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Post subject: Random Tube Brands | New Custom Twin 68
Posted: Sat Aug 10, 2019 7:37 am
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I recently purchased a "new" custom twin reverb 68 from Guitar Center. When I took it home there was a persistant hum that increased as you dialed up the reverb. Looking online I saw that it may be due to loose RCA cables going to the reverb tank.

Upon further investigation I noticed that the several of the pre-amp tubes varied in brands. One was Ruby, Electro-harmonix etc.. Is this to be expected or are they supposed to be fender rebranded tubes?

Thanks for the help


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Post subject: Re: Random Tube Brands | New Custom Twin 68
Posted: Sat Aug 10, 2019 12:23 pm
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Personally, I'd return it. Make them replace it with a "new" out of the box replacement, Fender owns Groove tubes brand, so anything that doesn't say Fender or Groove tubes means Guitar Center is trying to hose you.


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Post subject: Re: Random Tube Brands | New Custom Twin 68
Posted: Sat Aug 10, 2019 12:35 pm
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Hiss and hum is a common malady among all of the "Custom" models -- replacement tubes may accomplish nothing.

And this post should be relocated to the "modern amp" sub-forum. The "Custom" amps have absolutely nothing to do with true vintage editions.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Random Tube Brands | New Custom Twin 68
Posted: Wed Dec 18, 2019 12:54 pm
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Regarding the '68 Custom Twin Reverb noise issue(s)

If you want to lower the noise floor hiss, a simple fix is to change V4 tube (4th from the right looking at the back) from the stock 12AX7 to a 12AY7 low gain tube.

They say this will change the characteristic of the amp, as it is meant to be a high gain amp, though going with a lower gain tube on the reverb output, we find that it simply lowers the amount of overall reverb, yet usually you would only have your reverb at 2 or 3; with a 12AY7 you may want to turn your reverb to 3 or 4.

Have fun


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Post subject: Re: Random Tube Brands | New Custom Twin 68
Posted: Wed Dec 18, 2019 6:03 pm
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marthasmusic wrote:
Regarding the '68 Custom Twin Reverb noise issue(s)

If you want to lower the noise floor hiss, a simple fix is to change V4 tube (4th from the right looking at the back) from the stock 12AX7 to a 12AY7 low gain tube.

They say this will change the characteristic of the amp, as it is meant to be a high gain amp, though going with a lower gain tube on the reverb output, we find that it simply lowers the amount of overall reverb, yet usually you would only have your reverb at 2 or 3; with a 12AY7 you may want to turn your reverb to 3 or 4.

Have fun


And this is relevant to the OP's original question how?

:roll:
Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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