bluebird
Well-known member
Yea all the big caps are EXR
Rode NTK with NOS Telefunken 6922. Where to get tube in US?
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Category 5
Well-known member
Well, I got the Telefunken tube today. It took 5 days to get here from Berlin, much quicker than I expected.
The tube is brand new, the printing is perfect, and the box was exactly as the picture the dealer sent me. It was $85 plus $15 for air mail shipping (US, paypal). The tube is marked both on the box and the tube itself as a 6922, made in June of 1968. Most Tele tubes of this type are marked E88CC, but the dealer explained that since it was a military stock tube it was listed as 6922 in order that foreign equipment using "6922" labeled tubes could be fitted with the same part number without confusion. the e88cc and 6922 are identical in every way (he even e-mailed me pictures if them side by side). Nevertheless I requested the 6922 just to be sure. He matched me a tube for like triodes, even though the NTK only makes use of one.
So how does it sound? Well, I did some quick dry vocals trhough the API before the swap and after. Both times I let the mic warm up for exactly one hour. I did not touch the preamp except for the initial level set.
1. The stock tube sounded good (I always liked the NTK) except for a little bit of a fuzzy sound on loud passages. I always noticed this since the mic was new, but just attributed it to the fact that the NTK is a tube mic. I also noticed (based on the comparison) that the stock tube has a little less low end, almost making it seem like there is a stronger upper midrange (around 1k'ish to 1.5k).
2. After changing the tube to the Tele I notice that the fuzzy distortion is pretty much gone. I guess it was an artifact of the Sovtek tube. Like guitar tubes there are probably grittier and cleaner tubes, and the Sovtek is definitely grittier than the Tele. You may find the grit desirable. The Telefunken tube also gives the mic some sort of upper frequency range harmonic that was not very present with the Sovtek. It is reminiscent of the character that I love in the ISA110, Neve 1081, Millennia HV-2, and Aphex 1100. I can only imagine it is the even order harmonics that I always read about. Whatever, overall the Tele is more smooth and has a more pleasant saturation. I also noticed that the low end was a bit more pronounced too, much like what I heard on the Mic Pre CD with the Manley mic. For what it's worth, the low end is on the verge of being "too" fat and warm, but I thought the Mic Pre CD had the same effect to an even greater degree (this was one of my initial gripes with the pre CD) so I have a feelling I am in the minority on thinking of this as a negative. After backing a little further off the mic the problem was solved, so I chalk it up to increased proximity effect. After a few listens, I am certain that the Telefunken is the preferable tube. The difference is noticable, and the loss of fuzz and addition of the extra smooth high end saturation makes the NTK a much nicer mic.
If anyone is interested I can make some MP3s of the samples and load them on my FTP. If not, I won't, so speak up.
For $100.00 I would say the upgrade is a no-brainer. It is evident that the "hand picked" tube that comes in the NTK as stock is just that..."hand picked" out of a box full of tubes. I imagine the Siemens, Mullard, and even Phillips JAN Military tubes will offer some improvement. The more I listen to the comparison the more I dislike the Sovtek. It sounds like there is a distortion pedal on the mic (very slight, but once you hear it it starts to really stand out).
I did not test the mic through any other preamps, so the low boost may be a combination of the mic and the preamp... I did not drive the preamp very close to peaking because I wanted to be sure I wasn;t hearing any clipping on behalf of the inout chain. I will try through the 1272, Millennia and MP20 next to see which I like the best. The API is my favorite pre right now so I went straight for it.
So has anyone got the schematics? Seems pointless to start replacing caps before we know how the circuit will benefit. After the tube change I am having fun with a "new" mic already.
Shane
The tube is brand new, the printing is perfect, and the box was exactly as the picture the dealer sent me. It was $85 plus $15 for air mail shipping (US, paypal). The tube is marked both on the box and the tube itself as a 6922, made in June of 1968. Most Tele tubes of this type are marked E88CC, but the dealer explained that since it was a military stock tube it was listed as 6922 in order that foreign equipment using "6922" labeled tubes could be fitted with the same part number without confusion. the e88cc and 6922 are identical in every way (he even e-mailed me pictures if them side by side). Nevertheless I requested the 6922 just to be sure. He matched me a tube for like triodes, even though the NTK only makes use of one.
So how does it sound? Well, I did some quick dry vocals trhough the API before the swap and after. Both times I let the mic warm up for exactly one hour. I did not touch the preamp except for the initial level set.
1. The stock tube sounded good (I always liked the NTK) except for a little bit of a fuzzy sound on loud passages. I always noticed this since the mic was new, but just attributed it to the fact that the NTK is a tube mic. I also noticed (based on the comparison) that the stock tube has a little less low end, almost making it seem like there is a stronger upper midrange (around 1k'ish to 1.5k).
2. After changing the tube to the Tele I notice that the fuzzy distortion is pretty much gone. I guess it was an artifact of the Sovtek tube. Like guitar tubes there are probably grittier and cleaner tubes, and the Sovtek is definitely grittier than the Tele. You may find the grit desirable. The Telefunken tube also gives the mic some sort of upper frequency range harmonic that was not very present with the Sovtek. It is reminiscent of the character that I love in the ISA110, Neve 1081, Millennia HV-2, and Aphex 1100. I can only imagine it is the even order harmonics that I always read about. Whatever, overall the Tele is more smooth and has a more pleasant saturation. I also noticed that the low end was a bit more pronounced too, much like what I heard on the Mic Pre CD with the Manley mic. For what it's worth, the low end is on the verge of being "too" fat and warm, but I thought the Mic Pre CD had the same effect to an even greater degree (this was one of my initial gripes with the pre CD) so I have a feelling I am in the minority on thinking of this as a negative. After backing a little further off the mic the problem was solved, so I chalk it up to increased proximity effect. After a few listens, I am certain that the Telefunken is the preferable tube. The difference is noticable, and the loss of fuzz and addition of the extra smooth high end saturation makes the NTK a much nicer mic.
If anyone is interested I can make some MP3s of the samples and load them on my FTP. If not, I won't, so speak up.
For $100.00 I would say the upgrade is a no-brainer. It is evident that the "hand picked" tube that comes in the NTK as stock is just that..."hand picked" out of a box full of tubes. I imagine the Siemens, Mullard, and even Phillips JAN Military tubes will offer some improvement. The more I listen to the comparison the more I dislike the Sovtek. It sounds like there is a distortion pedal on the mic (very slight, but once you hear it it starts to really stand out).
I did not test the mic through any other preamps, so the low boost may be a combination of the mic and the preamp... I did not drive the preamp very close to peaking because I wanted to be sure I wasn;t hearing any clipping on behalf of the inout chain. I will try through the 1272, Millennia and MP20 next to see which I like the best. The API is my favorite pre right now so I went straight for it.
So has anyone got the schematics? Seems pointless to start replacing caps before we know how the circuit will benefit. After the tube change I am having fun with a "new" mic already.
Shane
bluebird
Well-known member
Hey thats great to know!!!
Gus is checking out my NTK and is tying to trace the circuit. some caps will be replaced. He might wire it for a 12AY7 also.
I have another NTK to compare it too. It might be a while but I will keep you posted.
Gus is checking out my NTK and is tying to trace the circuit. some caps will be replaced. He might wire it for a 12AY7 also.
I have another NTK to compare it too. It might be a while but I will keep you posted.
b3groover
Well-known member
I've got two of these that I only really use on Leslie bass or electric bass. I changed the tubes out to some relatively inexpensive new Phillips Miniwatt PCC88 tubes. Even with those the sound was much improved. More output, better bass response.
I'm definately interested in a cap upgrade. This place rules.
I'm definately interested in a cap upgrade. This place rules.
The Hitano electros don't have good measurements IMO. ESR of the three 47uf at 160V were .62ohms .62ohms and .65ohms. A 47uf at 250V cap I wanted to use but is too big ESR is .25ohms. The Hitano 220uf at 16V ESR .08 ohms and the 47 at 50 ESR .7ohms
I have measured the SMD ceramics What a pain smaller than a match head. Schematic is almost done. It is a little different design. Need to do some thinking on the tube type to mod it for.
I have two plastic mystery caps in a critical part of the circuit. I don't know what they are (they look like a stacked film od some type) and I don't know the voltage rating. They look like they might be hard to remove without melting them.
Some small suprises.
I have measured the SMD ceramics What a pain smaller than a match head. Schematic is almost done. It is a little different design. Need to do some thinking on the tube type to mod it for.
I have two plastic mystery caps in a critical part of the circuit. I don't know what they are (they look like a stacked film od some type) and I don't know the voltage rating. They look like they might be hard to remove without melting them.
Some small suprises.
NewYorkDave
Well-known member
$100 for a f*cking tube?
At that price, I hope it cooks you dinner and opens your beer for you as well.
:green:
At that price, I hope it cooks you dinner and opens your beer for you as well.
:green:
Category 5
Well-known member
[quote author="NewYorkDave"]$100 for a f*cking tube?
At that price, I hope it cooks you dinner and opens your beer for you as well.
:green:[/quote]
That's actually a really good deal for that tube considering that the tube itself was only $85. Usually they go for 100-150 for a used tube that tests new. This tube was new old stock from 1968 so there was surely a premium. Keep in mind this isn't a Sovtek though...or anything like any Chinese tubes made today.
Shane
At that price, I hope it cooks you dinner and opens your beer for you as well.
:green:[/quote]
That's actually a really good deal for that tube considering that the tube itself was only $85. Usually they go for 100-150 for a used tube that tests new. This tube was new old stock from 1968 so there was surely a premium. Keep in mind this isn't a Sovtek though...or anything like any Chinese tubes made today.
Shane
Schematic is almost done. It different than some might expect.
From looking at the circuit I see two thing so far that should make more of a difference than the tube used.
Using a 6dj8 type does not make alot of sense to me does anyone know the russian tube specs gain etc? I have not found link yet.
A 12a_7 of the same gain should be a better tube as it is use in this circuit. Maybe out of all the current made tubes the one rode picked works the best.
More to come.
From looking at the circuit I see two thing so far that should make more of a difference than the tube used.
Using a 6dj8 type does not make alot of sense to me does anyone know the russian tube specs gain etc? I have not found link yet.
A 12a_7 of the same gain should be a better tube as it is use in this circuit. Maybe out of all the current made tubes the one rode picked works the best.
More to come.
b3groover
Well-known member
Can't wait. Gus, are you going by pictures or did someone loan one to you?
look at bluebirds post I have just the board.
For owners of the microphone use it with phantom ON and tell me if you hear a difference give it about 1 hour or more before testing.
Bluebird voltages look to be right. Its fun to reverse something that is not a direct copy of something else(as far as I know I have not been inside a m147,49 or 150 or the sanken microphones).
The schematic is at its third redraw. Its now at the time where I let is sit for a day or two and then go back to check it.
For owners of the microphone use it with phantom ON and tell me if you hear a difference give it about 1 hour or more before testing.
Bluebird voltages look to be right. Its fun to reverse something that is not a direct copy of something else(as far as I know I have not been inside a m147,49 or 150 or the sanken microphones).
The schematic is at its third redraw. Its now at the time where I let is sit for a day or two and then go back to check it.
b3groover
Well-known member
Ah, I should learn to read. I was going to offer to loan you one of mine.
schematic done. waiting for parts for the upgrade. tube type should matter little in this circuit except for noise. Maybe the stock tube does not like being underheated. 6dj8 grid construction (frame grid) might not good for tube microphones. Yes I read the EAR microphone uses one but I think the grid does not "touch" the capsule in that microphone.
I think rewiring the socket for an ef86 would be better. A 12a_7 type with a gain of about 30 might work. Cool thing about ef86 and 12a_7 with this circuit is the heater voltage should go up a little because of less current drawn by the fil compared to a 6dj8. With the 12a_7 you would lite only 1/2 of fil for the side you are using and then connect the grid ,cathode and plate of the unused side together and...................................................................................
I think we can get this microphone to be grill and capsule limited.
I think rewiring the socket for an ef86 would be better. A 12a_7 type with a gain of about 30 might work. Cool thing about ef86 and 12a_7 with this circuit is the heater voltage should go up a little because of less current drawn by the fil compared to a 6dj8. With the 12a_7 you would lite only 1/2 of fil for the side you are using and then connect the grid ,cathode and plate of the unused side together and...................................................................................
I think we can get this microphone to be grill and capsule limited.
b3groover
Well-known member
Can't wait! Thank you for all your work.
Kev
Well-known member
excussed me ... just passing
http://www.diyfactory.com/projects/gus/ntk2.GIF
or
http://www.diyfactory.com/projects/gus/ntk2.gif
carry on
:thumb:
http://www.diyfactory.com/projects/gus/ntk2.GIF
or
http://www.diyfactory.com/projects/gus/ntk2.gif
carry on
:thumb:
Thanks Kev
I like this circuit with its use of positive ground and the use of 4 output transistors for good drive current and headroom. Not a circuit that will add tube color but one that is very clean with high headroom. I went to buy a K2 yesterday to mod and test for myself but the store did not have one. Changing the triode to a fet BJT cascode that can work at the voltages would be a cool thing to do.
FWIW I have been thinking about a SS circuit microphone with a power supply for some time now.
Looking at the schematic I drew. I think the NTK should be used with phantom on to keep C2 formed.
Ethan this is a type of balanced drive circuit that I posted about in another thread.
I like this circuit with its use of positive ground and the use of 4 output transistors for good drive current and headroom. Not a circuit that will add tube color but one that is very clean with high headroom. I went to buy a K2 yesterday to mod and test for myself but the store did not have one. Changing the triode to a fet BJT cascode that can work at the voltages would be a cool thing to do.
FWIW I have been thinking about a SS circuit microphone with a power supply for some time now.
Looking at the schematic I drew. I think the NTK should be used with phantom on to keep C2 formed.
Ethan this is a type of balanced drive circuit that I posted about in another thread.
I just noted I forgot to show C4 in the schematic it is across the 33k resistor as a bypass on the 1st transitor after the tube the one with the 15 comp cap.
The shipping and web based coast to coast mod of the microphone is close to being done.
Hopefull Bluebird will post about his 1/2 of the mod.
The shipping and web based coast to coast mod of the microphone is close to being done.
Hopefull Bluebird will post about his 1/2 of the mod.
bluebird
Well-known member
So I got the modified board in the mail from Gus (Thanks!) and put it back into the mic.
I did some tests at my practice space.
I put the mic straight into my Lynx II sound card. The level was kind of low but I didn't want the slight differ ring sound of 2 different sides of a mic pre to get in the way.
I put the modified NTK right next to the stock NTK, as close as I could get them.
I stood about 3 feet away and talked and hummed into the mics.
I then faced them towards a drum set about 8 feet away and played a little (I'm not a drummer).
here are the files I recorded. I kept them as wav. files for fidelity. It might take a while to download.
You can put the two files up next to each other in an editor and compare with solo/mute.
http://www.onthespeakers.com/TEC/RT_Stock_SC.WAV
http://www.onthespeakers.com/TEC/RT_Mod_SC.WAV
My opinion:
I could barely tell the difference between the two mics. On headphones I couldn't tell at all.
On my NS-10's I heard a LITTLE bit more high with the mod.
The difference was VERY subtle.
You can judge for your self though.
NEXT: NEW TUBE
I cut the trace going to pin 5 and wired to pin 9 so I could use a 12AY7.
The mic didn't work at first.
THERE IS A TRACE FROM PIN 9 TO PIN 3 THAT WAS UNDER THE TUBE SOCKET.
I had to remove the tube socket and cut this trace.
The mic worked great after that.
The 12AY7 made a difference. it had a bit more gain and sound slightly crisper in the high end.
I don't have any sound file of this, but trust me, it makes a pretty big difference.
So there you have it. I've very happy with how this mic turned out. I think the circuit is now limited by the capsule.
I like to thank Gus for helping me with this. I was basically just the tester. It was fun corresponding from coast to coast.......
:guinness: :grin: :guinness:
I did some tests at my practice space.
I put the mic straight into my Lynx II sound card. The level was kind of low but I didn't want the slight differ ring sound of 2 different sides of a mic pre to get in the way.
I put the modified NTK right next to the stock NTK, as close as I could get them.
I stood about 3 feet away and talked and hummed into the mics.
I then faced them towards a drum set about 8 feet away and played a little (I'm not a drummer).
here are the files I recorded. I kept them as wav. files for fidelity. It might take a while to download.
You can put the two files up next to each other in an editor and compare with solo/mute.
http://www.onthespeakers.com/TEC/RT_Stock_SC.WAV
http://www.onthespeakers.com/TEC/RT_Mod_SC.WAV
My opinion:
I could barely tell the difference between the two mics. On headphones I couldn't tell at all.
On my NS-10's I heard a LITTLE bit more high with the mod.
The difference was VERY subtle.
You can judge for your self though.
NEXT: NEW TUBE
I cut the trace going to pin 5 and wired to pin 9 so I could use a 12AY7.
The mic didn't work at first.
THERE IS A TRACE FROM PIN 9 TO PIN 3 THAT WAS UNDER THE TUBE SOCKET.
I had to remove the tube socket and cut this trace.
The mic worked great after that.
The 12AY7 made a difference. it had a bit more gain and sound slightly crisper in the high end.
I don't have any sound file of this, but trust me, it makes a pretty big difference.
So there you have it. I've very happy with how this mic turned out. I think the circuit is now limited by the capsule.
I like to thank Gus for helping me with this. I was basically just the tester. It was fun corresponding from coast to coast.......
:guinness: :grin: :guinness:
Flatpicker
Well-known member
[quote author="bluebird"]My opinion:
I could barely tell the difference between the two mics. On headphones I couldn't tell at all.
On my NS-10's I heard a LITTLE bit more high with the mod.
The difference was VERY subtle.
You can judge for your self though.[/quote]I kind of wished you hadn't said which was which so I could have done this blind-folded, but the modified version sounds better to me. It's a little louder, but definitely more "open" sounding.
After doing many of these kinds of test myself, I?ve learned what to listen for. It's not night and day, mind you, but once you hear what I'm talking about, the un-modded version just sounds dull by comparison.
I could barely tell the difference between the two mics. On headphones I couldn't tell at all.
On my NS-10's I heard a LITTLE bit more high with the mod.
The difference was VERY subtle.
You can judge for your self though.[/quote]I kind of wished you hadn't said which was which so I could have done this blind-folded, but the modified version sounds better to me. It's a little louder, but definitely more "open" sounding.
After doing many of these kinds of test myself, I?ve learned what to listen for. It's not night and day, mind you, but once you hear what I'm talking about, the un-modded version just sounds dull by comparison.
Category 5
Well-known member
Just though I'd chime in. I have one of the original NTK mics (bought right after it came out) and my board is a tad different.
Mine has no surface mount components, and is labeled RODE NTK Microphone. the board in the pictures is labeled RODE K2 Issue 2. that suggest the K2 and NTK share the same circuit.
Shane
Mine has no surface mount components, and is labeled RODE NTK Microphone. the board in the pictures is labeled RODE K2 Issue 2. that suggest the K2 and NTK share the same circuit.
Shane
