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845 - Progress so far

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#21
Its' that classic Marantz blue!!!
Marantz, with its blue lighting , brushed aluminum and wood made for a look to behold.......
Here we're doing pewter & ol' copper.........simply wonderful.
Ingenious the use of ceramic tiles....is that for heat issues I wonder?
__________________________________________Rick......
 
#22
Hi again Nick,

I checked with the electroplaters (Astor) for any interested locals.

They have told me that the pewter look is achieved with a Nickel undercoating and then a Nickel/Zinc top coat (black Nickel) which is then polished back revealing the shiny nickel but leaving some of the darker finish on top giving the pewter look.

Richard Ellis said:
Its' that classic Marantz blue!!!
Marantz, with its blue lighting , brushed aluminum and wood made for a look to behold.......
Here we're doing pewter & ol' copper.........simply wonderful.
Ingenious the use of ceramic tiles....is that for heat issues I wonder?

__________________________________________Rick......
Click to expand...

Rick, heat was part of the issue. The problem that I faced was that the 845 ceramic sockets are designed to mount on top of a panel. I wanted to mount it underneath. The HV connections are at the top of the socket and mounting it under the panel would have left only about 5mm between the HV connection and the metal of the chassis. Perhaps this would have been OK but I thought that this was probably too close considering I am approaching 1KV. The ceramic spacer/insulator sets the HV connection 11mm from the chassis (5mm air/6mm ceramic) - probably way over the top, but better safe than sorry. It also helps to remind me that I am dealing with HV here!

When considering the issue, I felt that ceramic was the best option. Good electrical insulating properties, heat resistant and relatively easy to work with. I cut it up with an angle grinder and drilled the screw holes with a ceramic drill and cut out the centre hole with a Dremel ceramic cutting tool. I only broke a couple of tiles!

Rob
 
#23
I don't know Simon - wait till I get those bias meters in there. They really are the real deal. I have modified them with a blue LED backlight
Click to expand...
Maybe, but that's really an unfair competition. We can only imagine what Michelangelo's David would have looked like if the good man had LEDs at his disposal 😱

Simon
 
#24
Rob11966 said:
Hi again Nick,

I checked with the electroplaters (Astor) for any interested locals.

They have told me that the pewter look is achieved with a Nickel undercoating and then a Nickel/Zinc top coat (black Nickel) which is then polished back revealing the shiny nickel but leaving some of the darker finish on top giving the pewter look.



Rick, heat was part of the issue. The problem that I faced was that the 845 ceramic sockets are designed to mount on top of a panel. I wanted to mount it underneath. The HV connections are at the top of the socket and mounting it under the panel would have left only about 5mm between the HV connection and the metal of the chassis. Perhaps this would have been OK but I thought that this was probably too close considering I am approaching 1KV. The ceramic spacer/insulator sets the HV connection 11mm from the chassis (5mm air/6mm ceramic) - probably way over the top, but better safe than sorry. It also helps to remind me that I am dealing with HV here!

When considering the issue, I felt that ceramic was the best option. Good electrical insulating properties, heat resistant and relatively easy to work with. I cut it up with an angle grinder and drilled the screw holes with a ceramic drill and cut out the centre hole with a Dremel ceramic cutting tool. I only broke a couple of tiles!

Rob
Click to expand...


Ahha Nickel, I should have know that, it does have a nice subdued sheen and Zinc, that I wouldn't have though of. Well with Nickel in it you shouldn't have to worry about any corrosion LOL it's though stuff. Word to the wise though with zinc in it, be careful how hot it gets. When zinc gets hot it oxidized very quickly in air and produces toxic gases.

So don't try to use a torch on it to do anything LOL



I buy stuff from fair radio sales all the time, there a pretty good place.



David with led's,,,,,,,,,,,,,,,,,,,,, :bigeyes: I find that wrong in so many ways, but strangely I feel drawn to the idea LOL


Nick
 
#26
Hi Gordon,

I wanted a tube with a little less gain than the original 12AX7.

The different options were discussed at length in a thread on Andreas 'new 845' (it got quite heated if I recall) and I also put it up to the forum to help me out.

Here is the thread from a while ago looking at some of the different options and the rationale? behind my decision to go with the 12AUY7.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=132320

I was also tempted by the 6SN7 but it is too late now...

Cheers,

Rob
 
#28
rcavictim said:
A 12AUY7 should work very well in this application! :clown:

Those meters are very pretty with the blue LED backlight. How many LED's in each meter case? This amp is gonna look really nice.
Click to expand...

Thanks for the vote re the 12AU7. I am obviously a little apprehensive about the final result, this being an essentially untried design in it's present form.

With regards to the LED, just one 5mm, 6500 MCD blue lens.

I have included a photo of the dissembled meter with the LED in place.

Rob
 

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#29
Finished !!

Hi Folks,

I have finally finished my 845!!

Thanks to Andrea Ciuffoli for sharing his design through the forum here.

Thanks also to all of you guys for helping out over the last 6 months. I would not Have been able to do this without all of your help. Thanks especially to Sy, Rick, Chris (and for the Bus wire), Boywonder, Ty, Geek, Ray_moth, Nick, Gingertube, Rcavictim, Robert, Poindexter, Richy, Hollowstate and Sheldon. Apologies to anyone I have inadvertently missed. This project would not have been possible without you guys😎

Some brief technical notes (in no particular order)

1. The heater supplies are DC and the heater wires are twisted post rectification out of convention only.

2. The power transformers are custom made Edcors.

3. The bias meters are switchable between the EL34's and the 845's and the bias can be adjusted through small holes on the back without opening the chassis.

4. For anyone contemplating the build, this thing makes lots of heat!! Think barbecue or small steelworks smelter!:hot: I over rated all of the power resistors by a factor of 3 - 4 x and I am glad that I did. Big heatsinks, especially for the heater rectifiers are a must.

Finally, how did it work out? I am really pleased with the final result. It is very quiet at rest and has a clear crisp sound with strong bass. i can't fault it and would highly recommend the design to anyone interested in an 845 SE design. Furthermore it was a real learning exercise for me and I have learned a hell of a lot.

Once again, thanks folks.

Rob
 

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#39
--Artwork--

Rob..
I can say with the most sincerity that..you have arrived!
Crafted with the poise of a professional, massaged with the hands of an Artist, circuits designed/debated with your cohorts/friends.....the final decisions weighed & then finalized by your own inate intelligence.
And see the results of your own hands, with your own eyes......That gleeming, glowing masterpiece before you........and it produces the sound of music...the gateway to the soul.

Did you see Susan Boyles musical performance on Youtube? That is what its all about.music that moves you.
____________________________________________Rick.......
 
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