SE Z5600a II schematic

Anyone have a schematic for this mic and power supply?

I got asked to do some work on one. I can only imagine there is something terribly wrong in this mic as it's one of the worst sounding mics I've ever heard.

hello here are ...
I have the same microphone I changed the tube and mounting 6072A / 12AY7
the sound is much improved
if you can improve other things let me know ...
CIAO!!!

and this is the PSU!!!

There must be something wrong as i have 2 5600s and love em......far from the worst mic i have heard ! ;D

Thanks for the schmatics  ilfungo

Looksn like it could be similar t that SE Icis whic I traced here. It sounded good.

The only SE mic I played with had a faulty capsule, fwiw.

I haven't heard the 5600, but from the schematic posted it has a DC coupled cathode follower. Makes me think they were looking for an overtly 'tube' sound, which isn't what everyone wants in a mic.

Your Meat, My Veg, etc.

zebra50 said:

I haven't heard the 5600, but from the schematic posted it has a DC coupled cathode follower. Makes me think they were looking for an overtly 'tube' sound, which isn't what everyone wants in a mic.

Click to expand...

Cathode followers won't give an overtly tube sound. They have intrinsic negative feedback which reduces voltage gain to unity, makes them more linear and reduces output impedance, but makes them clip more sharply and removes a lot of the interaction with the output transformer if there is one. A lot of tube mic enthusiasts don't like them. The classic tube mic circuit uses a common cathode output stage.

In this case there will be some "tube sound" from the common cathode first stage, but with most of the transformer interaction removed.

John,

It wasn't the cathode follower per se that I meant to point out, but the DC coupling between the stages....

http://www.freewebs.com/valvewizard1/dccf.htm

The dc coupling doesn't change the sound. The first stage is biased so that the dc voltage on its anode is at the right level to bias the output stage, so there's no reason to add a blocking capacitor and add extra bias resistors for that.

The author of the link you posted expresses the opinion that this is "bad design" when used to drive a passive tone circuit in a guitar amp. It's actually good design, as the low output impedance of the cathode follower is needed to drive the tone circuit. It's only after amp designers started putting in master volume circuits that use that as the distortion stage (instead of doing it properly with a dedicated distortion stage with softer clipping) that problems arose.

Hi John,

Thanks for pointing that out. I had got bogged down with the concept of "stealing current from the previous stage", and the 'scope traces in that article.

Still learning!

Stewart

To be fair, the article's author gives a good analysis supporting his opinion, but in the mic circuit the bias conditions are quite different. I wouldn't expect a cathode follower running at such a low anode current to draw much current through its grid.

I'm not the final authority on tube circuits, but I don't see second tube stage doing anything worthwhile. The cathode resistor for the second stage is fairly large (270K), so it likely doesn't do much in terms of current drive. The transformer coupling cap (for full range) is 1u, which means the transformer must be something like 10:1. You might as well discard the second stage and use a traditional plate out circuit; just reduce the anode resistor to 100k. Or maybe parallel both halves of the tube (what is it anyway?) like in the Lucas mic.

Rossi said:

I'm not the final authority on tube circuits, but I don't see second tube stage doing anything worthwhile.

Click to expand...

Hi Rossi! If the cathode follower wasn't there, the HPF wouldn't work as expected. Check attached graph with cath follower. As almost all tube mics, there's a VLF hump. It is probably not as big in reality, but it's difficult to model this without taking measurements on the actual unit.

And here is the graph without the cath follower. I have used the same Y-axis, so you can see that, because the output impedance is very high, the level is attenuated. Since the cap's reactance is in series with this large impedance, the HPF is all over the place.

Hi Abbey,

Can you just clarify. How did you model the output transformer inductance & ratio or is it just a best guess?

the HPF is all over the place.

Click to expand...

And is the green line with the HPF in both cases? looks like blue & green are swapped between the two charts, unless things are seriously screwed.

Thanks!

zebra50 said:

Hi Abbey,

Can you just clarify. How did you model the output transformer inductance & ratio or is it just a best guess? 

Click to expand...

Yes, I modeled it for 100H primary inductance with 1k DCR. If the actual value is different, the frequency of the hump will change accordingly, but the overall characteristics is more or less the same.

the HPF is all over the place.

Click to expand...

And is the green line with the HPF in both cases? looks like blue & green are swapped between the two charts, unless things are seriously screwed. [/quote] You're right, I should have mentioned it, but it's pretty obvious.

Hi Abbey, yes, if you just delete the CF stage, the circuit wouldn't work as expected. But if you lower the plate resistor to the usual 100k and use an appropriate tube e.g. a 12AT7, the basic response won't look too different from your first plot (after all, that's how most tube mics are constructed).

The low cut response wouldn't look quite as good, that's true. But there are other ways to implement a low cut, if you really need one, e.g. reducing the cathode bypass cap, which gives a shelving filter response.

My feeling is that they used the 2nd tube half just because it's there.

I agree, there's many ways to skin a cat, and the chinese are probably good at inventing new ones.

I think you'll find that a lot of that "tube sound" will be coming from the monstrously large anode resistor on the first triode stage.

Has anyone got any better quality schemos for this? Trying to read the values off those ones is a joke, and sE sent the exact same ones :/

Cheers