Carnhill VTB 2457M “input” (mic?) transformer

[emi2345]

I bought one of these, which is described as 200r:9800r, intending to use it as a 1:7 tube mic preamp input transformer, loading the secondary with a 100k resistor grid to ground to present a 2k bridging input for the mic.

I now see that it is described as an “Audio signal (Line level interstage)” transformer. Would it make a good 1:7 mic input transformer, similar to the sowter 4935?

It also says the windings are dual primary and secondary, does that mean 0.5+0.5:3.5+3.5 or 50r+50r:2450r+2450r? I can’t work out a wiring scheme. The info provided on the site is pretty scant and this transformer is not listed on the carnhill design guide pdf. Perhaps it’s the same schematic as the VTB 9045M in the guide. Anyone have any luck with this transformer?

https://www.audiomaintenance.com/acatalog/CA-18-VTB2457M_extended_info.html

 

[ruffrecords]

Wiring both primary and secondary in series should give you 1:7 step up. Without knowing the core material it is hard to say if it will make a good mic transformer.

Cheers

Ian

 

[HerbertR]

I bought one of these, which is described as 200r:9800r, intending to use it as a 1:7 tube mic preamp input transformer, loading the secondary with a 100k resistor grid to ground to present a 2k bridging input for the mic.

I now see that it is described as an “Audio signal (Line level interstage)” transformer. Would it make a good 1:7 mic input transformer, similar to the sowter 4935?

It also says the windings are dual primary and secondary, does that mean 0.5+0.5:3.5+3.5 or 50r+50r:2450r+2450r? I can’t work out a wiring scheme. The info provided on the site is pretty scant and this transformer is not listed on the carnhill design guide pdf. Perhaps it’s the same schematic as the VTB 1847 in the guide. Anyone have any luck with this transformer?

https://www.audiomaintenance.com/acatalog/CA-18-VTB2457M_extended_info.html

It's the perfect 1:7 input transformer for a Redd47 build. Collin used these Input TX in his EZ247 AML 19" Redd47 Mic Style Preamps. For the output transformer, the 7:1 VTB2460 with 9.8K:200 is the perfect pair. I used these Transformers also for a Dual Redd47 19" build. Cool that Collin now officially offers these transformers on his website.

 

[emi2345]

It's the perfect 1:7 input transformer for a Redd47 build. Collin used these Input TX in his EZ247 AML 19" Redd47 Mic Style Preamps. For the output transformer, the 7:1 VTB2460 with 9.8K:200 is the perfect pair. I used these Transformers also for a Dual Redd47 19" build. Cool that Collin now officially offers these transformers on his website.

Great to know, thank you. Are you able to confirm the pinout and winding schematic? Is it the same as the 9045M mic transformer in the carnhill design guide?

 

[HerbertR]

Great to know, thank you. Are you able to confirm the pinout and winding schematic? Is it the same as the 9045M mic transformer in the carnhill design guide?

I'm not 100% sure as I did the build over three years ago. But as far as I can remember and what the original email from Colin from September 2020 says:

"The VTB2457 is mechanically the same as a VTB2424M and pinout is the same.

The VTB2460 is mechanically the same as a VTB2407 and wiring/pinout is the same."
I hope this helps. I think this TX really represents an authentic British sound, with matching impedance, ratio, ... for a HQ Redd47 build. Colin is a hero and he really designs great pieces. Regards, Herbert

 

[emi2345]

I'm not 100% sure as I did the build over three years ago. But as far as I can remember and what the original email from Colin from September 2020 says:

"The VTB2457 is mechanically the same as a VTB2424M and pinout is the same.

The VTB2460 is mechanically the same as a VTB2407 and wiring/pinout is the same."
I hope this helps. I think this TX really represents an authentic British sound, with matching impedance, ratio, ... for a HQ Redd47 build. Colin is a hero and he really designs great pieces. Regards, Herbert

Thank you, this is the info I needed