M49c tag-board layout (Oliver Archut circuit with 5718)

[OneRoomStudio]

After receiving parts from AMI/Tab Funkenwerk to build an M49 based on this schematic, I realized that the pictures in the assembly instructions were not entirely clear, so I decided to draw my own layout before starting. I thought this might be handy for other folks as well. For my build, I'm using Moby's BV11 transformer, a 5718 tube (technically, a CV3930), and a 'Flat K47' capsule. Obviously, if you use a different tube, the tube legs will be different. Also, I decided to separate filament ground and B+/audio ground in the microphone, which means I'm using tuchel pin 3 to return the filament ground, unlike the schematic.

 

[rock soderstrom]

Also, I decided to separate filament ground and B+/audio ground in the microphone, which means I'm using tuchel pin 3 to return the filament ground, unlike the schematic.

Just out of interest, what advantages do you expect from this?

For my build, I'm using Moby's BV11 transformer, a 5719 tube (technically, a CV3930)

Interesting tube, do you have any experience with it? But it has different technical data than the 5840 or the other suspects. Does this match the Moby BV11 transformer?

 

[OneRoomStudio]

Just out of interest, what advantages do you expect from this?

Nothing spectacular. It's mostly due to having an unused pin and wire, so I have the ability to do so. I also like the idea of using slightly thicker (24awg) wire for filament return since there's more current there, vs the 28awg wire I'm using elsewhere for audio/B+ ground. Theoretically it would be better for noise as well, but I doubt it would be noticable.

Interesting tube, do you have any experience with it? But it has different technical data than the 5840 or the other suspects. Does this match the Moby BV11 transformer?

I realized I mis-typed. I meant to type 5718, not 5719. I have used them before (in a 251 build described here). 5718's (otherwise known as EC71) are highly regarded as AC701 replacements. You can read Oliver Archut's recommendation of them here.

 

[rock soderstrom]

I realized I mis-typed. I meant to type 5718, not 5719. I have used them before (in a 251 build described here). 5718's (otherwise known as EC71) are highly regarded as AC701 replacements. You can read Oliver Archut's recommendation of them here.

Yes, EC71/5718 are nice! If there is enough space available, I think the 5654/E95F/6AK5w family is very good too! If you're lucky, you can still find both types for very little money.

 

[OneRoomStudio]

Adding some build pics for reference since I finally got all my parts (minus the Flat K47 from @soliloqueen that I’m excited to stick in there!).

 

[Purplenoise]

Adding some build pics for reference since I finally got all my parts (minus the Flat K47 from @soliloqueen that I’m excited to stick in there!).

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Looks awesome. I have built one too with 5718 and original Neumann k47. It sounds really close to an original I tested for a little bit.
I used 450pf plate to ground cap for high end roll of instead of 600pf but if you are using ariennes capsule I would leave that cap out completely.
Also the type of the 0.01uf caps affect the tone somewhat. Polystyrene will give you a more “scooped” sound

 

[OneRoomStudio]

Looks awesome. I have built one too with 5718 and original Neumann k47. It sounds really close to an original I tested for a little bit.
I used 450pf plate to ground cap for high end roll of instead of 600pf but if you are using ariennes capsule I would leave that cap out completely.
Also the type of the 0.01uf caps affect the tone somewhat. Polystyrene will give you a more “scooped” sound

I omitted the high end roll off cap for the reason you mentioned. I used polystyrene for the 10nF caps, mostly because I had ones that fit and they look nice. Some people say that EC71/5718 tubes are slightly "mid-present," so maybe the polystyrene caps will cancel that out. Who knows. I'm betting it will sound nice once I have the flat capsule in any case.

 

[Purplenoise]

I omitted the high end roll off cap for the reason you mentioned. I used polystyrene for the 10nF caps, mostly because I had ones that fit and they look nice. Some people say that EC71/5718 tubes are slightly "mid-present," so maybe the polystyrene caps will cancel that out. Who knows. I'm betting it will sound nice once I have the flat capsule in any case.

I find the 5718 kinda even and flat sounding…maybe less high end than an ac701?…maybe? That’s why I went with the little white caps like the reissue m49…1839?…kinda scooped sounding also

 

[EarthTone]

Adding some build pics for reference since I finally got all my parts (minus the Flat K47 from @soliloqueen that I’m excited to stick in there!).

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Thanks for posting your layout and build pics! Looks awesome! May I ask what type of standoffs those are? Or is it just some type of fitted neoprene tubes around regular hexagonal standoffs? I want to use some like that on my upcoming m49 build!

Also may I ask one more question: What thickness of acrylic did you use? I just had some custom transformer cutout base plates made, and I asked him to use 1/8th” and 1/16” to try and see which works best without cracking when you drill and screw into it. The type of standoffs I have prevent me from using very thick acrylic. Maybe I need to rethink that though because your acrylic plates look thicker.

One more question sorry! Did you cut the circular acrylic and the transformer square cutout and drill everything yourself manually? Or if not, how did you do that? I don’t really have any drill presses or jigsaws or anything (I’m a musician- afraid of cutting my fingers off!) so I just had a guy on Etsy do it for me but I would love to be able to do those myself in a non-finger-threatening manner…

 

[Delta Sigma]

Nothing spectacular. It's mostly due to having an unused pin and wire, so I have the ability to do so. I also like the idea of using slightly thicker (24awg) wire for filament return since there's more current there, vs the 28awg wire I'm using elsewhere for audio/B+ ground. Theoretically it would be better for noise as well, but I doubt it would be noticable.

To make use of the extra wire, why not pop in a reed relay for a cardioid only switch?

 

[OneRoomStudio]

Thanks for posting your layout and build pics! Looks awesome! May I ask what type of standoffs those are? Or is it just some type of fitted neoprene tubes around regular hexagonal standoffs? I want to use some like that on my upcoming m49 build!

Also may I ask one more question: What thickness of acrylic did you use? I just had some custom transformer cutout base plates made, and I asked him to use 1/8th” and 1/16” to try and see which works best without cracking when you drill and screw into it. The type of standoffs I have prevent me from using very thick acrylic. Maybe I need to rethink that though because your acrylic plates look thicker.

One more question sorry! Did you cut the circular acrylic and the transformer square cutout and drill everything yourself manually? Or if not, how did you do that? I don’t really have any drill presses or jigsaws or anything (I’m a musician- afraid of cutting my fingers off!) so I just had a guy on Etsy do it for me but I would love to be able to do those myself in a non-finger-threatening manner…

These acrylic discs are from TAB Funkenwerk, although I had to modify them slightly to fit the Moby transformer and run the backplate a little differently. It was easy enough to cut with a dremel and drill with a press.

 

[OneRoomStudio]

To make use of the extra wire, why not pop in a reed relay for a cardioid only switch?

Not a bad idea, but I wanted to keep this one fairly simple.

 

[rock soderstrom]

Where do you get the soldering support points? Thank you for the documentation.

 

[JohnnyM]

Sorry if it’s a dumb question, but how do the solder tags adhere to the acrylic? Some sort of rivet press into the hole?

 

[Delta Sigma]

Not a bad idea, but I wanted to keep this one fairly simple.

Most reed relays I've found are too large to fit into an M49. I found one that fit in mine, but I'm not sure where or what the part number is. Works great!

 

[OneRoomStudio]

Where do you get the soldering support points? Thank you for the documentation.

Sorry if it’s a dumb question, but how do the solder tags adhere to the acrylic? Some sort of rivet press into the hole?

I think maybe you're both asking the same question - these are press-fit turrets with solder tabs. You can buy the discs from TAB Funkenwerk with these pre-installed.

Also, the stand-offs are just standard round metal stand-offs with heat shrink around them to insulate.

 

[EarthTone]

I think maybe you're both asking the same question - these are press-fit turrets with solder tabs. You can buy the discs from TAB Funkenwerk with these pre-installed.

Also, the stand-offs are just standard round metal stand-offs with heat shrink around them to insulate.

Ah I see! Thank you for the clarification on the standoffs. I sort of thought from the pictures that they were the same type of mount as the M7 capsule mount you are using, which created a bit of pressure and helps it not to shift after tightening (sans lock washer), but that’s good to know. Cheers. Great looking build!

 

[SparkleBear]

Most reed relays I've found are too large to fit into an M49. I found one that fit in mine, but I'm not sure where or what the part number is. Works great!

I’ve been loving the littlefuse reed relay in my m49 P2P. I couldn’t find any coto that fit under my acrylic top. Littlefuse were more compact and worked great!

https://m.littelfuse.com/products/magnetic-sensors-and-reed-switches/reed-relays.aspx

 

[Delta Sigma]

I’ve been loving the littlefuse reed relay in my m49 P2P. I couldn’t find any coto that fit under my acrylic top. Littlefuse were more compact and worked great!

https://m.littelfuse.com/products/magnetic-sensors-and-reed-switches/reed-relays.aspx

That's the little bugger I used! Works great.

 

[SparkleBear]

That's the little bugger I used! Works great.

Cute and small. I was a bit bummed i couldnt use the coto... LOL I love the look in the mic nudes. *shrug*

What voltage did you use for your relay in your mic, delta?