Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BrainDeadAmps on January 03, 2022, 09:21:30 am

Title: Relay install
Post by: BrainDeadAmps on January 03, 2022, 09:21:30 am

After reading what I could find on the amp forum, I understand the fail-safe method is to float the Hoffman Relay PS common whether or not you have your CT referenced to ground.

My amp does not have the 6.3v CT connected directly to ground. I have an artificially elevated 6.3v ct with two 100R resistors connected to the cathode of one of the power tube sockets.

This amp also has a bias-vary tremolo wiggling the grids of the power tubes. I do not really have room in the chassis for another relay board to control the tremolo F/S and hadn't planned on it, considering it is not connected to the audio path.

Would their be an issue referencing the relay PS to chassis ground? in order to use a - 1/4" stereo jack - for the footswich connector. Allowing me have both the tremolo on/off (Tip) and OD relay (Ring) switched running through the same jack, thus sharing the ground (sleeve).

This is the answer I've come up with in order to control both of these switches externally combining one relay and one non-relay, but perhaps there is another way to think about it while still utilizing a 1/4" jack?

Your thoughts would be greatly appreciated.

Title: Re: Relay install
Post by: sluckey on January 03, 2022, 09:36:54 am

Elevating the heater circuit to the power tube cathodes makes it even more important to float your relay control circuit.

DO NOT CONNECT ANY PART OF THE RELAY CONTROL CIRCUIT TO CHASSIS GROUND! This includes the FS jack. I suggest you use a Cliff style stereo jack that naturally has the sleeve isolated from chassis. Like this...

(https://hoffmanamps.com/MyStore/catalog/images/IMG_2287.jpg)

Title: Re: Relay install
Post by: BrainDeadAmps on January 03, 2022, 09:56:11 am

Sluckey thank you for the reply.

My issue still remains of combining both switches to one stereo jack.

One relay, one non-relay

With the floating relay common connected to the sleeve of jack. I no longer can ground the tremolo?

Title: Re: Relay install
Post by: sluckey on January 03, 2022, 10:37:31 am

Such a quandary.

Title: Re: Relay install
Post by: BrainDeadAmps on January 03, 2022, 11:05:29 am

So, the short answer is to either use Two seperate jacks or use a 5-pin din connector instead of 1/4” jacks?

Title: Re: Relay install
Post by: sluckey on January 03, 2022, 11:53:59 am

Quote from: BrainDeadAmps on January 03, 2022, 11:05:29 am

5-pin din connector instead of 1/4” jacks?

:thumbsup:

Title: Re: Relay install
Post by: BrainDeadAmps on January 03, 2022, 02:50:43 pm

Thank you very much Sluckey, will give the din connector a go.