dukasound
Well-known member
Any suggestion for ratio of transformer for 12AX7WA and circuit with both triodes in cascade like on MANLEY GOLD REFERENCE?
Thanks
Duka
Thanks
Duka
12AX7WA (CV4004) in tube microfones?
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In my opinion, 12AX7's does not have low enough grid leakage to be used sensibly in condenser microphones.
dukasound
Well-known member
[quote author="gyraf"]In my opinion, 12AX7's does not have low enough grid leakage to be used sensibly in condenser microphones.[/quote]
Hi Jakob
Manley changed 6072 to 12AX7AW (CV4004) in theirs MANLEY GOLD REFERENCE. I read on their site. If I understand they used both triode.
Hi Jakob
Manley changed 6072 to 12AX7AW (CV4004) in theirs MANLEY GOLD REFERENCE. I read on their site. If I understand they used both triode.
I would not use a 12ax7 in a tube microphone it has two high a gain IMO.
IMO part of the "magic" of a tube microphone is the lower gain tubes with the headroom provided by the power supply voltages.
Another part of the magic is the use of no global feedback simple cathode biased with a bypass cap on the resistor or fixed bias triode gain stages are hard to beat.
I have not seen the M circuit but from your post it sounds like it was designed for a 6072A. I would guess it has a feedback loop to control the gain. Is it a cathode gain stage into a CF with a feedback loop to the first tubes cathode resistor(no bypass cap)?
I am not a fan of 12ax7s even in guitar amps anymore.
IMO part of the "magic" of a tube microphone is the lower gain tubes with the headroom provided by the power supply voltages.
Another part of the magic is the use of no global feedback simple cathode biased with a bypass cap on the resistor or fixed bias triode gain stages are hard to beat.
I have not seen the M circuit but from your post it sounds like it was designed for a 6072A. I would guess it has a feedback loop to control the gain. Is it a cathode gain stage into a CF with a feedback loop to the first tubes cathode resistor(no bypass cap)?
I am not a fan of 12ax7s even in guitar amps anymore.
dukasound
Well-known member
[quote author="Gus"]I would not use a 12ax7 in a tube microphone it has two high a gain IMO.
IMO part of the "magic" of a tube microphone is the lower gain tubes with the headroom provided by the power supply voltages.
Another part of the magic is the use of no global feedback simple cathode biased with a bypass cap on the resistor or fixed bias triode gain stages are hard to beat.
I have not seen the M circuit but from your post it sounds like it was designed for a 6072A. I would guess it has a feedback loop to control the gain. Is it a cathode gain stage into a CF with a feedback loop to the first tubes cathode resistor(no bypass cap)?
Hi
Here is a part of text on their site. They are talking about 12AX7WA (who is different then 12AX7):
The all-tube electronics in the MANLEY REFERENCE SERIES MICROPHONES are built around two triodes in cascade forming an entire gain-block. We have recently switched to a dual-triode 12AX7WA, easily obtainable and replaceable, mounted in a ceramic socket. (We used to use 6072A until it became impossible to find quiet ones out of the NOS dreck left on the market.) The output is coupled through a MANLEY output transformer of unparalleled quality and substantial physical size employing nickel laminations with "hum bucking" bi-filar windings, encased in mu-metal.
Also. I didnt see schematic, I only want to know how works this circuit because everybody like this microphones.
IMO part of the "magic" of a tube microphone is the lower gain tubes with the headroom provided by the power supply voltages.
Another part of the magic is the use of no global feedback simple cathode biased with a bypass cap on the resistor or fixed bias triode gain stages are hard to beat.
I have not seen the M circuit but from your post it sounds like it was designed for a 6072A. I would guess it has a feedback loop to control the gain. Is it a cathode gain stage into a CF with a feedback loop to the first tubes cathode resistor(no bypass cap)?
Hi
Here is a part of text on their site. They are talking about 12AX7WA (who is different then 12AX7):
The all-tube electronics in the MANLEY REFERENCE SERIES MICROPHONES are built around two triodes in cascade forming an entire gain-block. We have recently switched to a dual-triode 12AX7WA, easily obtainable and replaceable, mounted in a ceramic socket. (We used to use 6072A until it became impossible to find quiet ones out of the NOS dreck left on the market.) The output is coupled through a MANLEY output transformer of unparalleled quality and substantial physical size employing nickel laminations with "hum bucking" bi-filar windings, encased in mu-metal.
Also. I didnt see schematic, I only want to know how works this circuit because everybody like this microphones.
dukasound
Well-known member
Any informations?
Thanks in advance
Duka
Thanks in advance
Duka
Marik
Well-known member
Duka,
I am afraid it is impossible to get anything worthwhile from the information from Manley's website, as "two triodes in cascade forming an entire gain-block" could mean hundreds different things, and without seeing actual schematics it is hard to say something specific.
I am with Jacob and Gus about 12AX7 use for mics. Also, I could add that this tube has a very high Miller effect, so working with such capacitive source as a microphone capsule it will have severe top roll off.
I don't remember a single "calssic" mic, which used this tube--and it is probably for a good reason, considering this tube has always been readily available.
The phrase (We used to use 6072A until it became impossible to find quiet ones out of the NOS dreck left on the market.) already makes me suspicious what kind of corners they cut.
And the last--the title MANLEY REFERENCE SERIES MICROPHONES doesn't say a thing about how good (or how bad) these mics are.
I am afraid it is impossible to get anything worthwhile from the information from Manley's website, as "two triodes in cascade forming an entire gain-block" could mean hundreds different things, and without seeing actual schematics it is hard to say something specific.
I am with Jacob and Gus about 12AX7 use for mics. Also, I could add that this tube has a very high Miller effect, so working with such capacitive source as a microphone capsule it will have severe top roll off.
I don't remember a single "calssic" mic, which used this tube--and it is probably for a good reason, considering this tube has always been readily available.
The phrase (We used to use 6072A until it became impossible to find quiet ones out of the NOS dreck left on the market.) already makes me suspicious what kind of corners they cut.
And the last--the title MANLEY REFERENCE SERIES MICROPHONES doesn't say a thing about how good (or how bad) these mics are.
[quote author="Marik"]I am with Jacob and Gus about 12AX7 use for mics. Also, I could add that this tube has a very high Miller effect, so working with such capacitive source as a microphone capsule it will have severe top roll off.
[/quote]
I won't argue for or against a 12AX7, but I have a general question:
Wouldn't a capacitive source and the capacitive feedback from the Miller effect fit together nicely? Source impedance decreasing with frequency, feedback impedance decreasing with frequency.
(I was surprised when I first saw a tube design that did this on purpose. In the Hammond B3 there's a mixer stage where the normal signal, the vibrato scanner signal, and the percussion signal are added. The vibrato scanner is capacitive by nature. What they did, is this: Using a feedback capacitor (instead of a resistor) from plate to grid. Then feeding all the sources to the grid via capacitors. Ok, this was no wideband circuit, of course. But if it's possible to use external capacitive feedback in order to adapt capacitive sources, it should also be easy to deal with the internal Miller capacitor of a tube, _especially_ when your signal source is capacitive. Don't know if this is relevant to the microphon thread, but I thought I'd just throw this in for discussion.)
JH.
[/quote]
I won't argue for or against a 12AX7, but I have a general question:
Wouldn't a capacitive source and the capacitive feedback from the Miller effect fit together nicely? Source impedance decreasing with frequency, feedback impedance decreasing with frequency.
(I was surprised when I first saw a tube design that did this on purpose. In the Hammond B3 there's a mixer stage where the normal signal, the vibrato scanner signal, and the percussion signal are added. The vibrato scanner is capacitive by nature. What they did, is this: Using a feedback capacitor (instead of a resistor) from plate to grid. Then feeding all the sources to the grid via capacitors. Ok, this was no wideband circuit, of course. But if it's possible to use external capacitive feedback in order to adapt capacitive sources, it should also be easy to deal with the internal Miller capacitor of a tube, _especially_ when your signal source is capacitive. Don't know if this is relevant to the microphon thread, but I thought I'd just throw this in for discussion.)
JH.
For microphones one needs to read alot about the finer design stuff in tubes. The input R wanted is so high >1gig That all kinds of design problems show up because most tube are designed for a 1 meg grid to ground.
Leakage currents
The spacing of the grid,cathode,plate, screens(if pentode as triode)
The way the grid, screens(if pentode as triode) are built and the metals used
The cathode oxide coating
The voltage to heat the cathode affects the temp some tube don't like to be underheated.
Look at the ELA M251 circuit that uses the 6072a not how low the input R is for a tube microphone.
The spacing between the elements has alot too due with the gain.
The size of the electron cloud also affects the sound.
That all posted, yes you can build a tube microphone with a 12ax7 why one would do this I don't understand, you can build a tube microphone with alot of tubes. If you are going to build one why not build it the best you can. I would think a 12at7 would be a better pick than a 12ax7 if one wants a current made tube.
FWIW I don't even like a good 6072a that much.
I am still learning alot about tubes for use in microphones. One thing now I am trying to understand it the heat temp vs the work function vs the emission of the electrons from the oxide vs the grid bias .
Leakage currents
The spacing of the grid,cathode,plate, screens(if pentode as triode)
The way the grid, screens(if pentode as triode) are built and the metals used
The cathode oxide coating
The voltage to heat the cathode affects the temp some tube don't like to be underheated.
Look at the ELA M251 circuit that uses the 6072a not how low the input R is for a tube microphone.
The spacing between the elements has alot too due with the gain.
The size of the electron cloud also affects the sound.
That all posted, yes you can build a tube microphone with a 12ax7 why one would do this I don't understand, you can build a tube microphone with alot of tubes. If you are going to build one why not build it the best you can. I would think a 12at7 would be a better pick than a 12ax7 if one wants a current made tube.
FWIW I don't even like a good 6072a that much.
I am still learning alot about tubes for use in microphones. One thing now I am trying to understand it the heat temp vs the work function vs the emission of the electrons from the oxide vs the grid bias .
Frank
Member
Did the AKG C12 use a 6072? That was a pretty popular mic from what I read on the net. Maybe they did something special with it.
Frank
Member
A hint of specialness? Of why they chose a 6072?
I have read they speced the 6072a for the USA market because it was advailable. IMO there is nothing special about the 6072a. The hint was to look at the grid resistors.
If you look at the schematics of microphones built by Neuamnn and AKG for the German market you will see the use of the AC701. That was a tube designed for microphone use I believe.
If you look at the schematics of microphones built by Neuamnn and AKG for the German market you will see the use of the AC701. That was a tube designed for microphone use I believe.
Marik
Well-known member
[quote author="jhaible"][quote author="Marik"]I am with Jacob and Gus about 12AX7 use for mics. Also, I could add that this tube has a very high Miller effect, so working with such capacitive source as a microphone capsule it will have severe top roll off.
[/quote]
I won't argue for or against a 12AX7, but I have a general question:
Wouldn't a capacitive source and the capacitive feedback from the Miller effect fit together nicely? Source impedance decreasing with frequency, feedback impedance decreasing with frequency.
(I was surprised when I first saw a tube design that did this on purpose. In the Hammond B3 there's a mixer stage where the normal signal, the vibrato scanner signal, and the percussion signal are added. The vibrato scanner is capacitive by nature. What they did, is this: Using a feedback capacitor (instead of a resistor) from plate to grid. Then feeding all the sources to the grid via capacitors. Ok, this was no wideband circuit, of course. But if it's possible to use external capacitive feedback in order to adapt capacitive sources, it should also be easy to deal with the internal Miller capacitor of a tube, _especially_ when your signal source is capacitive. Don't know if this is relevant to the microphon thread, but I thought I'd just throw this in for discussion.)
JH.[/quote]
J.H.,
IMHO, the microphone design is much more refined than the organ vibrato, which is essentially nonlinear. I just don't really see a good reason and benefits of feedback use in mics to overcome some problems, when more suitable tube could be used, first place. It is like conciously to create a problem and then desparately try to resolve it.
[/quote]
I won't argue for or against a 12AX7, but I have a general question:
Wouldn't a capacitive source and the capacitive feedback from the Miller effect fit together nicely? Source impedance decreasing with frequency, feedback impedance decreasing with frequency.
(I was surprised when I first saw a tube design that did this on purpose. In the Hammond B3 there's a mixer stage where the normal signal, the vibrato scanner signal, and the percussion signal are added. The vibrato scanner is capacitive by nature. What they did, is this: Using a feedback capacitor (instead of a resistor) from plate to grid. Then feeding all the sources to the grid via capacitors. Ok, this was no wideband circuit, of course. But if it's possible to use external capacitive feedback in order to adapt capacitive sources, it should also be easy to deal with the internal Miller capacitor of a tube, _especially_ when your signal source is capacitive. Don't know if this is relevant to the microphon thread, but I thought I'd just throw this in for discussion.)
JH.[/quote]
J.H.,
IMHO, the microphone design is much more refined than the organ vibrato, which is essentially nonlinear. I just don't really see a good reason and benefits of feedback use in mics to overcome some problems, when more suitable tube could be used, first place. It is like conciously to create a problem and then desparately try to resolve it.
[quote author="Marik"]
IMHO, the microphone design is much more refined than the organ vibrato,
[/quote]
No doubt aubout that!
JH.
IMHO, the microphone design is much more refined than the organ vibrato,
[/quote]
No doubt aubout that!
Neither do I. The one and only aspect of this topic at which my reply was aimed, is that I don't understand how the miller effect would be especially unpleasant with a capacitive signal source.
JH.
dale116dot7
Well-known member
I've been playing around with different tubes in mics, and I found one that sounds quite nice: 6AH6. It's like the 6AU6 but with a lower output impedance, higher gain, and higher capacitances.
The miller effect is your friend in this case. If you had no miller capacitance, a typical U47 would roll off below 150 Hz or so. The 60 Meg grid resistor on the VF14 combined with the 80pF capsule capacitance makes a filter. If you have a 6pF plate to grid capacitance (probably in that area on a VF14) and a voltage gain of somewhere around 100, you get a net source impedance of around 500pF instead of 80pF - with a 60 Meg resistor that makes sense.
The miller effect is your friend in this case. If you had no miller capacitance, a typical U47 would roll off below 150 Hz or so. The 60 Meg grid resistor on the VF14 combined with the 80pF capsule capacitance makes a filter. If you have a 6pF plate to grid capacitance (probably in that area on a VF14) and a voltage gain of somewhere around 100, you get a net source impedance of around 500pF instead of 80pF - with a 60 Meg resistor that makes sense.
scott_humphrey
Well-known member
Hi Duka,
Since you've made several mics, I was wondering if you would let us know how they compare to one another. It seems that you have made more microphones than most people here. What are your impressions of these different designs in terms of sound?
Best regards,
Scott
Since you've made several mics, I was wondering if you would let us know how they compare to one another. It seems that you have made more microphones than most people here. What are your impressions of these different designs in terms of sound?
Best regards,
Scott
Cool thread.
JustinS
Well-known member
Hey Dale,
Would you be prepared to share the schem for your 6AH6 tube mic circuit ?? I'm thinking about what circuit I'm going to build around one of your M7ish capsules & 6AH6's seem fairly available & reasonably priced, and hey if you think it sounds good with one of your M7's then
:grin:
Justin
Would you be prepared to share the schem for your 6AH6 tube mic circuit ?? I'm thinking about what circuit I'm going to build around one of your M7ish capsules & 6AH6's seem fairly available & reasonably priced, and hey if you think it sounds good with one of your M7's then
:grin: Justin
dukasound
Well-known member
[quote author="scott_humphrey"]Hi Duka,
Since you've made several mics, I was wondering if you would let us know how they compare to one another. It seems that you have made more microphones than most people here. What are your impressions of these different designs in terms of sound?
Best regards,
Scott[/quote]
Hi
Here are mine four microphones:
Royer mod, G7, C800D and Elam (not this string).
http://www.dukasound.cg.yu/Data/Four_microphones.mp3
I recorded on same distance through 1290 without any processing , EQ etc direct to sound card in Wave Lab. This is on my language and I talked how I made my preamp.
All of four are different.
Your opinion?
Duka
Since you've made several mics, I was wondering if you would let us know how they compare to one another. It seems that you have made more microphones than most people here. What are your impressions of these different designs in terms of sound?
Best regards,
Scott[/quote]
Hi
Here are mine four microphones:
Royer mod, G7, C800D and Elam (not this string).
http://www.dukasound.cg.yu/Data/Four_microphones.mp3
I recorded on same distance through 1290 without any processing , EQ etc direct to sound card in Wave Lab. This is on my language and I talked how I made my preamp.
All of four are different.
Your opinion?
Duka
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