Dumble relays....general explanation...story?

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jaysg
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Dumble relays....general explanation...story?

Post by jaysg »

Judging by the many threads on relays, I have the sense that his design is a bit odd or underpowered. I'd like to understand why before ordering parts.

1) It appears that some original amps use a 6V or 6.3Vac Radio Shack transformer with a voltage doubler, and an LM7812. Then he uses 5/6V relays instead of 12V parts. I don't understand why, unless the relay supply sags badly.

2) It appears that some amps use a 12V or 12.6V Radio Shack transformer and skip the doubler circuit...yes/no?

3) Are these circuits always 12Vdc with lower voltage relays?

4) Is there a true "standard" design?

5) What happens when you add an extra relay? This would be for the Mid-boost switch in my case.

I would add a protection diode for the regulator, fwiw.
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David Root
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Re: Dumble relays....general explanation...story?

Post by David Root »

1) I don't recall seeing anything other than 12V relays with the 6V3/doubler circuit.

2) Yes. I prefer this as the doubler circuit reduces your DC current to 28% of the transformer's AC capability.

3) No. 12V PS w/12V relays. Relays of this type will work over a wide range of voltages above and below nominal.

4) My standard has been 12V PS, 12V Relays, but I am going to try 5V in a bought out powered PC board, which looks better and is less work. Most people use 12V or 5V, but there is no cast-in-bronze "standard" that I'm aware of.
We're sort of like economists in that if you ask three of us for our opinion you'll likely get five different answers!

5) The wiring gets a bit more complex, especially in the footswitch. You may have to check your current draw if you use the doubler cct., see 2) above, with older relays that can be much higher current draw than newer ones.
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Luthierwnc
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Re: Dumble relays....general explanation...story?

Post by Luthierwnc »

I'd also add that you get the draw of the LEDs. I've put three relays in a couple of amps with LEDs on the footswitch using the 12v non-doubler (and a 7812 regulator) set-up and never had a problem.

One thing I do a little different than some of the guys here is I Liquid Nail a high-quality terminal strip in the footswitch and attach little 500R trimmers (as variable resistors) in parallel with the LEDs. Two reasons: one is that if the LED croaks, the switch still works and the other is to adjust the brightness of the different colored lamps.

sh
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jaysg
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Re: Dumble relays....general explanation...story?

Post by jaysg »

This is good. I only have clear shots of 124 and 234. I was misled by some of the discussions which were about what people did in their builds.

Guess I'll have to look at the footswitch design too.
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heisthl
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Re: Dumble relays....general explanation...story?

Post by heisthl »

You guys work way to hard at this, if you have a rectifier tap available or a 6 volt transformer just run it though a full wave bridge and stick a filter cap on it. works great with up to 6 5V relays (mouser 655-V23105A5301A201) and is extremely reliable and quiet. Bonus, easy way to get a pilot light at the same time
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talbany
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Re: Dumble relays....general explanation...story?

Post by talbany »

I agree.. pass on the voltage doubler.. We go w/ seperate 6v transformer or a tap off the power transformer..6v relays full wave bridge for low noise 1000uf filter give it it's own ground potential.. Regulator optional..Works great very reliable and is dead quiet.. You can do it all right on a tag strip...Have a nice day..
Tony
" The psychics on my bench is the same as Dumble'"
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heisthl
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Re: Dumble relays....general explanation...story?

Post by heisthl »

talbany wrote:I agree.. pass on the voltage doubler.. We go w/ seperate 6v transformer or a tap off the power transformer..6v relays full wave bridge for low noise 1000uf filter give it it's own ground potential.. Regulator optional..Works great very reliable and is dead quiet.. You can do it all right on a tag strip...Have a nice day..
Tony
Just use the same ground as the main B+, isolating the ground seems to add noise.
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paulster
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Re: Dumble relays....general explanation...story?

Post by paulster »

heisthl wrote:Just use the same ground as the main B+, isolating the ground seems to add noise.
That's been my experience too. Treat relay power like filament power. If it doesn't have a common reference then you'll get noise.
talbany
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Re: Dumble relays....general explanation...story?

Post by talbany »

I am not really interested is starting a big discussion on how to properly ground your relays.. That's just silly and I am sure your guy's amps are nice and quiet..However by definition Dumble isolates his relay supply and I and many others here who use that 124 layout I did find it to be the quietest one for this design..If you think other wise that's fine then we agree to disagree.. Just saying it won't always introduce noise that's all..

Tony
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Structo
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Re: Dumble relays....general explanation...story?

Post by Structo »

I wonder why HAD used two red positive wires to the relays?
I just ran one and then jumped it to the other relays.
Tom

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David Root
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Re: Dumble relays....general explanation...story?

Post by David Root »

I wondered about that too. Mine has three relays, so six leads.
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guitardude57
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Re: Dumble relays....general explanation...story?

Post by guitardude57 »

I've read that when using a 6-0-6 xfmr, use the 2 secondaries but not the ground tap.

If this is the case do you ground the back of the bridge, and filter caps together for reference?

Not having installed relays in an amp before, I want to understand ground relationship with the actual switching function .........not getting disrupted.
Mike


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David Root
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Re: Dumble relays....general explanation...story?

Post by David Root »

Yes you put the ground reference on the DC side.
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Re: Dumble relays....general explanation...story?

Post by guitardude57 »

OK, that's what I thought. So when switching the functions, you basically are completing the ground for the relay to actuate.

So if one were to use a TRS for footswitch jack(2 relay set up), then this has to be isolated from the ground. Correct?
I have an old MB Subway Rocket footswitch I would like to use.

Or for just one switch function/relay, just use the Tip and Ring for switching and use a grounded Sleeve (switchcraft jack) without problems. Is this also correct? Thanks, Mike
Mike


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Structo
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Re: Dumble relays....general explanation...story?

Post by Structo »

I used a TRS jack before I went with a 5 pin DIN and did not isolate the ground.
I grounded the jack then used the tip and ring for the two relays.

A DIN connector works a lot better because you can run a separate B+ out to the pedal to power the LED's.
That prevents loading down the relays with the additional current demand.
That being said, I had no problem powering two relays and two LED's with the TRS type.
Tom

Don't let that smoke out!
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