Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on October 19, 2022, 10:28:27 pm

Title: Relay capability
Post by: joesatch on October 19, 2022, 10:28:27 pm
Can i use a relay to pass ground to some cathode bypass caps on the preamp stage?  Also if the ground on the relay is fed with another relay is this an issue? anyone used relays like this?
Title: Re: Relay capability
Post by: Latole on October 20, 2022, 03:13:46 am
You may hear some "pop" when switching contact
Loud or not ?
Title: Re: Relay capability
Post by: joesatch on October 20, 2022, 06:47:16 am
havent tried yet. If so, how to eliminate the pop?
Title: Re: Relay capability
Post by: shooter on October 20, 2022, 07:11:47 am
when you remove ground the un-grounded leg "floats" to the DC voltage on the other leg.  Re-grounding the floating leg will generate a "spark", maybe not visibly, or with a crack sound, but you will see a transient spike on a scope.


Needs verified, I believe if you "add a cap to an existing cap" by adding the ground, (doubling the capacitance), it will less'n the spike, maybe to inaudible levels?
Title: Re: Relay capability
Post by: PRR on October 20, 2022, 05:00:42 pm
A relay is just a switch. Your finger is replaced by an electromagnet. Anything a switch can do, a relay can do. What is the worry?

The pop is a different unasked question.
Title: Re: Relay capability
Post by: joesatch on October 21, 2022, 02:19:18 pm
Quote from: PRR on October 20, 2022, 05:00:42 pm
A relay is just a switch. Your finger is replaced by an electromagnet. Anything a switch can do, a relay can do. What is the worry?

The pop is a different unasked question.

I worry about alot which is why i've never blown anything up or had catastrophic results on anything i've tried. I research things to death before i try them.  :l2:
Title: Re: Relay capability
Post by: sluckey on October 21, 2022, 04:18:46 pm
Quote from: joesatch on October 21, 2022, 02:19:18 pm
I worry about alot which is why i've never blown anything up or had catastrophic results on anything i've tried. I research things to death before i try them.  :l2:
You're missing a lot of fun!    :l2:
Title: Re: Relay capability
Post by: shooter on October 21, 2022, 05:46:30 pm
yep, nothing like the smell of smoking 'tronics in the late night  :laugh:
once you figure out what makes stuff blow up, make a note, move on to the next thing you're not too sure about, but will'n to try  :icon_biggrin:
Title: Re: Relay capability
Post by: acheld on October 21, 2022, 08:48:06 pm
Yah, research is completely overrated.
Title: Re: Relay capability
Post by: Willabe on October 21, 2022, 08:53:58 pm
Quote from: acheld on October 21, 2022, 08:48:06 pm
Yah, research is completely overrated.

     :laugh:
Title: Re: Relay capability
Post by: JPK on October 21, 2022, 09:16:57 pm
Ask Mesa about using relays. They love them. I had plenty in my 50 watt DC-5. It was the only warranty issue I had.


The 1 watt build I have a thread about here uses a little relay for channel switching. It uses heater voltage for the power supply on the board it's on. The board rectifies it to 5VDC. I'll attach the cut sheet here. Maybe you can use a variation of it. It's working just fine in my amp but they designed some filtering to keep the pop sounds out. The channel switching is dead silent.