Good thing to keep in mind. Im just using the stock chinex supply transformer right now... have an edcor on standby incase this one didn't do the job or made noise mechanically.
M49c Build p2p in Flea body.
- Thread starter SparkleBear
- Start date
Help Support GroupDIY Audio Forum:
gorgeous!!
Hey guys, I'm trying to wrap my head around this relay + pattern rotary. I have the 0-120v line working... Voltage for 24v relay is correct. I can't quite figure out how to get the 4.2k load resistor that will "replace" the coil when in position 5.
Do I need a 3rd deck?? I hope not, those switches start getting expensive.
(relay might not be the right symbol... but is a N.O. Reed relay.)
Thanks all!
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This seems overly complicated. Just use the 9 position switch for patterns, then use a separate SPDT (or DPDT) switch for cardioid only. The switch will switch the B+ (or H+) between the relay coil and the equivalent resistor. If you have a small enclosure, there are reasonably priced mini toggle sized switches that you could sneak into just about any enclosure.
Thats fair, I was just thinking about that separate switch solution... It would be nice to have it all tied together with the relay.
Actually I think I may have sorted it out! Using a DPDT NO/NC relay I can get the job done. 24v Dropper will be in the pattern switch in the PSU but the coil equivalent load resistor will live with the relay in the mic.
https://www.mouser.com/ProductDetail/816-7142-05-1010
This way in the de-energized state the the relay will connect 120v to ground through the load resistor, while keeping the rear diaphragm disconnected. In the energized state it will connect the rear diaphragm to the grid/front diaphragm and remove the 120v from the coil resistor.
I think this will do the trick.
Actually I think I may have sorted it out! Using a DPDT NO/NC relay I can get the job done. 24v Dropper will be in the pattern switch in the PSU but the coil equivalent load resistor will live with the relay in the mic.
https://www.mouser.com/ProductDetail/816-7142-05-1010
This way in the de-energized state the the relay will connect 120v to ground through the load resistor, while keeping the rear diaphragm disconnected. In the energized state it will connect the rear diaphragm to the grid/front diaphragm and remove the 120v from the coil resistor.
I think this will do the trick.
Although with the manual toggle switch I have more options as I also have two types of cardioid. I think I am going to go with this for now...
You don’t need a DPDT relay. You can connect the dropper resistor R9 to COM of the switch instead to the switch positions and go from the positions to the relay coil. Then you can connect the 4k2 resistor between position 5 and GND/0V.
I hope it’s clear what I mean. I can draw it later today.
I hope it’s clear what I mean. I can draw it later today.
Might still be a little confusion. For both my M49 and My EF47, I used a simple pot for variable pattern voltage into pin 6 of the mic. For the cardioid only, switch S2 from the schematic (front diaphragm to C1), I used a contact from an SPST reed relay. The reed relay is inside the mic and is activated when 5V or greater is applied to the coil via pin 7 (I think, from memory).
Inside the power supply, I have the pot with B+ across it and its wiper tied to pin 6 to allow variable pattern. I then have a separate DPDT switch that when up, connects H+ to a resistor with the equivalent value to the relay's coil (inside the PS). When the switch is down, H+ is disconnected from the equivalent resistor and connected to pin 7 to the microphone which energizes the relay and closes the contact between C1 and the front diaphragm. This means that when the cardioid only switch on the power supply is down, the pot on the power supply changes the voltage at the rear diaphragm, allowing variable pattern. When the cardioid only switch on the power supply is up, there is no connection between C1 and the front diaphragm, so you only have a cardioid pattern. The pot on the power supply would still adjust the voltage on pin 6, and the rear diaphragm, but the rear diaphragm is disconnected from the circuit.
I adjust the H+ in cardioid only, because that's the way I used the mic most of the time. When the cardioid only switch is down, and the relay is energized, there is probably a very small change in H+. Likely a few mV.
Inside the power supply, I have the pot with B+ across it and its wiper tied to pin 6 to allow variable pattern. I then have a separate DPDT switch that when up, connects H+ to a resistor with the equivalent value to the relay's coil (inside the PS). When the switch is down, H+ is disconnected from the equivalent resistor and connected to pin 7 to the microphone which energizes the relay and closes the contact between C1 and the front diaphragm. This means that when the cardioid only switch on the power supply is down, the pot on the power supply changes the voltage at the rear diaphragm, allowing variable pattern. When the cardioid only switch on the power supply is up, there is no connection between C1 and the front diaphragm, so you only have a cardioid pattern. The pot on the power supply would still adjust the voltage on pin 6, and the rear diaphragm, but the rear diaphragm is disconnected from the circuit.
I adjust the H+ in cardioid only, because that's the way I used the mic most of the time. When the cardioid only switch is down, and the relay is energized, there is probably a very small change in H+. Likely a few mV.
I get the first part, putting the r9 dropper after the common pin for the relay deck of the rotary. Then are you saying to connect from the positions themselves to the relay coil through the dropper? My intuition says what i've done below is wrong (and not what you are saying) as the coil is still seeing voltage and a path to ground... I think you drawing it out will help me understand specifically. Thanks Murdock.
A shift in a few mV of the B+ line might not be such a big deal in the long run so maybe I am chasing a dragon here ;P...
BTW, Thats a really nice pot @Delta Sigma
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I meant it something like that. I don't know what PSU you use so don't know if you draw directly from B+ for the second deck of the pol switch or if you filter it further like Neumann did.
I used the first position on the switch for cardioid just to simplify things. Ofcourse you can use any position you want. And I only found a 6 position switch in KiCad.
But that way you have to use a normally open relay. So it is open when no voltage is flowing through the relay coil and closed as soon voltage is there. So you always have the relay energized when using other patterns.
If you want to use a normally closed relay you just swap the connections. So RCoil goes to the other connected positions and only the cardioid position goes to the relay.
I used the first position on the switch for cardioid just to simplify things. Ofcourse you can use any position you want. And I only found a 6 position switch in KiCad.
But that way you have to use a normally open relay. So it is open when no voltage is flowing through the relay coil and closed as soon voltage is there. So you always have the relay energized when using other patterns.
If you want to use a normally closed relay you just swap the connections. So RCoil goes to the other connected positions and only the cardioid position goes to the relay.
Ahhh! there it is! Thanks so much Murdock. All clear now... I had to make the 9 position switch but its clear with the 6 pos too.
Cheers mate!
Just got the coto reed relay from mouser. Finally finished the backorder.... however, it seems too big for my plexi cover. Hmm... how did you get it to fit in yours @Murdock? Is mine the same model? (don't mind the fine dust, I already cleaned it... from filing the posts.
Tried snipping and filing the solder posts on the standoffs to make just a bit more room. No dice.
Thought about putting it under the top deck next to the transformer but concerned about longer signal run. Would also want to drill additional holes in decks to pass wires as short as possible if this is the solution.
The under-deck solution could be sleek if it is not technically incorrect for length it adds to signal runs.
Tried snipping and filing the solder posts on the standoffs to make just a bit more room. No dice.
Thought about putting it under the top deck next to the transformer but concerned about longer signal run. Would also want to drill additional holes in decks to pass wires as short as possible if this is the solution.
The under-deck solution could be sleek if it is not technically incorrect for length it adds to signal runs.
I designed the board to my needs. So the placement of the turrets and solder lugs are not identical to the original. My turrets are probably closer together.
I don't know if the "under deck" solution is ok. Seems like a quite long distance to the high impedance stuff. If you have to do it than I would do it the other way around, the capacitor on the bottom and the relay on top to get closer.
But I would be hesitant to drill holes or modify a plus 500 Dollar body...
Maybe you can design your own board?
Or just make it like the original with a solder lug switch.
I ended up going with the under deck solution for the time being. Rewired my pattern switch properly, added the coto relay next to the transformer, under the 1uf cap... wired it up and added a diode. Added the 1000pF dc blocking capacitor, from back capsule post leading to the relay in, relay out goes right to front capsule/grid lug... I also decided to put a little indicator LED with 1k current limiter resistor on the heater rail. It works great to just adhere it to the side of the transformer plate. Before buttoning it up, I cleaned the high z with isopropyl and blew compressed air to get any detritus out of there.
The high z relay wires are PTFE silver and I disassembled the decks and carefully drilled new holes to minimize the wire runs. I know its an expensive body but the modification is so minimal and nothing to the metal work... I would never modify the metal work on something like this. I don't think that I will design my own PCB at this point... Best case scenario would be to find a smaller reed relay that could fit in the space in the upper deck within the plexi.
Ohhh and I added little pattern symbols to the PSU.
LED is just standard led... kapton is just temporary to hold it in place while e6000 dries.
The light maybe too bright or distracting... in which case I will experiment with raising the led resistor to dim the light. Also may experiment with adding a little switch to turn it off all together. But for now it's cool and its working. ;P
Doesn't seem overly noisy from the LED or the longer wires. But i'll keep an ear out for this.
Super happy with this build, it was just an idea and a plan in my head for many years... thrilled it exists in my life now!
CHEERS!
Rewired my pattern switch properly, added the coto relay next to the transformer, under the 1uf cap... wired it up and added a diode. Added the 1000pF dc blocking capacitor, from back capsule post leading to the relay in, relay out goes right to front capsule/grid lug... I also decided to put a little indicator LED with 1k current limiter resistor on the heater rail. It works great to just adhere it to the side of the transformer plate. Before buttoning it up, I cleaned the high z with isopropyl and blew compressed air to get any detritus out of there.The high z relay wires are PTFE silver and I disassembled the decks and carefully drilled new holes to minimize the wire runs. I know its an expensive body but the modification is so minimal and nothing to the metal work... I would never modify the metal work on something like this. I don't think that I will design my own PCB at this point... Best case scenario would be to find a smaller reed relay that could fit in the space in the upper deck within the plexi.
Ohhh and I added little pattern symbols to the PSU.
LED is just standard led... kapton is just temporary to hold it in place while e6000 dries.
The light maybe too bright or distracting... in which case I will experiment with raising the led resistor to dim the light. Also may experiment with adding a little switch to turn it off all together. But for now it's cool and its working. ;P
Doesn't seem overly noisy from the LED or the longer wires. But i'll keep an ear out for this.
Super happy with this build, it was just an idea and a plan in my head for many years... thrilled it exists in my life now!
CHEERS!
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Finally getting to work on this guy again,
I replaced the coto relay, which was too big to fit in the upper deck enclosure beneath the plexi, with a smaller littlefuse 24v relay. Only difference is COTO is 4.2k ohm coil and LittleFuse is 2k ohm. So to complete the voltage drop I used 8k for the drop to get 24v with the 2k coil resistance. I had been working this out with @Murdock earlier in the thread. Curious if any of yall are using this relay scheme with an unregulated psu.
After experiencing a buzz in my own PSU (regulated HV and LV) I Built Dany's psu249, an unregulated PSU. I brought over the pattern switch and relay coil resistors... Used the above values to change for new relay...
Adding the switch and relay into the equation seems to add a 10k B+ to GND load.
like this (without capacitors and such) gives ~40-80v at B+ out over the throw of the 25k trim pot.
Realizing that using this schema is dropping the voltage incorrectly. Trying to wrap my head around how to do this properly.
So, the issue I am solving is not being able to tap the B+ line for the 24v relay with out dropping the over all voltage below useful levels. I was able to get to the right voltages (120v b+) by using the secondary in series. But if the relay circuit is removed the loaded voltage on the line goes up to close to 200v. This is not desired. Maybe this is the way but raising the wattage of the resistors on the line? I have decided that I don't want the chance that a broken wire on the relay circuit would blast the mic with almost double what it needs to see.
Another possibility is scrapping the whole relay and using one of those High Z mini switches to put it inside the mic for forced cardioid. Yet another possibility is to make a seperate psu rail just for the relay? My LV transformer gives me a 12v tap and a 24v tap. Maybe looking at that rail to supply the relay?
At this point, since the relay is N.O., I just have the relay switch circuit disconnected so that it just lives in forced cardioid and I do not have to use the secondary in series, but rather than the 120v parallel. So I will be able to use the mic for projects while I figure out the best way to implement the 24v relay schema.
I have a hunch that this load on the B+ line with the fully regulated supply was stressing the regulator out so much that it developed the hum or buzz. I don't yet have the knowledge to explain but thats my intuition.
Thanks so much y'all... Any advice from would be so appreciated.
I replaced the coto relay, which was too big to fit in the upper deck enclosure beneath the plexi, with a smaller littlefuse 24v relay. Only difference is COTO is 4.2k ohm coil and LittleFuse is 2k ohm. So to complete the voltage drop I used 8k for the drop to get 24v with the 2k coil resistance. I had been working this out with @Murdock earlier in the thread. Curious if any of yall are using this relay scheme with an unregulated psu.
After experiencing a buzz in my own PSU (regulated HV and LV) I Built Dany's psu249, an unregulated PSU. I brought over the pattern switch and relay coil resistors... Used the above values to change for new relay...
Adding the switch and relay into the equation seems to add a 10k B+ to GND load.
like this (without capacitors and such) gives ~40-80v at B+ out over the throw of the 25k trim pot.
Realizing that using this schema is dropping the voltage incorrectly. Trying to wrap my head around how to do this properly.
So, the issue I am solving is not being able to tap the B+ line for the 24v relay with out dropping the over all voltage below useful levels. I was able to get to the right voltages (120v b+) by using the secondary in series. But if the relay circuit is removed the loaded voltage on the line goes up to close to 200v. This is not desired. Maybe this is the way but raising the wattage of the resistors on the line? I have decided that I don't want the chance that a broken wire on the relay circuit would blast the mic with almost double what it needs to see.
Another possibility is scrapping the whole relay and using one of those High Z mini switches to put it inside the mic for forced cardioid. Yet another possibility is to make a seperate psu rail just for the relay? My LV transformer gives me a 12v tap and a 24v tap. Maybe looking at that rail to supply the relay?
At this point, since the relay is N.O., I just have the relay switch circuit disconnected so that it just lives in forced cardioid and I do not have to use the secondary in series, but rather than the 120v parallel. So I will be able to use the mic for projects while I figure out the best way to implement the 24v relay schema.
I have a hunch that this load on the B+ line with the fully regulated supply was stressing the regulator out so much that it developed the hum or buzz. I don't yet have the knowledge to explain but thats my intuition.
Thanks so much y'all... Any advice from would be so appreciated.
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Yes, this is definitely an option too... But I was advised to go with the reed relay because the impedance values are way higher than the standard relays. Most of my other designs just use the 5v relay with the heater line... it sources the h+ inside the mic and just uses switched ground on on pin 3 to activate/deactivate relay. I suppose I could just go there. I think i originally didnt want to mess with the heater supply because I had a tentative plan to put an ac701 in there once I have full confidence in the PSU... which has not been the case so far.
I would still like to understand how to implement a 24v relay into a mic.
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https://www.mouser.fi/c/electromechanical/relays-contactors-solenoids/reed-relays/?coil voltage=3 VDC~~6 VDC&instock=y&rp=electromechanical/relays-contactors-solenoids/reed-relays|~Coil Voltage&sort=pricing
You're welcome. The 5v relays seem to have "must close" voltage specs of just under 4v, and need a measly 10mA or so (500 ohm coil).
You're gonna need (oodles) more current than whatever you can pull from that RC-filtered B+ line before it droops to useless levels. Ohm's law...
You're welcome. The 5v relays seem to have "must close" voltage specs of just under 4v, and need a measly 10mA or so (500 ohm coil).
You're gonna need (oodles) more current than whatever you can pull from that RC-filtered B+ line before it droops to useless levels. Ohm's law...
Hey that looks great! Thanks a lot
I've wanted to build this one for a long time, I have the Flea body as well, and Beesneez's K47, and a 5840 tube. I'm not sure which POM to get, and wonder if you have any suggestion for a transformer?
Thank you!
I've wanted to build this one for a long time, I have the Flea body as well, and Beesneez's K47, and a 5840 tube. I'm not sure which POM to get, and wonder if you have any suggestion for a transformer?
Thank you!
