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Time to tackle the High Voltage Power Supply

174.113.86.183
Posted on January 1, 2016 at 10:28:40
Cousin Billy
Manufacturer

Posts: 243
Location: Greater Toronto Area
Joined: September 10, 2004
I will take this really slow.
Yes I have bled the storage capacitors of their charge.

There are 12, 100uF, caps now.
I will be replacing them with 6, 200uF, Mundorf TubeCaps.

The caps there now are directional. 600uF pointing to the right. 600uF pointing to the left.

1) The Mundorfs are film caps. No direction. Is this a drop in replacement. Is there something more I will need to do? I do understand about inner foil and outer foil. I will align them properly.

2) On this right side, all the caps appear to be connected. Is this true, or are my eyes deceiving me?




 

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RE: Time to tackle the High Voltage Power Supply, posted on January 1, 2016 at 13:30:20
Cousin Billy
Manufacturer

Posts: 243
Location: Greater Toronto Area
Joined: September 10, 2004
 In the previous posts picture.

Regarding the 'ELMACO' OR 'HAITI' 600 ohm resistors. If I was to change these, but I only have 560R and 680R, which would work best. And why?.

 

RE: Time to tackle the High Voltage Power Supply, posted on January 1, 2016 at 17:53:51
cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009
 "Regarding the 'ELMACO' OR 'HAITI' 600 ohm resistors. If I was to change these, but I only have 560R and 680R, which would work best. And why?. "

Would you care to give a clue, such as what the schematic is, or what amplifier you are talking about?

Chris

 

Atma-Sphere MA-1, posted on January 2, 2016 at 01:13:59
Cousin Billy
Manufacturer

Posts: 243
Location: Greater Toronto Area
Joined: September 10, 2004
 Hello cpotl
I'll get to your question after this first picture.
A few years ago I had a friend build 'risers' for my MA-1 amps.
In hindsight, 3" was not enough.
Good gosh are those 200uF Mundorf Tubecaps big!!!!





Let's get to cpotl

In this next picture, I have removed the orange drop cap and the 7.5 Ohm resistor. These two appear to make an RC circuit. A quick calculation puts the corner frequency at 212,314Hz. I will assume this RC filter filters out the Utility Companies ~200000Hz carrier signal. This signal is how different power stations 'talk' to each other.

I am not an electrical engineer.

The 'front' of the RC circuit is connected to the HV caps, and the 'back' of the circuit is also connected. This is through the 600 Ohm resistors.

I need help in understanding this.

The original HV power supply caps are directional?.
The new ones will not be. They are 'film'.

Question: Does current and voltage pass in both directions in the 'old' capacitors?

Do the 600 Ohm resistors connect the power, coming to the caps from the transformer, to the RC circuit, therefore 'cleaning' the power to the HV caps?

If yes, then any value around 600 Ohms will work.

Otherwise????





 

RE: Time to tackle the High Voltage Power Supply, posted on January 3, 2016 at 16:57:59
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 How are you planning to support the extra weight of the film caps?

When you sell the amp and ship it, and the film caps tear themselves off those terminal strips, then make a mess of the inside of the amplifier, are you at least going to keep the caps you pulled out so you can put them back?

 

RE: Time to tackle the High Voltage Power Supply, posted on January 3, 2016 at 17:14:49
Cousin Billy
Manufacturer

Posts: 243
Location: Greater Toronto Area
Joined: September 10, 2004
 The film caps will actually 'sit' on the bottom plate (the one with the ventilation slits).
There will be a piece of sorbothane between the bottom of the caps and the plate. Vibration control?
Twist ties, and more twist ties.
But let's think about this. The MA-1 is arguably one of the best amplifiers on the planet. I have installed IXYS full wave bridge rectifiers, oversized capacity. There are two Mundorf HC+ low voltage storage supply caps, 4-pole version. I've ordered CuTF 0.22uf coupling caps. The Mundorf film caps obviously. Some of the resistors will be upgraded to Kiwame. There may be other tiny changes.

Why, my friend, would I ever sell the greatest amps on the planet?

You would do me a great service if you'd just answer some of my questions. If you know the answers of course (I'm gonna pay for that one).

 

RE: Time to tackle the High Voltage Power Supply, posted on January 3, 2016 at 23:11:45
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 You haven't really asked any questions. I only speak from experience, seeing what these well intentioned modifications often end up doing in the end.

 

RE: Atma-Sphere MA-1, posted on January 4, 2016 at 04:44:21
Banat
 Cousin Billy

-That orange 0,1uF in series connected with 7,5 0hm power resistor forms output Zobel network which appear connected in parallel with amplifier output two terminals ,
-Those two 600 ohm power resistors are ground reference resistors for Circlotron OPS , and if they are not connected in proper way as is was originally from A-T manufacture your amp will make booom and fail !
-Further I think that those big Mundorf capacitors do not belong there ,
electrically maybe but physically don`t ,
- Personally I will never modified those great OTL amps in your way .

Happy New Year and all the best !

 

The resistors are not critical, except that, posted on January 5, 2016 at 11:01:19
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 -as Banat has pointed out, there presence is. The actual values are not.

What is happening is they provide a return path for the bias on the power tubes and also reference the output section to ground potential. Since the actual bias current is very slight, the values of the resistors is not critical. However it is important for them to be able to handle some power, in case the amplifier is given a signal without a load- then these resistors *are* the load and will heat up.

The 600 ohm 3 watt value has proven pretty steadfast over the last 30 years or so.

 

+1 on that! nt, posted on January 5, 2016 at 11:02:48
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 :)

 

You are looking at the ground side of the driver supply., posted on January 5, 2016 at 11:07:24
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 So they are all connected together.

Just a point of fact- differential amplifiers are inherently much more immune to power supply issues than single-ended circuits. IOW in addition to Common Mode Rejection, there is also a Cross Mode Rejection figure.

With a differential amplifier that employs a 2-stage constant current source, this value is quite high. IOW improving the differential effect of the voltage amplifier will yield more sonic improvement than increasing the value of the filter caps or changing their construction characteristics.

The one place this does not apply is the cathode follower driver circuit. It does benefit from good quality bypass. Once you have a 200uf value though you will find that additional increase does not yield further sonic benefit.

 

Picture of mod. Music is playing and no smoke, posted on January 7, 2016 at 12:57:55
Cousin Billy
Manufacturer

Posts: 243
Location: Greater Toronto Area
Joined: September 10, 2004
 I hooked up an old driver, played some music, and no smoke.

Measured the chassis in a number of spots. Wanted to make sure I didn't have a 'leak' anywhere. Big smile on my face.

Can't wait for my CuTF's to arrive. Can't wait to finish my new speakers.

2016 is gonna be a great year.

Too bad the stock market is taking a hit.





1

 

Technical question which will likely not be answered, posted on January 8, 2016 at 01:51:55
Cousin Billy
Manufacturer

Posts: 243
Location: Greater Toronto Area
Joined: September 10, 2004
 If we look at the picture in the previous post.
My grey wire is coming off a tag strip. A green/yellow striped wire is running from there to the transformer. I think Ralph called this a 'ground' reference wire. It doesn't matter what it's called. There are obviously other wires coming to the tag strip. This all on one side.

Here's my question;
Is voltage 'coming' from the this tag strip, and into my capacitors?
Or is voltage 'going' to the tag strip?

Which direction is the voltage travelling through the HV supply caps?

 

Vh Audio CuTF have arrived, posted on January 8, 2016 at 13:46:48
Cousin Billy
Manufacturer

Posts: 243
Location: Greater Toronto Area
Joined: September 10, 2004
 Another technical question.

If these coupling caps connect the 'top of the differential cascode' (V2) to the 'driver tube' (V4), then the voltage travels from V2 to the driver tube V4. Yes?

 

RE: Vh Audio CuTF have arrived, posted on January 15, 2016 at 08:51:32
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
 Plate of the top tube in the dual-diff cascode to grid of the driver tube, yes. Where else could the signal voltage (AC) flow but from one node to the other? You might want to observe the directionality indicated by the color-coded leads of the Vcaps.

 

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