Collins transformer experimental build in (hacked) C12 style.

[pinchemotherloaf]

Found this big Collins transformer 16:1 and wanted to see how it sounds in a (hacked) c12 style design. Typical bias to capsule and grid with coupling cap and 6072 tube. Cheap capsule. And plenty of that DSL cross-connect wire! The sound is not what I expected: It is hot loud and bright but interesting, maybe acceptable at lower levels. I was expecting something darker, but.. it's just an experimental microphone!

 

[Khron]

Is that rated for 10mA DC on the primary? Wouldn't that mean it could be placed (possibly with a series resistor) right on the tube plate, foregoing the need for a coupling capacitor?

Just a stupid thought...

 

[rock soderstrom]

Found this big Collins transformer 16:1

As far as I can see this is a 10k to 600R transformer, so it is 4:1. This will result in an impedance mismatch, thus the weak bass and the high output level.

I can't read it correctly, what is the bandwidth written on the transformer in Hz (cycles)?

 

[pinchemotherloaf]

As far as I can see this is a 10k to 600R transformer, so it is 4:1. This will result in an impedance mismatch, thus the weak bass and the high output level.

I can't read it correctly, what is the bandwidth written on the transformer in Hz (cycles)?

It indicates 100-10kc but the fellow I bought it from said he tested them to up to 30kc +/- 2dB

That would explain the high output and weak bass from the ratio, thanks.

 

[pinchemotherloaf]

Is that rated for 10mA DC on the primary? Wouldn't that mean it could be placed (possibly with a series resistor) right on the tube plate, foregoing the need for a coupling capacitor?

Just a stupid thought...

Interesting idea!

 

[rock soderstrom]

Maybe you can compensate the problem with a tube that can deliver more current and has a lower internal resistance, like an ECC88 or similar. Are you using both triodes of your tube?

 

[pinchemotherloaf]

Maybe you can compensate the problem with a tube that can deliver more current and has a lower internal resistance, like an ECC88 or similar. Are you using both triodes of your tube?

Just one side, but maybe using both would help! Thanks for the suggestion.

 

[kingkorg]

It indicates 100-10kc but the fellow I bought it from said he tested them to up to 30kc +/- 2dB

This will depend heavily on the properties of the source of the signal, you need to test for this in your circuit.

As far as I can see this is a 10k to 600R transformer, so it is 4:1.

May i ask how did you get to this conclusion knowing only dcr of the transformer?

 

[rock soderstrom]

May i ask how did you get to this conclusion knowing only dcr of the transformer?

Yes, of course. Usually, as far as I know, transformer manufacturers specify impedances, not the resistive value of the windings, on their casings.

 

[kingkorg]

Ok, i get it. I had opposite experience where they specify dcr.

 

[Murdock]

Is that rated for 10mA DC on the primary? Wouldn't that mean it could be placed (possibly with a series resistor) right on the tube plate, foregoing the need for a coupling capacitor?

Just a stupid thought...

I also had thought about the use of gapped transformers in microphones and why there is none I know of where it is used.
Especially because the current is quite small most of the time so the gap doesn't have to be so big.
Any reason why no mic use gapped transformers?

@pinchemotherloaf don't you want to try it for us all? Ditch that cap and tell us how it sounds

 

[rock soderstrom]

Any reason why no mic use gapped transformers?

The size? Bandwith and more $$?

 

[pinchemotherloaf]

I also had thought about the use of gapped transformers in microphones and why there is none I know of where it is used.
Especially because the current is quite small most of the time so the gap doesn't have to be so big.
Any reason why no mic use gapped transformers?

@pinchemotherloaf don't you want to try it for us all? Ditch that cap and tell us how it sounds

OK I'll try in out!