Popping again.....Cap across channel switch?

[FUCHSAUDIO]

Diode and capacitor across the relay coil, very important.

Make sure any signal capacitors NOT being loaded have a small resistor on them (1-M, 2-M, 4.7-M) to ground.

Put a 22-M across the relay contacts as well. If you need a diagram, send me an e-mail. Assuming nothing is oscillating or unstable, you should acheive silent switching with the right tweaks.

Our amps all channel switch virtually silent, using DPDT standard dip socket relays. And (BTW) the brand of relay can also matter. Some relays are noisier than others. We use Panasonics mostly, as they seem to have the smallest coil induced noise, and run at lowest currents. This is why putting them in a socket makes switching to different brands and types easier.

[ayan]

Diode and capacitor across the relay coil, very important.

Make sure any signal capacitors NOT being loaded have a small resistor on them (1-M, 2-M, 4.7-M) to ground.

Andy, evidently success changes people... You've made it big to where you even think of a 4.7Meg resistor as small now!

Gil

[pedro]

Thanks Bob, tried a 1M - didnt cure it.

I'm beginning to think its because of how I have approached this switching....

I have used 2 discrete DPST relays working in tandem - both fed from same supply - one relay taking care of 3 contacts - i.e. one 1/2 of a normal DPDT relay - and the other taking care of the other 3 contacts.
I'm wondering if its something to do with them not exactly firing across instantaneously ?

As i said before when I rewire to the Hybrid A type relay wiring everything is just fine.

Maybe I sould try a DPDT discrete relay and see what gives - pain though.. I epoxied the 2 discrete relays to the amp chassis in just the right place next to the preamp board and cant remove them without doing damage !!


Hmm.......

any relay techno wizards out there who can deduce the problem ?
Pedro

[pedro]

Fuchs - !!
thanks - I posted simultaneously without seeing your suggestions.

Funny how the wizards appear by magic....

I'll try all that..
cheers
Pedro

[pedro]

1 question Andy...

I do have diode across relay coil - but what Cap to use and is this in parallel with diode ?

Pedro.

PS : trying new DPDT Goodsky 5V relay.

cheers

[groovtubin]

stuck a .1uf 450v across the panel switch which switches the DC supply in and out - and still same problem.

Is it something going on with the signal not the supply ?

This has me stumped - does anyne else have ame popping issues - I think someone reported same problem for a few other builders - Tommy maybe ?

I think I will go back to overall Master and sep clean and OD levels feeding the Master. Frustrating...............Oh Well...........

Pedro

Pedro, e-mail me, i have a scheme, that just may work for you... Omegaamps@wilkes.net, jim

[ayan]

1 question Andy...

I do have diode across relay coil - but what Cap to use and is this in parallel with diode ?

Pedro.

PS : trying new DPDT Goodsky 5V relay.

cheers

Pedro, the reverse biased diode is in parallel with the coil. The capacitor, which can be a .01 or .02 uF (disc or otherwise) will be across the SWITCH you use to close the circuit that energizes the coil. So no, not in parallel with the coil, but in series with it as it were. [ I am not sure why Andy stated "diode and capacitor" across the coil, maybe he has other ideas... However, a cap across a conductive non switching element in a DC circuit will not accomplish anything. ]

Gil

[pedro]

thanks Gil,
as I thought.....

but tried that - cap across switch used to supply the DC ( series ) and reverse biased diode across the coil - and failed.

BTW : been reading some of your old posts etc and very glad to see you here contributing.
- found your "lead dress" article many moons ago and now I see where it came from !
All wisdom greatfully received. There arent many fellow amp building dumbophiles across here in the UK !

would love to hear some of your stuff - any links ?

cheers
Pedro

[ayan]

thanks Gil,
as I thought.....

but tried that - cap across switch used to supply the DC ( series ) and reverse biased diode across the coil - and failed.

BTW : been reading some of your old posts etc and very glad to see you here contributing.
- found your "lead dress" article many moons ago and now I see where it came from !
All wisdom greatfully received. There arent many fellow amp building dumbophiles across here in the UK !

would love to hear some of your stuff - any links ?

cheers
Pedro

Pedro,

Nos sure why you're getting the popping noise, but if you hung a large resistor (10 Meg) to ground from the input of the PI (piece of cake, you can do it at the RETURN jack, provided you have a "signal interrupt" FX loop in the amp) you shouldn't get a noise. Popping noises are often caused by switching of a capacitor that's not referenced to DC ground at all times. If you do the switching like in the 90s amps, the input to the PI switches from the output of the clean master volume control to the output of the OD master, and maybe that's enough time for the PI input cap to build some charge on it. Try and see what happens, if you haven't already.

As for "my stuff," well, I have a very old website here:

http://home.earthlink.net/~ayan/

where there are a couple of clips, and my band's website is here:

http://www.doctorwuband.com/music/music.htm

and we have some video clips there.

Cheers,

Gil

[pedro]

Update -
tried all sorts of things to cure the pop on channel switching.
10M resistors to ground on "floating" cap points, 10M to ground on PI input cap etc etc.

Now I'm wondering if its just the type of mechanical relays Ive used.

I just saw this posting from funk on the Hoffman forum from a while ago and wondered if its just because Ive used large mechanical relays that I have an issue.

I have a nice small 5V DPDT relay I will try. But do you think its because i am trying to use relays with beefy coils etc

I've also used the larger mechanical relays with solder lugs ala Silver chassis Dumble amps-Nothing will make them Not "pop" But with a band behind you no one will notice.....

Question - do the large relays on the original Dumbles cause a pop ??

Some observations for you :

1) loudness of click doesnt change with different levels of either clean or OD master vols.

2) with all controls fully down click is still there - at same level.

3) with V1 and V2 removed click is still there

4) with status LED run from relay DC supply disconnected pop is still there.

5) BUT with PI tube removed click is gone.

6) With PI input cap connected to ground through 10M resistor pop is still there.

Drivin me crazy.......and stopping me playing those min7b5 arpeggios !!!

any wise words very welcome. Sorry to be a bore on this subject now.

Pedro

[Tdale]

Have you tried Groovetubin/Jim's circuit?

Tommy

[jblues]

relays make noise optocouplers don't...fender soldano and boogie all use optocouplers the soldano lead 100 has a nice setup for 2 master volumes if i recall.... the optocouplers are always Vactec VTL5C1 and hey you can use the 6.3 volt supply to run them ...look at the slo 100 watt soldano at blue guitar. they are expensive though so now you know why ppl use relays...like 15$ each optocoupler.

[ayan]

relays make noise optocouplers don't...fender soldano and boogie all use optocouplers the soldano lead 100 has a nice setup for 2 master volumes if i recall.... the optocouplers are always Vactec VTL5C1 and hey you can use the 6.3 volt supply to run them ...look at the slo 100 watt soldano at blue guitar. they are expensive though so now you know why ppl use relays...like 15$ each optocoupler.

As per my own experience, I'll qualify that by saying that relays can make noise. Octocouplers (LDRs) are not without their quirks: they respond much slower than a relay, and they are not a transparent device (so much for an "all tube signal path" the minute you stick a solid state switch in there ).

A but of trivia: Boogie used relays in the Mark IIAs and IIBs, but their implementation resulted in noisey channel switching. By the time the Mark IIC came around, Boogie went for the last Fender idea it hadn't swiped yet and started using an opto-coupler (which Fender had used in their tremolo circuits) in the Mark IIC. However, years later in the Mark III, they used a relay for the the "Rhythm 1" to "Rhythm 2" switching.

Soldano, as the story according to his own word goes, bought a Mark XX Boogie to analyze it and see what would be desireable to change in it. He certainly changed a lot, but he used the LDR switching that Boogie had been toying with since the IIC.

Cheers,

Gil

[mlp-mx6]

Fender also used LDR switching in the Rivera-era amps(early 80's). I have a Princeton Reverb II and Concert from that era - stock LDR switching. That may be where Mr. Smith got it from - or at least the idea of it. (pretty sure the Fenders came out before the IIC)

[ayan]

Fender also used LDR switching in the Rivera-era amps(early 80's). I have a Princeton Reverb II and Concert from that era - stock LDR switching. That may be where Mr. Smith got it from - or at least the idea of it. (pretty sure the Fenders came out before the IIC)

Actually, Rivera used to be associated with Boogie before he took the gig with Fender in the early 80s. Also, the first channel switching Boogie dates from 1978, and the "new" Fenders came out a couple of years later. If anything, Rivera took the idea to Fender and if you think about it, those early 80s Fenders were "poor men's Boogies" in many ways.

Cheers,

Gil