C800-G k67 Type Question / Mod

I own a c800g and a vintage c12... I have always struggled with the harsh sandpapery sibilant top end that the c800g produces. de-essing and other post isn't a fix.

I am about to build the u67 type and since I have to order a k67 capsule from senheiser... it started getting me thinking if the Sony k67 TYPE would be compatible with the original neumann k67. I'm also thinking about the double layer headbasket and how that also may contribute to the harsh high end. I notice that the c800g doesn't include a filter cap to smooth of the top end like c12 circuit.

I have two c800g's and don't mind to mod one for personal gain. I also have a few stuffed ma-55 replacement circuit boards for the c800g which could be modded and switched out easily.

I love this mic but hate it for its harsh top end.

Cheers

J

Sell one of your c800g's, and use the proceeds to go mic shopping . I wouldn't dare take a soldering iron to it because of how expensive the mic is. FWIW, I've heard the Sony capsule is based on the K67 but is voiced differently.

Have you tried one of those thick foam windscreens? Not a pop filter, but a windscreen similar to the ones used on stage vocal mics. They tend to soften or dull the top end. It could help the situation.

-James-

Appreciate your reply, don't need the money and don't need to go mic shopping. I own a extensive mic collection This is very specific thread question... this is for one specific artist I vocal produce and I will only use the c800g on for other qualities and reasons.

I have taken soldering iron to one of these mics many times in past. they are tube mics, need maintainance and components go bad. not concerned for resale value.

I read before that sony k67 type is tuned darker to make up for c800g circuit but I think this was speculation.

Other ideas considered
Adding a 1000pf cap at capsule.
Swap out Electrolytics for Styrenes or polys
Swap out ERO MKP 1uf Coupling cap for PIO cap

Here is rare schematic from sony WITH voltages

Cheers

J

You have more balls than I do (and probably more money too).

Take a look at an ELA M 251 schematic. It has a smoothing cap right before the transformer coupling cap (100pF) to soften the C12 capsule that resides in it. I've seen some of the guys here using a higher value (500pF) to tame the K67-type capsule. If I were in your shoes, I would try different values between 50pF-500pF to try and tame that high end.

-James-

Even without a smoothing cap, CK12 capsules typically have their treble rise higher up, outside the sibilance range.

The (Neumann) K67 was designed with a treble peak below the air band and in the sibilance range. (Not that it can't be airy, too.) This was done deliberately and with a circuit to match.
A good and stock U67 actually works as a subtle de-esser.

This is where a Miller compensation scheme works well.  It's just a small cap from plate to grid that adds a low pass filter effect.  I used one in my C12 to bring the high end down just a taste (just going from memory, I think I used two 4.7pF C0G ceramics in parallel after many different values).

I would try values in the 10pF to 47pF range.  It's easy to add right at the tube socket and easily reversible as well.

Matador said:

This is where a Miller compensation scheme works well.  It's just a small cap from plate to grid that adds a low pass filter effect.

Click to expand...

A Miller capacitor doesn't reduce HF if the source is a capacitor like in this case.  It will mainly reduce the gain.

Have a look at U67 circuit where subtle feedback is used to reduce the peak in a U67 capsule.

At the end of http://www.groupdiy.com/index.php?topic=20652.40, David Satz posts a note by Neumann’s Gerhart Bore, on the U67.  It explains much Neumann philosophy & black magic, especially the special feedback arrangement which many gurus have scratched their heads over.  The U67 circuit is

http://recordinghacks.com/images/mic_extras/neumann/U67-schematic.jpg

I have a note on how to achieve the same with a modern Schoeps circuit in MicBuilders.

There is no guarantee these Neumann mods will cure the harshness on your Sony.

PS  The double mesh probably helps tame the harshness so don't destroy it if you want to see what's the effect of removing it.

Some interesting angles...

Tracking down the source of the problem is going to have to come first. Its not that there is too much HF (Although the sony has ALOT) its that its distorted in nature (Sandpaper/Harsh Sounding). When taming the HF I am still left with a harsh top end, just lower relatively in mix. This led me to believing it was the capsule or the component materials used. All c800g I ever used are like this.

Just took these pics of what we're working with.

There's a frequency response at http://pro.sony.com/bbsc/assetDownloadController/C-800G%20Frequency%20Response.pdf?path=Asset%20Hierarchy$Professional$sel-47426C-800G%20Frequency%20Response.pdf&id=StepID$C-800G%20Frequency%20Response$original&dimension=original

Well they show more HF peak than U67 but C800 doesn't have the U67 EQ.  U67 capsule has huge peak which is only partially tamed by the U67/87 circuits.

Is the harshness on both cardioid & omni?

You might like to put the Sony capsule in a U67/87 and see if the harshness goes away.  If so, its frequency response and there are a number of tested cures.

I wish we could see those pictures! Are the addresses correct?

zebra50 said:

I wish we could see those pictures! Are the addresses correct?

Click to expand...

The images work

Not for me (mac, safari, firefox) but no matter.

(Edit: back again now. You're not on GoDaddy are you? http://www.bbc.co.uk/news/business-19549367 )

zebra50 said:

Not for me (mac, safari, firefox) but no matter.

(Edit: back again now. You're not on GoDaddy are you? http://www.bbc.co.uk/news/business-19549367 )

Click to expand...

I am

Honestly, pick up the phone, call Tracy Korby and talk to him.  He can turn that mic in to helicopter if you want.  Get one of those cats who do this thing day and night, and you'll have the Sony you want.

My 2 cents.

i'm gonna try a 100pf from plate to ground like in the elam 251 circuit. also was thinking about throwing a neumann u67 capsule in there to see if its slightly darker. I read somewhere though that the c800g has the best u67 clone capsule built.

side note, sony schematic reads heater value of 5.7v but 6au6a spec sheet reads 6.3v

I would LOVE for you to try the Neumann K67 in your C800G and see how close/different it sounds to the Sony.

Melodeath00 said:

I would LOVE for you to try the Neumann K67 in your C800G and see how close/different it sounds to the Sony.

Click to expand...

I'm gonna try it first i think. I have a 87AI i can take borrow from and also a capsule from Eric i was about to throw in my u87 build.

Theres definitely something about the sony circuit i've always loved (the largeness and already mixed pop vocal sound) but it seems to be very common that all owners HATE the harsh top end. I'm going to get to the bottom of the culprit for this mic.

its very interesting to me that this capsule in this circuit can sound so different from a u67. I bet that everything everyone loves about this mic is probably the sound of the capsule and everything everyone hates about the mic is the circuit.

l can also try eliminating audio path elecrolytics, (any advice?) obviously no where to use styrenes other than adding filter cap.

cheers J

Well for my own selfish desires I'd be interested in hearing the Sony versus the Neumann without any changes to the circuit. It sounds like you have lots of K67-style options, though. It is interesting the U67 can sound so different, but yeah, circuit can make a big difference. Lots of Chinese mics are K67-style capsule, plus flat circuit. The Manley Reference Cardioid is another such mic (I own one). In one shootout I heard, the Manley was even brighter than the C800G.

cool, im gonna do it.. still want to look at upgrading c800g circuit though.

can anyone tell me what the switch SW101 on the PS295 board's purpose is? it seems to insert a cap 1000u (c107) to grid. im not sure on its purpose, it doesnt change the voltages. it seems to be part of the circuit that supplies the peltier element.

EDIT: seems its to give the option to slowly ramp up the voltage of the cooling element, not sure why it would matter and why you would want the option.

mkp output cap is good? could also easily be replaced... I have a spare board i could customize and hot swap