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Spider Valve Mkii 212 Master Volume Issues

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Thanks for the tip! It's quite a drive from my place, but they supply a 2 year warranty on their services, that rocks!

 

"He would have to be an authorized service center to get access to the service manual."

 

I Googled it, found a few schematics. Not sure if those are the official technicians guides or anything of that order, but there are some hefty scheme's and algebra in them.

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certainly the master volume is a real pain in the neck but can be easily solved with a volume poti which is linked between the Pre amp out and Power Amp IN, basically allowing a more sensitive volume adjustment, see http://stinkfoot.se/archives/2159 I used a 100 k ohm log/Audio pot and it works great, makes the amp soo much more responsive. see also attached diagram

 

Hope it helps!

 

Juergen

www.juka-sound-craft.eu

Oh this one worked for me ... briliant idea ...

 

First I lowered channels volume but ... Few times I almost died dialing by mistake the mode knob which reverts to higher channel volumes ... bad bad bad !

Then I experimented with extra resistor connected between wiper of Master Volume Pot and Ground but it requires  opening and making changes inside the amp ... I've made it on a cable but still ... why to do it? It also reduces the highest gain unnecessary ... also bad !

 

Juergen proposition is most elegant and working !

 

Now I have an extra box with second volume pot (100k log as suggested) connected to pre-out and amp-in (send/return) permanently so my channels volume is now around 70 so the popping (while preset switching at low chan vol) issue is solved by this !

 

Juergen - great thanks !

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SV MkII with Shortboard, gigging regularly.  Same issue - channel volumes saved as low as possible (any lower and I get the channel-switch pop), and yet with master volume barely on, stage volume is difficult to manage.  The sound guy would say "your amp can come up a bit," and I'd tap it - couldn't even tell if it moved - and he'd say "WHOA, way too much!"  Now he says "OK, I need you to BREATHE on your amp volume."  LOL

 

I'm thinking about trying the Shortboard volume pedal as a workaround.  I never use it while playing - my feet are just not coordinated enough for wah (I've tried - hopeless) and the volume knob on the guitar is fine.  Maybe I could physically block the volume pedal at 50% permanently...?  Thoughts?

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I answered my own question last weekend... YES for the MkI SV, but NOT the MkII.  I forgot that the MkII amp/shortboard combo treats the pedal settings the same way it treats the knob positions - stored as software when you save a tone.  So regardless of the physical position of the volume pedal, as soon as I click to another preset, channel volume reverts to 100%.  Ouch.  Got a few dirty looks during sound check for that.

 

Now I'll have to investigate if changing ALL 40 of my saved tones' pedal preset info can do what I want, i.e., lower the volume of all 40 presets evenly.

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Just passing thru, but I thought I would mention that a few people have modified the SV Mark 2 by replacing the LINEAR master volume post with a LOG pot...LOG pots tame the ramp up...Using a LINEAR pot was a huge mistake in this amp...Another way to tame it is to jump the loop with a Buffer...an old BOSS EQ pedal can do this...You can then knock the preamp gain down and free up the Master a bit...

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With Log pots there's a risk of non-linear distortions creeping in at

certain gain levels on the gain curve. So be careful and aware.

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With Log pots there's a risk of non-linear distortions creeping in at

certain gain levels on the gain curve. So be careful and aware.

That is hilarious! Tube amplifiers are non-linear devices... :lol:

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True,... but the processor board isn't.

And need to operate tubes in the linear range of their characteristic curve,

so as to not get non-linear distortions. Like with any amplifier.

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tubes are non-linear...but that is a decent conflation... :lol: 

 

The choice to use a linear pot was an enormous mistake imo...It should have been a log pot...

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Might want to discuss that with Rheinhold Bogner, since he designed the tube amp section.

I forget his reasoning on that one, it was 10 years ago.

 

Yeah, log pot is more conducive to an audio curve, makes sense, at least in an all analog

tube amp. Not certain about the reasoning in a hybrid (analog/digital) amp like this.

 

The analog tube section and the digital processor section have to to play nice with one another,

and that might also be part of the reasoning behind it.

 

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A normal volume control has 3 pins:
1- To the source
2- The wiper to destination
3- To ground
 

 

 

Edited by psarkissian
Shock hazard on this circuit is dangerous.

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General rule of thumb,... keep your fingers out of the insides of these amps, the shock hazard is too great. These are potentially lethal voltages if they touch the wrong thing.

 

Even with the power off and AC un-plugged, 200V cap discharge into your hand hurts like hell.
If you get a shock with both hands on the chassis, it could be lethal.

 

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On a basic amp, the current travels from one pot to the other. I did not look at my Spider Valve to see if that's how these fancy DSP units are designed. But if it is, poor (melted) solder joint(s) on just one pot can cut out volume and cause many issues. 

 

You may not be able to see the melted solder connection with the human eye. I'd personally touch up the solder joints on all of the pot legs. These amps get HOT. If you do, ensure that the nuts holding the pots to the chassis face are tight. 

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