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Post subject: Help! What is that noise in my DRRI?
Posted: Tue Jun 30, 2015 4:08 am
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My DRRI has started making a noise that sounds like radio static when I play a B note on the 5th and 6th strings. It lasts all the while the string is vibrating but sometimes cuts in and out. It also does it to a much lesser extent playing a Bb but not for any other notes.

It does it on both channels which I assume rules out microphonic tubes in V1-V5 or a reverb problem and I have also changed the tube in V6 and it still does it. Can power tubes be microphonic or can anyone suggest another cause of this noise, please?

One thing I have noticed is that the level of the noise seems to be the same whatever the volumes setting is such that it is hardly noticeable at higher volumes but very noticeable at lower settings.


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Tue Jun 30, 2015 8:24 am
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fifty4 wrote:
Can power tubes be microphonic or can anyone suggest another cause of this noise, please?


Yes. Power tubes are just as susceptible to becoming microphonic.

Another possible cause might be a loose fastener -- either a speaker screw or a screw holding the baffle board to the cabinet. Check all your fasteners, to include those holding the reverb tank to the bottom of the cab and those on the chassis itself.

Arjay

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Tue Jun 30, 2015 9:04 am
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Thanks Arjay. All the screws were tight but when I tapped the power tube in V7 there is a "tinkle" sound like something is loose. When I tap V8 it gives a solid sound so I guess V7 could be faulty. Unfortunately I've had the amp for almost 4 months so it is outside of the 90 day Fender tube guarantee.

What is recommended as a good power tube for the DRRI? I prefer warm tone/early breakup if that is an option but would not really want to run the amp hot or beyond spec to achieve it. I DO NOT want to buy Groove Tubes because my experience with those factory fitted in my amp has not been good! I have already replaced 3 of the pre-amp tubes due to microphonics or excess noise.

I have never changed power tubes that need biasing before but I do have a simple probe that sits between the chassis and tube and connects to my multimeter. I have read that the correct process is to determine the voltage, then take a percentage to arrive at the current. But is that necessary? Can I not just set the bias so that the current is the same as it is for the tubes that are in there at the moment?


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Tue Jun 30, 2015 10:53 am
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Sounds like you're ready for a new set of power tubes. Buy a matched pair from a reputable vendor. Though I do not care for them personally, the JJ 6V6S might serve you well. Electro-Harmonix also sells some pretty good bottles though I haven't yet tried their 6V6GTA. Tung-Sol offers this tube but early examples often red-plated for reasons not altogether known. Regardless of brand, the replacement set will need to be biased -- I would start at 18.5 or 19 mA and work up from there. Be sure to check your plate voltage before starting and take that measurement into account when calculating dissipation percentages.

Arjay

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Tue Jun 30, 2015 6:10 pm
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Retroverbial wrote:
...Electro-Harmonix also sells some pretty good bottles though I haven't yet tried their 6V6GTA....


Outstanding tubes, my "go-to" for almost every amp that uses 6V6. In the DRRI, considering typical Plate voltage of 430 VDC, a bias of around 23 mA Cathode is the sweet spot for me. I do prefer the GT branded EH 6V6 (GT 6V6 R), but I do use standard EH also, both with fantastic results. :D

The JJ 6V6 will give a much cleaner, tighter sound which doesn't have that warm, smooth, break-up, or the sparkly top-end of a traditional 6V6, and some people prefer that sound, which is really more like a 6L6.

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Tue Jun 30, 2015 11:58 pm
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shimmilou wrote:
Retroverbial wrote:
...Electro-Harmonix also sells some pretty good bottles though I haven't yet tried their 6V6GTA....


Outstanding tubes, my "go-to" for almost every amp that uses 6V6. In the DRRI, considering typical Plate voltage of 430 VDC, a bias of around 23 mA Cathode is the sweet spot for me. I do prefer the GT branded EH 6V6 (GT 6V6 R), but I do use standard EH also, both with fantastic results.


Thanks for the info, shimmilou.

I've got an old pair of Matsushita's in my blonde Spankmaster that are starting to fizz a bit. I may give the EH's a try when I decide to replace them.

Arjay

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Wed Jul 01, 2015 3:04 am
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I think that you will be pleased. I have them in both of my DRs (head and combo), my Laney Cub 10, a couple of Bell & Howell, and have put them in every customer amp that use 6V6 (Vibro Champ, DR, Super Champ, Champ 600, Bell and Howell, and probably others that I don't remember), with zero failures. I have tried a plethora of different 6V6 tubes, including a limited number of NOS US made, and I always prefer the EH. I even tried them in my HRDlx, pushing 470 VDC on the Plates, and although they sounded sweet, I wanted the 6L6 sound from that amp, so I switched back to 6L6.

Even though price isn't a factor for me, they are very inexpensive. :D

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Wed Jul 01, 2015 2:54 pm
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Seriously considering getting some EH 6v6GT after that glowing recommendation. May even eat my words and get the Groove a Tubes version.


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Wed Jul 01, 2015 4:37 pm
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As I just stated in another similar thread; I would not judge any brand of tube based on those that come stock in a new amp that has likely been subjected to a severe beating at the hands of UPS. :idea:

U...P...S.....the horror,......the horror.... :lol:

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Jul 04, 2015 9:53 am
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And lets not forget the rattling 5AR4 rectifier tubes that were coming in most DRRI's a year or so ago
I had two or three come in with extraneous noise / rattles and they were all buzzing recti tubes

Not sure if that has been rectified yet (pun intended) :lol:

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Jul 04, 2015 11:03 am
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In the end I decided to buy a matched pair of Tung-Sol 6V6GT tubes for the power section. I also decided to get a JJ GZ34 rectifier so that I will have replaced all of the Groove Tubes that came factory fitted in the amp even though not all of them had any problems.

The tubes are expected early next week and I have a techie lined up to bias them for me. I chickened out of doing it myself!


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Jul 04, 2015 11:12 am
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fifty4 wrote:
The tubes are expected early next week and I have a techie lined up to bias them for me. I chickened out of doing it myself!


No shame there, fifty4.

Working inside an energized amp chassis with high voltages present exceeds the comfort level of many. You were wise to let a pro handle the biasing.

Rawk on!

Arjay

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Fri Jul 17, 2015 8:39 am
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A final update on my new tubes.

Today we played in the studio for the first time since I installed the new Tung-Sol 6V6GT power tubes so I was able to see what the amp sounded like at a reasonable volume and I have to say I am more than pleased with what I heard.

The tubes were biased by a pro so I don't know what current he has set them to. The factory tubes were GT-6V6-S which I believe are JJs. The Tung-Sols seem to have a slightly lower output because I need the volume set a bit higher to get the same level. However, at the same level the Tung-Sols have more break-up.

I took the opportunity to shuffle the other tubes while I was at it so the amp now has Tung-Sol 12AX7 RI in V1 and V2, a JAN Philips 12AT7WC in V3, a TAD 7025WA in V4 and a Mullard CV4024 in V6. V5 is a JJ ECC83S and V9 is a JJ GZ34. I've always been pleased with the sound of my DRRI since I got it but it now sounds better than ever.


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Fri Jul 17, 2015 9:55 am
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Glad it worked out for you and that your amp is now free of noise.

Rawk on!

Arjay

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Jul 18, 2015 4:02 am
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Sounds like a great lineup of tubes. Tung Sol are among my favorites too, and come from the same factory as EH. 8)

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