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Post subject: Re: Hot Rod Dlx III & Mesa 6l6gc bias question
Posted: Sat Jan 18, 2014 2:56 pm
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beatles1909 wrote:
I thought all I needed was a plate level which is why I asked, so when I put the new Mesa tubes in I could just set the bias to the figure quoted to me earlier ei:70mv.

I will leave it alone until I learn more!
thanks for your help!


If you are going to be setting the idle bias (actually the idle WATTAGE of dissipation) for amps down the road --- realistically you will be --- get a idle kit adapter that measures both the anode plate voltages (hundreds VDC) AND the cathode dropping mV. Then, you won't have to wonder about each individual amp's plate voltages. Worth the price (IMHO).


Like one of these:

http://taweber.powweb.com/biasrite/br_page.htm

or these:

http://www.eurotubes.com/eurotubes-Bias ... oltage.htm


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Post subject: Re: Hot Rod Dlx III & Mesa 6l6gc bias question
Posted: Sat Jan 18, 2014 2:58 pm
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beatles1909 wrote:
shimmilou wrote:
Then you can't possibly set the bias, so I'm not sure why you asked about a bias setting if you are not going to check. :?


I thought all I needed was a plate level which is why I asked, so when I put the new Mesa tubes in I could just set the bias to the figure quoted to me earlier ei:70mv.
I will leave it alone until I learn more!
thanks for your help!


In order to set the bias to 70 mV, you must have some kind of probe or meter. Using a meter you can check at the test point in the amp.

I think I see what you mean now. You are asking about the grade/rating of the tube, as in the way Mesa rates their tubes, and if they would be a "plug and play" tube in your HRDlx. The Mesa tubes are rated the same as a GT 4 to 6, which would be the white GTs. Do you know the grade of your current GT output tubes? Typically, the HRDlx is biased cold from the factory and should be checked to be sure.

In all likelihood, if you have GTs in the range of 4 to 7 (white), and your sound is good, then your Mesa tubes should be plug and play in the HRDlx.

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Post subject: Re: Hot Rod Dlx III & Mesa 6l6gc bias question
Posted: Sat Jan 18, 2014 3:18 pm
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I thought all I needed was a plate level which is why I asked, so when I put the new Mesa tubes in I could just set the bias to the figure quoted to me earlier ei:70mv.
I will leave it alone until I learn more!
thanks for your help![/quote]

In order to set the bias to 70 mV, you must have some kind of probe or meter. Using a meter you can check at the test point in the amp.

I think I see what you mean now. You are asking about the grade/rating of the tube, as in the way Mesa rates their tubes, and if they would be a "plug and play" tube in your HRDlx. The Mesa tubes are rated the same as a GT 4 to 6, which would be the white GTs. Do you know the grade of your current GT output tubes? Typically, the HRDlx is biased cold from the factory and should be checked to be sure.

In all likelihood, if you have GTs in the range of 4 to 7 (white), and your sound is good, then your Mesa tubes should be plug and play in the HRDlx.[/quote]

my gt is 5 (white), I went to A1 Electronics store here in Toronto today to buy a bias probe but they didn't have any!! lots of old tube testers & other stuff tho!

You have been very helpful & I appreciate it,


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Post subject: Re: Hot Rod Dlx III & Mesa 6l6gc bias question
Posted: Sat Jan 18, 2014 8:17 pm
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beatles1909 wrote:
my gt is 5 (white), I went to A1 Electronics store here in Toronto today to buy a bias probe but they didn't have any!! lots of old tube testers & other stuff tho!

You have been very helpful & I appreciate it,


Read this:

viewtopic.php?f=13&t=88475

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Post subject: Re: Hot Rod Dlx III & Mesa 6l6gc bias question
Posted: Sat Jan 18, 2014 8:18 pm
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modwiz wrote:
bluesky636 wrote:
beatles1909 wrote:
Last week I replaced the pre amp tubes with 12at7 in V3 & 12ay7 in V2 & V1 but the Drive & more Drive cut out as if it was locked & I couldn't get it to switch so I put the 12ax7 back in V1 & V2 & all is fine now .


Using a 12AY7 in both V1 and V2 will make the Drive channel almost unusable. There is not enough gain with those two tubes to get much drive out of the amp without maxing out the controls. Use a 12AY7 or 5751 in V1 only and leave a 12AX7 in V2.


That was what I thought. I must be learning something. :P


Yes, you are. :D

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Post subject: Re: Hot Rod Dlx III & Mesa 6l6gc bias question
Posted: Sun Jan 19, 2014 12:18 am
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beatles1909 wrote:
shimmilou wrote:
...In all likelihood, if you have GTs in the range of 4 to 7 (white), and your sound is good, then your Mesa tubes should be plug and play in the HRDlx.


my gt is 5 (white), I went to A1 Electronics store here in Toronto today to buy a bias probe but they didn't have any!! lots of old tube testers & other stuff tho!

You have been very helpful & I appreciate it,


No problem. Since you have the white 5 GTs, you should be able to plug your Mesa tubes in and go....for the time being, but your bias is likely cold and you really should check it at the first opportunity.

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