Re: Microphone w/ built in compression? ¡°Lamplifier¡±
I think that might depend on where this is introduced into the signal path...
In the case of the Hammond circuit I posted above, the incandescent bulbs were fitted as two legs of the 'bridge' fitted across the amplifier output.
So no following gain stages, and no noise from the additional 'variable' resistors that the bulbs essentially were.
I don't think this type of compressor has much application at the mic preamp part of the signal path.?
3 main reasons:
? They need considerable audio power to function
? They're slow, so don't catch transients well.
? The attack and release times are essentially fixed, and are determined by the bulb characteristics?
As Wim has posted above though, they do still have some useful applications...
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On Wed, Apr 13, 2022 at 03:16 PM, Dibutil Ftalat wrote:
Would this technique not introduce a LOT of noise?
On the marketing side of things though it is a treasure chest: one could tune and sell lamps for different pre-sets of compression ratio, attack and release. And then charge extra for the sets of balanced lamps for stereo recording!
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Re: Microphone w/ built in compression? ¡°Lamplifier¡±
Le 13/04/2022 ¨¤ 16:16, Dibutil Ftalat a ¨¦crit?: Would this technique not introduce a LOT of noise? Why would it?
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Re: Microphone w/ built in compression? ¡°Lamplifier¡±
Would this technique not introduce a LOT of noise?
On the marketing side of things though it is a treasure chest: one could tune and sell lamps for different pre-sets of compression ratio, attack and release. And then charge extra for the sets of balanced lamps for stereo recording!
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Re: Pat's Mic (Fetzer Valve Mic)
Thank you Germar! The final version of the PCB will be available?as a PCBWay Shared Project. Just would like to have any feedback from the group before it goes final.
Regards!
HL
Hey?Homero, what a lovely way to remember P@T and a great idea too. I have only ever used the fetzervalve (FETs or Valve) as a guitar pedal and never would have dreamed of using it in a mic! Any change of you creating PCBs of this?
Kind regards, Germar Tischler
HI folks!
As some of you may know, one of the dreams of our friend Patrick Davis (aka. P@T, Enjoybiking) was the idea of designing a mic that could have the "tube" sound, but that could also be very cheap to build.
We discussed the topic many times, and the idea of having a solid state tube emulation was a really fascinating option that was always on the table.
Some time ago I found a paper from Dimitri Danyuk called "Triode Emulator", and in this paper he proposes very a simple way to "emulate" triode behavior using a JFET with very specific values for drain and source resistors.
Later, I found this page:
Which provides a way to calculate (look at the end of the page) the required drain and source resistor values using some JFET parameters like:
And also the input voltage of the circuit (VCC).
So, I decided to try a design using the Dimitri Danyuk approach, with the values calculated from the Fetzer Valve page.
You could find the schematic here:
/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.png
Circuit design uses a Charge Amplifier input stage, a JFET middle stage (providing the "valve" tone"), and finally a impedance balanced output stage with a Sallen Key HPF at about 19.XHz.
Also, a custom voltage regulator is used, using a BC549C NPN and a zener, very similar to the one used on some very known chinese mics. This VR provides about 9.4V for VCC.
I used two drain resistors and two source resistors, so it could be easier to approach the right values calculated by the Fetzer Valve page, by using the combination of two resistors.
As the JFET stage may have an amplification level on the signal, I also used two capacitors for the charge amplifier, this way you could reduce output level by placing an additional capacitor (some math required).
I know the design may have some room for improvement, but I can confirm I have working mic with this design, and it seems to my untrained ear, that it has a very sleek and warm sound, very similar to the sound of the valve mics.
For the build, I used a cheap Zramo donor mic from Amazon, which that very nice 26mm electret capsule we have talked about before.
I decided to name this schematic? "Pat's Mic"... in memory of our friend and former member of this group, P@T?(Patrick Davis, R.I.P.)
This post is for your review and consideration, and please if you have any ideas for improvement, don't hesitate to let me know.
Thank you, and kind regards!
HL
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Re: Microphone w/ built in compression? ¡°Lamplifier¡±
FWIW:
I still use that technique to protect tweeters in DJ speakers... Op wo 13 apr. 2022 om 11:34 schreef Arjay 1949 < info@...>:
This technique reminded me of the same thing that was employed in Hammond organs, back in the day (1960s/70s).
They used light bulbs to 'limit' the drive to the inductive drivers on the spring reverb units.?
They were connected to the output of a power amp, and included the bulbs in the signal path itself.
As Jerry has already commented, using an audio signal to light an incandescent bulb requires a fair amount of power !? ??
The assembly in the sketch below was connected to the output of the reverb audio amp, so the 'sig. input' would normally have been a loudspeaker....
It used to alarm some customers that they could see an intermittent 'glow' under an amp chassis, when the service tech had the back off the instrument! :)
On Tue, Apr 12, 2022 at 11:12 PM, M H wrote:
Was looking around at passive limiters and such, and came across an interesting implementation in ¡°Lamplifier Microphones¡±.? From what I can gather, the microphone has an internal preamp that lights a small incandescent bulb. Said bulb, as it starts to glow, becomes higher resistance to signal, functioning as a form of audio compression.
Just seemed clever in its simplicity.? Don¡¯t know how it sounds though..? The website Lamplifier.com seems to be defunct and their contract info email box is full.? That might give me my verdict right there. ?
?Thought it might be fun to try with a tiny ¡°grain-of wheat ¡° bulb..
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Re: Microphone w/ built in compression? ¡°Lamplifier¡±
This technique reminded me of the same thing that was employed in Hammond organs, back in the day (1960s/70s). They used light bulbs to 'limit' the drive to the inductive drivers on the spring reverb units.? They were connected to the output of a power amp, and included the bulbs in the signal path itself. As Jerry has already commented, using an audio signal to light an incandescent bulb requires a fair amount of power !? ?? The assembly in the sketch below was connected to the output of the reverb audio amp, so the 'sig. input' would normally have been a loudspeaker.... It used to alarm some customers that they could see an intermittent 'glow' under an amp chassis, when the service tech had the back off the instrument! :) 
On Tue, Apr 12, 2022 at 11:12 PM, M H wrote:
Was looking around at passive limiters and such, and came across an interesting implementation in ¡°Lamplifier Microphones¡±. ?From what I can gather, the microphone has an internal preamp that lights a small incandescent bulb. Said bulb, as it starts to glow, becomes higher resistance to signal, functioning as a form of audio compression.
Just seemed clever in its simplicity. ?Don¡¯t know how it sounds though.. ?The website Lamplifier.com seems to be defunct and their contract info email box is full. ?That might give me my verdict right there. ?
?Thought it might be fun to try with a tiny ¡°grain-of wheat ¡° bulb..
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Re: Pat's Mic (Fetzer Valve Mic)
Hey?Homero, what a lovely way to remember P@T and a great idea too. I have only ever used the fetzervalve (FETs or Valve) as a guitar pedal and never would have dreamed of using it in a mic! Any change of you creating PCBs of this?
Kind regards, Germar Tischler
HI folks!
As some of you may know, one of the dreams of our friend Patrick Davis (aka. P@T, Enjoybiking) was the idea of designing a mic that could have the "tube" sound, but that could also be very cheap to build.
We discussed the topic many times, and the idea of having a solid state tube emulation was a really fascinating option that was always on the table.
Some time ago I found a paper from Dimitri Danyuk called "Triode Emulator", and in this paper he proposes very a simple way to "emulate" triode behavior using a JFET with very specific values for drain and source resistors.
Later, I found this page:
Which provides a way to calculate (look at the end of the page) the required drain and source resistor values using some JFET parameters like:
And also the input voltage of the circuit (VCC).
So, I decided to try a design using the Dimitri Danyuk approach, with the values calculated from the Fetzer Valve page.
You could find the schematic here:
/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.png
Circuit design uses a Charge Amplifier input stage, a JFET middle stage (providing the "valve" tone"), and finally a impedance balanced output stage with a Sallen Key HPF at about 19.XHz.
Also, a custom voltage regulator is used, using a BC549C NPN and a zener, very similar to the one used on some very known chinese mics. This VR provides about 9.4V for VCC.
I used two drain resistors and two source resistors, so it could be easier to approach the right values calculated by the Fetzer Valve page, by using the combination of two resistors.
As the JFET stage may have an amplification level on the signal, I also used two capacitors for the charge amplifier, this way you could reduce output level by placing an additional capacitor (some math required).
I know the design may have some room for improvement, but I can confirm I have working mic with this design, and it seems to my untrained ear, that it has a very sleek and warm sound, very similar to the sound of the valve mics.
For the build, I used a cheap Zramo donor mic from Amazon, which that very nice 26mm electret capsule we have talked about before.
I decided to name this schematic? "Pat's Mic"... in memory of our friend and former member of this group, P@T?(Patrick Davis, R.I.P.)
This post is for your review and consideration, and please if you have any ideas for improvement, don't hesitate to let me know.
Thank you, and kind regards!
HL
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Re: Microphone w/ built in compression? ¡°Lamplifier¡±
No. They use small incandescent light bulbs.
This type of passive limiter requires substantial level to
operate. The signal from a microphone is too weak, so it must be
amplified. That means there should be a battery in the mic, which
is quite inconvenient.
Le 13/04/2022 ¨¤ 02:38, Tom Becker a
¨¦crit?:
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... Said bulb, as it starts to glow, becomes higher
resistance to signal, functioning as a form of audio
compression...
Probably a Vactrol optically-controlled variable resistance.?
Like:
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Pat's Mic (Fetzer Valve Mic)
HI folks! As some of you may know, one of the dreams of our friend Patrick Davis (aka. P@T, Enjoybiking) was the idea of designing a mic that could have the "tube" sound, but that could also be very cheap to build. We discussed the topic many times, and the idea of having a solid state tube emulation was a really fascinating option that was always on the table. Some time ago I found a paper from Dimitri Danyuk called "Triode Emulator", and in this paper he proposes very a simple way to "emulate" triode behavior using a JFET with very specific values for drain and source resistors. Later, I found this page: Which provides a way to calculate (look at the end of the page) the required drain and source resistor values using some JFET parameters like:
And also the input voltage of the circuit (VCC). So, I decided to try a design using the Dimitri Danyuk approach, with the values calculated from the Fetzer Valve page. You could find the schematic here: /g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/Pat%27s%20Mic.pngCircuit design uses a Charge Amplifier input stage, a JFET middle stage (providing the "valve" tone"), and finally a impedance balanced output stage with a Sallen Key HPF at about 19.XHz. Also, a custom voltage regulator is used, using a BC549C NPN and a zener, very similar to the one used on some very known chinese mics. This VR provides about 9.4V for VCC. I used two drain resistors and two source resistors, so it could be easier to approach the right values calculated by the Fetzer Valve page, by using the combination of two resistors. As the JFET stage may have an amplification level on the signal, I also used two capacitors for the charge amplifier, this way you could reduce output level by placing an additional capacitor (some math required). I know the design may have some room for improvement, but I can confirm I have working mic with this design, and it seems to my untrained ear, that it has a very sleek and warm sound, very similar to the sound of the valve mics. For the build, I used a cheap Zramo donor mic from Amazon, which that very nice 26mm electret capsule we have talked about before. I decided to name this schematic? " Pat's Mic"... in memory of our friend and former member of this group, P@T?(Patrick Davis, R.I.P.) This post is for your review and consideration, and please if you have any ideas for improvement, don't hesitate to let me know. Thank you, and kind regards! HL
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Re: Microphone w/ built in compression? ¡°Lamplifier¡±
... Said bulb, as it starts to glow, becomes higher resistance to signal, functioning as a form of audio compression...
Probably a Vactrol optically-controlled variable resistance.? Like:
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Re: Budget self-made condenser capsule (PCB based backplate!)
Though not Mylar (and not as tough), you maybe could try ultra thin aluminum like the ribbon mic folk use:?
could spray coat one side with a nonconductive lacquer if need be.
Or, if you want to go cheaper than that, you could get some ¡°imitation silver leaf¡±. ?But that is extremely fragile and frustrating to work with, so..?
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Microphone w/ built in compression? ¡°Lamplifier¡±
Was looking around at passive limiters and such, and came across an interesting implementation in ¡°Lamplifier Microphones¡±. ?From what I can gather, the microphone has an internal preamp that lights a small incandescent bulb. Said bulb, as it starts to glow, becomes higher resistance to signal, functioning as a form of audio compression.
Just seemed clever in its simplicity. ?Don¡¯t know how it sounds though.. ?The website Lamplifier.com seems to be defunct and their contract info email box is full. ?That might give me my verdict right there. ?
?Thought it might be fun to try with a tiny ¡°grain-of wheat ¡° bulb..
|
Re: Budget self-made condenser capsule (PCB based backplate!)
I have reskinned damaged capsules with aluminized mylar unrolled from film capacitors. The lower the voltage rating, the thinner the film is.?The capsules have sounded fine, though likely not good as new.
I tried making capsules with perforated aluminum sheet as backplate, Scotch tape, and mylar film. They did pick up sound: poorly, not as well as a cheap electret. Like you, I wonder how shape and backplate geometry affects tone. Your method is better because you can isolate the active area of the backplate by etching, and reduce the parasitic fixed capacitance. Good work!
The resistance of the diaphragm doesn't matter much, especially if signal is taken off the backplate. All it has to do is hold a constant charge.
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Re: Source of dynamic capsules?
Well that's precisely what bothers me: there seems to be no options...
I'm not a big fan of the 58 sound, and would like to get something less hyped, more extended...
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Re: Source of dynamic capsules?
I've tried different Chinese companies?for 57 and 58 diaphragms advertised on EBay. At about ?4 to ?5 delivered
I'm in the UK and cant tell the difference live on P.A? (I HAVE OTHER GENUINE SM57 AND SM58)?
Quality seems excellent and totally interchangeable.
Dow Fereday
LTSSTUDIO.COM
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Re: Source of dynamic capsules?
I went to AliExpress to see: there is a great many choice of capsules, unfortunately with about no information at all. Nosem and Takstar brands seem to be the most widespread. It's like shooting in the dark...
So I did that, and ordered an assortment of disparate capsules:
Nosem N-316 (very cheap at $2.38)
Something slated as replacement for Sennheiser EW100, unknown brand ($12.79)
Takstar TS-5 ($14.11). However, i'm told by the Takstar store they are unavailable. I don't know if that's temporary or permanent, I sure hope it's not permanent as this capsule seems to be the best around, from comments here .
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Re: Budget self-made condenser capsule (PCB based backplate!)
Hallo,? sorry for my mistake.? But, please let me say something to your comment. Just to clarify, you¡®re saying that Most backplates are made out of solid brass. You are completly right and this was exactly what I just wanted to say - they should be stiff. There is a different type of capsules which have a second membrahne of course. No matter of this membrahne is passive or used for pattern ?switching , this one works ?in a 180 degree? Greetings and thanks Ralf
Hi Ralf,
It's not me that's building a capsule, it's michaeljtbrooks.
However, I can make some comments:
"2- the backplate cannot be stiff enough. That is one reason
for partial cancelation of higher frequencies. This is because
if it is not it will probably cancel out frequencies by slightly
moving by soundpressure in the opposit direction of the
membrahne."
I'm not convinced. The backplate would need to be very flexible to
react in such a way. Most of the backplates are made of a piece of
metal (often brass) that is millions of times heavier and more
rigid than the diaphragm.
"3- the backplate had to be fairly thick so that you can make
some sackholes in it for damping ?reasons "
Indeed, blind holes (as well as through-holes) are necessary for
providing damping of the diaphragm
Le 12/04/2022 ¨¤ 12:38, Ralf Falk a
¨¦crit?:
Hey, Jerry Lee,
my namens Ralf and this is the first reply ?in
this forum. I¡® m writing from Germany so please ? ? excuse my
bad language.
About 10 years ago I made a very similar
experiment wich I stopped as I got me a lath to work with. I
found out the same things that you posted here and came to the
following conclusions:
1- It is important to get the membrahn streched
the same degree to all sides?
2- the backplate cannot be stiff enough. That is
one reason for partial cancelation of higher frequencies. This
is because if it is not it will probably cancel out frequencies
by slightly moving by soundpressure in the opposit direction of
the membrahne.
3- the backplate had to be fairly thick so that
you can make some sackholes in it for damping ?reasons?
4- to get rid of most of the parasitic
capacitance, you simply should take of the copper of your
backplate piece in the airia where the frame that holds your
membrahn will be positioned?
I hope that this will bring you in a good
direction.
Good luck?
I'm pretty suspicious of the
membrane resistance which is a few ohms per cm2 as the
culprit. So any suggestions for more conductive
aluminiumised Mylar would be greatly appreciated!
Whatever few ohms there don't matter compared to the
Gigaohm input resistance of the Alice circuit.
Look elsewhere. Surely 20 micron thickness does not help
with sensitivity, but all the parasitic capacitances are
probably the main culprit.
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Re: Budget self-made condenser capsule (PCB based backplate!)
Hi Ralf,
It's not me that's building a capsule, it's michaeljtbrooks.
However, I can make some comments:
"2- the backplate cannot be stiff enough. That is one reason
for partial cancelation of higher frequencies. This is because
if it is not it will probably cancel out frequencies by slightly
moving by soundpressure in the opposit direction of the
membrahne."
I'm not convinced. The backplate would need to be very flexible to
react in such a way. Most of the backplates are made of a piece of
metal (often brass) that is millions of times heavier and more
rigid than the diaphragm.
"3- the backplate had to be fairly thick so that you can make
some sackholes in it for damping ?reasons "
Indeed, blind holes (as well as through-holes) are necessary for
providing damping of the diaphragm
Le 12/04/2022 ¨¤ 12:38, Ralf Falk a
¨¦crit?:
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Show quoted text
Hey, Jerry Lee,
my namens Ralf and this is the first reply ?in
this forum. I¡® m writing from Germany so please ? ? excuse my
bad language.
About 10 years ago I made a very similar
experiment wich I stopped as I got me a lath to work with. I
found out the same things that you posted here and came to the
following conclusions:
1- It is important to get the membrahn streched
the same degree to all sides?
2- the backplate cannot be stiff enough. That is
one reason for partial cancelation of higher frequencies. This
is because if it is not it will probably cancel out frequencies
by slightly moving by soundpressure in the opposit direction of
the membrahne.
3- the backplate had to be fairly thick so that
you can make some sackholes in it for damping ?reasons?
4- to get rid of most of the parasitic
capacitance, you simply should take of the copper of your
backplate piece in the airia where the frame that holds your
membrahn will be positioned?
I hope that this will bring you in a good
direction.
Good luck?
I'm pretty suspicious of the
membrane resistance which is a few ohms per cm2 as the
culprit. So any suggestions for more conductive
aluminiumised Mylar would be greatly appreciated!
Whatever few ohms there don't matter compared to the
Gigaohm input resistance of the Alice circuit.
Look elsewhere. Surely 20 micron thickness does not help
with sensitivity, but all the parasitic capacitances are
probably the main culprit.
|
Re: Budget self-made condenser capsule (PCB based backplate!)
Hey, Jerry Lee, my namens Ralf and this is the first reply ?in this forum. I¡® m writing from Germany so please ? ? excuse my bad language. About 10 years ago I made a very similar experiment wich I stopped as I got me a lath to work with. I found out the same things that you posted here and came to the following conclusions: 1- It is important to get the membrahn streched the same degree to all sides? 2- the backplate cannot be stiff enough. That is one reason for partial cancelation of higher frequencies. This is because if it is not it will probably cancel out frequencies by slightly moving by soundpressure in the opposit direction of the membrahne. 3- the backplate had to be fairly thick so that you can make some sackholes in it for damping ?reasons? 4- to get rid of most of the parasitic capacitance, you simply should take of the copper of your backplate piece in the airia where the frame that holds your membrahn will be positioned?
I hope that this will bring you in a good direction.
Good luck?
I'm pretty suspicious of the membrane resistance which is a few
ohms per cm2 as the culprit. So any suggestions for more
conductive aluminiumised Mylar would be greatly appreciated!
Whatever few ohms there don't matter compared to the Gigaohm input
resistance of the Alice circuit.
Look elsewhere. Surely 20 micron thickness does not help with
sensitivity, but all the parasitic capacitances are probably the
main culprit.
|
Re: Budget self-made condenser capsule (PCB based backplate!)
I'm pretty suspicious of the membrane resistance which is a few
ohms per cm2 as the culprit. So any suggestions for more
conductive aluminiumised Mylar would be greatly appreciated!
Whatever few ohms there don't matter compared to the Gigaohm input
resistance of the Alice circuit.
Look elsewhere. Surely 20 micron thickness does not help with
sensitivity, but all the parasitic capacitances are probably the
main culprit.
|
Dibutil Ftalat