50 se shuntregulated supply

If they glow, this is the place to be
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#16

Post by IslandPink »

Oh, as far as white noise goes, I was thinking in terms of testing the power supply with a dummy load, and finding an oscilloscope setting of say 10 or 20mV full scale, for example, to see what the residual noise looked like .
Otherwise the tests look good, especially if the noise at the speakers is as low as you say - are you sure it's uV ? - would be tricky to measure something that low !
"Once you find out ... the Circumstances ; then you can go out"
vegard
User
Posts: 18
Joined: Fri Jan 25, 2013 6:53 am
Location: Oslo

#17

Post by vegard »

Thanks
I am in the moutains, eastern holiday with my family.
next week I'll meassure.
Yes I think the meassurement is quite accurate.
The instrument is calibrated, and it is also meassured with other instruments
by another diy'er.
I have repeated the noise meassurement several times, when I removed the second lc it went up to 100- 120µV. the needle is moving a little though.
Not shure why.
Andrew
Eternally single
Posts: 4206
Joined: Thu May 24, 2007 2:18 pm

#18

Post by Andrew »

To measure this I would take the output of the HP33A from the rear outputs into your scope, you'll see what's left over, after the fundamental is removed. Even better I would take the output into a decent sound card and use FTT software; the HP 3334 will 'protect' the soundcard from overload and other errors. You should be able to get an idea of the noise floor etc.

Andrew
Analogue, the lost world that lies between 0 and 1.
User avatar
Nick
Site Admin
Posts: 15706
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#19

Post by Nick »

Also, with that scope, you can stack the two input stages to give you a higher gain input, lake the output from the back on the first input, into the second input. Check with a on like instruction manual.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
vegard
User
Posts: 18
Joined: Fri Jan 25, 2013 6:53 am
Location: Oslo

#20

Post by vegard »

Spare time after eastern was absent. Preparing for autumn season.
I will catch up with the meassurements as to your suggestions then.
I have borrowed the psu from Stephie (not the first time).
I intend to make a testrig after summer vacation, and will post pics and more later
Attachments
preliminary circuit
preliminary circuit
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8863
Joined: Mon May 21, 2007 9:42 pm

#21

Post by Paul Barker »

I have used this method of Stephi often. It was first demonstrated at the first Eggborough meeting on a px25 amplifier. Last I used it at home on 801a.

This schematic you have drawn is great. You will love it.

There will needs be some means of altering the power supply to achieve correct. Current through the shunt valves. Mixing and matching dc resistance of chokes and trying different vr tubes gets you there. Whole thing looks simple on paper. Big heavy and difficult to fine tune. But worth it most definitely.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8863
Joined: Mon May 21, 2007 9:42 pm

#22

Post by Paul Barker »

Here is a direct link to my photobucket video of the 801a amp which used to be spread out in my man cave. Sadly the man cave had to go, and the amp was torn apart. It was my best amp ever. The sound on the video doesn't come over good it is my phone recording it. The actual sound is out of this world. Those a field coil open baffles, also the best sounding speakers I ever put together.

Completely capacitorless 801a amplifier including capacitorless power supply

I did some pictures of my workings for the guys here to show how it is arrived at.

This shows how you plan for the shunt regulator:
Image

One of the shunt valves voltage

Image

And it's current

Image

This picture shows the bias voltage of the shunt valve +21v

Image

You already know the size and weight of the power transformers and chokes is immense. You already know their current carrying capacity is immense. You already know that you have to mix and match them so you need a good variety to choose from, when you also decide on ressistorless, just using the dc resistance of the chokes as your only aid. That and the ability to mix and match the VR string in complement to mixing and matching dc resistances. It is not for the feint hearted who don't own a shed load of chokes and VR tubes. But oh boy is it worth it!
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8863
Joined: Mon May 21, 2007 9:42 pm

#23

Post by Paul Barker »

One option I did try for a while was a 13e1 series reg to help me out of the difficulty of arriving at the correct B+. This sort of power supply is an animal, which you have to adapt your requirements to, because it is not adjustable. Simply starting with over voltage and using a 13e1 series reg removes a large amount of difficulty. I cannot say that it sounded any worse. Though in the iteration in the video I see it was not there on the power supply. So I must have decided it sounded better without it, because I wouldn't have removed it otherwise. This particular video goes back maybe 2 or 3 years it was the last time I had that amp playing. I have enough knowledge of it in my memory banks to rebuild it but not the space and half the stuff is in hiding in my lockup, would take weeks to unearth. There are bigger fish to fry.

The px25 version I played at the first Eggborough many years ago was also an amp and a power supply with no caps and no resistors. At that time there were 4 shunt valves some 811a and some 572b. One of the 811a's I over cooked badly and melted the top pip off it, but after wards I just attached to the wires sticking out and it was fine. Those valves can be pushed way past their ratings and survive, Can't do that with a mosfet can you? I loved it, but there was a long pause in my life before I rebuilt that sort of amp, and for some reason or another I seem to have ditched two of the shunt valves. You can see the space they used to occupy in the recent version video'd. IT has been a journey fraught with difficulty when it may take years to discover you have a potted choke brightly arking away inside that you can't see, and you always have a noise in the supply you can't solve. Then one day the arking is sufficent to burn through the pot and you are listening with the lights off. Then suddenly the answer to your noise flaoor problem is found. It is a journey my friend. You are pushing components to the edge of sanity, and yourself. but you won't achieve these sounds without pain.

These days I am trying to make stuff small and safe enough to fit in a family room which sounds almost as good. So far I am not there. My small 750mW amp is about as good, maybe not quite. It has one black gate in the power supply, but just one, a compromise decided upon to make the supply a heck of a lot more compact than what you see in that video. Sometimes in our lives compromise is best. We all go through different stages in life. If I lived in a one room batchellor bedsit hell yer that thing in the video would be back in pride of place. But I would be miserable without my lovely family around me, so holistically I would be worse off!
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
vegard
User
Posts: 18
Joined: Fri Jan 25, 2013 6:53 am
Location: Oslo

#24

Post by vegard »

Paul ; Thanks alot! Great inspiration!
I am sure it was outstanding soundwise, what a pity it was dismanteled. Shouldn't one of those zillion EU impositions (wrong Word maybe?)
actually have protected Your psu ?

As you say : a time for everything. This supply is just one of the things I must make. I will post as I am progressing.
Vegard
vegard
User
Posts: 18
Joined: Fri Jan 25, 2013 6:53 am
Location: Oslo

#25

Post by vegard »

As for the dc resistance in mainstransformer+rectifier+choke

I thought of one way to settle the correct Rdc :
play With som r values in series With the choke . Once settled, have the choke custom made .

Or ?
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8863
Joined: Mon May 21, 2007 9:42 pm

#26

Post by Paul Barker »

Yes that would be the best way.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
vegard
User
Posts: 18
Joined: Fri Jan 25, 2013 6:53 am
Location: Oslo

#27

Post by vegard »

Time flies...
The 50 se came alive just before Christmas. The cap less psu 's are not made yet...(to little diy time)
Attachments
50 se
50 se
schematic
schematic
1w spectrum at output
1w spectrum at output
vegard
User
Posts: 18
Joined: Fri Jan 25, 2013 6:53 am
Location: Oslo

#28

Post by vegard »

Irons made by D Slagle
Attachments
input and driver<br />Colemans regulators on the chassis, heastsinks on the outside
input and driver
Colemans regulators on the chassis, heastsinks on the outside
vegard
User
Posts: 18
Joined: Fri Jan 25, 2013 6:53 am
Location: Oslo

#29

Post by vegard »

inputstage when the 50 is clipping
Attachments
112a  anode when the 50 is clipping
112a anode when the 50 is clipping
Post Reply