Sony c800(non G) noise issue help!

[Tubetec]

Some extra info on the Sony tubes here ,
https://gearspace.com/board/high-end/1155565-sony-c800g-w-7543-non-sony-6au6-tube.html

 

[ktziavos]

How many tubes did you try?
Are you using a Sony selected tube?
Are you using the same tube that Sony used?

You might need to try 10 or more non-selected tubes to find one that works with low noise.

If you are using real 6AU6s good luck finding one that works with low noise in the Sony 800 microphones.

Thanks Gus for your reply,
I used about 4 new non selected and all had the same but EXACTLY the same noise. Is it possible that different tubes can produce identical 'ocean noise' sound? It is like a carpet in there!!

 

[Tubetec]

You can find all the documents about the C800 and its associated PSU in technical docs section Rock .

Id very much like to see some pictures of the inside of the Sony mic if you can Ktziavos

 

[rock soderstrom]

You can find all the documents about the C800 and its associated PSU in technical docs section Rock

Yes, I had found these before. It also became clear to me that the non G version has nothing to do with the C800g version in terms of circuitry. It is a completely different microphone!

 

[ktziavos]

You can find all the documents about the C800 and its associated PSU in technical docs section Rock .

Id very much like to see some pictures of the inside of the Sony mic if you can Ktziavos

I will send you pictures from the inside mic and psu as soon as possible!!

 

[rock soderstrom]

You might need to try a number of tubes and they should be the tube Sony used because of the way Sony runs the tube in the C800 and C800G circuit

A search of this forum should help.

FWIW when I built a C800G like circuit with the 6AU6 tube operating points I found I needed to find a low noise tube and use super caps in the heater supply. I did not have any luck with real 6AU6s even ones built by Mullard etc.

The C800G is totally different. Again the non G version is a cathode follower with no gain.
Is the fierce selection really necessary?

 

[Lawrocker]

If you have tried different tubes in the mic, but nothing changes. Take another look at the filament voltage with the mic attached. Is it low? is it 'clean'? You would probably need a scope to see if it is super clean and stable. It has been my experience that changing the tube in the mic will solve that issue, but if it doesn't. It's a head scratcher for sure.

 

[Audio & Acoustics]

Put a new aluminum shield round the tube and be very careful when you are grounding the shield.
The low frequencies is modulation of high frequencies that are not shield out, high frequencies shielding is doing the job
RAW

 

[Gus]

The C800G is totally different. Again the non G version is a cathode follower with no gain.
Is the fierce selection really necessary?

Yes
Look at the schematics both models operate the tube close to the same.
Yes I know one is a CF and the other a simple plate out cap coupled to transformer triode amplifier.

I built a microphone with the Sony tube part of the circuit and found I needed to try a number of the tubes Sony uses until I found a low noise one.

I then did some reading and thinking and built a few circuits to run four tubes at a time for days before trying them in the microphone again.

 

[ktziavos]

hello there diy-ers!
Question! is there any possibility that the "ocean sound> is generated from the zener diodes D103 D104 D105? What do you think?

 

[Audio & Acoustics]

The filament is less sensitive to noise if the power supply is a current source.
This is a copy of AKG The Tube power supply.

 

[Audio & Acoustics]

Power Supply for AKG Solid Tube

 

[Tubetec]

I was reading up about supercaps like used in the Sony , seemed to suggest the usefull life of these components is only a few years .

 

[mjrippe]

hello there diy-ers!
Question! is there any possibility that the "ocean sound> is generated from the zener diodes D103 D104 D105? What do you think?

Zener diodes above 6V can often be sources of noise. Three in series across the 6V supply should be quiet.

 

[ktziavos]

I was reading up about supercaps like used in the Sony , seemed to suggest the usefull life of these components is only a few years .

I am planning to change them real soon to see if anything changes!! Probably tomorrow. I will come back with the results!! Thanks Tubetec

 

[ktziavos]

Zener diodes above 6V can often be sources of noise. Three in series across the 6V supply should be quiet.

So you mean it can happen? I have to check them too???

 

[Cappy]

What Ruud said is your best/first thing to check. Look at the Manley Audio website. Eveanna Manley has a video describing exactly what you are saying. Look at Support>Tech Tips>do I have a bad capsule?

 

[Tubetec]

Wow I did not know Manley was run by a girl ,

 

[ktziavos]

What Ruud said is your best/first thing to check. Look at the Manley Audio website. Eveanna Manley has a video describing exactly what you are saying. Look at Support>Tech Tips>do I have a bad capsule?

Hello Cappy, thanx for your answer. I've already checked the capsule with the capacitor replace trick and the noise is still there. I uploaded and two sound clips with and without the capsule.

 

[mjrippe]

Wow I did not know Manley was run by a girl ,

It's not, it is run by a woman. Though she has a reputation of being...nasty.