Gyraf G9 transformer

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

maxkriza

Well-known member
Joined
Sep 18, 2004
Messages
68
Location
uk

Hi there
I'm trying to build this preamp using parts I already have and would like to find a way of reducing the voltage from the transformer (250volts) to the required 220v. is this possible ? . also , my heater supply is 6.3AC ,is there a way to get 6.3DC supply out of that .
will appriciate any suggestions
thanks
max
 
6.3 volt AC will not give you 6.3 volt rectified and regulated DC. Somebody here already made a dual G9 but with AC heater and simple resistor/capacitor filtering of the HT voltage. So at least you know it will work. If you really want to use this trafo, then I would suggest AC heaters, but do the wiring off-board; don't use the PCB for this part but rather use separate wires that connect to the heaters and run as far away as possible from the PCB. The HT voltage will probably work fine, but increasing the value of the resistor after the rectifier is probably a good idea. Hopefully Jakob will stop by :wink:

On the other hand, why not build it using the transformers suggested? They are cheap, and that way it is easier for anyone who has built one here to help you troubleshoot. I think the chap who built a dual channel G9 using AC heaters and RC plate supplies did his point to point and was already good at that method of construction. AC heaters are tricky and for a preamp require very careful layout. Good luck with whichever direction you choose!

Bjorn
 
Thank you Bjorn for your reply . The G9 I'm building is a point to point version . I'm trying to make it as compact as I can so it can re used for my live setup . at the moment the heaters are 6.3AC , 2x470R between the transformer and bridge get me 250volts dc output , it all looks and measure fine. any idea about voltage chart for this project? am I supposed to see 82V on V1A cathode (pin3)?
thanks for your help
Max
 

Latest posts

Back
Top