DRRI question...........

paultelestrat

paultelestrat

New member
i have a 2005 DRRI . i'm getting some static/interference type noise. i know it's not the cable 'cause it does it without the cable plugged in.NOW..... if i tap on one of the power(??) tubes #6v6, i can hear the tapping through the speaker . this means the tube is "microphonic" right??? are these amps "fixed" bias or do i need to have them rebiased by a tech? and ....are there any "better" brands of tubes to chose from?? thanks in advance.
 
Re: DRRI question...........

You will usually hear the tapping through the amp, the tap test is used for pre-amp tubes (12AX7s, 12AT7s, etc.)
Power amps tubes can display strange colors or be dark and/or make the static noises or pops you are hearing. From what you describe it sounds like the power tubes, but tap test the pre-amp tubes just to be sure. You will know when you tap a bad pre-amp tube. You would usually order a full set of matched power tubes if that is the case. Fixed bias amps are usually biased cold for reliablity, so tubes are plug and play - no tech needed.

For tubes, a great brand are JJs (JJ/Tesla)
E-mail Bob at Eurotubes.com, he will square you away.
 
Re: DRRI question...........

Tap the preamp tubes. When they go microphonic, they'll often start to add a bit of extra noise you don't want. I've had amps where I took out a preamp tube, put it back in later that day and I guess my handling of the tube caused something to loosen up inside and it get noisy. Doesn't happen that often, but it can happen.

Have you recently changed anything in your environment? New location in the house? Added some florescent lighting nearby? Anything changed?
 
Re: DRRI question...........

cathode bias is actually non-adjustable - with a cathode biased amp just pop the tubes in, measure the voltage to make sure you arent gonna blow them up and go. some tubes will sound better than others so it might be worth your wile to try a few sets if you have the chance to do so.

fixed bias is adjustable - usually there is a pot inside the chassis that is used to adjust it. your amp falls into this catagory. fender dr tend to run their 6V6's really hot. i believe that the 6v6 was designed to handle 360v and lots of dr's run at over 425v, my '66 was running at 445v! jj's are a good choice for these amps since they can handle the voltage. you could pop your tubes in and it should work fine but re-biasing will make the amps sound way better and feel more responsive
 
Re: DRRI question...........

That is some pretty high voltage for a modern amp...

Just a note, even fixed bias with a trim pot will still bias cold on most modern amps when all the way up (with most 6L6s, not sure on 6V6 - the same amp will bias a little warmer with EL34s if capable) That Fender sounds like an odd duck for current production models
 
Re: DRRI question...........

i dont think thats all that high, my jcm 800 was running around 500v

my knowledge is of real dr's not the ri's so there may be some differences, i havent biased a ri recently but i imagine that they still have to run over 400v. lower voltages tend to brown out the sound
 
Re: DRRI question...........

scott f(quote)
Have you recently changed anything in your environment? New location in the house? Added some florescent lighting nearby? Anything changed?

not really.i don't think the wiring in my apartment is that great.i say this because even my les pauls buzz/hum without my hands touching the guitar and as soon as i do touch the guitar the buzz/humm goes away,like a strat would(60 cycle hum?)
 
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