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Spider Valve HD100 mkI turn master no change in volume

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Hi,

 

Preface:

I kind of browsed the forum but couldn't find anything matching my problem. I bought a Spider Valve HD100 Mk1 to use while my main amp is being serviced. The seller went through the paces with the amp and informed me the master volume didn't work. being as it was super loud and controllable through channel volume I still bought it. I plan on keeping it as a backup so id like to see if  I can fix this issue.
 

Issue:
Master Volume sounds to be at about 7 id say compared to other 100 watt amps ive used. I can turn the knob from 0 - 10 and no change in volume, no static, zero response. The volume can be controlled by the channel volume but switching presets will blow ears out if not careful. Could this be remedied by a simple pot change or could it be something more. Looking on suggestions on troubleshooting the circuit maybe? I have some electronics experience so I know about high voltages etc going into the amp. 

Thanks

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1) What are the brand and numbers of the tubes?

 

2) Are the speakers connected to the correct outputs for the speakers being used?

They have to be impedance matched.

 

3) Are you using proper speaker cable and not guitar cable to connect the speakers?

That also goes to impedance matching issues.

 

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1. The amp is not with me, I do remember they are ruby 6l6 tubes on output, 12ax7s are unknown brand at this time, I was told it was freshly tubed and biased about a month ago. 


 2 & 3: the cab is 16 ohm and a speaker cable is in the 16 ohm tap. the amp sounds good its just the master volume does nothing. the channel volume controls the volume on active setting. 

 

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Power tubes should be Sovtek 5881WXT, not Ruby 6L6. The standard spec biasing won't work with these

tubes in this amp. The characteristic curves are close, but not close enough, so using our standard biasing

will throw things off.

 

These aren't the all analog amps of the 1960's, the digital board and analog sections need to talk to play nice

with each other, not using specified parts has an affect.

 

Check my post here on this subject,....

 

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ill double check on the actual tube number tonight. I know its hard to say without the amp in front of you,  but in your opinion, if they are 6l6 could components in the amp be damaged or could replacing the 6l6 with sovtek 5881s remedy the problem?

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Not my opinion, my experience and being an old guy who's been dealing with tubes a long time.

Dealt with Spider Valve from its beginning. Dealing with tube gear in general since I was a teen.

 

Have the 5881WXT match quartet installed and biased by a Line 6 authorized service center with

the correct info. 12AX7B China or 12AX7EH is fine.

 

 

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I meant in your opinion is it possible the difference between 6l6 and 5881 tubes can physically damage the internal components of the amp or if I put sovtek 5881 tubes as suggested the master volume should work?

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Yes. It does cause problems with internal circuitry if let go for too long.

Have had several on my bench in the past.

  • Thanks 1

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