I built this as an experiment and I loved it so much I’m building myself a dual mono version in a larger chassis.
- 3 balanced inputs and one balanced output
- Pin 1 is attached to audio ground so you can use xlr adapters for single ended inputs and outputs (attaching pin 1 to the chassis adds hum to the single ended inputs and headphone jack)
- RK27 Alps 4 gang pot
- Grayhill Selector switch
- balanced headphone output
- Single ended headphone output
- VRDN PSU set up for wall wart
- AC-AC Triad Wall Wart
Attachments
interesting. a couple of questions:
for dual mono it seems you just need to double up/ separate power supplies. why not pull out the VRDN, use separate regulators for each channel -- maybe super regulators... they should fit -- and do a remote two-transformer PSU?
I've been struggling with how to combine balanced and unbalanced connections for input and output. I've been thinking switching grounds as well as signal. Would that work? Are you using single-ended outputs too?
Whats the switch beside the power connector for?
for dual mono it seems you just need to double up/ separate power supplies. why not pull out the VRDN, use separate regulators for each channel -- maybe super regulators... they should fit -- and do a remote two-transformer PSU?
I've been struggling with how to combine balanced and unbalanced connections for input and output. I've been thinking switching grounds as well as signal. Would that work? Are you using single-ended outputs too?
Whats the switch beside the power connector for?
Last edited:
Yea. I had two matching VRDN boards plus two more Wayne’s boards so I decided to use them. My other build will use transformers with the VRDN boards and I have a Goldpoint volume attenuator.
I’ve played around some building balanced preamps and at first I connected Pin 1 to audio ground but read the Pin 1 problem article and switched my main system Balanced BA3 with F4 monoblocks to have all pin 1 to chassis. My Rel subs did not like that and they both hummed really bad and I couldn’t find a solution. I wired it all back with pin 1 to audio ground and the hum went away. Both ways I did it the speakers were dead quiet so I left it to audio ground.
I’ve read a lot of threads here where the feedback is 50/50 on Pin 1 to ground vs chassis. I think it depends on if you use SE inputs and outputs or not and the rest of the setup. I’ve built a preamp with three inputs and the 3rd input has a pair of rca connectors that have the inner barrel hooked to Pin 2 and the outside of the rca to pin one. A couple jumpers may or may not be needed to tie pin 1 and 3 together in the xlr female.
I think the switches may work that connect audio ground to the xlr Pin 1 for single ended. Maybe the switch either toggles pin 1 to chassis or toggles it to ground. I’ll try this on my new build and see.
I’ve played around some building balanced preamps and at first I connected Pin 1 to audio ground but read the Pin 1 problem article and switched my main system Balanced BA3 with F4 monoblocks to have all pin 1 to chassis. My Rel subs did not like that and they both hummed really bad and I couldn’t find a solution. I wired it all back with pin 1 to audio ground and the hum went away. Both ways I did it the speakers were dead quiet so I left it to audio ground.
I’ve read a lot of threads here where the feedback is 50/50 on Pin 1 to ground vs chassis. I think it depends on if you use SE inputs and outputs or not and the rest of the setup. I’ve built a preamp with three inputs and the 3rd input has a pair of rca connectors that have the inner barrel hooked to Pin 2 and the outside of the rca to pin one. A couple jumpers may or may not be needed to tie pin 1 and 3 together in the xlr female.
I think the switches may work that connect audio ground to the xlr Pin 1 for single ended. Maybe the switch either toggles pin 1 to chassis or toggles it to ground. I’ll try this on my new build and see.