MK7 - tube mic project

[Kingston]

Just let us know if (and how) they do anything good to the sound.

 

[smallbutfine]

Jonkan, great sound on your clip, great tone for beeing completely unprocessed!
The mids fit the singers slight nasal pronounciation (a typical thing for nordics singers I guess, like the sharp 's' )...
(for some seconds I thought it was the mic before I noticed it is the singers voice...)
I could not notice the noise level really, because there was no silent passage, but I guess it is acceptable-

I hope it sounds even better with the new cap, is it?

Kind regards,
Martin

 

[Jonkan]

Thanks! The slight nasal quality might have something to do with the singer having a cold also...?

Anyway, i can confirm that it sounds exactly like it sounded in the room, only a bit "thicker" or "slightly larger than life" so to speak.

My friend who heard the playback with his back turned to both the speakers and the performer had a bit of trouble hearing when it was live and when it was recorded material being playbacked. Thats got to be a good thing i think.

I havent been able to try the new caps yet, looking forward to it!
/J

 

[Jonkan]

So i listened really quick to the PIO caps, and first impressions are that they sound really good. Havent done any scientific comparisons to the polyprop caps, but im very satisfied with the sound now so they will probably get to stay. Plus they make the mics heavier (feels like better quality) and looks cool.

Added another 10000uf cap in the psu to see if i could get the noise down a little.

Its a bit tight in there also, but works.

/J

 

[ioaudio]

btw i see the pic of your psu for the first time . remember when i was talking about coupling between the caps?
the first cap after the rectifier will have to tame the biggest amount of ripple, the last one before the heater output is highly sensitive to picking up noise.
caps also have inductive properties and can act like transformers bleeding noise&hum between each other, so layout is critical and you should experiment with it (quite a challenge in the small box i know) and listen to hum and HF noise.
-max

 

[seavote]

io- can you give some PSU layout tips? im guessing the last cap befor heaters should be as isolated as possible. tranny should be as far from rest of circuit as possible? twist wire sets? i'll probably go with a bigger case.

 

[ioaudio]

im guessing the last cap befor heaters should be as isolated as possible. tranny should be as far from rest of circuit as possible? twist wire sets? i'll probably go with a bigger case.

yes 

 

[Jonkan]

I have no audible hum at all even when amplified at around 60dB:s. The grounding scheme I found to be the best for my mics got rid of that. Took quite a bit of experimenting, but it was totally worth it!

I didnt twist my wires together in the psu, perhaps i should have? The way I had to ground everything might not allow for it though.
I did twist all the wire pairs in the mic though.

My only concern is that of static noise (like hiss), but that isnt too severe either unless i really crank the gain on low volume sources.

The noise tended to vary in level depending on which tube i stuck in the mic, so i just figured it was the tube that was making all the noise.

Thanks for the suggestions!
/J

 

[ioaudio]

test if the hiss disappears in the few seconds after you turn of the psu, that way you can rule out hf noise from the lm317. 
please do not forget about HV voltage standards when you build tube stuff.

 

[Jonkan]

test if the hiss disappears in the few seconds after you turn of the psu, that way you can rule out hf noise from the lm317. 
please do not forget about HV voltage standards when you build tube stuff.

Can you explain a bit more what you mean about HV voltage standards?

/J

 

[ioaudio]

isolation - security.

 

[Jonkan]

Ok, I get it.

Since you mention it, have you spotted a potential security problem in my psu:s?

/J

 

[ioaudio]

you wouldnt get CE approval with that psu, if thats what you´re asking  8)
but i know space is an issue in this small box.
if you are the only user its ok and will probably live for centuries.
just be sure, that there is NO WAY that the HT can touch the audio xlr (imagine the thing falls down etc)

however please understand that i cannot take responsibility for the DIY builds.

-max

 

[Jonkan]

Ill add more heatgun glue to the critical parts when i get home to make sure it cant happen!
The only things that can really come loose though are the heater filtering caps, everything else is on the pcb except for the pattern switch. I built two for a friend also, so Ill go over his psu:s later on to make sure that theyre safe. These two are only for me.

/J

 

[EEMO1]

Started on my PSU. thought that this is a piece of cake stuffing the caps to the heater section. got cocky and s**t tapping myself on the back for being so good.

wanted to finish today. got to this point:

wait a minute... this is not going to fit. I guess im not finishing this yet.

 

[ioaudio]

new batch is available http://www.groupdiy.com/index.php?topic=34638.0

 

[nhaudio]

Hi Guys almost ready to make a Thiersch order,

but the big question: PVC film or MCF film ?

any empirical fact/personal experience to go for one or the other?

cheers,

Nhaudio

 

[rodabod]

any empirical fact/personal experience to go for one or the other?

Try listening to Martin Kantola's blind M7 test.

 

[audiovisceral]

any empirical fact/personal experience to go for one or the other?

Try listening to Martin Kantola's blind M7 test.

http://www.panphonic.com/M7/tellme.html

I thought the Thiersch mylar sounded best. Mylar I think gives you a better bass and mid response and has better longevity, so that's my preference.

 

[MATTI]

Yep -but on a limited budject Dale compares really good ( thanks )

Matti