearing the transistion and reducing the switching transient. If too much voltage drop or power supply sag is to be avoided then a small value of say, 10 or 22 ohms, 3W should be sufficient.