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Audio note M7 question.
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6516
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Author:  Woodo [ 28 Apr 2019, 06:37 ]
Post subject:  Re: Audio note M7 question.

That’s some serious workmanship @M. Gregg . Can’t wait to see the end result.
:up:

Author:  M. Gregg [ 28 Apr 2019, 06:48 ]
Post subject:  Re: Audio note M7 question.

A bit of a distraction,

Looking at Velleman kits dual infrared boards driving a motor.

Well the boards don't bring out the NC contacts, so a small mod and they now do.

Looking at a simple 12v dc regulator board, quick mod to voltage double and output 12VDC and variable DC.

12DC drives the board variable volts set the motor speed.

However, the Vellemen boards are either latch or momentary so (set the step distance with the voltage).
Copy the transmitter code to a learn remote (volume) set the other buttons for everything else.
Well it’s a mad idea but I'll give it a whirl, I think an Arduino is a bit overkill and I don't like H bridge.
Anyways it’s another interesting distraction so I can choose the pot I want not all are motorised.
It might work... :) if not I'll look again.

Regards
M. Gregg

Author:  M. Gregg [ 28 Apr 2019, 06:50 ]
Post subject:  Re: Audio note M7 question.

Woodo wrote:
That’s some serious workmanship @M. Gregg . Can’t wait to see the end result.
:up:


Thank's for the interest..and comment.
I'll probably use a TKD pot...


Regards
M. Gregg

Author:  M. Gregg [ 08 May 2019, 13:33 ]
Post subject:  Re: Audio note M7 question.

Just looking at a few components.

Trying to stay in the Audio Note theme using audio note solder.

I don't like running audio through fibre glass PCB. So I have been looking at the old chestnut PITA >>Kite board "tufnol paper" and looking at a selector board using Duelund silver wire. AMRG 100K because there are 4 ...it will be a new trial they sounded similar to tantalum in previous designs.

Its a slow process stopping the chassis tarnishing was a bit of a struggle until trying Everbrite, and I'm compacting the design. :eek:
Looking at PSU 6x4>10uF>11K>100uF>1K>100uF so its just a sloooow build :D

Regards
M. Gregg

Author:  Gab [ 08 May 2019, 18:33 ]
Post subject:  Re: Audio note M7 question.

Your chassis is just awesome. I have a favor to ask : I would love to see what you have used to build it and how ! If you have anything about the build itself, I would love to see it ! Thanks in advance and keep up the good work !

Author:  M. Gregg [ 09 May 2019, 12:43 ]
Post subject:  Re: Audio note M7 question.

Gab wrote:
Your chassis is just awesome. I have a favor to ask : I would love to see what you have used to build it and how ! If you have anything about the build itself, I would love to see it ! Thanks in advance and keep up the good work !


I didn't photograph the machining, I didn't think anyone would be interested :(
Remember copper and brass are toxic so wear a mask and wash your hands!

The design started by buying a sheet of copper on line. I guillotined it at work and bent the two ends of the centre piece.
The end plates were drilled by hand after marking out. the Two ends were clamped in place using toolmakers clamps so I could use a blow torch and the same solder as used on copper pipe. The toolmakers clamps are all steel so it doesn't matter if they get hot.
The aluminium angle was from a hardware store and cut to the same length as the outside of the bend from end to end of the centre piece. I made two front plates with the copper plates clamped together so I could then use one of them to make the support for the potentiometers and the holes would line up for the brass drive rods.

Brass square section rod is used for the aluminium coupling these were held in a vice and drilled straight through the brass and aluminium with a tapping drill size from a Zeus manual and soldered to the front and rear plates. These held with toolmakers clamps after indelible marking in place then putting flux on the brass and clamped in place then soldered. I was going to braze but after an initial test the blue colour on the copper could not be cleaned off. However, with soldering the discoloration was removable with Solvol Autosol. I tested the soldered joint (not soft solder) with a test piece and could bend and twist the copper plate holding the brass section with mole grips the copper failed with a split without the joint breaking so I decided the joint was good enough. The hole sizes for the socket etc was marked out, chain drilled, and hand filed. PITA :)

The brass was bought on line as close as I could get to size then jig sawed to size and filed, I wanted to guillotine it but after an initial cut I wasn't happy with the finish. The countersinking is all hand drilled and then countersunk with a countersink bit and an electric screw-driver(more control low speed).


After some time working with the copper, I found it a PITA to drill. It can sometimes clog up the drill bit and then cause the drill to wander half way through the cut. This gives a run off which can be un acceptable, the holes are all pilot drilled first. It is possible to use a centre drill to give the drill a more rigid cut for the holes.

The initial fit for all parts were clamped in place and hand filed. It needed about 1.5-2mm removing after the first solder between the brass plate and aluminium angle. The top and bottom plates were marked out with indelible pen and a square.

Tarnishing was a problem, I tried using spray lacquer but it still discoloured after trying a few products and stripping it off with acetone I tried Everbrite which is how it is at the moment.

So sorry I can't show photos. I do have others but not machining.


Regards
M. Gregg

Author:  Gab [ 10 May 2019, 10:31 ]
Post subject:  Re: Audio note M7 question.

Very interesting ! You took the least travelled path and the result looks awesome ! I took note of the product you used to stop tarnishing. I’d like to use copper or brass for the top plate of my tubelab SSE power amp. With at least 30 pounds worth of transformers on top of it, I don’t know if copper will be rigid enough without using a 1/4" thick plate, wich would be pretty expansive.

Regarding the drilling process, wouldn’t a drill bit for softer materials and higher speed make the job easier ? I am not an expert in machinig, but I know that different drill bit pitches are available depending on the material you intend to work with, and each material has a particular speed at witch drilling works best. I guess you already know that by seeing your work, maybe you just did what you could with the tools you had on hand.

Thanks for the explanations. I really appreciate !

Author:  M. Gregg [ 10 May 2019, 11:27 ]
Post subject:  Re: Audio note M7 question.

[ With at least 30 pounds worth of transformers on top of it, I don’t know if copper will be rigid enough without using a 1/4" thick plate, wich would be pretty expansive.*]


The trick is to use copper or brass and support it with aluminium angle. Bolt the transformers through the plate onto the aluminium angle.

Everbrite coatings have 2 versions one is gloss and will stand up to weather and salt etc. But don't get any solvents near it or metal polish or you will destroy the coating. You can use polyurathane but I had very little success with it, and once its applied your in a world of hurt to get it off again. Everbrite can be removed with acetone or nail varnish. So you need to research it before use.
All the coatings I have tried are not mechanicaly strong. But everbrite didn't tear and rip off the surface when turning screws etc.

From the point of support I used a few ideas with an OTL PIC. Its created in layers using Aluminium angle screwed to the wood chassis and held in place with 6mm all thread. Its just for interest. (off topic but might give you a few ideas) Its very heavy with 500VA toroidal transformers on the bottom layer. Another guy used all thread and spacers through the plates which seemed to work very well.

Regards
M. Gregg

Author:  M. Gregg [ 11 May 2019, 03:49 ]
Post subject:  Re: Audio note M7 question.

[Everbrite can be removed with acetone or nail varnish*]

Sorry just noticed I said nail varnish oups :blush:
I meant nail varnish remover which has acetone in it.

NB nail varnish remover is also good to remove indelible pen after marking out on metal.

I'm just going to get some glass beads to use as standoffs on the Kite tufnol, with a bit of luck I can get red black and green.
Just working on the input board.


Regards
M. Gregg

Author:  M. Gregg [ 13 May 2019, 17:54 ]
Post subject:  Re: Audio note M7 question.

A quick question,

Has anyone had any experience with voltage clamping the output on the M7 circuit.
Its a simple idea using Zener's :eek: shock horror shown here:
http://sound.whsites.net/project167.htm
The reason I ask is the M7 circuit with output fed via a capacitor from the anode of the driver tube.
Obviously if the cap fails then its B+ on the output, which "maybe" why the circuit changed.

However that is not an issue if its clamped sinking the voltage in the 50K (2X 2Watt100K in parallel) anode load in fault condition.

Zeners are noisey in conduction but in no conduction situations? looking at the junction capacitance maybe.
Its obvious that the way to go is a self healing capacitor but that defeats the point when I'm looking at oil/ foil caps etc.
NB there were problems in the past with some old Jensen caps failing.
There are other ideas using neons in non conduction etc.
So any thoughts would be interesting.

Regards
M. Gregg

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