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Post by robbieee on Aug 25, 2012 12:02:05 GMT -7
I’m using the 66 a lot as a pedal platform for events and function gigs. The dials are set to around noon with the amp on the edge of breakup. I’ve got a nice Keely TS and a Fuzz Head set to slightly push things. All excellent … until I kick in an Xotic BB pedal for solos. It’s set to push the front end more and gets a fair amount of distortion out of the amp. Sounds ok but the high notes (anything above E on the twelfth fret) are having their sustain cut short and the high frequencies sound a bit out-of-control and screechy.
Weirder still, with an airbrake keeping the volume down, the problem is not so bad but fully unleashed, the high notes just drop like flies. It doesn’t make sense to me and is rather embarrassing on gigs of late. (I’ve ruled out the cab and the BB for problems)
So, I’m gonna start with a different NOS rectifier (5AR4), get the thing tuned up and see what happens. If any of you more knowledgeable folk have any ideas before I re-valve the whole thing, I’d really appreciate your help.
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Post by prspastor on Aug 25, 2012 13:52:44 GMT -7
Hummmm, How old is your amp? I wouldn't think that a different rectifier would help with this problem, but I could be wrong.
I wonder if what you are hearing is compression from the BB adding gain to the signal? Any soundclips to help us identify the culprit?
You may want to try a different EF86 to see what happens.
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Post by robbieee on Aug 25, 2012 15:39:36 GMT -7
The amp is about five years old but not heavily gigged. I'll try and get some sound clips up very soon.
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Post by Deleted on Aug 25, 2012 23:30:39 GMT -7
Could just be a mismatched set of output tubes.
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Post by Deleted on Aug 26, 2012 0:21:06 GMT -7
Try replacing the Phase Inverter w/a new matched one. See if that helps.
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Post by prspastor on Aug 26, 2012 4:27:29 GMT -7
doc001 has given you some great advice... the phase inverter (preamp tube next to the KT-66 tubes) does see a lot of wear in any guitar amp. A Sovtek 12AX7LPS is the factory tube in this position, I think.
Does your amp have any hum when you turn it up to 11:00 with no guitar in it? If you have some hum, you might have a set of mismatched powertubes. They tend to drift over time as the tube ages.
Also, do you have any idea what your plate current is on your amp? You can measure it with a tool called a bias probe., if you have one. I'm wondering if the bias has drifted over time too and you are running too cold.
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Post by robbieee on Aug 26, 2012 6:49:41 GMT -7
The wife's out so I've quickly made loud recordings.
They're both recordings of a high E major scale through a Suhr bridge humbucker to click at 59bpm in 5/4 time, one note per bar (4/4 too short).
Clip one: The amp volume is set to 3 oclock and BB pedal not pushing the Route. Clip two: The amp volume is set to noon and BB pedal is pushing (volume 10 oclock)
Many thanks for your advice, see what you think...
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Post by robbieee on Aug 26, 2012 6:52:06 GMT -7
Clip two...
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Post by smolder on Aug 26, 2012 7:53:48 GMT -7
it sounds like a tube issue, most likely preamp.
That said, if you really want sustain out of a 66 try a 5U4 rectifier (and obviously re-bias)... it will lower the power output a bit, but add sustain and some compression.
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Post by prspastor on Aug 26, 2012 18:44:15 GMT -7
My guess in hearing that is a slightly microphonic EF86 preamp tube. The brake light helps because you are reducing the volume and this results in less microphony.
Change out the EF86 and see what happens.
I agree about increasing sustain with a 5U4 as smolder suggested - your Route can handle that rectifier beautifully and it is the stock tube now. Your notes will "bloom" on the Route more with the 5U4.
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Post by robbieee on Aug 31, 2012 12:29:55 GMT -7
I've now tried a new phase inverter valve and no difference.
I picked up a replacement EF86 yesterday before a classic/hard rock gig. The amp is perhaps a tad more sparkly but I'm still getting the same problem; certain notes at the top of the neck at high volume are dieing very quickly. Apart from that though, this amp was fab on this gig.
So it's two valves down, three to go. My gut feeling is to put a NOS rectifier in which I'll do soon. I'll be back!!
R
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Post by Deleted on Aug 31, 2012 14:31:15 GMT -7
Mismatched output tubes can give you dead spots on your fretboard. Go to Myles Rose's website: www.guitaramplifierblueprinting.com . You can find out that and a lot more about vacuum tubes there.
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Post by Deleted on Aug 31, 2012 14:32:15 GMT -7
Rectifiers are usually either good or bad. They either work or they don't.
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Post by robbieee on Sept 14, 2012 6:04:27 GMT -7
AMP FIXED I visited the most amazing amp techs today who found two things: 1) Bias was way out (serviced only two years ago???) 2) Power valves were no longer working together properly which was causing the sustain loss on certain high notes. (All explained perfectly on Myles Rose's website.) Also, since starting this thread, the power of this amp has gradually diminished. By the time it got to the bench today it was putting out 16 watts. So there you go. Thanks for all your kind help and advice. This forum is one more reason why I wouldn't switch from Dr Z. I'm a bit wiser and have resolved to get this amp serviced once a year. For any Brits reading, Essex Amp Repairs have proved fabulous and incredibly thorough. Cheers to us all, Robbie
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Post by prspastor on Sept 14, 2012 8:39:28 GMT -7
Robbie, Great to hear it all worked out well!
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Post by edoetsch on Oct 23, 2012 12:16:27 GMT -7
This post makes me really think my Route is highly likely to be badly biased or with tube problems. I run the amp in a TINY practice studio with the all knobs right around noon through a single 12" Celestion Heritage and always feel like turning up more. Most folks seem to think is amp is very loud, but I find all noon just enough to keep up with the drummer. I biases the amp myself with the Weber Bias Rite taweber.powweb.com/biasrite/br_page.htm with specs I picked up from ztalk. How much would I expect to pay to take the amp to a tech?
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Post by Deleted on Oct 23, 2012 19:51:48 GMT -7
edoetsh,
I haven't used a tech in years. New tubes, properly biased, will be like night and day. Figure the cost of the tubes and maybe a bench fee of $50. A rebias is so simple it shouldn't be that costly. You might want to consider sending your amp to DRZ. They check voltages and make sure everything is working properly.
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