High-pitch squeal from my Herbert-solved

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BrianVaughn

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I recently purchased a Herbert (as I previously posted on this forum). I took a week off for the holidays, planning on spending the entire time writing and recording with the new amp. At first it was amazing but yesterday I started noticing a high pitch squeal from the amp. At first, it seemed at least partially dependent on the direction I sat (facing it, facing away from it, etc.). Gradually that made less of a difference. I tried turning the amp off and back on once or twice which seemed to reduce the squealing for a short while. It eventually came back though.

Here is a recorded sample of the squeal for anyone who is curious:


I should also mention that at one point toward the end of the day I noticed that the channel light was blinking. I was unable to find any mention of the blinking in my owners manual though I did find a post where Peter seemed to touch on something that may be related: viewtopic.php?f=14&t=59562

As for the high-pitch squeal, the only possibly-related thing I could find in my manual was:
"The overall performance of a pre-amp tubes is easily influenced by mechanical factors from the outside. This would manifest itself by a sudden feedback sound with high pitch. The input stage is especially suspect to this phenomena. If one encounters this microphonic tube behavior, then the first tube should be checked as a rule. Pre-Amplifier tubes can also cause hum or other bad noises, like crackling or ticking"

My amp is currently powered off a Monster Power Pro 2500 conditioner and running through a Palmer speaker simulator (8 ohm load box) into my Mac Pro. (Not sure if any of that is relevant just trying to answer any "what is your setup right now" type questions.)

Hopefully someone who knows much more than me about amps (Peter?) can chime in and offer some advice. Thanks in advance if so!
 
Try changing 1st preamp tube or at least try swapping it with another.
 
RG955TT":4422k0ld said:
Try changing 1st preamp tube or at least try swapping it with another.
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Thanks for the suggestion, but I know just enough to realize that I probably don't belong on the inside of that amp (even for something as simple as changing a preamp tube). Unfortunately, the town I live in is rather small so if the amp needs to be tinkered with internally, I'll have to make a drive to a nearby city. Probably going to hold out for Peter's response before doing so though.
 
BrianVaughn":2oiydmxl said:
RG955TT":2oiydmxl said:
Try changing 1st preamp tube or at least try swapping it with another.
Click to expand...
Thanks for the suggestion, but I know just enough to realize that I probably don't belong on the inside of that amp (even for something as simple as changing a preamp tube). Unfortunately, the town I live in is rather small so if the amp needs to be tinkered with internally, I'll have to make a drive to a nearby city. Probably going to hold out for Peter's response before doing so though.
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If you can change a light bulb, you can change a tube... It doesn't require that you "open the amp up." Just take the back plate off and grab the tube with your hand (make sure it has cooled down) and pull that sucker out.
 
Oh ok Ill give it a try then when I get home. The manual warned against changing tubes unless you were a professional but that maybe just meant the power tubes? Anyway I don't have a spair pre-amp but I could swap 2 of the ones in there.
 
BrianVaughn":34b6muob said:
Oh ok Ill give it a try then when I get home. The manual warned against changing tubes unless you were a professional but that maybe just meant the power tubes? Anyway I don't have a spair pre-amp but I could swap 2 of the ones in there.
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Changing power tubes and preamp tubes is easy. Just gently wiggle them as you pull them out. Don't bother touching the power tubes. For preamps, if one is microphonic it needs replacing. Swapping them around just helps you narrow down (by process of elimination) which tube is the culprit. So, you will need to get a new preamp at some point.

Currently, Peter recommends Ruby 12AX7AC5 HG+ for V1 and V2 and 12AX7AC5 HG for the rest.
 
BrianVaughn":2lg0rqpl said:
Oh ok Ill give it a try then when I get home. The manual warned against changing tubes unless you were a professional but that maybe just meant the power tubes? Anyway I don't have a spair pre-amp but I could swap 2 of the ones in there.
Click to expand...

Just make sure you line up the pins correctly... The Wide space between pins points to the front... Go slow and you'll be ok.

Best,

Roid RAGE
 
There seem to be 6 of the smaller tubes, which is for V1? Is it the first one (far left)? Also, will temporarily swapping them with each other indicate if there is a problem? I tried switching the amp to V2 but it squealed too. In fact, amp now squeals incredibly loud when I turn it on (worse than it did yesterday).

I ordered a couple of 12AX7AC5 HG+ and 12AX7AC5 HG tubes in the meanwhile so I'll have replacements on hand.

PS. Sorry for my noob-ness, I'm just trying to take this slowly to avoid making any expensive mistakes. I appreciate all of the help so far! :)
 
BrianVaughn":3n12x2dk said:
There seem to be 6 of the smaller tubes, which is for V1? Is it the first one (far left)? Also, will temporarily swapping them with each other indicate if there is a problem? I tried switching the amp to V2 but it squealed too. In fact, amp now squeals incredibly loud when I turn it on (worse than it did yesterday).

I ordered a couple of 12AX7AC5 HG+ and 12AX7AC5 HG tubes in the meanwhile so I'll have replacements on hand.

PS. Sorry for my noob-ness, I'm just trying to take this slowly to avoid making any expensive mistakes. I appreciate all of the help so far! :)
Click to expand...

V1 is usually the preamp tube closest to the amp's input jack.
 
Peter (or anyone else who knows),

I've been having a bit of a hard time tracking down the HG+. It seems most online vendors don't even specify the difference (they just say 12AX7AC5). I did find one site that sells the HG+ specifically but they don't offer rush-shipping options and I'd rather not be without an amp for an entire week, specially given how new it is.

I called Chuck Levins (where I purchased the amp) and they informed me that they carry the Groove Tubes (Soft Tech, 12AX7WC, Russian-made) but not the Ruby 12AX7AC5. I told them that it seems like you were recommending the 12AX7AC5 HG+ specifically for V1 and I'm not sure if the 12AX7WC is comparable or would work.

I apologize for my general lack of knowledge in this area. I don't know much about the inside of my amp currently, which is certainly not to my credit. Again, I'm trying to avoid an expensive mistake and I appreciate any word of advice you're able to offer.

PS. Happy new year :)
 
man, i can't stand the sound of those palmer units...they're certainly handy for cutting rough tracks and guide guitars. but man i find the sound god awful compared to how good the herbert sounds mic'ed up.
 
scoeb city":1i4wmab4 said:
man, i can't stand the sound of those palmer units...they're certainly handy for cutting rough tracks and guide guitars. but man i find the sound god awful compared to how good the herbert sounds mic'ed up.
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I've been pretty happy with the sound of my Herbert+Palmer. I'd be happy to send you a clip or two if you're curious. Sure, it's not perfect, but it's pretty ideal when you live in a townhouse (as I do).

Just a bump too. Anyone know if Groove Tubes (Soft Tech, 12AX7WC, Russian-made) are comparable to the 12AX7AC5 HG+? I can pick up the Groove Tubes (somewhat) locally but the others are still in transit for a few days and I'm going stir-crazy not being able to use my new amp.
 
Just a follow-up for all of you who were kind enough to help me. My replacement Ruby tubes arrived today and I put in a new HG+ for V1. The amp sounds marvelous again! Not even a hum. Thanks so much for all of the posters who helped here! \m/
 
BrianVaughn":2smh0fze said:
Just a follow-up for all of you who were kind enough to help me. My replacement Ruby tubes arrived today and I put in a new HG+ for V1. The amp sounds marvelous again! Not even a hum. Thanks so much for all of the posters who helped here! \m/
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Nice! Where'd you get the tubes? I'v been trying to find a place to buy them. The places I've found had the HG+ but not the HG's or had the HG's and not the HG+'s. I want to buy them all from the same place. And I'm in the same boat as you were: squealing/feedback on high-gain channels.
 
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