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Post subject: DRRI retubed and rebiased
Posted: Fri Apr 29, 2011 9:05 pm
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i went with
V1 tungsol 12ax7
V2 mullard 11ax7
V3 Jan Phillips 12at7wc
V4 Mullard 12ax7
V5 tungsol 12ax7
V6 Jan Phillips 12at7wc balances for PI
Power tubes tungsol ri 6v6 biased at 22.5
Sovtek GZ34 rectifier tube
The bias probe came with a chart for 6v6 vp
Between 400-450vp. 18- 25 ma
The DRRI vp was at 420
By the way tone was awesome,
Is the bias ok?
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Post subject: Re: DRRI retubed and rebiased
Posted: Fri Apr 29, 2011 10:12 pm
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Perfect!

Expect years of dependable service from that tube ensemble.

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: DRRI retubed and rebiased
Posted: Sat Apr 30, 2011 1:57 am
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Good choice of tubes.
I know bias draws a lot of discussion,but I run my DRs at 28 mA which is a little hotter but sounds good to me....check it again after playing for awhile to see if the tubes have drifted.


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Post subject: Re: DRRI retubed and rebiased
Posted: Sat Apr 30, 2011 7:01 am
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i may lower the bias a bit,
i found another biasing chart that read if vp 420, 6v6 should be biased at 17.5
i dont have any issues right now, it is breaking up a little sooner, maybe too hot?

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"Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the present."

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Post subject: Re: DRRI retubed and rebiased
Posted: Sat Apr 30, 2011 4:30 pm
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Location: australia
Hi nice tubes those tung sol 6v6gt Sweet tone...Cheers..from..Aus...


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Post subject: Re: DRRI retubed and rebiased
Posted: Sat Apr 30, 2011 6:27 pm
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The bias at 22.5mA is ok at 420 volts you are at about 68% dissipation on the tubes,Most say you should go past 70% but if you dig the tone you can go up higher but the tube might not last as long.

I just retubed my deluxe as well i put it at 20.5mA at 442 volts which is about 65% dissipation.I like mine in the 65% range it's not too hot or too cold for me.

But now you know how to adjust the bias,and you can try out some other tube companies as well.I am really starting to like Tube Amp Doctor tubes

Also recheck the bias after a couple hours of use. tubes like to drift after the first 10-30 hours for break in


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Post subject: Re: DRRI retubed and rebiased
Posted: Sat Apr 30, 2011 6:32 pm
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joncarr1979 wrote:
Also recheck the bias after a couple hours of use. tubes like to drift after the first 10-30 hours for break in


+1

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: DRRI retubed and rebiased
Posted: Sat Apr 30, 2011 7:01 pm
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Thanks guys, it was fun learning to bias, and to get the vp
I'll have to recheck tomorrow,
Tomorrow I bias the scxd

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Post subject: Re: DRRI retubed and rebiased
Posted: Sun May 01, 2011 3:11 am
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bluesstrattone wrote:
Thanks guys, it was fun learning to bias, and to get the vp
I'll have to recheck tomorrow,
Tomorrow I bias the scxd
The super champ should be cathode bias and you should have to do anything beside put in the new tube.It will self bias it's self


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Post subject: Re: DRRI retubed and rebiased
Posted: Sun May 01, 2011 3:28 am
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If I am not wrong, according to this http://www.webervst.com/tubes1/calcbias.htm

the 22.5ma mentioned is above 70%, the Tungsol RIs are 12w, not 14w 6V6s....


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Post subject: Re: DRRI retubed and rebiased
Posted: Sun May 01, 2011 5:23 am
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they could be above 70% i have never seen any specs on the tung sol 6v6.I just have to assume they are 14 watt tubes like everyone else.I know the 6l6's are 25 watts when most 6l6's are 30 watts. Well what's the worst that is gonna happen the tubes will die prematurely. But i would really like to see a spec sheet on this tube


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Post subject: Re: DRRI retubed and rebiased
Posted: Sun May 01, 2011 5:58 am
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I thought the only 14W new production 6V6 tubes were JJ's. :?:
Anyone have the exact info?


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Post subject: Re: DRRI retubed and rebiased
Posted: Sun May 01, 2011 6:04 am
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I just found this.....
http://www.newsensor.com/TubeSpecification.aspx

There you find a spec-sheet for the Tun-Sol 6V6, where it says the max. dissipation is 12W.


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Post subject: Re: DRRI retubed and rebiased
Posted: Sun May 01, 2011 2:12 pm
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I rechecked the bias today
This is the vp
Image
This is tube 1 or v7
Image
This v8
Image
Is this the stable bias now?

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"Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the present."

oogway, kungfu panda 2008


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Post subject: Re: DRRI retubed and rebiased
Posted: Sun May 01, 2011 2:36 pm
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Congrats on the new tubes! Hope you had better luck with those Mullards, I just got 2 of them for my DRRI and both were microphonic :(

For 6V6 at 420 I wouldn't go higher than 20 mA, that should be right at 70%. My RCA 6V6GTA are rated at 14W, I run those 22-23 mA.

Forgot to add the link to the Weber bias calculator...

http://www.webervst.com/tubes1/calcbias.htm

6V6 (12W):

12/420=0.028
.028X.70=0.02 that's 20mA.

6V6GTA (14W):

14/420=0.033
.033X.70=0.0233 that's 23.3 mA.


Last edited by cedarblues on Sun May 01, 2011 2:55 pm, edited 1 time in total.

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