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Post subject: Re: HRD: Loud & Scary Noise
Posted: Mon Mar 04, 2013 2:38 pm
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Aspiring Musician
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Update: It happened again, this time with only the guitar plugged into the amp using INPUT 1.

I'll post back after I take the amp in for servicing.

Cheers!
BM

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Mon Mar 04, 2013 6:17 pm
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That tells me that it probably isn't the jack(s). It could still be a poor solder joint somewhere, or as you surmised, a tube issue.

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Mon Mar 04, 2013 6:39 pm
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shimmilou wrote:
That tells me that it probably isn't the jack(s). It could still be a poor solder joint somewhere, or as you surmised, a tube issue.
    Thanks, shimmilou. I'm taking the amp in for servicing tomorrow.

    Just for my own education, I'm wondering how an amp tech determines if a tube is faulty. If the amp is not working and he swaps a tube and then it works, well it's pretty obvious that the tube was faulty. However when a problem is intermittent the same approach won't work. Is there a tube tester? If so, what does it test for?

    Cheers!
    BM

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Mon Mar 04, 2013 9:41 pm
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There are tube testers, with different levels of testing depending on the tester. The best tube tester is the amp itself, and there are various ways to test the tubes performance while in the amp. Typically, in a case like this with an intermittent problem, I would thoroughly check every solder joint and connection point in the amp first, including the tube sockets, then start looking at the tubes. Some people would replace all of the tubes first and see if the problem recurs, but that wouldn't be my approach. A good tech should be able to find the problem in short order. Poor solder joints are a very common problem in most any modern amp. An intermittent problem is usually a poor connection somewhere, and not likely a tube problem, although possible.

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Sat Mar 09, 2013 6:37 pm
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Aspiring Musician
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    Got the news from the amp doctor today and the culprit is .... drum roll .... you guessed it folks, the usual suspect, the tube. Specifically the 5751 in V2. As for the solder joint conspiracy theory, the technician said he checked and everything's fine. I had also asked him to check the bias - might as well since he's in there - and he told me that he checked using a scope and that it's nice and "warm".

    I understand that tubes can go at any time and that there's no guarantee as to how long they will or could or should last. On the other hand there are members on this forum who've kept the same tubes for years and years without any issues. The stock GT 12AX7 in my HRD died after six months. The 5751 in V2 had only four months of service before it crackled and popped away. Does this fall under the "normal" range? Admittedly I'm using the amp several hours on a daily basis but at reasonable not head-banging levels so it's not as if the tubes are going to their death in a glowing blaze. :lol:

    I didn't have a spare 5751 so right now I have the stock GT 12AX7 in V1, a JAN-5751 in V2, and a balanced Mullard 12AT7 in V3. The amp sounds fine on the clean channel but not as crunchy as before on the drive channel. I was planning to order another JAN-5751 for V1 but since I'm going to be placing an order perhaps I could try something else?

    Cheers!
    BM

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Sat Mar 09, 2013 7:45 pm
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Not normal, but it happens. The "years and years" of tube service is more normal. What brand was the 5751, a JAN? But, as you pointed out, no tube type/brand is immune from early failure. In this case, I would put the 5751 in V1 and the 12AX7 in V2, as V2 will have more affect on the drive channel. In fact, in my HRDlx, that's what I have now, a GE 5751 in V1, a GT12AX7-C in V2, and a GT 12AT7 in V3. The 5751 is NOS only a couple of months use, and I have a few years on the others and have swapped them around in different amps a few times.

Good to hear that it was nothing serious with your amp.

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Sat Mar 09, 2013 9:05 pm
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    I'm going to swap V1 and V2 like you suggest and check out the sound before ordering another 5751.

    I'm also curious about the 12AY7 and wondering how this could affect the sound. I'm thinking the amp should be even more quiet and have an early breakup. Would these be a good choice? http://www.tubedepot.com/eh-6072agp.html

    Cheers!
    BM

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Sat Mar 09, 2013 9:19 pm
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A 12AY7 might be a good choice for V1. I like a little lower gain in V1 (5751), and the higher gain in V2, with the even lower gain in V3, as this suits my taste for sound, a little warmer clean and a smoother/bluesier drive channel. For my taste the AY was a little bit too low in gain, but others prefer it. Taste test for yourself, they're not so expensive, and easy to swap. In the little Greta that I have, I liked a 12AY7 in V1 and a 12AU7 in V2, but that's the only amp that I've ever liked the sound with either of those tubes.

BTW, the lower gain tubes typically give a cleaner sound, later breakup, less distortion than a higher gain tube.

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Sat Mar 09, 2013 9:49 pm
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I wouldn't recommend as 12AY7 in V1 unless you are looking to really clean up the sound. The drive control sits right between V1A and V1B. Putting a 12AY7 there will really drop the gain of that stage. I wouldn't go lower than a 5751.

http://support.fender.com/schematics/gu ... ematic.pdf

I've had a 2 year old JJ 6L6GC die as well as an NOS JAN Phillips 5751 go microphonic after a few months use. Tubes fail. Doesn't matter if they are NOS or new production. Sometimes they go out in a blaze of glory, othertimes its a slow, noisy death. :lol: :lol: :lol:

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Sun Mar 10, 2013 5:46 pm
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    I swapped V1 and V2 as shimmilou suggested and boy what a difference! Going from stock 12AX7s all around to 5751s in V1 and V2 with a Mullard 12AT7 in V3 made the HRD quieter and more Bluesy but a 5751 in V1 and a GT 12AX7 in V2 gives an even crunchier over drive channel. I think I'll keep this combo for a while. :!:

    bluesky636 wrote:
    I wouldn't recommend as 12AY7 in V1 unless you are looking to really clean up the sound. The drive control sits right between V1A and V1B. Putting a 12AY7 there will really drop the gain of that stage. I wouldn't go lower than a 5751 ...
      Thanks, Bill. You just saved me $39.90 plus tax and shipping. :wink:

      Cheers!
      BM

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Post subject: Re: HRD: Loud & Scary Noise
Posted: Sun Mar 10, 2013 8:40 pm
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Bluer Monkey wrote:
    I swapped V1 and V2 as shimmilou suggested and boy what a difference! Going from stock 12AX7s all around to 5751s in V1 and V2 with a Mullard 12AT7 in V3 made the HRD quieter and more Bluesy but a 5751 in V1 and a GT 12AX7 in V2 gives an even crunchier over drive channel. I think I'll keep this combo for a while. :!:

    bluesky636 wrote:
    I wouldn't recommend as 12AY7 in V1 unless you are looking to really clean up the sound. The drive control sits right between V1A and V1B. Putting a 12AY7 there will really drop the gain of that stage. I wouldn't go lower than a 5751 ...
      Thanks, Bill. You just saved me $39.90 plus tax and shipping. :wink:

      Cheers!
      BM


I think you hit on the right combination for your needs. :D

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