DIY Tube Mic project

[Emmathom]

[a sE2300 in cardio pattern] -- Is this an "sE Electronics" microphone? If so, I have a pair of the "sE 2500" microphones that I have used to record piano with and they sounded terrific!!!

In related news.....if you could send me even just a sketch of your "perfboard PCB" with its mechanical dimensions carefully detailed on it, I could create a PCB-outline CAD-file for you that you could then use to place your microphone circuitry onto. Just a thought.....

/

Well you don't say a word about the test / which one you like and why...

The 6AK5 schematic has been posted by @thor.zmt page 3 of this thread and as you could see, this schematic is so simple that no interested to create a pcb for it. And depending on body-donor the size of the pcb will change...
So thank you... but no.

 

[Emmathom]

Emmathom,
Very kind of you to include me in the panel of judges.
This time I'll refrain from wine...
Again listening on my phone but
a) I remembered I have an external USB DAC box. Big quality difference.
b) I loaded files into an app which allows me to seamlessly switch between recordings.
Big help.

I do so myself (switching tracks) in my Logic Pro

Anyway, in order SC400, X1S, e2300: dullest, balanced, not enough low/mid - worst.
SC400 sounds muted, lacking upper frequencies. The guitar sounds fine to me but probably as a result of this HF cut - I prefer bass and cello to violin

Yes SC400 is a bit dark but personally I don't like "sibilant" mics or highs to much in front, so that's my choice (SC400)

X1S sounds very well on your voice, best of the three mics. Scale of the guitar seems well rendered. Maybe a bit too much"spikey" in HF but it may be my dislike for higher pitches. Hard to tell not having heard the instrument live. It might be 100% accurate. All in all this mic sounds best.

Yes the X1S capsule is very interesting too... too bad you can't buy it as spare (they send me a price for it because I'm already a sE owner : 110€ + shipping > no thanks)

e2300 - nothing to write home about.

Hum... I would like to get your feeling anyway about this mic. I suppose that it would sound great with, for ex., an Arienne K47 flat

Thank you for participating

 

[My3gger]

6AK5 Mic samples

Hi folks !
So I recorded the same session with the 2 mics identicaly built except for the capsules. The X1S file is labelled X1S and so with the SC400. At last I found interesting to add a third mic for comparison : a sE2300 in cardio pattern.

6AK5 SC400

6AK5 X1S

sE2300 cardio

I listened to the samples without reading what this mics are, how tracks were recorded, the only known thing i knew was 6AK5 tube in first two mics. Differences were a lot more consistent than in previous tests, where speakers made comparisons almost impossible for me because i do waaay less studio work than years back. They mostly call me for the tests, diy gear, wiring problems, some repairs, or if they want opinion about recording and mixing. Don't count me as one of those people who really know a lot about mics and/or do studio work almost every day.
SC400 sounded more natural than others, suits your vocal best, guitar is quite good, but not as good as with second mic due to lack of highs, or too much lows. I think low frequencies are boosted with this one.
X1S lacks some low frequencies, highs are a lot more pronounced, maybe a bit "sibilant" (or just bright), pretty good on guitar. It probably has good potential with different capsule
SE2300 doesn't sound as natural as SC400 and X1S, although it has more even frequency response. I can't say if it has potential for better sound, will read what you wrote about the circuit and capsule used.
-------
Listening was done straight out of computer's motherboard converters into Adam T5V, it took me about 30 minutes including troubles with files dropping out because i should do it from program and real daw. This setup has "good enough" monitors, files stopping playing is annoying because i would have to switch between track a lot faster. Btw, do you have more than only a few seconds of useful memory for sound when doing such tests?

 

[Emmathom]

Thanks you for your input !

-------
Btw, do you have more than only a few seconds of useful memory for sound when doing such tests?

Don't understand your question...
I recorded these files on Logic Pro (so with a MacBook pro) thru a DIY tube mic pre and a Presonus 1810C audio interface

 

[My3gger]

Thanks you for your input !

Don't understand your question...
I recorded these files on Logic Pro (so with a MacBook pro) thru a DIY tube mic pre and a Presonus 1810C audio interface

To get general opinion about how mics sound i went through all of them first, without switching between track. For smaller differences i need to switch between track every 5-10 seconds, sometimes 3 seconds. I noticed this at the start of my career, others i talked to about this "memory issue" said they are testing the same way, some of them have even shorter memory, more like 3-5 seconds when listening for details.

 

[Emmathom]

Well, depends on the file but I like to listen to the whole thing first (only if the file does not last for hours) and then come back on certain parts defined by locators, and switch between tracks from several seconds to... one word if necessary.

Thank you for your input !

It appears that a mixed capsule between X1S (lack of lows) and SC400 (lack of highs) would be great, according to your comments and my firts impressions. A better capsule like an Arienne K47 flat ? A good K67 with de-emphasis ? I have also a few more "cheap china capsules" to test (but I doubt they will be great)

I love this little mic for its sound & simplicity : it no doubt deserves a good quality capsule...

 

[Emmathom]

On the SC400 (only) I've installed a thin foam disk under the capsule to damp reflections : I don't know if it's a good thing and how it modifies the sound (maybe the cause for the lack of highs ?)

 

[Emmathom]

I repost the link to the first 6AK5 version sample (Philips tube / 1uF Ali Express Audiophiler / Neutrik NTE10/3 / X1S capsule)

6AK5 first version

 

[pmfalcman]

(...) "Yes SC400 is a bit dark but personally I don't like "sibilant" mics or highs to much in front, (...)

I'm not a fan too. But on your voice SC400 is a bit too muted. X1S is IMO much better, slightly sibilant but only just.
S2300 - sibilants more pronounced.
SC400 for guitar and X1S for your voice - this would be my choice if I went for pleasant rendition for myself.
Cannot say if accurate.

 

[Emmathom]

Thank you @pmfalcman but as I want to make a pair I have to choose 2 same capsules... without spending an arm or a leg.
Tough challenge... I could try with my Arienne K47 flat ? Wouldn't it be too dark too ? Let's try soon...

About sE2300 : as I already said, I'm confident with sE Electronics circuits & transformers (a good circuit is not a big deal anyway) but they install cheap capsules in low budget mic (if 340€ is a low-budget). I want to try this mic with Arienne K47 flat !

Back to 6AK5 : trying a K67 would be interesting but I don't know how to install a de-emphasis filter to damp around 10K... I guess it's one tiny capsule (somewhere in the signal path)

 

[Emmathom]

I don't know if somebody (@Wordsushi ?) has already tried this BAIFEILI capsule and how it sounds :
https://fr.aliexpress.com/item/1005...=scene:pcDetailTopMoreOtherSeller|query_from:

 

[MicMaven]

6AK5 SC400
6AK5 X1S
sE2300 cardio

At the risk of being hounded out of the principality for heresy or treason ... here is my take.

The SC400 is slightly subdued and lacks verve compared to the others. I do not hear more bass - just less treble. It is less sibilant and less gritty than the other two - pleasant and relaxed on voice, lacking zip on the guitar. If you placed any sort of baffle or damping material in the grille, it shows. Perhaps this diminished its luster or shine above 5 MHz.

The X1S is more balanced and best overall - more sibilant and punchy than the SC400 but less so than the SE2300. The X1S is more articulate on voice - consonants are more crisp and punchy, but with some percussive puffing and chuffing. The is more lively, with more string dynamics, more ringing and more percussive, again more than the SC400 and less than the SE2300. Speaking voice is generally more realistic and live sounding - compared to the SC400 it is somewhat analogous to the difference between open air and closed cup earphone receivers.

The SE2300 lacks bass and is harshly sibilant and percussive, ringing highs and excessive guitar string dynamics. I want to turn the treble control down. Overly percussive.

The SC400 may be best for speaking voice and long term listening without fatigue. The X1S is most realistic and musically exciting. I would retune the SE2300 or swap its capsule for a less sibilant, less percussive one.

Parenthetically, I like the variable pick action at the end of the guitar sample which adds a helpful informative dimension.

Yesterday, I listened to each sample in its entirety, seriatim. Today, I micro-compared short snippets of each sample against the same snippet of the other two. They sounded closer yesterday, and more distinct today. And, that is just MY take. / James

 

[Emmathom]

Thank you James for this complete report !

* SC400 : I have to admit it's too dark and a bit mufled
* X1S : more detailed, yes more punchy, but a bit too sibilant for me (the "sss" are disturbing my ears)
* sE2300 needs a much better capsule since I'm sure sE puts cheap ones in their low-budget mic (a random chinese everybody can find at around 20-30€ I guess)

The problem is, as I already said, sE does not sell capsules as spare parts. I have 2 of them but unfortunately one has its diaphragm "sticked". I put it for one month in silica at a warm place of my house but it didn't do anything. When replaced in the mic, it worked for a couple of minutes and then sticked again under high pressure (shout from 20cm to the mic and capsule sticks). I replaced it in silica (for 2 months now) and I will do a last try. If it works (would be great!) I'll install it in place of SC400 and add a de-emphasis network.

Besides that, I have 2 Arienne K47 flat waiting for a decent mic and I ordered a chinese K47 which is supposed to be a good one... Circuits are easy (!) but finding & matching good capsules that not cost an arm or a leg is a whole brain teaser...

 

[Emmathom]

Hi !
by retesting between the two 6AK5 I discovered a suspicious noise on one of them , a kind of HF interference...
this noise is not depended on PSU
do you know where it comes from? when mic is "resting" no noise, when I speak into it > noise

6AK5 HF ?

 

[rock soderstrom]

Link doesn't work.

when mic is "resting" no noise, when I speak into it > noise

Oscillation (excited by microphony?) Not all tubes are suitable for microphone duties.

Edit: It may also be due to the high impedance wiring or the tube is simply defective. Some of my EF12k do the same --> garbage can

 

[Emmathom]

Link doesn't work.


Oscillation (excited by microphony?) Not all tubes are suitable for microphone duties.

Edit: It may also be due to the high impedance wiring or the tube is simply defective. Some of my EF12k do the same --> garbage can

Did you listen to the short sample ?

Last time plugged, for capsules test, no noise...

Garbage can ??? Remember I paid 58€ for the Mullard pair ! (+ shipping + customs)

Edit : I opened the mic, redo solders, unplugged then replugged the tube : noise has gone.
I will leave the mic powered and plugged in my soundcard for some hours to keep an eye on it...

 

[rock soderstrom]

Did you listen to the short sample ?

As I said, the link doesn't work, at least for me. But I can well imagine what that sounds like, as I've already had that too...

Last time plugged, for capsules test, no noise...

Such problems can occur sporadically, at least that's how it was for me.

Garbage can ??? Remember I paid 58€ for the Mullard pair ! (+ shipping + customs)

Yes, painful. What do you think a EF12k costs at the moment? This can also happen to you with VF14, AC701 or other very expensive tubes. One reason why I prefer relatively cheap tubes like 6Ak5w, EF800 etc for this job. Just a reminder, most tubes are used in microphones outside their specifications.

Very few tube sellers test for this very specific application! In general, tubes for microphones have always been selected, even in the past.

Is this the Mullard tube with the weaker emission in the mic with the problem?

What does it look like when you swap the tube with the good mic? Does the problem move with the tube? If not, it may be due to your cable wiring.

That would be easy to fix.

 

[rock soderstrom]

Edit : I opened the mic, redo solders, unplugged then replugged the tube : noise has gone.
I will leave the mic powered and plugged in my soundcard for some hours to keep an eye on it...

That would be good news, good wiring and solder joints are very important for high impedance matters.

Yes, watch that. Such problems tend to come and go very sporadically, unfortunately.

But I hope that was the solution to the problem.

 

[Emmathom]

I repost a new link on the dedicated message #214

I want to redo test between SC400 & X1S (for myself > I won't bother you all one more time) because when I listen to the files in my DAW the difference is not so blatant. Maybe it's the conversion from 24-48 to 16-44 ?

Let me check that...

 

[Emmathom]

Well a quick voiceover test :
- X1S has a bit less bass & low medium and a bit more highs
- SC400 has a bit more bass & low medium and a bit less highs
hard to measure but I would say that the range is about + or - 1dB/1,5dB maximum.

but it's not as evident as in the last test I posted ! the mics are closer to each other.
I can now say that the 2 mics can seduce by their respective qualities which are a bit different but really not so much