kip.duff

Re: advice for first tube mic clone build
« Reply #20 on: October 11, 2018, 02:06:25 PM »
I would said a little bit opposite. Capsules aren't bad (depending on revision and definately not their center terminated k67 type) but most of the circuits are horrible. It isn't CK12 type capsule, rather like many chinese edge terminated k67. Still it can sound truly good outside the rode circuits ;) After many years of NT1 (a) manufacturing they finally improved circuit (which what's funny use exactly all the mods i was making for the years in NT1a). Finally polarisation voltage is in decent range (65V instead 75V), more linear response etc. It is decent microphone for the money but not my thing completely.
For K2, this microphone truly sucks due to transformerless circuit, this is common for transformerless tube  mikes (or there is any fan of m147/m149 or lauten etc? ), but of course it isn't only related to output buffer. Currently working on a pair, but here's different goal - completely new circuit with 6au6 pentode and transformer at the output. Then owner will decide does he like it or will swap exactly to Tim CT12 ;)  Anyway, i tested original circuit with original CK12 and this is a little waste of potential of the capsule in my opinion. Still K2 have really great enclosure and the psu is also truly good design.
PSU use negative voltages in both sections. For my needs high voltage section need to be converted to positive. Heater voltage in both PSU on my bench is -5.8V. It can be easily reset inside PSU - there's trimmer potentiometer for that.

Thanks for posting- I've seen and appreciated many of your other posts.

Some of the things you said confirmed my uneducated guesses. 

I am not married to this mic- and am not defending it or dissing it.  I got the setup near new for $399 and thought I would check it out.  It may be a mic that I will just leave alone with the 1967 Mullard or 1961 Valvo- not consider any major surgery.  Maybe some relatively minor tweaks if there are any?  Looking at a hand drawn schematic by Gustav, eventhough I'm not real knowledgible about circuits, I can see that this is very different, has a lot of transistors, no Tx, and heater voltage of 5V.  Nothing like the popular C12 clones with Tx and 1/2 6072 triode- which I wanna try.

I'm going to take the time to study the 123 page C12 clone  thread by Matador and chunger and maybe go that route.  Don't wanna be sourcing parts one-by-one and I see they have some complete looking BOMs.  I like the idea of the MParts PS with adjustable voltages.  Big choices which capsule and Tx.

One question: I'm new to microphones- but so far, I think I would prefer the  donor mic bodies that have ability to be mounted via the threaded flange at bottom.  That way can use clamp mount or bottom mount technique.  I like the K2 because it actually has two sets of threads at the bottom- one larger diameter for the body/sleeve install- and the other (20mm) for a large  knurled finger nut for mounting at any degree of rotation position in the basket.  So I'm looking for a donor body that has something like that.  Many only have enough thrteads for installing the sleeve (22mm I think)- others have extended threads at that location which I believe is for bottom mounting.

Would it benefit to bring the K2 heater voltage up to 6.3?

Thanks, Kip.....


Recording Engineer

Re: advice for first tube mic clone build
« Reply #21 on: October 11, 2018, 02:29:55 PM »
Not the main factor, but pretty important - that's why i wrote before - "but of course it isn't only related to output buffer".
Take for example M147/M149 - ultra great metal work, one of the best capsules ever made and truly good tube (i used it and its twin 6112 in different builds) - so what sucks here?  ;)

Certainly not the simple fact that they’re transformerless. I’m sure there are at least a few people here who could take those capsules and bodies and design a transformerless circuit that would make them sing.

But I digress, maybe I’m completely wrong and no one can... But regardless, I always remind myself that a microphone is a system. I guarantee, there are transformerless mics (tube or not) that do not suck!
« Last Edit: October 11, 2018, 02:33:41 PM by Recording Engineer »

Re: advice for first tube mic clone build
« Reply #22 on: October 11, 2018, 05:18:26 PM »
Wow, now i am kind of puzzled. Quite a few people whose opinion i respect don't share my opinion about Rode's K2.

Maybe i just got lucky with the ones i used, but i truly remember them as exceptional mics. Could have been just different version of capsule/circuit?

Ln76d, do you think that transformerless idea is badly implemented, or you generaly don't aprove that?

I remember interview with Doug Ford desinger of Røde mics where he said they used transformerles design to avoid mismatches between transformer coupled preamps. He even  called it "heresy", but claimed that the design is superior, and cleaner. In Røde Classic II he used transistor between tube and internal transformer.

For example that is the mic Simon Philips uses as main vocal mic and room mic. He even calls it the best vocal mic of all times. And he could have anything. Not that it means anything, but his production skils are insane, and that mic has a Røde capsule, and a transistor after the tube.

In video about NT1000 (transformerless tube) Doug explains negative voltages, crazy 155db spl that mic can take with 1% thd, 143db signal/noise ratio, and several other advantages. And it could be even quieter with aditional biasing in the area of NT1A!

Not sure though if he designed K2.

Not defending my opinion, but there might be some advantages (like high spl/dynamic range) not possible with classic circuits. I just wish there were more videos like these, they are absolutely priceless, and that guy loves to share knowledge.

He explains burn in (aging) process of tubes used in Røde mics, so one might re evaluate if simple change of the tube for something else is actually an upgrade.

He also explains heater voltage of 5v, not that they couldn't have used 6.3 if they wanted.

All these things said kind of explain why i think K2 shouldn't be moded to something in a way inferior (don't kill me for this). This is a modern mic, and it has it's own story and design decisions which arr ment to be improvement over traditional design. I think it's better to sell it than to turn it into something it's not ment to be. Kind of like modding Sony C800 into u47.

Of course capsule upgrading is something else if you want different voicing. Just check those voltages, the guy at Røde said that polarization voltage of 70v is not in all polar patterns, what ever that might mean.
« Last Edit: October 12, 2018, 03:20:55 AM by kingkorg »

ln76d

Re: advice for first tube mic clone build
« Reply #23 on: October 11, 2018, 06:20:06 PM »
Thanks for posting- I've seen and appreciated many of your other posts.

Some of the things you said confirmed my uneducated guesses. 

I am not married to this mic- and am not defending it or dissing it.  I got the setup near new for $399 and thought I would check it out.  It may be a mic that I will just leave alone with the 1967 Mullard or 1961 Valvo- not consider any major surgery.  Maybe some relatively minor tweaks if there are any?  Looking at a hand drawn schematic by Gustav, eventhough I'm not real knowledgible about circuits, I can see that this is very different, has a lot of transistors, no Tx, and heater voltage of 5V.  Nothing like the popular C12 clones with Tx and 1/2 6072 triode- which I wanna try.

I'm going to take the time to study the 123 page C12 clone  thread by Matador and chunger and maybe go that route.  Don't wanna be sourcing parts one-by-one and I see they have some complete looking BOMs.  I like the idea of the MParts PS with adjustable voltages.  Big choices which capsule and Tx.

One question: I'm new to microphones- but so far, I think I would prefer the  donor mic bodies that have ability to be mounted via the threaded flange at bottom.  That way can use clamp mount or bottom mount technique.  I like the K2 because it actually has two sets of threads at the bottom- one larger diameter for the body/sleeve install- and the other (20mm) for a large  knurled finger nut for mounting at any degree of rotation position in the basket.  So I'm looking for a donor body that has something like that.  Many only have enough thrteads for installing the sleeve (22mm I think)- others have extended threads at that location which I believe is for bottom mounting.

Would it benefit to bring the K2 heater voltage up to 6.3?

Thanks, Kip.....

Kip, from my experience change of tube in K2 give some different feeling about the sound of it but not so huge as you could expect. Body isn't the best as a donor (except it is truly great from many reasons), because there's not much space for example for the custom PTP board, transformer with decent core etc. Original circuit since use a lot of smd isn't best for mods, especially  for beginners.
With proper heating and underheating there are truly different opinions. Some tubes datasheets will tell you that underheating will decrease lifespan, some people that it will increase. Here heaters aren't part of (for example) biasing scheme, so change it definately will not give you any audible difference like different biasing point, sensitivity etc.  You can experiment, there's potentiometer to do that ;)

Certainly not the simple fact that they’re transformerless. I’m sure there are at least a few people here who could take those capsules and bodies and design a transformerless circuit that would make them sing.

But I digress, maybe I’m completely wrong and no one can... But regardless, I always remind myself that a microphone is a system. I guarantee, there are transformerless mics (tube or not) that do not suck!

I didn't tested any transformerless tube microphone which i would like to be honest. All three mentioned earlier, are much different from eachother, but all have some similarity in sound which i don't like. It doesn't sound fully like tube mike, it doesn't sound like FET microphone ;) There's a lot of truly great transformerless FET microphones, i can truly agree here.

Wow, now i am kind of puzzled. Quite a few people whose opinion i respect don't share my opinion about Rode's K2.

Maybe i just got lucky with the ones i used, but i truly remember them as exceptional mics. Could have been just different version of capsule/circuit?

Ln76d, do you think that transformerless idea is badly implemented, or you generaly don't aprove that?

I remember interview with Doug Ford desinger of Røde mics where he said they used transformerles design to avoid mismatches between transformer coupled preamps. He even  called it "heresy", but claimed that the design is superior, and cleaner. In Røde Classic II he used transistor between tube and internal transformer. For example that is the mic Simon Philips uses as main vocal mic and room mic. Not that it means anything, but his production skils are insane.

In video about NT1000 (transformerless tube) he explains negative voltages, crazy 155db spl that mic can take with 1% thd, 143db signal/noise ratio, and several other advantages. And it could be even quieter with aditional biasing in the area of NT1A!

Not sure though if he designed K2.

Not defending my opinion, but there might be some advantages (like high spl/dynamic range) not possible with classic circuits. I just wish there were more videos like these, they are absolutely priceless, and that guy loves to share knowledge.

He explains burn in (aging) process of tubes used in Røde mics, so one might re evaluate if simple change of the tube for something else is actually an upgrade.

He also explains heater voltage of 5v, not that they couldn't have used 6.3 if they wanted.

All these things said kind of explain why i think K2 shouldn't be moded to something in a way inferior (don't kill me for this). This is a modern mic, and it has it's own story and design decisions which arr ment to be improvement over traditional design. I think it's better to sell it than to turn it into something it's not ment to be. Kind of like modding Sony C800 into u47.

Of course capsule upgrading is something else. Tim's capsule costs more than that mic, so it would be improvement. Just check those voltages, the guy at Røde said that polarization voltage of 70v is not in all polar patterns, what ever that might mean.


Matija, you wouldn't believe how often people ask me about any mods for K2 or NTK. I don't think it is bad idea of transformerless tube circuit, but still didn't heard any which i would like. Personally i have no need to experiment with that i just like good iron at the bottom of the body and that's it :)
Change of the tube, for "selected", NOS, blah, blah, blah 200euro 6072 doesn't change here so much, a little bit gain a little bit impedance etc. But many people believe in that. After - still want to sell the mike :D This is not night and day difference. Also from modern tube mikes, K2 is one of the most common in auction sales microphone i'm seeing.  Many people even prefer just sold it for cheap than modify it. I'm asking frequently what's wrong in K2 - most answers are like - i don't like how it sounds, it is useless and takes only dirt in my locker.
Personally i tested few  K2 and few ntk from different manufacturing period i also don't like the sound of it on any source, maybe except the room ambience, but most microphones cand do the same work (depending on room, source and needs of course).
Rode truly goes to specs than sound, i love mechanical work definately, but truly not the circuits, even if you can get really nice specification on the paper. Main sin for many years was oversized polarisation voltage, to get better specs on the paper. It ended (especially NT1a) on dying microphones, when capsules get a little bit dirty. Even more common to versions with center terminated k67. Current NT1 have 65V and it's still low noise, not dying so frequently ;)
In K2 original circuit i've tried very different capsules. None was sounding as it should in my opinion. Also with pair of capsules i tried AB vs other tube circuits.  Rode is trying to make truly universal microphones with great specs but like many universal things... AKG had the sam route from the 90's, still people looks for the old models much more than newer.
Transformerless buffer is also saving of few bucks, rather not some miracle thing. Why? Ask yourself why their flagship model is transformer based microphone and what is true difference between over half less priced K2 and classic. Little bit different body, but the capsule is the same  ;)
Why i could "kill you" for this? :D For example the pair i'm making it isn't even a mod. K2 here is just donor of great body, PSU which is modified and probably the capsule - but this will be decision of owner.  It's just custom build like i'm making with many different donor mics, chinese bodies, Aputis and many others. It wouldn't be K2 anymore ;) And why K2 as a donor? Because of mechanical work look and properties and because the owner didn't used it at all because he also didn't liked the sound :D


kip.duff

Re: advice for first tube mic clone build
« Reply #24 on: October 11, 2018, 07:04:26 PM »
In76d:

Ya... no intention of using K2 as a donor.  Very solid craftsmanship- nice PS- too nice to hack up and not right platform for clone.  Just mentioned the nice mounting setup at bottom.  Maybe no other microphones like it- haven't seen anyway.  I know other mics mount at bottom with 22mm thread; but once you've bottomed out, I don't see how secure to desired position.  But I have  no experience here.

Thanks for tip on heater voltage- some one posted at design you posted that had 5V heater, so I guess not a big deal. 

Thanks.......

analogguru

Re: advice for first tube mic clone build
« Reply #25 on: October 11, 2018, 07:27:38 PM »
.......
I remember interview with Doug Ford desinger of Røde mics .....
.....
In video about NT1000 (transformerless tube) Doug explains ..... 143db signal/noise ratio....
What ? 143 db S/N ?  This guy must be god, a magician and/or the mics are cooled with liquid helium....
« Last Edit: October 11, 2018, 07:32:47 PM by analogguru »

Recording Engineer

Re: advice for first tube mic clone build
« Reply #26 on: October 11, 2018, 08:11:53 PM »
Must be a different mic? NT1000 is not “tubed”.

Re: advice for first tube mic clone build
« Reply #27 on: October 11, 2018, 08:23:53 PM »
Piotr, i get everything you say. I just seemed to like this one stock, for what ever reason :)


What ? 143 db S/N ?  This guy must be god, a magician and/or the mics are cooled with liquid helium....

It starts at about 23.28.
https://youtu.be/niZizzHBanA
That would be s/n ratio at maximum 155db SPL. He did say dynamic range though.

@RecordingEngineer, must be a blooper. Could be k2 or NTK he talks about? The same link 20.28

I hate bringing up names in this maner, but i just have to, sorry :)
NTK-Chad Kroeger Nickelback

Classic II - Adelle (On Skyfall for example part of the song is Classic II and part is Neumann U49)

That would be the same capsule.
« Last Edit: October 11, 2018, 08:37:43 PM by kingkorg »

Recording Engineer

Re: advice for first tube mic clone build
« Reply #28 on: October 11, 2018, 08:28:04 PM »
I agree with ln76d, where NOS tube-rolling in mics, a lot of times, is not much at all of an improvement to justify it; a lot of times not really at all. On occasion though, it certainly does, big-time; especially if track-count starts adding-up with the same mic on somewhat similar sources.

Tim Campbell

Re: advice for first tube mic clone build
« Reply #29 on: October 12, 2018, 02:08:26 AM »
kingkorg the last time I checked the Rode K2 cost 700 dollars even at Sweetwater's discounted price so my capsule costs a little more than half that. Perhaps you meant the NT1000 or NT1a.

I actually have an NT1000 that I use in a test rig for measuring comparative output of capsule halves. I chose it because it's quiet, multi-pattern and I got it for free :)



Recording Engineer

Re: advice for first tube mic clone build
« Reply #30 on: October 12, 2018, 02:52:16 AM »
In general, I find Røde perfectly designs their circuits to get their capsules to sound the best they can.

I’ve no experience with the K2, but the NTK is muh to me. The NT1000 I think can sound decent at times, but a friend does circuit mods to them and I feel it reveals the capsule flaws.

Re: advice for first tube mic clone build
« Reply #31 on: October 12, 2018, 03:18:58 AM »
kingkorg the last time I checked the Rode K2 cost 700 dollars even at Sweetwater's discounted price so my capsule costs a little more than half that. Perhaps you meant the NT1000 or NT1a.

I actually have an NT1000 that I use in a test rig for measuring comparative output of capsule halves. I chose it because it's quiet, multi-pattern and I got it for free :)

Sorry, i had the price of used mic on my mind. Will edit that.

ln76d

Re: advice for first tube mic clone build
« Reply #32 on: October 12, 2018, 05:19:52 AM »
The cheapest K2 i saw in second hand was below 200euro. Average 300euro.
Rode NT1000 is practically the same circuit as NT1a, but the body is much better, especially headbasket.
NTK is almost the same as K2, just only cardioid and different headbasket shape.

BTW. about the circuits, since Tim mentioned that he use NT1000 "in a test rig for measuring" - in college we used for some measurements very often NT2a in a pair with measurement microphone. Here NT2a was really good microphone from several reasons, especially that it is dead quiet.

So that's why people hates Nickelback :D :D :D
Just kidding, anyway of course it can be usable, don't know about Kroeger singing much, but i think that tracking Adelle with the cheapest chinese tube mike also would be good.
Any recording engineer have it own weapons, i can believe that someone likes it and makes good work with it. Personally as many other people somehow i just don't like the sound of it.
From the other point of view!
Many people likes mojave (royer mod exactly) with the cheapest 32mm 3um chinese transducer. Flat circuit practically, some "star" advertised it as similar to U67. Damn, same thing, just under chinese brand and for the 1/3 of the mojave price probably would be dissed as hell.

mhelin

Re: advice for first tube mic clone build
« Reply #33 on: October 12, 2018, 06:09:46 AM »
People seem sadly to think all tube mics are similar, meaning have the "vintage" sound with all the harmonics and warmth. K2 is a great mic, but the circuit doesn't bring any own sound, you definitely have to rely on mic pre amp and other gear or plugins in DAW to get the sound you want. On the other hand it could be used to record a symphonic orchestra if you had the recorder capable of recording that huge dynamic range. Maybe the capsule is the weakest link there, you should really use something like a titanium or aluminium diaphragm capsule there, and maybe with an adjustable polarization voltage.

Now I think Doug Ford explained that NT1000 (which has additional T-filter in feedback loop to raise 6khz area) and K2 use the same circuit, and in K2 (and NTK) the first FET is just replaced with a tube. I think you could also use a high voltage FET there in place of the tube,maybe some depletion mode MOSFET like LND150. could do the job. K2 also uses negative supply (kind of), B+ is grounded and ground is made B- to get the proper output phase.
« Last Edit: October 12, 2018, 06:44:06 AM by mhelin »
Mikko

Re: advice for first tube mic clone build
« Reply #34 on: October 12, 2018, 08:42:16 AM »
The circuit with T network he talks about is Rode NT3. I removed T network in mine and made it my favorite (kind of pecil condenser) ever.
Doug answered though email an lead me through it, no problem! What a guy! Nt1000 has flat circuit.

ln76d

Re: advice for first tube mic clone build
« Reply #35 on: October 12, 2018, 01:46:34 PM »
NT1000 and NT1a aren't flat, there's low end roll-off ;) There's few other things also ;)

kip.duff

Re: advice for first tube mic clone build New
« Reply #36 on: October 15, 2018, 11:30:10 PM »
I left the Mullard CV2492 on for a few days in the K2 and let my recording system listen to my stereo quite a bit.  Made some brief recordings and it exceeded my expectations considerably.  Gonna do some more takes to try to fine tune.   I will post some brief samples. 
« Last Edit: Today at 02:22:15 AM by kip.duff »


 

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