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Post subject: Hissing HR Deluxe
Posted: Sun Dec 05, 2010 11:22 am
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Hey Folks,
I really hope all is going good for musicians out there!
I would like to ask a question about a 90's HR Deluxe. This amp has been well taken care of..it's used in a recording studio here in the OKC area.
Okay, When on, no guitar, and in the clean channel, it is "very quiet." When you kick in the over drive(yellow led) it produces a loud hiss...when in more over drive (red led) it gets louder. Of course you can turn down the drive and master pots to zero and it's quiet. It's gets louder and louder as you turn them up and both do interfere with the sound of a guitar playing.
The tubes are all okay. I have tested them and they are all good. I have even put in a pair of my NOS RCA 6L6's balanced pair and 3 NOS RCA 12AX7's. The tubes are not the problem. When the amp in in this hiss mode, the 6L6's get very touchy. If you tap them or even if you bump the cab/chassis, you hear it thru the speaker.
I am about to remove the caps and test them on an Eico 950B Cap tester.
I have tested many of the test points and so far all are at or close to the specs on the schematic.
Anyone have any idea of the cause of this hissing? What would cause the tubes to become so micro phonic? I have removed and tested all the cathode resistors......What about the 2-3 op amp? Do these break down slowly or do they break down quickly like a diode would?
Sorry to be so wordy, but I am trying to describe in detail as clear as I can.
Oh, and it's not the shielding!
Thanks very much to any one who can help!
PEACE
Tube Dude


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Post subject: Re: Hissing HR Deluxe
Posted: Sun Dec 05, 2010 11:36 am
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tube dude wrote:
Hey Folks,
I really hope all is going good for musicians out there!
I would like to ask a question about a 90's HR Deluxe. This amp has been well taken care of..it's used in a recording studio here in the OKC area.
Okay, When on, no guitar, and in the clean channel, it is "very quiet." When you kick in the over drive(yellow led) it produces a loud hiss...when in more over drive (red led) it gets louder. Of course you can turn down the drive and master pots to zero and it's quiet. It's gets louder and louder as you turn them up and both do interfere with the sound of a guitar playing.
The tubes are all okay. I have tested them and they are all good. I have even put in a pair of my NOS RCA 6L6's balanced pair and 3 NOS RCA 12AX7's. The tubes are not the problem. When the amp in in this hiss mode, the 6L6's get very touchy. If you tap them or even if you bump the cab/chassis, you hear it thru the speaker.
I am about to remove the caps and test them on an Eico 950B Cap tester.
I have tested many of the test points and so far all are at or close to the specs on the schematic.
Anyone have any idea of the cause of this hissing? What would cause the tubes to become so micro phonic? I have removed and tested all the cathode resistors......What about the 2-3 op amp? Do these break down slowly or do they break down quickly like a diode would?
Sorry to be so wordy, but I am trying to describe in detail as clear as I can.
Oh, and it's not the shielding!
Thanks very much to any one who can help!
PEACE
Tube Dude


That was one of the bozillion reasons I dumped mine. That and it was always in the shop. In drive/more drive it hissed like a herd of cats. I just attributed it to cheap parts and poor design. Changing the preamp tubes helped slightly. I rarely used the drive channel. The HRDlx is not one of the quietest amps on the market in its drive modes. Be careful with the soldering iron, the traces lift pretty easily. They used a thin, single sided board on the HRD series amps. Sure the power tubes aren't microphonic?

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Post subject: Re: Hissing HR Deluxe
Posted: Sun Dec 05, 2010 11:48 am
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63supro wrote:
In drive/more drive it hissed like a herd of cats.


LMMFAO!!!

Actually, my HRDlx featured "fizz" and "more fizz" channel modes.

Arjay

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Post subject:
Posted: Sun Dec 05, 2010 12:05 pm
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Hi tube dude,

My 98 HRDlx is the same as far as the hiss in the drive/more drive modes, that is the norm with this amp. I could never turn the volume up past about two when using more drive, due to the loud hiss. That is part of the reason that I really don't use the drive channel in mine very much. I get much better results using effects on the clean channel to get the sound that I like, and I like the clean channel.

You might want to try a lower gain tube like a 12AT7 in V2, half of that tube is used only for the drive channel. If changing V2 isn't enough, try one in V2 and V1. Of course changing either tube will affect the clean channel, but it might sound OK with lower gain tubes also. Almost all tubes will make some sound through the speakers when tapped on, especially in the drive channel, that's normal too. :idea:

P.S. If you have the original caps (IC?), they should probably be changed anyway, to something better. I changed all of my PS caps when I recently found a couple leaking, I used F&T. And the op amps typically fail like a diode. :)

P.P.S. If you can find a reverse 12DW7, referred to as an ECC823, that would be a great tube to try in V2, but they are hard to find. In the reverse 12DW7 (ECC823), half of the tube, for the clean channel, has a gain of 100 so it will be the same as a 12AX7, while the other half, for the drive channel, will have a gain of 19. The regular 12DW7 (ECC832) will be the opposite of what is needed in this case, you don't want that. :idea:

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Post subject:
Posted: Sun Dec 05, 2010 3:31 pm
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Tube Dude, sorry to use your topic.
Shimmilou, can you tell me more about "And the op amps typically fail like a diode"

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Post subject:
Posted: Sun Dec 05, 2010 3:43 pm
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Hi Tissan,

I just mean that an op amp typically won't slowly go bad like a capacitor over time. They will either be good or bad, shorted or open, similar to a diode failing (using the OPs analogy). Interestingly, I have read accounts that claim a difference in tone from different op amps though. One site, the author put in a chip socket that allowed the quick change of op amps, and he claimed a noticeable difference in tone between different brands of op amp. I can believe it, different brands have different specs, and they are in the signal path. :)

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Post subject:
Posted: Wed Dec 08, 2010 7:54 am
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Hey People,
Thanks very much! I really mean it!
When I first ever opened one of the HR Deluxes, I said to myself....what a cheaply built amp...and this also applies to many more amps that are out there today.
I will try the 12AT7 suggestion.
I am almost scared to try and unsolder the op amp to check it.
Can these op amps be tested while in the circuit?

So at this point, "Do I tell my customer that the problem can't be found?"
If I have the right caps or some that are equal or higher in uf's and voltage,
I'' check these out!
Thanks again to all!
PEACE!
Tube Dude


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Post subject:
Posted: Wed Dec 08, 2010 8:06 am
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My tech absolutely hated working on my HRDlx because the board and traces were so fragile. These are just noisy amps in the drive channel. It is what it is. Lowering the gain with a 12AT7 or maybe a 5751 might help. I wouldn't be soldering on a thin single sided board but that's just me and I've been soldering since I was ten years old and I'm 55 now.LOL

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Post subject:
Posted: Wed Dec 08, 2010 8:24 am
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Don't worry about the op amps, they are probably fine, if they were bad, you would hear a problem in the clean channel also. The op amps are a PITA to remove with only a soldering iron and wick or solder sucker, and you can do more damage to the circuit traces by trying to remove them. Besides, if you did remove it, you would need a pin-out to know where to check for what. Replacing the power supply caps is recommended though for an amp that old.

While you have the amp open, with the amp unplugged from electricity, and caps discharged, touch up all of the solder joints on the tube socket connections to the circuit board, they are accessible without disassembly. Also, if you disassemble to replace the power supply caps (and you should), touch up all of the solder joints on the main circuit board before putting back together. Just be careful that your iron doesn't touch (and ruin) the ribbon cables and other wiring.

With this amp, the hiss is not really something that can be fixed by replacing any components, it is just inherent in the amp. Lower gain tubes may help, but the drive channel will have some hiss no matter what you do. Like I said before, on mine I don't use the drive channel, I use the clean channel with pedals for drive if I want drive. :)

Here's a great site for lots of HRDlx info.

http://www.justinholton.com/hotrod/

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Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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