Royer mod for NT1 is a No Go!

So I pulled appart my NT1 last night to see if I coild figure out how to do the Dave Royer MXL mod, and I came to two major road blocks.

1) The PCB is about 4mm thick and holds the capsule in place. So it isn't just the circuit board, but a structural part of the mic.

2) Since the PCB can't really be moved without devising another way of supporting the capsule there is no room for the output transformer.

Any ideas?

Make a new PCB to do the whole job ... including the mounting of the capsule ...

pictures please
... and some accurate dimensions of the original PCB.

[quote author="Kev"]Make a new PCB to do the whole job ... including the mounting of the capsule ...[/quote]That's right! This is DIY, so you're not getting off the hook that easily! :wink:

yeah sucka. this is DIY. you know how to get to Apex. make it happen.

Head over to C&H Surplus on Colorado. Many bits of circuit card material, metal pieces. West from C&H there's Marvac Dow. Upstairs they've got a surplus department full of NOS useful for tube circuit junk.

Come on guys, I'm not 12. A trip to C&H and Marvac is a weakly ritual for me. Give me some credit :grin:

I think I've decided to scrap the project, well at least using the NT1. I don't mind engineering a way to make it happen I would just hate to spend a ton of time an energy into converting a bad sounding NT1 into a bad sounding Tube Mic. I say this because I have read several times that the harshness of the later batch NT1s comes from the diaphragm. I'd rather just start with the MXL 2001, like Dave Royer did, and just sell the NT1.

I'll planed to post photos last night but got side tracked. I'll post them tonight.

Anyone want to give me $100 for an NT1?

Ok, you can check out what the guts look like...

http://www.459audio.com/NT1.jpg

Whoopsie, doodle.

Guess I got mixed up when I read the term "any idea." Which, to my immature mind, meant, well, "any idea", and hence my apparently 12 year old suggestion to head out to C&H or whatever.

I've modded this very mic you speak of and I purchased the mechanical bits and pieces at C&H.

That looks like a 797 audio capsule a good thing. I think that post in the back should go, I think that is to mimic the mount of the CK12 in a AKG C12 microphone.

I think you could fit a royer circuit in that microphone.

A little more about the post. Find a condenser microphone you like set to or just cardiod pattern. Whit headphones and a short clean signal path move your finger around the grill talking, singing or playing a cd etc. Note the change in sound.

Gus,
we want more from you
when are we going to start the Gus pages at the Factory ???

give give give

W.H.! You doin ok?
:grin:

[quote author="Frank"]I've modded this very mic you speak of and I purchased the mechanical bits and pieces at C&H.[/quote]

Hey Frank, I'm not complaining, It just cracked me up that someone suggested that I go to C&H and Marvac when I have been going there since I was a kid. I know it is still a valid sugestion, after all you don't know me, and there are probably many people in the area that are totally clueless to those places.

Any ways, what all did you do to mod the NT1, did you remove the board and replace it with a new one or build metal frame to support the capsule? Could you post some photos?

[quote author="Gus"]That looks like a 797 audio capsule a good thing. I think that post in the back should go, I think that is to mimic the mount of the CK12 in a AKG C12 microphone.

I think you could fit a royer circuit in that microphone.

A little more about the post. Find a condenser microphone you like set to or just cardiod pattern. Whit headphones and a short clean signal path move your finger around the grill talking, singing or playing a cd etc. Note the change in sound.[/quote]

So are you saying, if I remove the post it would radically change the sound? Why is that thing even there?

I also have an NT1, and I don't see the problem with the capsule. I would just remove the entire rubber surround and capsule from the PCB and shove it down the tube to where it's supposed to be. The rubber sleeve should stick it in place. If it doesn't stay, a bit of glue will do it. Am I way off here?

I'd be interested in this mod as well. Do you have any links to what you're doing? And how exactly are you applying the mod to the NT1? Feed the curious.
Thank you.

Removing the rod MIGHT help the sound. I have not worked on a NT1. I can't tell by the pictures how many transistors

1 fet as a phase splitter into two PNP EFs and a 4th transistor in a DC to DC converter circuit is a very common circuit. If that is the circuit, cap upgrades can make a nice change to the sound. Are the caps polypro or mylar(PET) I can not read then to google the part numbers

Look at the MXL2003 thread for ideas.

Ok, I got a plan. I think I'm just gonna cut the PCB into an A frame thing, something like this.

http://www.459audio.com/nt1plan.jpg

Why not use fiberglass perfboard? I think the stock circuit could be improved so you might want the board.

[quote author="Gus"]Removing the rod MIGHT help the sound. I have not worked on a NT1. I can't tell by the pictures how many transistors

1 fet as a phase splitter into two PNP EFs and a 4th transistor in a DC to DC converter circuit is a very common circuit. If that is the circuit, cap upgrades can make a nice change to the sound. Are the caps polypro or mylar(PET) I can not read then to google the part numbers

Look at the MXL2003 thread for ideas.[/quote]

Sorry for bringing up this thread again.

The FET is (difficult to read) J105A, is that possible, isn't it primarily a switching FET, and it's also got a quite a large capacitance (I think) which isn't good? The 1000 pf cap is WIMA FPK3 which is polyprop. Is it worth trying to replace this with polystyrene?
The PNP's are 1084 (low noise parts used on many mic pres).

Stupid question: which way the capsule is intended to be used. The rod towards the singer or the other side?

I like the title Hoew to make an nt1 get awesome. Keep us posted...

I tried to backtrack the circuit (of an older NT-1, not NT-1A). It's very much like the 603S circuit with some changes. The source and drain resistors are only 200 ohm, with 580 ohm from the PNP collectors to drain resistor. The caps to PNP bases are only 0.1uF (film), I think they need bigger ones, at leas 1 uF films. Also the pnp (2x 2SA1084) bases are bypassed to common collector circuit with 470pF film caps (I could remove these or use rather smaller values). Resistors from bases to collector(s) are only 10k (rather small input impedance). It seems that Rode has been trying to keep impedances really down all the way after the FET. The output rf caps are smd soldered directly to wire connections on pcb though there are places fro through hole components on the pcb (not used). The FET is really a J105 (A) with 20pf input capacitance (which Vishay datasheet tells is a low number, don't know so much about FET's myself). I'm going to replace the caps first. It may be the grille after all which is a major part of the harshness of the NT-1 sound (I couldn't see how to remove it). I have a feeling that standard 603S type circuit with good caps would be sonically an improvement over this one, which is tried to make ultra-low-noise but doesn't so good in the end. Also you could fit a tube there (cathode follower circuit).

The 797 capsule is with 16 screws, btw. The other end connected to gnd, the other via 1G resistor to supply voltage and via 1000 pf to FET gate.

mhelin

I would check your resistors again the 200 should be 2000. The 797 audio LD capsules I have seen have 14 screws a side. Base to collector should be 75K to 150K if it is the standard Shoeps circuit.

I think you might be reading the resistors wrong are they Blue 1% metal film with 4 color bands for value?

Someone has a NT1 schematic on the web, I do not remember were I saw it.