Marshall MXL V77 tube mic tube change...need help

my bad then, thanks Gus.

guess all you can do is play around with tube changes and upgrade any caps.
does the quality of the PSU play any reasonable role in the sound quality with tube mics?

yes the power supply can be a part of the sound. I have not worked on or been inside a 77 however the 69 power supply is built OK IMO.

I have worked on MXL v69s that people have replaced the stock tube with a 12ay7/6072 and liked the sound better with a 12ay7/6072

Yes increasing the current can sometimes help a circuit but you need to know what the input voltage range is before you change the operating points

I think I read that the tube runs on 200v 5mA. Could be wrong though, and I don't remember where I saw that.


The grille seems to have a pretty dense inner mesh... could possibly try cutting that part of it out (if you can get at it) for a less diffracted high end.

What is the big piece below the tube that's covered in blue?

I know I'm a newbie, so don't beat me for saying this....but doesn't the V77 have a transformer...I thought it's that metal thing in the bottom of the mic as shown in my pictjres. (looks like a rectangle of layered sheets of meta..covered by Blue tapel) :?: I think I'm going to try that other recommended tube also.

Sounds like a transformer to me Can you get a close-up, good angle of it?
Don't have mine yet but I'll definitely let you know of my thoughts on it, and any mods I do, in the next few days.
I've also got two NOS GE/Jan 6072's on the way, so I'll let you know how that tube switch goes. Didn't get the "M" version though (the one made for mics specficially, supposed to be lower noise) as it's about triple the price. E'gad.

I'm no good at figuring out the ratio of transformers, but maybe the folks here can help walk us through it and recommend a better one. Transformers tend to be the weakest link in Chinese mics.

I'd experiment w/mic placement first before swapping a tube in a mic. It might be semi-harmless in the pre in a guitar amp, but as Al said, the two tubes have different charcteristics and require different passives values in the circuit. If sounds okay, well then, go on. But I wouldn't make it standard practice to swap mic tubes just to fiddle the sound. Also changing for a good quality NOS 6072 might give you the change you're looking for.

rgrds,
Brad

dasbin,
did you get your V77 mic yet?

Turned out they couldn't find the PSU in store for the one I was buying, which was going to be such a good deal (darn it).
I've turned my modding sights on an Apex 460 instead. Sorry.

found this thread again because of a new thread today asking about the v77. I noted that I thought the v77 was transformerless in one of the posts but looking at the pictures it looks like a nice size output transformer.

I just got a hold of a V77 but I only have the mic :sad:

NO Power supply, cable... nothing but the mic.

I have a ton of spare parts around & have no problem building the rest to get this working.

Are these any good or worth the effort? I have plenty of tech experience but never messed with mics before.

I could really use a schematic for the mic & the box :!:

Also, is the 7 pin cable ( & connector) something I'd need to get from MXL?

Thanks,
Kevin

studiotimezone(at)yahoo(dot)com
(if anyone has the schematics you can send them to this address) :green:

Just reverse the schematics and figure out XLR pinout. You should have ground, B+, heater, and +- signal.
Each of them is very easy to figure out. Just ask if you need help with that.
You can get XLRs from Markertek. Or if you are stuck contact me and I could spare a couple.

If you deside it is not worth the effort I'd buy the thing, if the price is right.

[quote author="Marik"]Just reverse the schematics and figure out XLR pinout. You should have ground, B+, heater, and +- signal.
Each of them is very easy to figure out. Just ask if you need help with that.
You can get XLRs from Markertek. Or if you are stuck contact me and I could spare a couple.

If you deside it is not worth the effort I'd buy the thing, if the price is right.[/quote]

OK so the XLR (7 pin) that connects the mic to the supply is "standard" & available?

I don't have the SCHEMATIC :?

I NEED one.

I'd really like to have some fun with this thing & get it working. Are they any good or what?
I looked inside & it looks pretty well built... WIMA caps, tranny, tube, etc...
so everything looks to be there except the supply & cable.

Marshall doesn't even list these on their site :roll:
...is it discontinued?

Just curious, what capsule is this one modeled after?


Marik,
If your in the states & have parts or info for me PM me your phone # if you want.

Thanks for your help.

Kevin
studiotimezone(at)yahoo(dot)com

O,
sinse I'm building the supply from scratch... if there's any improvements I should make PLEASE let me know.

Kevin

Lets think about this

It is a tube microphone I would guess plate out

Look for the plate resistor and maybe RC from the B+ to the plate

Whats the tube number? Go to franks tube page and look up the pinout. Are a bunch of pins connected together and to ground?

cathode resistor value.

The resistors and tube number can be used to make a very good guess of the B+

Or post front and back pictures of the pcb inside the microphone

Gus,
Sent you a PM... I have to open it again to check the GND Pins.

I called Marshall about the Parts:

7 Pin Cable = $45 (Guitar Center)
Power Supply = $50 (MXL)
Shock Mount = $35

By the time I go thru all the effort & cost to get these items it "MAY" be better to just buy one of their NEW "Tube" mic packages with all this included + a case & extra mic for about $50 more.

But which one should I get? They have a V67 (tube mic) :?
The guy is going to call me Monday to let me know if the supply is the same or not.

The BIG question is... is the V77 worth this investment at ALL :?:
or the V67 (if the supply will work with mine)

Thanks,
Kevin