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Audio note M7 question.
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6516
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Author:  M. Gregg [ 14 May 2019, 10:51 ]
Post subject:  Re: Audio note M7 question.

Just a few thoughts.

I was thinking about the effect of a copper chassis, ie why use copper whats the point vs aluminium etc.
Its interesting to note that in a squirrel cage induction motor, induction magnetises the rotor through induced current.

But while looking I noticed this which I found interesting:
https://www.youtube.com/watch?v=sENgdSF8ppA

Regards
M. Gregg

Author:  M. Gregg [ 14 May 2019, 11:27 ]
Post subject:  Re: Audio note M7 question.

Input board,

Kite input board wired with Duelund silver in cotton / oil using Audio Note solder.
The back of the board is sprayed with CPL which you can solder through if you need to modify.
I will probably give a timed mute start up, but it depends if its necessary.
Tufnol <<<wear a mask to stop the dust (Safety first :D )
I tend to use the CPL on the back of boards but not the front.
Its a good way to stop Vero tarnishing and give higher voltage protection.
I had the old can a few years. CPL can also be removed with IPA 170.

Regards
M. Gregg

Author:  M. Gregg [ 19 May 2019, 04:27 ]
Post subject:  Re: Audio note M7 question.

The hole is now in for the 6x4 rectifier.

I didn't have a cutter for the B7g so half hour with a Dremel.
The layout is just a test to set some positions for holes and the final position of the potentiometers isn't decided yet.
The N20 motor mounting was a slight problem so again fabricated from vero pad board and epoxy (rough initial build).
It will have a suppressor and braking resistor and better finish.
The transformer manufacturer likes flags :D
The valve bases are Audio Note. :confused:


Regards
M. Gregg

Author:  M. Gregg [ 19 May 2019, 04:37 ]
Post subject:  Re: Audio note M7 question.

One idea at the moment,

is to build the M7 valve board on Kite Tufnol as a module and then build the other variation with the cathode driver.
Then it is possible to interchange the modules. However its all just ideas at the moment.


Regards
M. Gregg

Author:  M. Gregg [ 19 May 2019, 05:36 ]
Post subject:  Re: Audio note M7 question.

Just for interest,

The N20 motor can be fixed with an angle bracket with M1.6 pins.
However I want total electrical isolation from the chassis.
These motors are available with different voltages and speeds.
In this project its lowest speed motor, I'm going to try 6 to 1 ratio for the motor to pot drive.
I'll have to see how it goes.

Regards
M. Gregg

Author:  M. Gregg [ 08 Jun 2019, 13:25 ]
Post subject:  Re: Audio note M7 question.

slow progress,

just thinking about compacting the circuit.
The motor bracket is cleaned up and epoxy coated.
The HT board is completed (silver wire audio note solder) on "kite" following audio notes ideas.
I mounted the resistors and first cap on turret tags for ease of mod / replacement if needed.
Input is via 500 ohm ohmite WW feeding (Audio Note caps)10uF 500V to 11K feeding 100uF 500V split to two circuits 2.2K WW welwyn feeding 100uF 500v. There are other things going on but still in design "fun" stage.
Reading about Kondo ideas there seems to be an idea of "adding" inductance. I assume that's the idea of the WW resistors in the PSU. (but I could be wrong) ;)

Regards
M. Gregg

Author:  M. Gregg [ 11 Jun 2019, 16:43 ]
Post subject:  Re: Audio note M7 question.

Hybrid bridge (Teflon board).

Just a few ideas. An hour looking at ideas.
UF4007 >>ferrite bead immortal rectifier / BA157 Hybrid bridge using toshiba ammo bead suppression.
https://toshiba.semicon-storage.com/us/ ... beads.html

NB for anyone not familiar with ammo beads they are not the same as ferrite beads and are not interchangeable.
https://toshiba.semicon-storage.com/con ... s_Work.pdf


Thermistor inrush suppression.

Regards
M. Gregg

Author:  ILoveHiFi [ 11 Jun 2019, 20:46 ]
Post subject:  Re: Audio note M7 question.

Use a schocky didoe, the reverse recovery dosen't exist, but due to charged didoe capacitances, very little reverse recover will occur.
Ultra fast etc diodes are only cheaper and for higher voltages.

You can also get very high voltage schocky diodes but is more expensive. Hint is that from china you can get geniune schocky diodes for very cheap , not sure about the capacitances voltages and current ratnings, but is geniune socky without reverse recovery. aslong as your not pushing way near max specs its working solid for me.
I wouldn't really take a risk for china diodes, unless you perform tests to ensure the diodes aren't going to blow for this HV project.

Seems like you got some fancy pots and trasnformer, good start. looking good.

Lookling at what toshiba said, by the ferrite to make the recovery soft, you make the reverse recovery time 3x as long. Some trade off between soft recovery and short recovery time.

Author:  M. Gregg [ 12 Jun 2019, 02:53 ]
Post subject:  Re: Audio note M7 question.

Quote:
Use a schocky didoe, the reverse recovery dosen't exist, but due to charged didoe capacitances, very little reverse recover will occur.
Ultra fast etc diodes are only cheaper and for higher voltages.


I don't like Schottky diode's in valve PSU its just a personal thing. :D
A lot of people do like them, I do use them in diode biasing in the cathode.
This circuit drives into a 6X4 hybrid bridge.

I tried a few things in the past.
viewtopic.php?f=5&t=5632
Just for interest ref:Reverse breakdown:
https://www.electronics-notes.com/artic ... meters.php

In the cathode bias I normally fit a standard diode in series with Schottky.
I find that using capacitors to snub the commutation colours the sound (YMMV) :D

Regards
M. Gregg

Author:  ILoveHiFi [ 12 Jun 2019, 04:20 ]
Post subject:  Re: Audio note M7 question.

Theriotically speaking, the diode that sounds best is the one that has least change in foward voltage as current varries.
Schottky didoes have lowest foward votlage and for the same current ratings the change infoward votlage is less.

Also the one has to have lowest reverse recovery.

I never place any influence on the power supply and tend to minize the cost here.

I don't see a point of expensive diodes in biasing though, because these will never turn off so any diode is the same.

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