Exactly. A simple, quick, elegant, engineering hack that solves the speaker protection problem for a few pennies in a few minutes. Perfect!
-Gnobuddy
That’s a pseudo-split supply amplifier where ground floats - similar to classic QSC but with a discrete front end instead of an op amp. The output is effectively capacitively coupled if that center connection between the 2 caps is not connected to the transformer center tap. They do work, and are quite bulletproof. The only caveat is that multiple channels cannot share power supplies. At all. Separate secondaries on the same core can be used, but with some crosstalk. Bifilar windings should not be used - if you use a toroid they should be wound separately. Separate transformers is of course the best option. For a single channel, like a powered loudspeaker, they are a great choice.
This is a perfect retro amp: all-in-one pcb, low distortion, low power consumption, great sounding
DanWATT - Google Photos
DanWATT - Google Photos
Thanks for the insight. That's a problem I had completely ignored when I planned to use a 50+50VAC wound toroidal transformer in a small stereo amplifier recently. It was a bargain but now I'll have to rethink that whole idea.
The differential voltages between adjacent turns can get high, and the windings are tightly coupled both inductively and capacitively. Signal will spill over from one power supply to the other, and you can even arc between secondaries. I’m pretty sure the toroids used in the QSC RMX amps have two sets of bifilar windings - separated from one another by an electrostatic shied. The older ones in the USA series used UI cores with half the primary and one secondary on each side.
As long as I've sold my soul to google I would be allowed to look at it. Not playing that game.
Thanks wgski for pointing out problem with tiefbassuebert "disconnect the center tap from ground & double the rail cap voltage" DC protection scheme. 2 transformers required for stereo.
Think apex GA100 with one 2sa1943/2sc5200 is in serious soa danger at 113 vdc. OTOH with mje15030/31 drivers, with a heatsink, 2 pairs OT is possible. Since it is a triple, changing drivers to MJL4302/4281 with heatsink, and predrivers to something TO220 with a heatsink, could drive 3 or 4 pairs OT. 2n5401/5551 doing the VAS could be upgraded to TO18 transistors with heat sinks too, and the 100 ohm collector resistors dropped to 82 or so for more drive current. Newark is keeping around one 10 W TO18 pnp and npn most of the time, multicomp copies of something real.
Actually could hot rod my AX6 to more than 5 seconds 72 watts with two or three pairs outputs. The VAS is a GE D44R4 TO220 with heatsink, and the drivers are mje15028/29 with heat sinks. So the main reason I don't do it is no room in the chassis for more OT heat sink.
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Simply using four 5200/1943 pairs would be enough to make it robust. Upgrading the drivers to NJW0281/0302 would be nice as well. You don’t need to add much more to it than that.
The original DC300A (same power supply voltage) used 4 pairs of 3773, later changed up to 2N5631 in newer rev’s, and you could beat the snot out of it.
The original DC300A (same power supply voltage) used 4 pairs of 3773, later changed up to 2N5631 in newer rev’s, and you could beat the snot out of it.
I'm with you on the crazy spying and tracking, with Google being one of the worst offenders at the heart of it.
However - I don't have a Google account, and I have no problem viewing those pictures. Did you try to view them, or did you assume you'd need to log into Google?
-Gnobuddy
Saw a hextet of blank boxes, with a prominent request to sign in to google. similar problem with the vacation pictures emailed me by my wife from her gmail account - 800x600 thumbs only available unless I sign in.
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One of many reasons our IT department forbids logging into gmail at work. That means you need to have some personal email sent to the work account because there’s no other way to get it - with a lot of content blocked and every byte filtered. Lesser of two evils - a lot easier to control everything than by letting Google do it’s magic. I’m kind of surprised they even let (in some cases require) us to use Chrome. Some of their bull$ intranet crap won’t work with IE, some won’t work with Firefox, and all of it is garbage code that could get hacked by a kindergartener. And crashes constantly, and the circle has to sit and spin for 20 or 30 seconds on practically every operation, even when it is “working”.
And no DIYAudio from the work machine either - they forbade that about 5 years ago because of all the international content. Won’t run it on my windows machines at home either. ONLY on my iPad. And now that I’m working from home, I do not allow any other windows machine to be even operating on our wi-fi when I’m using my laptop on VPN. Power switches must remain off till I’m off-line.
And I STiLL get banner ads here related to anything I’ve been working on (on my windows machine) regardless of whether I’m using Google for anything. But if I do google something it will show up first thing i the morning. That’s without signing in, and on a totally different machine.
And no DIYAudio from the work machine either - they forbade that about 5 years ago because of all the international content. Won’t run it on my windows machines at home either. ONLY on my iPad. And now that I’m working from home, I do not allow any other windows machine to be even operating on our wi-fi when I’m using my laptop on VPN. Power switches must remain off till I’m off-line.
And I STiLL get banner ads here related to anything I’ve been working on (on my windows machine) regardless of whether I’m using Google for anything. But if I do google something it will show up first thing i the morning. That’s without signing in, and on a totally different machine.
Have you tried Brave browser? Built on the same source-code as Chrome, without the nasty spyware Google added. Stated goals include privacy protection.
Because it's built on the same open-source code base that Google used for Chrome, there's a good chance Brave might run those web applications that otherwise only work on Chrome for you.
Brave browser: Secure, Fast & Private Web Browser with Adblocker | Brave Browser
I install Disconnect, Cookie Auto-Delete, and Adblocker Ultimate on all my browsers. Not being a computer security researcher, I can't tell you exactly how good (or not) they are, but I can tell you that ads don't follow me around from one computer to another, and in fact, I very rarely see any ads at all. And I didn't have to log into Google to see those pictures in the earlier post here, either.
-Gnobuddy
Okay guys, useful info. But if this goes on moderator will move this thread to lounge, and all discussion of 50 W 6 transistor amps with <.1% HD will stop. Which can be built with wire on bare board. Please continue with PM's or a new thread.
I intended to prod LKA into uploading schematics of his danwatt, and he can't be bothered. As with most other external links, even if one is a member of lockbox or whatever, external links die. At least Apex/Mike Stavkovic uploads his alternate suggestions. The 25 W Apex 6 was quite appropriate for the budget builder.
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My 50cent on an single supply amp. Its not really retro - or is it. Why I want a single supply amp? Well as I am also building an active subwoofer with a series cap to interact with the woofer, why not let the cap be part of the amp... And of course, also for curiosity and learning.
So any comments and improvements from your side? Would love to here your opinion. At the moment is simulates pretty well.
So any comments and improvements from your side? Would love to here your opinion. At the moment is simulates pretty well.
