I honestly am not sure where to put this: not tube, not solid state; not really analog, but certainly not digital...

mhardy6647

mhardy6647

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Credit and full disclosure:
This was the brainchild and handiwork of my friend, one of the regional vacuum tube/analog hifi gurus, who -- now and again -- posts to these august* fora under the inexplicable moniker @forkliftman15 :)

heh.
heh.
heh.

Yes, you can.

Roll your own AVC, that is.
Proof of concept (alpha test, I suppose you might say).

16327

:)

On loan from its creator, en route to another local via my house (always an irrestible temptation!); I am fiddlin' with it as I type this, and it's -- rather remarkably good.

:smoke

The only problems (fairly minor though they be in a proof of concept design/build):
1) it's dual mono (two knobs to turn)
2) it's not audio taper... it's Variac taper. 🤭






Rumour has it that Dave Slagle started out somewhere along these lines before he had his run-in with the Iron Devil down on at the crossroads. ;)

DSC_6670 (2).JPG
_________________________
* yeah, yeah -- I know it's September... work with me, here!
 
The answer to your dual-mono separate knob dilemma is to use the method popularized by the Redgum Audio people, in Australia. The made dual-mono components, complete with separate volume knobs. An elastic band, of appropriate size and elastomeric properties, when slipped over the two knobs, will drive both knobs, when only one is turned.

To synchronize the two knobs, turn both to minimum, slip the band over the knobs, adjust the band so that tension is equal, in the upper and lower transverse sections. Good to go.

Nota Bene: You don't want a rubber band that is too soft and stretchy. Likewise, you don't want to apply too much lateral force on the shaft of the knobs. You'll know when you have the right one.
 
Ernie said:
The answer to your dual-mono separate knob dilemma is to use the method popularized by the Redgum Audio people, in Australia. The made dual-mono components, complete with separate volume knobs. An elastic band, of appropriate size and elastomeric properties, when slipped over the two knobs, will drive both knobs, when only one is turned.

To synchronize the two knobs, turn both to minimum, slip the band over the knobs, adjust the band so that tension is equal, in the upper and lower transverse sections. Good to go.

Nota Bene: You don't want a rubber band that is too soft and stretchy. Likewise, you don't want to apply too much lateral force on the shaft of the knobs. You'll know when you have the right one.
Click to expand...

I always thought that was a nice solution for an annoying issue. I'll never buy a unit with separate, manual volume controls.
 
Ernie said:
The answer to your dual-mono separate knob dilemma is to use the method popularized by the Redgum Audio people, in Australia. The made dual-mono components, complete with separate volume knobs. An elastic band, of appropriate size and elastomeric properties, when slipped over the two knobs, will drive both knobs, when only one is turned.

To synchronize the two knobs, turn both to minimum, slip the band over the knobs, adjust the band so that tension is equal, in the upper and lower transverse sections. Good to go.

Nota Bene: You don't want a rubber band that is too soft and stretchy. Likewise, you don't want to apply too much lateral force on the shaft of the knobs. You'll know when you have the right one.
Click to expand...
As soon as I started reading your post (and knowing nothing about Redgum Audio save the name itself), I knew where you were goin'. :)
 
I guess the point is that a few bucks spent at a ham radio fleamarket (or at the warm-weather "Flea at MIT" for those of us close enough to the Hub of the Universe :) ) can net the basis of an experimental AVC.

Tip o' the ihat to @forkliftman15! I certainly would've never thought of it, much less actually tried it!

I guess I (we) should always think of Niels Bohr's famous quip.
We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct.

Said to Wolfgang Pauli after his presentation of Heisenberg's and Pauli's nonlinear field theory of elementary particles, at Columbia University (1958), as reported by F. J. Dyson in his paper “Innovation in Physics” (Scientific American, 199, No. 3, September 1958, pp. 74-82; reprinted in "JingShin Theoretical Physics Symposium in Honor of Professor Ta-You Wu," edited by Jong-Ping Hsu & Leonardo Hsu, Singapore; River Edge, NJ: World Scientific, 1998, pp. 73-90, here: p. 84).
Click to expand...

source: Niels Bohr - Wikiquote

16357
 
Speaking of variac's and hamfest, it's funny that you mentioned that. I was at the Mullica Hill NJ hamfest today, met up with Steve (Musiqlovr) and we were hunting for treasure.
I score a nice variac. I already have a nice vintage 10A Powerstat but you know the way we are. Power, hell, there is never enough power! I want MORE power!
I have to make a box to cover the connections, probably put a few outlets in it as well. I love the construction, looks like the top and bottom castings are bronze and it's heavy as can be. I'll add some feet to the threaded rods on the bottom and think about what to do on top. This thing was BRAND NEW in the box! I got a great deal on my tiny Powerstat, 10A is tiny, right? Paid the same for this. I haven't put it on a scale but I figure it was about a buck a pound. Now you guys got me to thinking, maybe I need two of these. LOL
I'm shocked! The plate says 15A, figured by the size of it probably 25A or more. Anyway, it's more than enough to power anything I might play with.
20190915_155922_resized.jpg20190915_160027_resized.jpg20190915_160109_resized.jpg20190915_160125_resized.jpg

BillWojo
 
Variable autotransformers are easily available in "ganged" form, usually triple ganged for three phase but it also would be very easy to convert the ones you have with a long piece of drill rod of the same diameter as the rotor shaft. Just gang them. and for god's sake put them in a copper box.

Something like this but using the three amp rated variacs you showed.

www.mouser.com

1520-3 Staco | Mouser

1520-3 Staco Industrial Control Transformers 3-Phase, WYE, 9.5A 240/480Vin, 480/560V datasheet, inventory, & pricing.
www.mouser.com www.mouser.com
 
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Hi Gene, I actually have one of those 3 gang variac's. It was used at Bridgeport Machine Tools in the CNC control division. We could run a CNC mill with it.
It's in storage, really just need to sell it off as I'll never use it. It's mounted on a roll around dolly as it's to heavy to lift.

BillWojo
 
gable said:
Interesting idea. What's the bandwidth like I wonder?
Click to expand...
flat at 60 Hz ;)

I should let @forkliftman15 respond for himself (i.e., with his own opinions) but my sense was, within my own ancillary hardware and my hearing limitations, it was pretty good. :) 20 to 20k? Not bloody likely. ;)

Whatever specs are available can be found in the catalog PDF at http://lcweb2.loc.gov/master/mbrs/recording_preservation/manuals/Powerstat Catalog P258G.pdf

The model of these particular Variacs Powerstats is apparently "Type 10".
By a Simple Twist of Fate ;) this gizmo is still here :) Consequently, I'll take & post a rear-view photo anon :)

EDIT: Looks like it's flat from 60 Hz to 2kHz, at least! :rolleyes:

16464
 
mhardy6647 said:
flat at 60 Hz ;)

I should let @forkliftman15 respond for himself (i.e., with his own opinions) but my sense was, within my own ancillary hardware and my hearing limitations, it was pretty good. :) 20 to 20k? Not bloody likely. ;)

Whatever specs are available can be found in the catalog PDF at http://lcweb2.loc.gov/master/mbrs/recording_preservation/manuals/Powerstat Catalog P258G.pdf

The model of these particular Variacs Powerstats is apparently "Type 10".
By a Simple Twist of Fate ;) this gizmo is still here :) Consequently, I'll take & post a rear-view photo anon :)

EDIT: Looks like it's flat from 60 Hz to 2kHz, at least! :rolleyes:

View attachment 16464
Click to expand...

Looks like your smiley key is sticking, doc.

:)
 
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Is that one of Dave Slagle's new products? 🤭

Chain drive.... the Schiit boys shoulda tried that with their Sol...

oh, as to smilies or emoticons or emojii or whatever -- note the subtle variation in the chosen... umm... whatever they ares.

🧐
 
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