[Icantthinkofaname]

I would also put in a plug for a kit microphone, like those from Microphone Parts, or some of the ones available through the community here for a beginner.

Yes, for M-P, you could do it more cheaply, but for a rank beginner, learning to solder, deflux a Board, deal with the high Z parts of a circuit, handle a delicate capsule,  etc, are essential skills,and the instructions are very good. You won’t have to bias a FET mic your first time out if that is the route you choose because the bias resistor is chosen for you, so you don’t need expensive test equipment to start.  There are tube options.

I considered the extra expense part of my initial education,  and now have moved on... just a thought. ..

My G7 build follows Banzai’s KM84s....once you get the bug, it never stops...

—Mark

I don't think the PCB kits are nearly as bad of a deal if you don't already have a useable donor mic, as long as you don't pay MP $150 for a $30 Chinese capsule. If you're spending that much on a capsule go with Maiku or 3U Audio, not an iSK capsule you're paying 5x the factory price of.

[Gus]

I have been mixing for a while. I normally use a u87 and Manley although the manley sounds similar to the Sony it’s just not the same. I am spoiled after traveling to la and finally getting to use one in a session myself. I don’t have the money to buy a legit original one. I have also never built a microphone but I am eager to learn. Do any of you have any recommendations on how I can  learn how to build a clone of the Sony C800G? Or a link to a kit of some sort? I know the Russian tubes sound better on it and it replicates a k67 capsule. Anyways, if any of you can point me to the right direction on how I can achieve my goal and learn to do this please respond!!

Is it your u87? and what Manley microphone?
If it is a u87 you could remove the lowpass

[Khron]

IF we're talking learning to solder, there are other cheaper electronic assemble-it-yourself kits out there - not necessarily microphones.

Deflux boards? A q-tip and some IPA / rubbing alcohol (the higher concentration, the better). Never had to / bothered to do that outside the Hi-Z areas in mics (not to mention anywhere else), and i've yet to encounter any issues due to that (in 15+ years of soldering).

Hi-Z parts? A (clean) pair of tweezers. Or two.

FET biasing? An audio interface, even a cheap one, some free software, and a bit of elbow-grease

Yes, for M-P, you could do it more cheaply, but for a rank beginner, learning to solder, deflux a Board, deal with the high Z parts of a circuit, handle a delicate capsule,  etc, are essential skills,and the instructions are very good. You won’t have to bias a FET mic your first time out if that is the route you choose because the bias resistor is chosen for you, so you don’t need expensive test equipment to start.

—Mark

[Icantthinkofaname]

IF we're talking learning to solder, there are other cheaper electronic assemble-it-yourself kits out there - not necessarily microphones.

Deflux boards? A q-tip and some IPA / rubbing alcohol (the higher concentration, the better). Never had to / bothered to do that outside the Hi-Z areas in mics (not to mention anywhere else), and i've yet to encounter any issues due to that (in 15+ years of soldering).

Hi-Z parts? A (clean) pair of tweezers. Or two.

FET biasing? An audio interface, even a cheap one, some free software, and a bit of elbow-grease

A bit off topic, but how does one bias the FET using an audio interface and software? Got a link to an article or thread?

[Khron]

Not 100% sure if or where one might find a / the bespoke article, but it's quite simple (imho).

DAW - signal generator - interface output - [optional signal pad / attenuation] - coupling capacitor (1nF) - JFET gate
Mic - XLR cable - interface input - DAW - oscilloscope plugin (most DAWs have one in the stock library)

Start with said output at minimum, slowly raise it until the circuitry (not the interface input) starts to clip on the top or bottom of the test-sinewave, turn the bias trimpot to remove the clipping, increase signal level, "rinse and repeat" until both the top & bottom clip around-about the same time (or level)

Exactly the same as you'd do with a physical, hardware signal generator and oscilloscope. Minus the expensive test gear Mind you, you'd still need the mic connected to something that provides phantom power anyway.

[Edit] Found a video, too - https://youtu.be/SHD4Rrwqy_Q?t=1014 Arguably a bit "long-winded", but pretty damn thorough - includes a description of how the circuitry in that particular mic works, etc.

A bit off topic, but how does one bias the FET using an audio interface and software? Got a link to an article or thread?

[Mworthin]

I wish I had had this thread when I was starting out!

[kingkorg]

Been there done that, i really think it's a waste of time. Hats down to anyone who can hear 0.1% thd difference recorded at 140db. I had to inject pretty high levels of signal into FET to make it show some serious harmonics, the kind capsule is never going to be able to produce.

While it's a great idea to check it for a clean mic build, or if something is wrong with one, FET swap, but re-biasing stock mics never did anything for me.

[thecr4ne]

I was looking into something along these lines too. Have a look at this http://www.foxaudioresearch.ca/c800clone.htm

Also, I did email Dave at Advanced Audio and he suggested using a Nady TCM 1050 (the good version with the actual tube socket and better capsule) keeping the original capsule and doing his Apex 460 Mod with AA's BV-18 transformer to get pretty close.
*It's worth noting this was his recommendation for a DIY version and is not what the CM-800 is.

[kingkorg]

I don't mean to sound like a smartass, but DT said pretty much what i did before.

"The Sony design is not an exact replica and shows a response that has less mid-range lift than a typical K67.  The high-end lift is about the same amount as a K67. This is the single most important part in setting the tone of the c800 in our opinion."

Find the capsule that nails that sound and stick it into almost anything and you are there. The 32mm Nady capsule is not even close IMHO. I would rather go with something like 797audio's k67, or the capsule Manley uses in their Cardioid reference, that is also found in 100$ Sterling Audio ST51(cardioid only though)!!!

[Khron]

PS: I know this might be borderline blasphemous, but... I seem to recall reading somewhere (possibly even here) that the whole tube-cooling stuff is just a gimmick 

Which kinda makes sense, if you stop and think about it a bit. According to the service manual, plate voltage is 90v and idle plate current about 1.4mA, which works out to about an eigth of a watt (datasheet quotes the maximum as 3.5W).  Plus about 1.7W from the heater.
The Peltier element itself burns off almost 5W all on its own.

Is the temperature - noise correlation in (such) small-signal pentodes / triodes really that severe, that would warrant all the extra complexity?

So how come extra-cooling-less tubes have been just fine for decades, everywhere else (i'm thinking other tube mics and preamps), anyway?

[kingkorg]

+1

I think Jacob mentioned somewhere it theoretically could reduce tube noise for couple of db at best, but that's about it.

[Gus]

The tube cooling is a type of cryopump the gas molecules will adsorb to the glass wall keeping them more often on the glass than in the vacuum envelope.  This helps with the higher current.
You can do this with a microphone that costs what this does.  I wonder why the heatpipe/heatsink was not pointed down?

Other things the web gets wrong the capsule voltage divider is lower value resistors to act as a shunt load on the power supply. 

Super caps in the heater supply

The tube diodes in the power supply will help get rid of diode switching on and off edges and things that can cause.

Nothing wrong with a 6AU6 it is pentode wired as a triode like other pentodes wired as triodes in microphones

EI lamination core transformer. EIs sound different than DIs to me as well as alloy, winding, stacking of the lams.

You can underheat some tubes it depends on the Ni alloy and oxides best way to test is trying different heater voltages. In my tube testing most 6.3VDC can be under heated to 5.8VDC sometimes lower. Note tube transconductance can drop with lower heating.

There is more.

[JessJackson]

Gus is right..

I own two c800g and they run 5.7v heater.

playing around with circuits I discovered most of sonics of this mic due to 6au6a (long body Russian style)

Hey Gus ?!!! your C800G is not a clone, it's the real !!

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Sony C800G Peltier gizmo

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Here is the Sony C800G PSU schematic

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