Actually I'm doing/have done a number of evaluation boards to tweak the Bogen industrial amps I bought.
Most people may be unaware of these "sleepers" I bought while they were still cheap, because they look...well "industrial", (some say horribly ugly!) and usually spent the last 30-40yrs on some shelf running ice rink/stadiums or other distributed audio systems.
It's becoming common knowledge, the units have very hi quality hifi transformers stuck inside using excellent interleaved winding techniques and superb core material.
The potential is there for a very high power amp, with superb wide band performance and extremely low distortion, not a PA amp at all....but then you can sense the PA roots, with the sheer PUNCH of the unit under load.
Recently I had a very close look at the different secondary taps, and they all have the same wire gauge.
That's simply NOT done in cheap low quality transformers.
Then,-
Most people turn their nose up at anything with 25V, 70v, 100v or 140v output line systems assuming they must be rubbish...
Nothing could be further from the truth.
Being as I already made a substantial change to the driver system and feedback arrangements, I figured it could be interesting to make a change to the output transformer configuration too.
I began to test bi wiring and tri wiring the amplifiers to an array of different speakers, in order to achieve a semi active cross over arrangement.
This is a totally different idea from anything traditionally ever done with valve amps, but can be done quite easily, (unlike units built with sand inside).
People assume 8 ohm is best and everything else has to fit into this rather narrow reality.
In fact it's reflected impedance is the thing we have to be looking at, and matching what we need with what we can get.
This article particularly caught my eye, because the MO100A/MO200 are the only amplifiers I know with both centre tapped 25V and centre tapped 70V outputs.
Some of the older 1940s, 807 based units have a mix of 8/15, 70V and 140V outputs.
Those are now getting extremely rare and start to get sought after, because they turn out to be one of the best, unburstable guitar and bass heads you could ever wish for.
Industrial quality, 70years many of them are still running like the day they were made.
That has giant advantages, as you are about to find out.
The article of august last year is especially interesting.
https://www.tubecad.com/2017/08/blog0393.htmhttps://www.tubecad.com/2017/09/blog0394.htmand 2years before:-
https://www.tubecad.com/2015/06/blog0324.htmHere's a gold plated quote from JB:-
It sums up a lot I agree with....
What he thought the world really needed was new Stereo-70, but with a larger chassis, a chassis far wider and deeper than it need be, an almost silly spaciousness, so it would not only allow modification, but it would positively invite it.
As he saw it, American teenagers needed something to hotrod, something to modify that would personify and exemplify the modder's character, temperament, emotions, and personality.
And since cars were now too expensive and too complicated and too regulated (is it even legal to create a hotrod today?) for ready modification, something else would have to take their place. As he saw it, tube-based audio gear could fill that void, as it was simple and yet yielded deeply satisfying results. Thus, our long phone calls, while we discussed how a universal Stereo-70 could be designed and built.
During one such call, he told me what I already knew. He had originally manufactured toys and he had decided to create a tube-audio company named "Tube God." His plan was simple: he would hire the best electronic designers and use the best parts to build the best audio equipment, which would then be housed in ugly boxes, as he wanted to sell sonic performance, not jewelry boxes. His effort failed. A few years later, he came out with the same products in fancier boxes and he was successful. Audiophiles will not buy ugly boxes.
Topic: studio monitoring/valve amp based (Read 6367 times)