Sony C800G or U67 built - which capsule?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

kolabaer

Member
Joined
Dec 8, 2015
Messages
14
Location
Berlin
Hey guys,

I follow this forum quite a while and love it!
I'm planning to built a Sony c800g, but since it's not the easiest diy project it could be a U67 as well.

I wonder if somebody can recommend a capsule. I cannot decide between mbho and real u67 capsule from ebay or sennheiser.
Any experience?

Thank you already!
 
What is hard about a C800G build? It is a triode out to transformer.  However if you build it with the pelter cooling it is more involved
Are you going to buy a Sony transformer?
You will need to select tubes, prepare to test a lot of tubes

Do you know what one of the  good design things are in the C800G circuit that you don't see in a lot of tube microphones?
 
Gus said:
You will need to select tubes, prepare to test a lot of tubes

I still have a bunch of 6AU6 tubes left over from my early mic pre experiments, I am happy to send any C800 owner/builder half a dozen for the cost of shipping + Paypal.

Cheers

Ian
 
Gus said:
What is hard about a C800G build? It is a triode out to transformer.  However if you build it with the pelter cooling it is more involved
Are you going to buy a Sony transformer?
You will need to select tubes, prepare to test a lot of tubes

Do you know what one of the  good design things are in the C800G circuit that you don't see in a lot of tube microphones?

Thanks for your replies folks!!
I thought it will be tricky with the peltier element and that there is no build kit for the circuit. I have the schematics though. I also want to built the transformer, after the sony ac-mc800g paper.
I already got some tubes from Ian already btw  ;) Need to test them soon. I guess the tube for the mic should be very clean, the others could be used for the traffo.

I also hoped that you reply gus, (your mailbox is full btw :D) Thanks for that!
I don't know too much about the circuit right now tbh, but I like the sound of this mic a lot and want to get into the subject. Maybe that the tube is cooled down?? But must be something else, otherwise it would be like a u67...

Cheers
 
Gus said:
Do you know what one of the  good design things are in the C800G circuit that you don't see in a lot of tube microphones?

Hi Gus.
The H.T.  is 230V and current through the valve is 1.4mA, both of which are higher than the norm.
The Stanley Church 'Cinemic' was similar in that regard.

Edit:  Oops, I didn't see your own answer above. 
 
Don't worry about peltilier element, sony just wanted to be "special" and over design the psu and cooling. no need to cool this tube.

I own a few originals of these mics and have modified the circuits many times.

having built other circuits with this tube (u47 type circuits, m7 capsules, c12 capsules, i can safely say that most of the "sony" scooped and bright sound comes from the tube type.

the long russian 6au6a's sound way better than the short american types.
 
JessJackson said:
Don't worry about peltilier element, sony just wanted to be "special" and over design the psu and cooling. no need to cool this tube.

I own a few originals of these mics and have modified the circuits many times.

having built other circuits with this tube (u47 type circuits, m7 capsules, c12 capsules, i can safely say that most of the "sony" scooped and bright sound comes from the tube type.

the long russian 6au6a's sound way better than the short american types.

Would be much easier without the peltier element. They say it decreases noise by 2db or something . Don't know if you would hear that. And maybe you have to do some small changes in the psu?
Thank's for your input!
 
ricardo said:
kolabaer said:
They say it decreases noise by 2db or something .
Anyone have a pukka C800G and can test if this is true by disabling the Peltier element?

TBH I don't see how that could be the case. I'm not going to do it, waste of time and energy. I think by sticking a refrigerator on a tube causes the low life in the c800g 6au6a. hence the stigma that these tubes burn out quickly.

Please show me proof that cooling the tube lowers the noise.

Jess
 
The concept is questionable. I don't think you can cool any crucial parts inside the tube, i.e. the anode and cathode. There has to be a heater for the tube to work, and there's a vaccum inside. So what the peltier does is just cooling the glass valve. How could that lower the noise? Most probably it just creates stress around the heater pins.

And why not do a much simpler thing: experiment with a lower heater voltage? If the valve can take underheating, it might lower the noise.
 
Please show me proof that cooling the tube lowers the noise.
[/quote]

https://www.dropbox.com/s/v5sfopuo28muyn2/Sony_C800_Article_04.gif?dl=0

I don't know if this proofs anything. But I think I will build it without peltier, now and search for an original neumann capsule.
 
The peltier introduces a lot of condensation  into the mic over time. This can be seen in older mics that have seen heavy use.
 
Vacuum technology is a deep subject
Atoms are adsorbed at the surfaces and in the molecular range sit on the surfaces inside the vessel
They stay at lower temperature surfaces a longer time than higher temperature surfaces before leaving
Cryropumps are sometimes used in vacuum systems
After a time when you start to pump down a clean system without lots of virtual leaks most of what you are pumping (if there is not a bad noticeable leak rate) is water
You can see this on a RGA
I am guessing Sony uses the cooler to hold the atoms inside to the glass and away from the grid
 
ricardo said:
kolabaer said:
They say it decreases noise by 2db or something .
Anyone have a pukka C800G and can test if this is true by disabling the Peltier element?
Duu.uuh!  Anyone here interested in doing a simple experiment and getting HARD DATA instead of pontificating  :(

Let's start at the beginning.

Does anyone here have a pukka Sony C800G?
 
Rossi said:
The concept is questionable. I don't think you can cool any crucial parts inside the tube, i.e. the anode and cathode. There has to be a heater for the tube to work, and there's a vaccum inside. So what the peltier does is just cooling the glass valve. How could that lower the noise? Most probably it just creates stress around the heater pins.

And why not do a much simpler thing: experiment with a lower heater voltage? If the valve can take underheating, it might lower the noise.

The heater voltage on C800G is set at 5.7v
 

Latest posts

Back
Top