My first mod (Trion 8000 valve mic)
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burdij
Well-known member
The common value for the capsule to grid coupling capacitor is 1Kpf. Changing the value will not have a great effect on the "sound" as the impedances on each side of it are extremely high. Using t=.69RC you can see that as R > infinity the value of C doesn't really matter that much. Keeping it small has the advantage that you have a wider range of high quality capacitor types to choose from.
Regarding the output capacitor, if you want to go beyond 1 uf make it as large as you can fit, I suppose. The better audiophile caps get pretty large pretty fast with increase in value. The biggest effect is going to be the noticable difference between an electrolytic and non-electrolytic, rather than the particular value. I think a bit too much emphasis has been placed on the capacitors in these circuits. I would peg their contribution to the overall performance of the microphone at <10%.
Adky: Have you checked the loading of the microphone by the preamp regarding your loss of low frequencies. The core of the typical mike transformer is fairly small so the inductance will be low. The inductance will determine the impedance that the microphone will drive while retaining flat frequency response. The result of too low an impedance will be reduced low frequency response.
In the case of microphones vs. let's say antennas, you don't need to match the source and driving impedances. We are not trying to eliminate line reflections since we are dealing with audio frequencies. If you look at the average mike output trans datasheet, you will see that the impedance specified for the test load is often 1K Ohm or more. Of course, there is a tradeoff in driving an actual preamp. You don't want the load impedance to be too high as it will dramatically increase the input noise figure.
Regarding the output capacitor, if you want to go beyond 1 uf make it as large as you can fit, I suppose. The better audiophile caps get pretty large pretty fast with increase in value. The biggest effect is going to be the noticable difference between an electrolytic and non-electrolytic, rather than the particular value. I think a bit too much emphasis has been placed on the capacitors in these circuits. I would peg their contribution to the overall performance of the microphone at <10%.
Adky: Have you checked the loading of the microphone by the preamp regarding your loss of low frequencies. The core of the typical mike transformer is fairly small so the inductance will be low. The inductance will determine the impedance that the microphone will drive while retaining flat frequency response. The result of too low an impedance will be reduced low frequency response.
In the case of microphones vs. let's say antennas, you don't need to match the source and driving impedances. We are not trying to eliminate line reflections since we are dealing with audio frequencies. If you look at the average mike output trans datasheet, you will see that the impedance specified for the test load is often 1K Ohm or more. Of course, there is a tradeoff in driving an actual preamp. You don't want the load impedance to be too high as it will dramatically increase the input noise figure.
@ Adky and/or burdij,
Hi any chance one of you could post a circuit diagram with component values please?
And just to make sure here the blue disc shaped caps value is 1000pf?
Im going to replace it with a polystyrene and see how that goes as I search for a mill spec EF95.
Finaly are there any 'must avoid' components for this type of project? EG. I have been getting mixed reports about Black Gate components i.e. great for amps that are left on 24-7 but sound crap for hours from cold.
Thankyou again,
FTI
Hi any chance one of you could post a circuit diagram with component values please?
And just to make sure here the blue disc shaped caps value is 1000pf?
Im going to replace it with a polystyrene and see how that goes as I search for a mill spec EF95.
Finaly are there any 'must avoid' components for this type of project? EG. I have been getting mixed reports about Black Gate components i.e. great for amps that are left on 24-7 but sound crap for hours from cold.
Thankyou again,
FTI
Please explain
If it is so easy how am I asking for a lot?
Like I have said I am the noob here so forgive my lacking in ability or knowlege. It is not my intention to be a burden on anybody, or to ask people to bend over backwards.
@ Anybody who wants to help or remembers what it is like to be a strugling noob.
I work as a technician and teach young people music tech and production subsequently I like helping people if I can.
I also like this kind of forum for the same reason.
I am greatfull for the help I have recieved so far and I will be greatfull for any more help that I can get.
IF you have an oppinion or experience in these matters It would be hugely beneficial for me to read them.
IF this is the wrong place to be asking these questions or seeking this kind of help please redirect me to a more opropriate forum.
FTI
If it is so easy how am I asking for a lot?
Like I have said I am the noob here so forgive my lacking in ability or knowlege. It is not my intention to be a burden on anybody, or to ask people to bend over backwards.
@ Anybody who wants to help or remembers what it is like to be a strugling noob.
I work as a technician and teach young people music tech and production subsequently I like helping people if I can.
I also like this kind of forum for the same reason.
I am greatfull for the help I have recieved so far and I will be greatfull for any more help that I can get.
IF you have an oppinion or experience in these matters It would be hugely beneficial for me to read them.
IF this is the wrong place to be asking these questions or seeking this kind of help please redirect me to a more opropriate forum.
FTI
There is no one good setup of a microphone. It is about "taste"
Sometime the stock stuff is the best for a certain need
I change the caps to taste, IMO one of the most important is the capsule to grid. You need to buy a bunch of caps and try them yourself. Don't believe what you read on the web, test it if you can.
Every thing is like an EQ overlay on the other parts.
One person unwanted transformer sound is what someone else might want.
The cheap ceramic cap might be part of what you want or maybe not
Most caps are not that much money so buy a few and try them yourself.
read my posts carefully.
Blackgates, cheap electros, expensive electros, tants again taste. poly this or that to taste
Maybe the china tube is good.
It is most likely a simple plate out triode(pentode as triode) circuit. Maybe a cathode bias standard single triode gain stage circuit the details are what it all about.
Look at schematics of different tube microphone. Look in the meta. If from china most likely a KIND of copy of some Microphone.
To get much deeper than the hack stuff(blindly changing caps and other parts) you read on the web. You need some knowledge of the operation of a tube, the oxides, the mu, the curves know a little chemisty and physics know a little about electronics. Ohms law and power helps alot.
A good tube microphone is all about the little things.
Sometime the stock stuff is the best for a certain need
I change the caps to taste, IMO one of the most important is the capsule to grid. You need to buy a bunch of caps and try them yourself. Don't believe what you read on the web, test it if you can.
Every thing is like an EQ overlay on the other parts.
One person unwanted transformer sound is what someone else might want.
The cheap ceramic cap might be part of what you want or maybe not
Most caps are not that much money so buy a few and try them yourself.
read my posts carefully.
Blackgates, cheap electros, expensive electros, tants again taste. poly this or that to taste
Maybe the china tube is good.
It is most likely a simple plate out triode(pentode as triode) circuit. Maybe a cathode bias standard single triode gain stage circuit the details are what it all about.
Look at schematics of different tube microphone. Look in the meta. If from china most likely a KIND of copy of some Microphone.
To get much deeper than the hack stuff(blindly changing caps and other parts) you read on the web. You need some knowledge of the operation of a tube, the oxides, the mu, the curves know a little chemisty and physics know a little about electronics. Ohms law and power helps alot.
A good tube microphone is all about the little things.
burdij
Well-known member
Sorry, I don't have this mike so I don't have a schematic of it.
tommypiper
Well-known member
Go with Gus' comments.
Sounds like you don't know what you want, really. Sounds like there is no particular "problem" with the mic as stock, except you think it can be better in some ways based on what others have said. Have you compared it to a mic you like better?
You can spend years messing with these things. That's part of the fun. Gus is telling you there is no one particular fix or formula. You have to experiment and decide what you like.
My advice is to use the mic for a while, compare it to other mics, make music. Don't obsess over it.
Learn how mics work, learn about tubes, theory, and the things Gus mentions. It's likely to be a take-off on an established design. Find someone who knows tube mics and talk with them. Everyone you talk to will have a different take on things.
In the meantime, you could try a few easy mods that others have done - but as Gus says, they may not necessarily improve it to your taste. You'll learn a lot and educate your ears and have fun.
Sounds like you don't know what you want, really. Sounds like there is no particular "problem" with the mic as stock, except you think it can be better in some ways based on what others have said. Have you compared it to a mic you like better?
You can spend years messing with these things. That's part of the fun. Gus is telling you there is no one particular fix or formula. You have to experiment and decide what you like.
My advice is to use the mic for a while, compare it to other mics, make music. Don't obsess over it.
Learn how mics work, learn about tubes, theory, and the things Gus mentions. It's likely to be a take-off on an established design. Find someone who knows tube mics and talk with them. Everyone you talk to will have a different take on things.
In the meantime, you could try a few easy mods that others have done - but as Gus says, they may not necessarily improve it to your taste. You'll learn a lot and educate your ears and have fun.
thinking about increaseing or decreasing the value of the Plate to Transformer Cap Value... will anyone know about that? Like wise what will happend on increasing or Decreasing? any rules or basic about that such as increasing the value will cut more bass? I mean things like that...
Honestly you get what you pay for , you dont expect a little bit of MOD or by changing a bad looking Cap will make your mic sounds like those BIG BROTHER! it just wont happen, like I must say changing the capsule does get me a unexpected tone. but it does solve the boosty high end that I dont like , I like the looks and the size of this mike but not the first impressions on the sounds so I took apart of mic that I got with the capsole sounds that I like and put it in to see what will happen as Having FUNand gain experience, seriousely there's is nothing wrong with the mike. and most the pasrts inside are pretty nice too, and after all , I do enjoy the sounds on it prety much , but no matter what It just wont Beat any of those Big Brother such as the M149 ... after all you get what you pay for , but into this I really get to know what sounds is much more and how to record sounds correctly and I can get to know what I actually like and how my taste to sounds are.... I am trying to put in another Capsule very soon , and maybe I will try to FIT in the nicest Plate to transformer CAP that I can get my hand on to increase the FUN! it's all Craftmentship and Heart while building a MIC. also the size and metal does matter too. just found out Bigger the capsule chamber is the better the sounds is.....maybe....
Honestly you get what you pay for , you dont expect a little bit of MOD or by changing a bad looking Cap will make your mic sounds like those BIG BROTHER! it just wont happen, like I must say changing the capsule does get me a unexpected tone. but it does solve the boosty high end that I dont like , I like the looks and the size of this mike but not the first impressions on the sounds so I took apart of mic that I got with the capsole sounds that I like and put it in to see what will happen as Having FUNand gain experience, seriousely there's is nothing wrong with the mike. and most the pasrts inside are pretty nice too, and after all , I do enjoy the sounds on it prety much , but no matter what It just wont Beat any of those Big Brother such as the M149 ... after all you get what you pay for , but into this I really get to know what sounds is much more and how to record sounds correctly and I can get to know what I actually like and how my taste to sounds are.... I am trying to put in another Capsule very soon , and maybe I will try to FIT in the nicest Plate to transformer CAP that I can get my hand on to increase the FUN! it's all Craftmentship and Heart while building a MIC. also the size and metal does matter too. just found out Bigger the capsule chamber is the better the sounds is.....maybe....
http://www.silentarts.de/lab/Mikrophone/AKG/C24_Schematic.pdf
look at the bottom right you most likely have a cathode biased circuit.
look for a 1.5K to 3.3K resistor with an electro cap of 22uf or more in parallel
Simple and works most of the time
pentode as a triode
120 VDC china seems to like big 100K metal oxide plate R look for the first R off the plate sometimes there is an RC network between the plate resistor and power supply in the microphone. Often 10K and an electro cap xxuf and 450V
The pattern control should be like the G7 but the switch is in the body
Look at the G7 the microphone is most likely just like that but 120VDC and a different tube
The pattern control might be like the G7 but the switch is in the body
Here is something simple
print the G7 schematic and match up the parts in the microphone. Thats a "standard" type tube 3 pattern microphone circuit
Have you read the microphone metas? lots of good stuff in the first older one.
easy stuff for a tube microphone
look at the bottom right you most likely have a cathode biased circuit.
look for a 1.5K to 3.3K resistor with an electro cap of 22uf or more in parallel
Simple and works most of the time
pentode as a triode
120 VDC china seems to like big 100K metal oxide plate R look for the first R off the plate sometimes there is an RC network between the plate resistor and power supply in the microphone. Often 10K and an electro cap xxuf and 450V
The pattern control should be like the G7 but the switch is in the body
Look at the G7 the microphone is most likely just like that but 120VDC and a different tube
The pattern control might be like the G7 but the switch is in the body
Here is something simple
print the G7 schematic and match up the parts in the microphone. Thats a "standard" type tube 3 pattern microphone circuit
Have you read the microphone metas? lots of good stuff in the first older one.
easy stuff for a tube microphone
OK! I replaced the 1uf Plate to Transformer Cap from those Electic to a Hugh Cap like those Orange Drop and also replaced that Ceremic cap to a Philip Audio Grade cap. the result of replacing the plate cap changed the sound to a deeper tone and more Steady , by replacing the Blue cap to the philip cap it cleans up those dirty feeling in the Highs and still remain pretty Airy(Smoother). I will try to replace the capsule again to another one and see whats zup with that . I am one happy man now 
Went to a local music store and looked at a 8000.
The cable was not clamped well to the XLR
The capsule was not centered in the grill two of the mount were bigger than the other mount
I could not see the capsule well enought to tell what make/style
I did not try it.
But looking at it I would rework the cable clamp at the XLR
maybe rework the capsule mount
The cable was not clamped well to the XLR
The capsule was not centered in the grill two of the mount were bigger than the other mount
I could not see the capsule well enought to tell what make/style
I did not try it.
But looking at it I would rework the cable clamp at the XLR
maybe rework the capsule mount
I should also add that the old cap is a ceramic disc and the new one is a radial.
The leads are very fine and there is no mount to the board. Do I want to have the leads tight so the body of the cap is suspended or loose and fix the cap down with silicone?
Any advice apart from 'use search' or 'just try it, and its hard chese if you make a mess' would be great.
Thanx in advance,
FTI
The leads are very fine and there is no mount to the board. Do I want to have the leads tight so the body of the cap is suspended or loose and fix the cap down with silicone?
Any advice apart from 'use search' or 'just try it, and its hard chese if you make a mess' would be great.
Thanx in advance,
FTI
I dont get what you mean? what kind of cap are you replacing with and what cap are you trying to replace? are you talking about the Little Blue cap? you should just let it hang there no glue at all and no touching things either
Right, the little blue ceramic cap is out and I have replaced with a Panasonic polyprop.
Forget the mounting issue I was worried about vibration (I dont think this is an issue) what I am concerned about is that the origional blue ceramic is rated at 1KV and the new one is reted at 50V.
I took a reading across the conection of 1.37V that stableised out as 1.38V.
What I need to do -unless you guys think that this is not needed- is create a data log on power up so I know that 50V is enough for any spike that I may get during power up (I think?).
Any advice as per usual would be very uesfull.
Thankyou for the help so far,
FTI
Forget the mounting issue I was worried about vibration (I dont think this is an issue) what I am concerned about is that the origional blue ceramic is rated at 1KV and the new one is reted at 50V.
I took a reading across the conection of 1.37V that stableised out as 1.38V.
What I need to do -unless you guys think that this is not needed- is create a data log on power up so I know that 50V is enough for any spike that I may get during power up (I think?).
Any advice as per usual would be very uesfull.
Thankyou for the help so far,
FTI
