I want to build a tube mic preamp. Any recommendations?

[ruffrecords]

oh thats really great - thanks so much Ian - that circuit is pretty similar to what i was talking about - do you know offhand what that resistor value is?  9k6 gives us 5mA if we follow the same thinking of maintaining a more constant current flow…

would this work over 16 channels tho? would it be too much? that would mean there would be at least an 80mA draw off the phantom power tap…

Can't remember the resistor value but I suspect it was about 10K. For 16 channels you PSU has to be designed to supply all 16 at once so it is no different if the phantom on a channel is on or off.

I really have no concept of what  i need to keep in the bank for this stuff…

For the phantom power power you can use my phantom power PCB available via my white market page. The largest expense in tube mic pres is in the iron. Good input transformers are in the $75 region and output transformers will be in the region of $40. Notice the little 6 into to has no output iron. For simple systems you can get away with unbalanced outs.

i'd love to hear about that variable HPF - is that helios inspired?
[
thanks again Ian.

The HPF was specified by the original client who was going to use the mixer for on location recording of classical music. There were 3 frequencies with a 6dB/octave slope and a couple with a 12dB/octave slope. The main idea was to cut rumble from this like air conditioning systems I think.

Cheers

Ian

 

[ze marcelo]

Sem problemas. Aqui está o esquema do meu circuito de pré-microfone original. Eu construí dois deles em um rack de 19 polegadas como uma unidade de demonstração, daí o título do esquema 'canal duplo'. Eu enviei isso para um cara nos EUA que estava muito interessado e prometeu fazer uma demonstração para várias pessoas e me fazer encomendas de mixers. Ele disse que emprestou para uma banda de C&W que nunca devolveu. Ele nunca pagou por isso.

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/TwinChannel/micprecct.jpg

Saúde

Ian

PS Acabei de encontrar este documento sobre isso:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/TwinChannel/twinchannelassisy.pdf

Sir @ruffrecords, first of all I would like to say that I love the way you share your knowledge, thank you very much. I'm trying to open this link but it seems to be down, how could I access this and other of your schemes?
Many thanks

 

[ze marcelo]

Sir @ruffrecords, first of all I would like to say that I love the way you share your knowledge, thank you very much. I'm trying to open this link but it seems to be down, how could I access this and other of your schemes?
Many thanks

Sir @ruffrecords Sorry if I bother, I kept looking and found this link https://www.customtubeconsoles.com/diy

many thanks

 

[ruffrecords]

Sir @ruffrecords Sorry if I bother, I kept looking and found this link https://www.customtubeconsoles.com/diy

many thanks

No problem. The original link it to my old web site which unfortunately I can no longer access. As you have discovered all the documentation for my designs is now to be found on my new web site at:

https://www.customtubeconsoles.com/diy

but unfortunately what you are looking for is not available from there. Fortunately I have them backed up to my Google drive so here is the schematic of the mic pre:


Cheers

Ian

 

[ruffrecords]

An I just found the assembly instructions which includes schematics for the power supply and pics of the PCBs I made at the time but this is easy to build point to point.

Edit: and yes, you can use a 6SN7 instead of the 6CG7.

Cheers

Ian