Question:
Guitar Center had a used one for a good price. I went in there to try out a Blues Jr. but this was cheaper and better sounding. All but one of the 5 tubes have been replaced. It has a pair of Electroharmonix 6L6 power tubes. Two JJ ECC833s and one Groove Tubes 12AX7F-2 (original). I haven't looked at specs yet, but I'm guessing the Groove Tubes drives the reverb. Anyway, I compared it to a brand new one with all factory tubes, and this one sounded better and cost less.
I love the clean tone. A pair of 6L6s is one of my favorite sounds ever. Just a tiny bit of reverb and this thing makes my randal SS sound like a piece of poop (and it's a decent sounding SS amps). The 1st of 2 distortion channels is also pretty good.
However, I did discover one problem once I got it home: The high gain channel squeals really bad when I crank the drive even with a relatively low setting on the master volume. But it goes away almost completely if I roll off the presence control. Is this normal? If not, what can I do to fix it?
I doubt I'll get much use out of the high gain channel on it anyway, but if this is a sign of a serious problem, I have 30 days to take it back.
Answer:
The squeal probably means a microphonic preamp tube, or possibly pickup, if you didn't unplug your guitar. Turning up the presence control accentuates the high-frequencies, which helps the tube to resonate microphonically to a particular high frequency. Take a pencil, and tap the tubes at a point before they get microphonic to see which is causing the issue.
Answer:
you'll be disappointed (maybe) to hear that the reverb is SS driven, not tube driven.
as far as the squeal goes...what kind of guitar are you using through it...and what are your EQ settings? I'd try tweaking those around, though my first instinct was "microphonic pre-amp tube".
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Aye, I envy you. That is a great amp.
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Originally Posted by Rainer. The squeal probably means a microphonic preamp tube, or possibly pickup, if you didn't unplug your guitar. Turning up the presence control accentuates the high-frequencies, which helps the tube to resonate microphonically to a particular high frequency. Take a pencil, and tap the tubes at a point before they get microphonic to see which is causing the issue.
Microphonic pickups was my first thought... it's a relatively new guitar, but the pickups are cheap. Sometimes I get microphonic squeal when I'm trying to get string vibrating feedback. But I unplugged the input chord completely and it still did it.
Could you elaborate on this pencil tapping test? This is the first tube amp I've ever owned, so I'm new to trouble-shooting them. If it is a microphonic tube, do you think GC would replace it even though it's used?
And I'm probably getting ahead of myself not knowing for sure what the problem is, but does anyone have any recomendations for replacement tubes if GC won't replace them? Like I said, what's in it sounds better to me than all GrooveTubes, but I don't know if it's because of the EH's or the JJs or the combination. About all I know about replacement tubes is that Sovteks are cheap and Telefunkens are the holy grail.
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Turn your amp on without plugging a guitar in, then turn on your drive channel, keep the drive a few notches under where it starts to feedback, and turn the volume up decently, not too loud. Take a pencil eraser, and tap each preamp tube. If one noticibly amplifies the tap more than the others, or the tap drives the amp into feedback, then you've found the microphonic tube.
I don't think that GC would replace it, you chould try. It's a bit like strings on a guitar.
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I used to have GTs (12ax7s) in my HRDlx and now I have JJs (ecc83)...I honestly can't tell the difference between the two.
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Its probably a tube causing that problem, my guess would be one of the 3 12AX7 preamp tubes. Little microphonicities and other tube idiosyncracies really manifest themselves with high gain. You should have a spare 12AX7 anyway, you can get 'em for 12 bux or so - buy one and swap it out in each position - if the problem goes away, that's the one...
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I have a Hot Rod Deluxe, and the squealing on that channel is normal. I've replaced the tubes several times in my amp, and it always does that. The third channel sounds like garbage anyways, so it's not really a big deal for me.
Also, if you get the opertunity, try the amp through a different speaker cab. It'll sound 10x better. I had a 1x12 cab made for me with a Celestion speaker that I run through most of the time.
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I've got a HRD as well. I'm with guitargeek, the "more gain" channel sounds fizzy and bad to me. I've never had it squeal, though. Maybe I haven't turned it up loud enough...
-Nick
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I have the almost-the-same HR DeVille 4x10. I never turn the gain up high, so I have never experienced that. It could just be a quirk of the amp; an oscillation that occurs under certain conditions/settings. What are you feeding into it? Just the guitar? What kind of pickups? pedals?
Try this for a "fix" Put a lower gain tube in V2 (the middle preamp tube) like a 12AY7 or 12AT7. That amp's high gain channel is too saturated IMO at low gain settings, and the master volume is mostly pegged at about 4 (and it goes to 12 !), even with a modest input level. IMO, that's a design flaw. The lower gain tube lowers the saturation, but there's still plenty of distortion on tap, at least for the non-metal crowd, and it extends the range of the master volume so that its less touchy trying to dial it in; it goes a long way toward fixing that inherent design problem. Everyone that I've recommended that "mod" to so far has liked it. The slightly lower overall gain may make that squealing disappear. In any case, give that a try, its only 12 bux or so.
One other thing - tube amps are very sensitive to the level of signal you feed into the input. The higher the signal level, the more saturated it wil be in the early stages, which of course affects the later stages. You may prefer feeding it with a hot level, but the downside might be something like a squealing oscillation...?.... Any amp is going to have a practical limit to the amount of overall gain, especially ones like the HR series which were not intended as mega-distortion amps. Crossing the limit of that threshold would probably result in squealy oscillation. Personally, with most amps I like to give it a signal about the level of a stock fender tele or strat. When I use humbucker equipped guitars, I cut the signal level with an active device - like the output level of a multiFX or buffering pedal like an EQ. Try cutting your signal in front of the input if its a humbucker or other hot signal.
OK, while I'm here.... The presence control is different than a "regular" eq knob, it affects the negative feedback loop (NFB), which changes the character of the distortion and even the clean channel. It also adds some gain. I prefer to keep the presence all or mostly up, and then control the highs with the treble control. A hidden gain control in your amp - the bass/mid/treb controls. They are cut - type controls; as you turn them up, you increase gain at that stage.
Good luck !
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Originally Posted by Major Tom Try this for a "fix" Put a lower gain tube in V2 (the middle preamp tube) like a 12AY7 or 12AT7. That amp's high gain channel is too saturated IMO at low gain settings, and the master volume is mostly pegged at about 4 (and it goes to 12 !), even with a modest input level. IMO, that's a design flaw. The lower gain tube lowers the saturation, but there's still plenty of distortion on tap, at least for the non-metal crowd, and it extends the range of the master volume so that its less touchy trying to dial it in; it goes a long way toward fixing that inherent design problem. Everyone that I've recommended that "mod" to so far has liked it. The slightly lower overall gain may make that squealing disappear. In any case, give that a try, its only 12 bux or so.
I think I'll give that a shot. I'll probably mess around with putting my volume pedal in the effects loop too.
Btw, this is a little off topic... but I noticed you're from Cinci. I was wondering if you've been to that Sam Ash store off of 275 by the Tri County Mall. If so how's their stock? And is it any less crowded with 14 yr. old metal head wannabe's than the Guitar Center down the road?
I'm from Dayton, so it's a good 50 minute drive from my house but not too far away if it's a worth while visit. I went to GC first because I knew they stocked Fender amps. Does Sam Ash have anything amp-wise that GC doesn't?
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Originally Posted by jbm222 I think I'll give that a shot. I'll probably mess around with putting my volume pedal in the effects loop too.
Btw, this is a little off topic... but I noticed you're from Cinci. I was wondering if you've been to that Sam Ash store off of 275 by the Tri County Mall. If so how's their stock? And is it any less crowded with 14 yr. old metal head wannabe's than the Guitar Center down the road?
I'm from Dayton, so it's a good 50 minute drive from my house but not too far away if it's a worth while visit. I went to GC first because I knew they stocked Fender amps. Does Sam Ash have anything amp-wise that GC doesn't?
The Sam Ash store is very similar to GC in what they carry, but I think they have fewer mfr's. Amp-wise they have Fender, Vox,... Marshall maybe.... I don't really look at the amps much, but I don't think I've seen anything there that GC doesn't have. I'll have to stop in and check. Sam A's is huge inside compared to GC, so it doesn't feel crowded. GC I think has a lot more used amps. You can check their website, I'm not sure if everything on the site is in the store though.
I live north of Cincy, right off of I-75, about 1 minute off of the 129 West/Hamilton exit (past Monroe, before Tylersville exits) on the way to either of those stores. If you come down, we oughta get together, I'd love to go along and trash some guitars & amps with a bro from the forum... I'd be glad to help you troubleshoot that amp problem if you want to bring it down to the house, I have tubes to swap out and see if that fixes it... We could compare it to my HR DeVille.
Tom