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Old 13th January 2012, 08:37 AM   #371
crt is offline crt  Indonesia
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@ Chris

more image please ?
looks gorgeous
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Old 13th January 2012, 08:37 AM   #372
generg is offline generg  Germany
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Hi Chris, would be happy if my prototypes would look like this....

I will start with the second channel today and try again in direct comparison the Mufollower and all the CCSs Salas suggested....

the last try with the Mu was a bit unfavorable , I choked the upper SemiS by only implementing the bias network but no 47k to prevent the signal going the sides away....

So repetition is matter of honor...
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Old 13th January 2012, 08:46 AM   #373
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Default Seems interr.....

Quote:
Originally Posted by Chris Goldring View Post
Hope everyone have a great time, i certainly do!

The prototype amp is now done and works very fine indeed.. I'm running it at 32V and about 1.6-1.7a (each channel), i think the heat sinks are good enough for that as they "only" get to about ~50C..And the resistors? a whopping ~150C at current power

The sound is awesome, the sweetness, the speed, the NUANCES, the big SPACE between the notes are just nothing but amazing.. It's just that, the timeless and sweet feeling and almost infinite space between the notes Is sure has that "sitting up all night" quality to it too. I can't wait to get some more proper cooling and push the power a little..

A tip might be to use a BJT based cap-multiplier in the PSU, just a thought.. I use it total hum-free with a total of 15,000uF for both channels as i don't like amps running something like 80,000uF+ (sounds slow with dull nuances if you ask me)
Hi Chris!

Your solution seems like a "easier" solution - with not so high voltage and smaller caps! The big heat sinks that is req is ok - but the somewhat smaller size on the the PSU is more to my liking.

I have not yet decided how to build my LÀmp - so my SK82 is still waiting for a "sound" solution. Whatever that means?

So Chris - will you provide some info, schematic how your amp is - when it is more or less finished? And what speakers you are driving your version with?

Will be VERY grateful for an answer( and my B1 - that is soon to be finished) will be a happy partner - somewhere in time!

Greatings to all.

Olav
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Old 13th January 2012, 12:24 PM   #374
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Quote:
Originally Posted by OlavHaal View Post
Hi Chris!

Your solution seems like a "easier" solution - with not so high voltage and smaller caps! The big heat sinks that is req is ok - but the somewhat smaller size on the the PSU is more to my liking.

I have not yet decided how to build my LÀmp - so my SK82 is still waiting for a "sound" solution. Whatever that means?

So Chris - will you provide some info, schematic how your amp is - when it is more or less finished? And what speakers you are driving your version with?

Will be VERY grateful for an answer( and my B1 - that is soon to be finished) will be a happy partner - somewhere in time!

Greatings to all.

Olav
Hello,

My PSU is super simple using just a single 2n3055 BJT. i made a simple schematic too

at the moment i'm only using one single PSU as in the schematic (except i use discrete diodes instead of the bridge)

I might make a schematic for the amp too if anyone really want that

I'm using a couple von schweikert VR2 at the moment, have no trouble with insufficient volume levels, and that is at 32V supply

When i get more serious with my heat sink i probably will make a 45-50V PSU with another gyrator/cap-multiplier, using one or two "transformers+rectifiers+first-cap"

And Thank Michael for making the Great article about this project, super-fun read indeed!
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Old 13th January 2012, 12:58 PM   #375
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Beautiful construction, Chris.

I know you'll be really pleased with the higher power. And, remember you can play with the harmonic seasoning by adjusting the bias ever so slightly in either direction.

I'm glad you're having fun
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Old 14th January 2012, 12:45 AM   #376
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Quote:
Originally Posted by Chris Goldring View Post
...I'm running it at 32V and about 1.6-1.7a...
That sounds just about right. With a 32V supply, 12 Ohm drain load, 8 Ohm speaker, Vds = 12V, Id=1.62A I see .4% THD @ 1W. I'd call it a 2.5-3 Watt amp. At 2.5W, we're at around 1.35% THD. I'd say you've got it dialed-in pretty well, now you can fine tune it to taste.
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Old 14th January 2012, 10:25 AM   #377
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Quote:
Originally Posted by Michael Rothacher View Post
That sounds just about right. With a 32V supply, 12 Ohm drain load, 8 Ohm speaker, Vds = 12V, Id=1.62A I see .4% THD @ 1W. I'd call it a 2.5-3 Watt amp. At 2.5W, we're at around 1.35% THD. I'd say you've got it dialed-in pretty well, now you can fine tune it to taste.
I wish i had a THD analyzer (or even better, a spectrum analyzer) too, would be great fun. I might work on some fine tuning later on, but not too sure that it would do much good without measuring the THD/spectrum.

I get quite nice level of volume with 1-1.5V RMS input and using it directly with the outputs from my DAC, no volume control or preamp for uttermost purity

Would you or anyone else using (BIG)C+R+(BIG)C PSU consider building the one i use at the moment and compare the different sound? Would be fun to see if we get at the same results

PS: I might add that i use 1000uF located in the amp for each channel and running a power cord for each channel to the PSU.

I was thinking how i was going to construct the more final version, dual mono block or a separate PSU+amp.. I am leaning towards the later with or without true dual PSU..

Last edited by Chris Goldring; 14th January 2012 at 10:42 AM.
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Old 14th January 2012, 01:07 PM   #378
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Quote:
Originally Posted by Chris Goldring View Post
Would you or anyone else using (BIG)C+R+(BIG)C PSU consider building the one i use at the moment and compare the different sound? Would be fun to see if we get at the same results
Sure, I think you should post your current and final designs for power supply, and the amplifier schematic as well.
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Old 14th January 2012, 01:37 PM   #379
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I just use the meter to get in the "zone".

The fine tuning is all up to your ear-brain interface and it often will not be the extreme null spot.

Last edited by Michael Rothacher; 14th January 2012 at 01:39 PM.
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Old 14th January 2012, 05:42 PM   #380
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YEEPEEEEEEEE YEAHHHHHHHH , wonderfull , merveilleux ,c'est Formidable!!!!

my SIT is on fire, 17V , 2,77 amp a BIG sound a little hum with my 102db horn speaker. but definitly too much gain with my threshold SL10 , i make a mistake not too buy a BC1 ..

pics to come...

for the hum do you have a resistor between hot and ground of the input RCA ?
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