Like this:
How to attach images to your posts.
Edit... I've removed a link in your earlier post as it was affecting page loading/viewing. Your second attempt now shows OK (it didn't before
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How to attach images to your posts.
Edit... I've removed a link in your earlier post as it was affecting page loading/viewing. Your second attempt now shows OK (it didn't before
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The freq counter will detect static oscillation, but not sporadic oscillations.
one test would be to apply a 10KHz square wave into a 8 ohm load and look on a high freq scope.
You are correct, all you need these days is a selector, level control and a buffer to drive the cable and amp input resistance.
The old school audio gear needed more gain since the sources where phono and tape, typ 100-150mV, so you needed gain for the amp sensitivity in the 1V range.
^ Thanks rsavas , but I don't have a scope .
That's just it , the level control at the preamp stage is mostly at or near its minimum (for your ears and neighbors), to drive the poweramps that have too much gain. They should call a preamp : the PreAttenuater . Still Elektor and others keep offering these sensitive poweramps.
Clobber the 16 bit audio down to 200 mVpp , means 3 uV steps , 24 bit audio : 0,12 uV . Those have to be pretty good opamps & amps to make sense of that.
I don't know if anyone on this forum has raised this problem . Same goes with HP amps that constantly work in the mV range.
That's just it , the level control at the preamp stage is mostly at or near its minimum (for your ears and neighbors), to drive the poweramps that have too much gain. They should call a preamp : the PreAttenuater . Still Elektor and others keep offering these sensitive poweramps.
Clobber the 16 bit audio down to 200 mVpp , means 3 uV steps , 24 bit audio : 0,12 uV . Those have to be pretty good opamps & amps to make sense of that.
I don't know if anyone on this forum has raised this problem . Same goes with HP amps that constantly work in the mV range.
Hi RickTH,
Welcome to DIYAudio!
Please work on getting an oscilloscope. It is your most important go-to instrument along with a multi-meter. Note that an analogue scope is probably best, and if you can afford a 100 MHz two channel one, you'll have your needs met. See if you can get the original probes with it as they are better than the inexpensive ones you find on Ebay.
Some times an AM radio can pick up some amplifier oscillations, but the thing you really need is an oscilloscope. Do pass on the USB instruments, but a USB sound card makes a dandy signal source.
-Chris
Welcome to DIYAudio!
Please work on getting an oscilloscope. It is your most important go-to instrument along with a multi-meter. Note that an analogue scope is probably best, and if you can afford a 100 MHz two channel one, you'll have your needs met. See if you can get the original probes with it as they are better than the inexpensive ones you find on Ebay.
Some times an AM radio can pick up some amplifier oscillations, but the thing you really need is an oscilloscope. Do pass on the USB instruments, but a USB sound card makes a dandy signal source.
-Chris
Never underestimate producers of an expensive high-end gear, they eat Elektor kind of amps for the breakfast. The hissing you have heard is a system noise, sum of all contributing noise sources, which means your amp in that system could probably result in to hiss even more. Regarding the sound quality, always compare two amps in the same system, changing nothing less or more than just the amps.
I had a 30 MHz scope in the nineties , but sold it because I thought I would stop with electronics . I was wrong ! The electronics bug came back . As a hobbyist , it's too expensive to buy another one. (and I'm an expat living in another country , so keeping such a big device is near impossible). There are good and small USB ones ... but too expensive PC Oscilloscope, Data Logger & RF Products | Pico Technology .
Sure , comparing Elektor's Compact Amp with commercial high end Amps of 1000's of $/€ is out of place . I had the guy in the hifi shop short the input of the amp , and there was still some hissing coming from the tweeter . No switch box , just amp to speaker . Well no hissing through my tweeters with the compact amp.
I made it for about 300 € , payed 10,5 € a piece for the GT20D101-201 .
So glad for DIY amps . I designed the protection circuits for the amp and a different supply power . I can switch 'em on-off remote controled .
Sure thing, very convenient. Other than that, your amp could simply heavily oscillate and blown that speakers apart. Who knows what kind of burden hanged on a little hissing amp, no blame deserved.
Hi Rick.
I think that original Toshiba IGBT pairs are: one black other green package? You have all black IGBTs? Thay, originals are 3 times more expensive per piece and not easy to find theese days...
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I build one piece of that very good amp. Before decades. This was in the article Ultrafast high end design. Still working in the pro studio for monitor amp... I run it about 400mA Io. Somehow when I remember for 300mA these heatsinks are at the edge? Probably should be bigger. Mine was. I remember that the one og the key point was to pair the input BJTs not only smple Hf but thermaly. The device for pairing is also published in some later elektor magazine. And of course huge power transformer. I put dual mono 2 x 400W, with not much uF after rectifiers...
...
It was for my oppinion one of the best 50W amps.
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But from what You are accomplish this PCB from parts of tank T34?
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Well did say that I build it in 2001 ... 18 years ago . Back then you bought in electronic component shops and got the original Toshiba transistors . Not that much fake/immitations like there is nowadays. So the 10,5 € /IGBT is the 2001 price too .
I (unfornunately ) live in an apartement so I can't play loud . 300 mA is enough to stay in class A at low levels. In hot summers I turned it down to 250 mA . I don't want my heatsink temp higher than 40-45 C . These are big a$$ headsinks btw.
Yes the input transistors and the constant current sources are thermally coupled , as you can see in the pic I posted in my second post .
My transformer was as Elektor's BOM , about 160 VA but with 4 x 10.000 uF to each supply line.
I (unfornunately ) live in an apartement so I can't play loud . 300 mA is enough to stay in class A at low levels. In hot summers I turned it down to 250 mA . I don't want my heatsink temp higher than 40-45 C . These are big a$$ headsinks btw.
Yes the input transistors and the constant current sources are thermally coupled , as you can see in the pic I posted in my second post .
My transformer was as Elektor's BOM , about 160 VA but with 4 x 10.000 uF to each supply line.
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