Nixie Sockets for Nady 1050 - anyone try it?

[McIrish]

I've got a Nady TCM1050 mic that I've put a new capsule in and did the modifications to. I'd like to socket the tube for easier swapping. What a horrible design for a mic. Way too short to put a regular socket in it. I have been looking at Nixie sockets. Has anyone tried that?

Nixie Sockets

 

[kingkorg]

I've got a Nady TCM1050 mic that I've put a new capsule in and did the modifications to. I'd like to socket the tube for easier swapping. What a horrible design for a mic. Way too short to put a regular socket in it. I have been looking at Nixie sockets. Has anyone tried that?

Nixie Sockets

Some people have placed regular sockets but between the pcb and headgrille. So that tube goes through the pcb into the socket. Hope that makes sense.

 

[McIrish]

I'll take a look at the and see if it's possible. What a bad design. I shouldn't have bought it but I thought it would be fun to play around with a couple years ago. So far, it hasn't been much fun, even with a different capsule.

 

[McIrish]

 

[kingkorg]

View attachment 114740View attachment 114741View attachment 114742

I have modified quite a few of these. You definitely have to swap the tube, and optionally do some circuit mods. Stock circuit with that tube has way too high THD and possibly quirky frequency response. You can also remove that transformer shielding can in order to get some extra space for the socket. Transformer doesn't need shielding.

 

[LevinGuitar]

Some people have placed regular sockets but between the pcb and headgrille. So that tube goes through the pcb into the socket. Hope that makes sense.

I've done that to my GT2B but it was a lot of work and very little space. It can be done but next time I would use a submini tube with flying leads

 

[McIrish]

Sort of makes me wonder if this mic is even worth putting the extra time into it. Seemed like a good idea at the time

 

[LevinGuitar]

Since it's a cheap mic (but a nice body) and it don't sound as you want, spending time will always worth. For a submini, try a CV4502 pentode, I tried only one but it sound quite nice, had a bit more coloration than the TFK EF86 but still a nice curve.

 

[kingkorg]

Sort of makes me wonder if this mic is even worth putting the extra time into it. Seemed like a good idea at the time

Ymmw, but I buy these on regular basis every time I find them used for decent price. I think they are amazing for what you get, many mod routes to choose. I am quite familiar with the circuit, and it doesn't take more than an hour to mod them. If you're not familiar with the circuit, it could seem confusing, and might take longer to complete.

 

[McIrish]

I do understand the circuit. I was thinking of changing the original design to a plate follower. It's just a little cramped to mess with various tubes. Swapping one is a real PITA as it's soldered to the PCB.
What mods have you done on it. Mine currently has an M7 capsule but I don't much care for this particular one. I think it's defective. Mostly curious about circuit changes. I did the usual things that are fairly well documented. I think AA did a paper on the mods, which I did. Hard to remember, but I believe there was the zener changes in the supply and removing a few components from the mic PCB and swapping out some lower grade parts with other better parts.

This is what I did per Dave, though I did not change the transformer


____________________________________
The following changes should be made to the 1050 circuit.

1) C9 & C10 should be removed. They can be cut out and are not required into today's modern world. C9 & C10 where meant as RF filter from the days of Taxi cab's operating their 2-way radios on the upper AM radio frequencies.
These capacitor values were spec'd to low in the 1050. So, C9 & C10 in parallel to ground causes the distortion at 11khz to increase 4 times because of the inherent resonance between these capacitors and the low buget output transformer.
SIMPLY REMOVE THESE CAPACITORS...DO NOT...STRAP THEM WITH A WIRE JUMPER AS THIS WILL SHORT THE OUTPUT OF THE TRANSFORMER TO GROUND.

2) C6 & C7 should be removed. These bypass the cathode resistor in the 1st stage. However, they are not necessary in the 1050 circuit and only necessary in a single stage C12 type circuit.
Once properly modified the 1050 circuit is superior to any single plate output circuit. With C6&C7 removed the circuit is more linear without any LF roll-off. The gain drops 4db but this increases the headroom and signal to noise ratio by 4db.
AGAIN SIMPLY REMOVE THESE CAPACITORS...DO NOT... STRAP THEM WITH WIRE JUMPERS AS YOU WILL SHORT OUT THE CATHODE BIAS RESISTOR.

3) Replace C8 the 1ufd outut electrolytic coupling capacitor with a 2.2ufd metal film. This will place any resonance between C8 and the output transformer down into the sub-sonics where it will not negatively effect the audio signal.

4) Replace the 12AX7 with a 6072a this lowers the gain another 2db but the output impedance on the first plate is much lower. A new Sovtek 6072a selling for around the $20 is more than adequate in this clever CCDA type circuit.

Now, you will have optimized the 1050 circuit which is a 2-stage CCDA (constant current draw amplifier) with an output impedance 10 times lower than the venerable original U47 circuit.

5) Replace the stock economy transformer which has a 10.5:1 turns ratio with our BV8 having a 6.5:1 ratio. The green wire goes to pin 6 and the black wire to pin 5 on the 7 pin connector. The white wire goes to pin 4&7 on the 7 pin.
The red wire is attached to the red wire that goes to the output of C8. Remember, the gain has dropped by nearly 6db in the front end but the BV8 has 5db less loss than the economy 10.5:1 transformer.

6) The economy 32mm (k67) type capsule with its 3-5 micron thick diaphragms is replaced by our AK47 capsule which is a single back-plate w/dual 6 micron diaphragms having identical specs to the original K47 used in the U47 & M49.
The K47 will fit onto the existing saddle but will mount either 2mm closer to the front or the rear. I prefer to move it back 2mm.

7) Next replace Z5 & Z6 sometimes noted D5 & D6 inside the power supply with two 62v Zener diodes. This will drop the power supply B+ voltage to 124v dc + and - 2%. These supplies are usually set for 144v dc and this will place about 70v dc on the capsule. The AK47 and the original K47 capsule seem to give optimum results when they are polarized between 55 and 60v which is what you will get from a 124v dc supply. These are located behind the pattern switch on the board.

That's it!!! If this is all done correctly then the microphone should fire up and sound like a WORLD CLASS MICROPHONE.

I will try and take some pictures of the next 1050 we get in for upgrade.

Cheers, Dave
___________________________________________________________________

 

[LevinGuitar]

You can turn it into a plate follower without removing the tube, just changing the wiring (cutting some traces also). I would leave the stock transformer until you have the mic sounding as you want. Play a bit with the quality and capacity of the cathode capacitor, also the bias, maybe you can like more some combination.
Instead of changing the Zeners, I would install one more stage of RC filter inside the psu, and you can lower the voltage as much as you want with the resistor.

 

[kingkorg]

I do understand the circuit. I was thinking of changing the original design to a plate follower. It's just a little cramped to mess with various tubes. Swapping one is a real PITA as it's soldered to the PCB.
What mods have you done on it. Mine currently has an M7 capsule but I don't much care for this particular one. I think it's defective. Mostly curious about circuit changes. I did the usual things that are fairly well documented. I think AA did a paper on the mods, which I did. Hard to remember, but I believe there was the zener changes in the supply and removing a few components from the mic PCB and swapping out some lower grade parts with other better parts.

This is what I did per Dave, though I did not change the transformer


____________________________________
The following changes should be made to the 1050 circuit.

1) C9 & C10 should be removed. They can be cut out and are not required into today's modern world. C9 & C10 where meant as RF filter from the days of Taxi cab's operating their 2-way radios on the upper AM radio frequencies.
These capacitor values were spec'd to low in the 1050. So, C9 & C10 in parallel to ground causes the distortion at 11khz to increase 4 times because of the inherent resonance between these capacitors and the low buget output transformer.
SIMPLY REMOVE THESE CAPACITORS...DO NOT...STRAP THEM WITH A WIRE JUMPER AS THIS WILL SHORT THE OUTPUT OF THE TRANSFORMER TO GROUND.

2) C6 & C7 should be removed. These bypass the cathode resistor in the 1st stage. However, they are not necessary in the 1050 circuit and only necessary in a single stage C12 type circuit.
Once properly modified the 1050 circuit is superior to any single plate output circuit. With C6&C7 removed the circuit is more linear without any LF roll-off. The gain drops 4db but this increases the headroom and signal to noise ratio by 4db.
AGAIN SIMPLY REMOVE THESE CAPACITORS...DO NOT... STRAP THEM WITH WIRE JUMPERS AS YOU WILL SHORT OUT THE CATHODE BIAS RESISTOR.

3) Replace C8 the 1ufd outut electrolytic coupling capacitor with a 2.2ufd metal film. This will place any resonance between C8 and the output transformer down into the sub-sonics where it will not negatively effect the audio signal.

4) Replace the 12AX7 with a 6072a this lowers the gain another 2db but the output impedance on the first plate is much lower. A new Sovtek 6072a selling for around the $20 is more than adequate in this clever CCDA type circuit.

Now, you will have optimized the 1050 circuit which is a 2-stage CCDA (constant current draw amplifier) with an output impedance 10 times lower than the venerable original U47 circuit.

5) Replace the stock economy transformer which has a 10.5:1 turns ratio with our BV8 having a 6.5:1 ratio. The green wire goes to pin 6 and the black wire to pin 5 on the 7 pin connector. The white wire goes to pin 4&7 on the 7 pin.
The red wire is attached to the red wire that goes to the output of C8. Remember, the gain has dropped by nearly 6db in the front end but the BV8 has 5db less loss than the economy 10.5:1 transformer.

6) The economy 32mm (k67) type capsule with its 3-5 micron thick diaphragms is replaced by our AK47 capsule which is a single back-plate w/dual 6 micron diaphragms having identical specs to the original K47 used in the U47 & M49.
The K47 will fit onto the existing saddle but will mount either 2mm closer to the front or the rear. I prefer to move it back 2mm.

7) Next replace Z5 & Z6 sometimes noted D5 & D6 inside the power supply with two 62v Zener diodes. This will drop the power supply B+ voltage to 124v dc + and - 2%. These supplies are usually set for 144v dc and this will place about 70v dc on the capsule. The AK47 and the original K47 capsule seem to give optimum results when they are polarized between 55 and 60v which is what you will get from a 124v dc supply. These are located behind the pattern switch on the board.

That's it!!! If this is all done correctly then the microphone should fire up and sound like a WORLD CLASS MICROPHONE.

I will try and take some pictures of the next 1050 we get in for upgrade.

Cheers, Dave
___________________________________________________________________

I've done several mods including plate follower, modded stock circuit (ccda) with 12ay7 following AA recommendations. Next is adapting stock circuit with some feedback in order to use 12ax7, but tame the THD and 12ax7 gain, something like Manley reference cardioid. Also experiment with some switching using phantom power for different voicing. I have to admit I mostly use 6s6b-v and related tubes, so i haven't had issue with space.

You can turn it into a plate follower without removing the tube, just changing the wiring (cutting some traces also). I would leave the stock transformer until you have the mic sounding as you want. Play a bit with the quality and capacity of the cathode capacitor, also the bias, maybe you can like more some combination.

12ax7 acts weird as plate follower arangement in this circuit, i remember frequency response issues, but can't remember what exactly.

 

[kingkorg]

Swapping one is a real PITA as it's soldered to the PCB.

I just cut the legs and solder that stick above the pcb as best as i can, use extra solder to cover all the legs, and wiggle it out.

 

[LevinGuitar]

I've done several mods including plate follower, modded stock circuit (ccda) with 12ay7 following AA recommendations. Next is adapting stock circuit with some feedback in order to use 12ax7, but tame the THD and 12ax7 gain, something like Manley reference cardioid. Also experiment with some switching using phantom power for different voicing. I have to admit I mostly use 6s6b-v and related tubes, so i haven't had issue with space.


12ax7 acts weird as plate follower arangement in this circuit, i remember frequency response issues, but can't remember what exactly.

But his tube (in the pics) is the EH 12AY7 isn't it? That one could be nice in plate follower

 

[LevinGuitar]

I just cut the legs and solder that stick above the pcb as best as i can, use extra solder to cover all the legs, and wiggle it out.

That's what I do but when the tube is a nice one (even some Chinese are) it's a bit sad

 

[McIrish]

But his tube (in the pics) is the EH 12AY7 isn't it? That one could be nice in plate follower

Yes it is an 12AY7. I had replaced the stock tube

 

[Disco Volante]

Ah, but a cheapo solder sucker would remove enough of the solder to get it out?
I agree, that design is a royal PITA... Not a lot of options for a dual triode. Some very small single pentodes out there, but that's a whole other story...