Audio Note M10

the road not taken.
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dave slagle
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Audio Note M10

Post by dave slagle »

Had a friend email me about the M10 he built from a schematic floating around the web. He sourced the inductors locally and reported flat response from 100 to 1Khz but severe roll-off on either side.

here is the phono schematic:
Image

and here is my simplified Sim of the circuit with the inductors nearly ideal. Try adding some parasitics and see what happens.
Image

I built the entire front end up with the 6072 tubes and things didn't change much. (if at all) so my hunch of some "Kondo trick's" outside of the inductors didn't pan out. I'll attach both .asc's below, the simple doesn't use tubes so anyone should be able to run it, the other uses stephies drop down tube models.

discuss.

dave
Attachments
audio note m10.asc
to chance from the dropdown you need to delete the tube symbols and replace them with your 6072 model.
(5.22 KiB) Downloaded 905 times
audio note m10 simple.asc
(3.09 KiB) Downloaded 778 times
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sbench
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Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

me thinks the schematic floting ion the web kinda got waterlogged.

There are a couple mistakes in your "sim" schematic... The .01u (C6) you have returned to source, and in the net schematic it is returned to ground, and C5 ought to be 100u not 100p.

It doesn't make too much sense to bypass the 500 ohm resistor in the cathode and leave 2k unbypassed. If you assume the coupling into the filter is 2.2u instead of .22u, the LF problem is fixed. Given your parasitics, if you assume someone left off an assumed 700p on the left side of the 7.6H (making it a PI filter) the HF is better as well.

It gets pretty good with those changes, and L1 parasitic of 90p parallel, rparallel=2.5Meg and for L2 a 95k rparallel with 34p of parallel capacitance.

Incidentally, bypassing all of the cathode in the first stage yields 10dB more gain.

Is this thing supposed to sound any good?

Stephie <3

Funny how strays can affect things.
andyopus
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Joined: Thu May 20, 2010 9:29 pm

Post by andyopus »

Hello, I am Andy, this one is my problem, thank you for your insight into this, your comments re the C6 are true and furthermore what is strange is your comment re: C5 , I thought this looked strange as the front end of the circuit is exactly as per the M7 and it is this the one detail that is different. I can say that the M7 circuit certainly works well for an RC RIAA so this is what spurred me on to make the M10 :oops: but I am too far in to give up: well I can remove some components and add a few and just covert to an M7, whilst I cool off.
From your comments perhaps all may work out yet, I had suspected for while that it all looked too simple and ideal but I have seen this happen before with AN schematics (the Ongaku is a no feedback design yet it has a feedback loop on the revised schematic!), it may be a deliberate ploy to prevent copy but also a fall out did occur between AN Japan and AN UK maybe this is the "poisoned chalice"
Thank you once again. Andy.
andyopus
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Joined: Thu May 20, 2010 9:29 pm

Post by andyopus »

[quoteThe partnership started to fall apart around 1996/97. There are two different versions to the story but the long & short of it was that Audionote Japan stopped supplying Audionote UK.

This taken from another website kind of supports my thoughts about this schematic and how it may be incomplete. All my other schematics that I have from the early 90's have worked as built and without modification but AN UK used to supply components to D.I.Y these circuits, I am not sure this was what Kondo San had wanted. What is also interesting is how AN UK don't publish their own circuits any more and even stranger still is how they replaced the M10 with the M9......... yes a transformer RIAA and even filed a patent on certain aspects of the design.

Back to the first subject does anyone fancy putting a spice simulation together on Steve's suggestions and putting it on here. [/quote]
izzy wizzy
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Location: Folkestone, UK

Post by izzy wizzy »

I had a quick play about and changing the coupling cap from 0.22u to 2.2u makes a huge difference. Oh and keeping the 100p at the 2nd stage input also improves things. Maybe get rid of it altogether. It gets quite close then.

After that, fiddle about a bit with the other values if you fancy in a real circuit.
andyopus
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Joined: Thu May 20, 2010 9:29 pm

Audio Note M10 circuit Inductors / Capacitors

Post by andyopus »

Well moving this one along for anyone who may be interested, the .22uf capacitor was changed to a 2.2uf and the bass measures flat to 20HZ even though the simulation shows a little roll off, I will experiment with reducing this value a little to see what I can get away with as experience has shown me capacitor values are best kept to a minimum. I will report on this a little later. I have given up on my original inductors as even with a parallel resistor fitted to L2 I could not get the thing to run flat . I have taken the step of ordering a set from Dave and am looking forward to receiving them and hopefully finally getting my vinyl running once more. :)
piotr_grzesik
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Location: UK

Post by piotr_grzesik »

I simmed this a while back and found the same. It needs a few "corrections". I'll try and find the ASC...
Too much stuff and not enough time!
piotr_grzesik
Posts: 68
Joined: Mon Feb 07, 2005 9:59 pm
Location: UK

Post by piotr_grzesik »

So here's the response I got after changing the coupling cap (C1) to 1uF, The 700p (C2) to 7p and the 7.6H inductor (L2) to 8.7H.

Image[/img]
Attachments
Kondo_M10_mod.asc
M10 ASC with mods
(5.93 KiB) Downloaded 695 times
Too much stuff and not enough time!
andyopus
Posts: 9
Joined: Thu May 20, 2010 9:29 pm

Audio Note M10 now working!

Post by andyopus »

If anyone has been following this thread here is the news:
I have fitted a set of inductors made by Dave the response was better but still rolling off, I fitted a 100K parallel resistor to the 7.6H and nothing more and "hey presto" I have 20hz-20Khz with very little deviation. Not even the bass roll off that the simulation shows. Within the limitations of my facilities to test this all is well. Using a reverse RIAA and attenuator in line with my DAC I am able to play music that plays shockingly good through the phono stage. I have yet to mount the inductors in an enclosure and they will need it as they a picking up a fair amount of noise. I have the largest type from Farnell electronics and will have to house the 2.22uf capacitor(s) in there as well as I originally used a Jensen silver PIO 0.22uf and wanted to retain this so have added a Jensen copper PIO 2.0uf .
Currently I have left it running as it is to burn it in (please no debate about this subject) whilst some wire and sundry items arrive in the post. I will post some photo's once it is all sorted out
Attachments
Kondo_M10_asbuilt.asc
(6.09 KiB) Downloaded 730 times
IslandPink
Posts: 56
Joined: Thu May 12, 2005 8:01 am
Location: Denbigh, North Wales

Phono

Post by IslandPink »

Andy
This looks like an interesting unit.
Seeing as how you are in the Leeds area, would you be able to come along to the next meet in Owston ( Doncaster ) or Eggborough ?
There's some info on the AudioTalk forum -

http://www.audio-talk.co.uk/phpBB2/view ... &start=135

Mark J
quadmad
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Joined: Fri Sep 24, 2010 5:06 pm

Post by quadmad »

If you are up for making a 2nd, i would be willing to make a bespoke case for your pre, i am a woodworker who builds Tannoy cabinets and garrard plinths.

I live just down the road in Doncaster
andyopus
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Joined: Thu May 20, 2010 9:29 pm

Audio Note M10 LR PHONO UPDATE

Post by andyopus »

Well much time has passed and various things have prevented me from icing this cake I baked a long time ago but recently I have managed to get back to it and finally I can report this is one hell of a circuit once implemented correctly. The changes I have made are:
1. Changed the 6072's for the Russian 6N1P-EV, involved the rewiring of the heaters, I did this by running them series connected to 19 volts. Also connected pin 9 to ground. Instant improvement as I could not get 6072's of any manufacture or age to be totally noise free, the 6N1P-EV were quiet straight out of the box and cost me £15 for 6 close matched,
2. Played around with the 700p capacitor and finally selected 2 that were 680p but measured at 700p.
3. bypassed the 7.6H inductor with 100K resistor (this I believe is missing from the schematic)
4. Bypassed the 15K resistor with 100K (actually 13K would replace it totally)
5. Measured response now is:
Fed with IRIAA:
20Hz-20Khz within 0.25 db mostly flat with error at 30-20hz
goes to 50Khz flat then 100khz @-3 db

The amazing thing is it has almost followed the SIMSPICE model to the letter. I will post the SIM and amendments if anyone wants to see them.

A BIG THANK YOU TO DAVE AND EVERYONE ELSE WHO KEPT ME GOING WHEN I THOUGHT ALL WAS LOST!
:D
andyopus
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Joined: Thu May 20, 2010 9:29 pm

Post by andyopus »

plot and schematic as promised
Attachments
anm10phono.asc
(6.25 KiB) Downloaded 772 times
andyopus
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Joined: Thu May 20, 2010 9:29 pm

Post by andyopus »

hope this works!
but it did not allow!
andyopus
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Joined: Thu May 20, 2010 9:29 pm

Post by andyopus »

Well my PC ability strikes again but at least you can open it your self and run it.
PET-240
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Location: BrisVegas, Austalia

Curiosity,

Post by PET-240 »

So how does it sound?

Thanks,

Drew.
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