G-Pultec Trafo-less, is it possible?

[Xab13r]

Hi guys,

I have to say I'm pretty newbie on tubes and transformers.

I'd like to know if there are any chances to build a Gyraf Pultec PEQ1A (using the SRPP tube stage) without the output trafo because I really don't need a balanced out.

Thanks in advance.

 

[ruffrecords]

Basically, yes. The transformer is ac coupled so you can just put a 100K resistor in its place to make sure the output capacitor gets charged up at power up and take the output across the resistor. You need to be aware that the drive capability will be reduced but as long as you load it only with 10K bridging inputs it will be fine. You will also have an extra 6dB of gain because the transformer had a 6dB loss. You can either leave this as it is or add a pre-set pot at the grid of the SRPP stage to allow the overall gain to be adjusted to unity.

Cheers

Ian

 

[Xab13r]

Thanks a lot!! It's been really helpful.
I suppose I could port the same design on the MEQ5 (gyraf schematics). Always paying attention on input impedance.

 

[rafafredd]

Most inputs today are 10k or more.

Just don't try to drive an old 1176, some older vari mu compressors or other passive EQs. These are generally 600ohms inputs.