DIY Tube Mic project

[MidnightArrakis]

Your link sounds like someone trying to tune-in an AM radio station with an old 1970's radio that has a rotary-dial tuning knob.

/

 

[Emmathom]

Ok I'm posting anyway the 2 short samples in 24-48.
They have been done like that (some home noises behind but one can ear clearly the mics'sounds)

6AK5 // SC400 24-48

6AK5 // X1S 24-48

 

[MicMaven]

Your link sounds like someone trying to tune-in an AM radio station with an old 1970's radio that has a rotary-dial tuning knob.

With due respect (really) to Captain @MidnightArrakis ... as an avid short wave listener and long time amateur radio operator with AM transceivers sitting right here on my desk. I think it sounds more like rubber boots on a wet tile floor. Um ... I think.


All in good fun!

It was good to read the problem was solved by re-flowing some solder. I love the smell of solder smoke in the morning!

We now return to our regularly scheduled program. James

 

[rock soderstrom]

Attached is also the .tsc file (as zip archive) that was used in the simulation - just download free Tina-TI and open the TSC file....

Many thanks for the Tina project! I'm currently on vacation and am taking the opportunity to take a closer look at Tina. I am a simulation beginner, your project file is the right starter kit for it, I am currently simulating the hell out of various SELA T12 derivatives, very interesting. I'm curious to see how realistic the whole thing is, when I'm back home I'll compare my results with a real test setup...

 

[Emmathom]

I usually take this Sommer cable. You do not need the 7 cores but there are 2 x 0.50 mm² for the heater, big plus. Price is the same.
https://www.thomann.de/gb/sommer_ca...PR0yxStGBzO5GN2MQ9FGRiaC714x49exoC_tAQAvD_BwE

Hi Rock ! you were right about this cable Sommer SC Octva tube. I ordered 8 meters @Thomann for 2 mics to replace the cable I bought on Ali (5 x 24AWG wires + shield). This Ali thing is a real s**t : soooo microphonic that you can ear where you hit it (even very gently) ! And it cracks like popcorn when you move it...

Otherwise you'll be able to listen to the new files when you come back, X1S capsule vs SC400. In the two case I must say that this 6AK5 mic is very pleasant and performing.
I guess that the difference in the first test samples came from converting the 24-48 files to 16-44 because when I go back listening to the recorded files in my DAW it's not so evident. So the last files posted are 24-48...
The Tamura output Tx can handle much more level so I loose the little (and pleasant) compression heard on the first version but I gain cleaner sound. A choice to make in my case (already made for Tamura).

A friend of mine has already ordered from me one 6AK5 mic based on his Studio Project B1 body and (maybe?) capsule. I hope the tube will fit in the body (fingers crossed). I will put the Neutrik NTE10/3 in his version.

BR

 

[Emmathom]

You said you use the 2*0,5mm for heater, it means for V+ and ground I presume, same ground for audio... and choose 3 wires (among the 5*0,14mm) for HT / Signal + / Signal -

 

[rock soderstrom]

Hi Rock ! you were right about this cable Sommer SC Octva tube. I ordered 8 meters @Thomann for 2 mics to replace the cable I bought on Ali (5 x 24AWG wires + shield). This Ali thing is a real s**t : soooo microphonic that you can ear where you hit it (even very gently) ! And it cracks like popcorn when you move it...

The Tamura output Tx can handle much more level so I loose the little (and pleasant) compression heard on the first version but I gain cleaner sound. A choice to make in my case (already made for Tamura).

I have had similar experiences and am still positively surprised at how good (compared to "real" transformers) these ridiculously small things from Neutrik and Beyerdynamic sound. As long as you don't overdo it with the level, they add a lot of positive things to the sound of the microphone. Ideal for low budget projects.

A friend of mine has already ordered from me one 6AK5 mic based on his Studio Project B1 body and (maybe?) capsule.

That sounds familiar to me.
I had the B1 a long time ago. I think you can continue to use the capsule, the B1 wasn't bad back then. I remember the body as being a bit prone to vibration, so you might have to dampen it a bit mechanically.

I hope the tube will fit in the body (fingers crossed). I will put the Neutrik NTE10/3 in his version.

That's going to be tight.

You said you use the 2*0,5mm for heater, it means for V+ and ground I presume, same ground for audio... and choose 3 wires (among the 5*0,14mm) for HT / Signal + / Signal -

Correct. I actually ran the grounds separately first, but it makes no difference.

 

[Emmathom]

I had the B1 a long time ago. I think you can continue to use the capsule, the B1 wasn't bad back then.

Cool

I remember the body as being a bit prone to vibration, so you might have to dampen it a bit mechanically.

Ok I will (adhesive tar ?)

That's going to be tight.

I'm afraid yes... but NTE10/3 is so small

Correct. I actually ran the grounds separately first, but it makes no difference.

Anyway the ground is common in the PSU (heater / HT / audio)

 

[rock soderstrom]

I hope the tube will fit in the body (fingers crossed).

I'm afraid yes... but NTE10/3 is so small

BTW, you can also use the 5840 tube. It is technically quite similar to the 6AK5, it is the the subminiature twin of the 6AK5 and needs less space. This tube (or similar) has been used successfully in numerous microphones. However, I prefer the 6AK5/5654/E95F if sufficient space is available.

Ok I will (adhesive tar ?)

Have a look at it first, maybe foam or a damping suspension will do.

 

[Migs 31]

Hi Rock ! you were right about this cable Sommer SC Octva tube. I ordered 8 meters @Thomann for 2 mics to replace the cable I bought on Ali (5 x 24AWG wires + shield). This Ali thing is a real s**t : soooo microphonic that you can ear where you hit it (even very gently) ! And it cracks like popcorn when you move it...

Otherwise you'll be able to listen to the new files when you come back, X1S capsule vs SC400. In the two case I must say that this 6AK5 mic is very pleasant and performing.
I guess that the difference in the first test samples came from converting the 24-48 files to 16-44 because when I go back listening to the recorded files in my DAW it's not so evident. So the last files posted are 24-48...
The Tamura output Tx can handle much more level so I loose the little (and pleasant) compression heard on the first version but I gain cleaner sound. A choice to make in my case (already made for Tamura).

A friend of mine has already ordered from me one 6AK5 mic based on his Studio Project B1 body and (maybe?) capsule. I hope the tube will fit in the body (fingers crossed). I will put the Neutrik NTE10/3 in his version.

BR

It WILL fit in there, just solder the pcb with valve socket at the back of one of the two PCB’s (you do need two pcb’s Parallel) in order to have enough clearance. And yes two PCB’s sandwiched to hold the capsule mount. Unless you find another way.

Also Rock’s suggestions to use a 5840 subminiature would make sense. I tried with a M49 C simplified circuit in it. I Had to clean the capsule as the black soft rubber at the bottom of the capsule holder had disintegrated with time.

Yes, Neutrik NTE 10/3 transfo on my pic.
And I added a porous spongy material at the base of the capsule holder, to dampen the reflections in my final version.

M

 

[Emmathom]

It WILL fit in there, just solder the pcb with valve socket at the back of one of the two PCB’s (you do need two pcb’s Parallel) in order to have enough clearance. And yes two PCB’s sandwiched to hold the capsule mount. Unless you find another way.

Also Rock’s suggestions to use a 5840 subminiature would make sense. I tried with a M49 C simplified circuit in it. I Had to clean the capsule as the black soft rubber at the bottom of the capsule holder had disintegrated with time.

Yes, Neutrik NTE 10/3 transfo on my pic.
And I added a porous spongy material at bottom of the capsule to dampen reflections in my final version.

M

My friend sent me his SP mic yesterday : I will discover it in a couple of days (never opened this mic before) but I don't need the DC/DC PCB so I'll gain space in there... I like mechanical challenges : I WILL find a solution for an EF95.

Yes I install a foam ring (~5mm thickness) under my capsules too.

 

[Emmathom]

I received the SP mic today and gave it a try : I found the capsule's sound very pleasant and very well balanced too ! A good surprise with this 797audio part !

 

[thor.zmt]

I received the SP mic today and gave it a try : I found the capsule's sound very pleasant and very well balanced too ! A good surprise with this 797audio part !

797 Audio is basically the continuation of Beijing Electronics Factory #797 (next door to Factory #798 - now dubbed 798 Art Zone) in a factory complex established in the 1950's by East Germany, as part of Soviet/Eastern Block economic assistance to China.

It was originally # 718 Joint factory in a huge development, 640,000 square meter area in Dashanzi, then a low-lying patch of farmland northeast of Beijing. The complex was to occupy 500,000 square meters, 370,000 of which were allocated to living quarters.



The equipment was transported directly through the Soviet Union via the Trans-Siberian railway, and a 15 km track of railroad between Beijing railway station and Dongjiao Station was built especially to service the factory. Caltech-educated scientist Luo Peilin (罗沛霖), was Head Engineer of Joint Factory 718 during its construction phase.



Joint Factory 718 began production in 1957. The factory quickly established a reputation for itself as one of the best in China. The Joint Factory produced a wide variety of military and civilian equipment.

Civilian production included acoustic equipment for Beijing's Workers' Stadium and Great Hall of the People, as well as all the loudspeakers on Tiananmen Square and Chang'an Avenue. Military components were also exported to China's Communist allies, and helped establish North Korea's wireless electronics industry.

After 10 years of operation, Joint Factory 718 was split into more manageable components, such as sub-Factories 706, 707, 751, 761, 797 and 798.

Factory #797 did audio while #798 was military electronics. Microphone making in #797 was started with tooling and training from "Neumann Ost", aka Microtech Gefell.



Later after the big state owned factories struggled or shut down under Deng's reforms in the 90's and very early 00's, a lot of smaller companies broke off from state factory 797 (it was of the incubators of Audio in China) including makers of Tube Amplifiers (e.g. Opera), Microphones (797 Audio) and others.

In the 00's many consumer electronics Factories covering "specialist audio" (like Tube Amplifiers) were located in the area of 797 / 798 factories in Peking, spinoffs and breakouts of former 797/798 engineers.

So if you get a sufficiently early capsule from 797, it will be very "Neumannish".

Many later relocated south to Guangdong Province, where for example Ulli Behringer, in the immortal words of Coleridge "A Stately Pleasure dome decreed" and started making everything in house...



Over the last few decades everything in China was subject to serious quality fade (as result of many many factors, but mostly price/cost pressures), so I entertain doubts that current production is as good.

When I lived in Peking 798 Art Zone was a a favourite weekend hangout of mine, despite being on the other side of town, before the massive Subway constructions, necessitating long taxi rides.

Art Galleries love the natural light in the Bauhaus style "sawtooth roof with angled skylights" factory buildings erected by East Germany, quite unique in architecture in China and possible Asia.





Some of the lathes and other machine tools preserved on some gallery floors had name plates tracing them back to what where at the beginning small independent factories in my home state, the Free State of Saxony.


While later machines clearly from the same factory held plates showing them coming from state owned enterprises after the private owners had been expropriated by the East German communist government.

A bit of pointless history and background to 797 microphones and factories in Peking.

Thor

 

[Emmathom]

My friend bought his one a long time ago. I can say before 2010 for sure.
And yes I confirm this B1 capsule is balanced and pleasant sounding. Will do a great couple with 6AK5

 

[rock soderstrom]

And yes I confirm this B1 capsule is balanced and pleasant sounding. Will do a great couple with 6AK5

In the 00s, when I was still actively producing, Studio Project mics were the go-to mics if you didn't have any budget. They were quite popular and we made very good recordings with them. In my memory, the resolution was good, the sound was a bit treble-heavy, but this was more due to the (schoeps-style?) impedance converter circuit.

The SELA T12 circuit with the Neutrik transformer fits the capsule very well, as it softens the high frequency peak somewhat in my experience.

 

[Emmathom]

Studio Project B1 mods : first step is to build a board which fits the size of the microphone and will receive the tube support... difficult construction requiring great precision (hand-made pcb) but I keep on thinking that it will do
to be continued (as soon as I receive the tube socket)

 

[rock soderstrom]

It WILL fit in there, just solder the pcb with valve socket at the back of one of the two PCB’s (you do need two pcb’s Parallel) in order to have enough clearance. And yes two PCB’s sandwiched to hold the capsule mount. Unless you find another way.

Also Rock’s suggestions to use a 5840 subminiature would make sense. I tried with a M49 C simplified circuit in it. I Had to clean the capsule as the black soft rubber at the bottom of the capsule holder had disintegrated with time.

Yes, Neutrik NTE 10/3 transfo on my pic.
And I added a porous spongy material at the base of the capsule holder, to dampen the reflections in my final version.

M

Hi Migs, are these the original capsules of the Studio Projects B1? I think so, can you post photos of it in the capsule photo thread, please?

Cheers

 

[kingkorg]

797 Audio is basically the continuation of Beijing Electronics Factory #797 (next door to Factory #798 - now dubbed 798 Art Zone) in a factory complex established in the 1950's by East Germany, as part of Soviet/Eastern Block economic assistance to China.

It was originally # 718 Joint factory in a huge development, 640,000 square meter area in Dashanzi, then a low-lying patch of farmland northeast of Beijing. The complex was to occupy 500,000 square meters, 370,000 of which were allocated to living quarters.

View attachment 133649

The equipment was transported directly through the Soviet Union via the Trans-Siberian railway, and a 15 km track of railroad between Beijing railway station and Dongjiao Station was built especially to service the factory. Caltech-educated scientist Luo Peilin (罗沛霖), was Head Engineer of Joint Factory 718 during its construction phase.

View attachment 133652

Joint Factory 718 began production in 1957. The factory quickly established a reputation for itself as one of the best in China. The Joint Factory produced a wide variety of military and civilian equipment.

Civilian production included acoustic equipment for Beijing's Workers' Stadium and Great Hall of the People, as well as all the loudspeakers on Tiananmen Square and Chang'an Avenue. Military components were also exported to China's Communist allies, and helped establish North Korea's wireless electronics industry.

After 10 years of operation, Joint Factory 718 was split into more manageable components, such as sub-Factories 706, 707, 751, 761, 797 and 798.

Factory #797 did audio while #798 was military electronics. Microphone making in #797 was started with tooling and training from "Neumann Ost", aka Microtech Gefell.

View attachment 133650

Later after the big state owned factories struggled or shut down under Deng's reforms in the 90's and very early 00's, a lot of smaller companies broke off from state factory 797 (it was of the incubators of Audio in China) including makers of Tube Amplifiers (e.g. Opera), Microphones (797 Audio) and others.

In the 00's many consumer electronics Factories covering "specialist audio" (like Tube Amplifiers) were located in the area of 797 / 798 factories in Peking, spinoffs and breakouts of former 797/798 engineers.

So if you get a sufficiently early capsule from 797, it will be very "Neumannish".

Many later relocated south to Guangdong Province, where for example Ulli Behringer, in the immortal words of Coleridge "A Stately Pleasure dome decreed" and started making everything in house...



Over the last few decades everything in China was subject to serious quality fade (as result of many many factors, but mostly price/cost pressures), so I entertain doubts that current production is as good.

When I lived in Peking 798 Art Zone was a a favourite weekend hangout of mine, despite being on the other side of town, before the massive Subway constructions, necessitating long taxi rides.

Art Galleries love the natural light in the Bauhaus style "sawtooth roof with angled skylights" factory buildings erected by East Germany, quite unique in architecture in China and possible Asia.

View attachment 133648



Some of the lathes and other machine tools preserved on some gallery floors had name plates tracing them back to what where at the beginning small independent factories in my home state, the Free State of Saxony.

View attachment 133651
While later machines clearly from the same factory held plates showing them coming from state owned enterprises after the private owners had been expropriated by the East German communist government.

A bit of pointless history and background to 797 microphones and factories in Peking.

Thor

This is a magnificent post. Thank you for sharing!!!

 

[Emmathom]

End of 6AK5 Poject...
Got a pair with SC400 capsules
Ready to record !
I will use one of them next monday to record a cello in a classical quartet ensemble

 

[Migs 31]

End of 6AK5 Poject...
Got a pair with SC400 capsules
Ready to record !
I will use one of them next monday to record a cello in a classical quartet ensemble

Bravo! Well done.

Let me get this right: did you use two SC400 bodies & capsules to mod, in addition of one SP B1 body/capsule?
Or am I misunderstanding your post ?

In any case, can you share some pics of the finished insides of both models?
Just as future reference/tech porn.

M