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LOUIS ELECTRIC AMPS FORUM
GOT TONE?
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jcshirke
Super
Joined: 01 Oct 2008
Posts: 51
Location: USA
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 Posted: Wed Dec 03, 2008 7:23 pm Post subject: |
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| davebc wrote: |
Invest in a Mullard rectifier; you will feel the difference.
Lou biased my amp for my Mullard EL34's; and a set of something else with the same points. |
Do you know the bias point for your Mullards in your KR12? |
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mitchema
Deluxe
Joined: 17 Nov 2008
Posts: 5
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| Posted: Sat Jan 03, 2009 9:16 pm Post subject: Bias setting for Mullard EL34 in KR12 |
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Lou,
I've a NOS set of matched Mullard EL34 xf2's. Where should the bias be set for these tubes? |
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uniphasian
Deluxe
Joined: 21 Jul 2008
Posts: 8
Location: Denver, CO
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| Posted: Sun Jan 04, 2009 10:02 pm Post subject: |
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| jcshirke wrote: |
Anyone know what the bias should be on NOS KT66 tubes in the Baby Bluesbreaker? I'm on the verge of buying a pair of GECs that are 70 and 70.5 milliamps. Sound right? If I get them, I will have them sent straight to Lou to put into my amp when he builds it.
Just curious if anyone can let me know if I should pull the trigger on these tubes or not. The price is right, that's for sure. Here's a description from the seller (Note: They have GEC on the label...brown bottoms, so it appears):
KT66 Kinless Tetrode Pentode
Filament: 6.3 Volts
Anode and Screen Volts 250
Negative Grid: -15
Standard value of the KT66 in current is 65mA the you can see from meter left that both test at 70mA and 70.5mA that is 100%. Also they have double getter of the 1960's and not the single getter of the 70's. I use in my audio amps and they are stunning.
Thanks,
Jeff |
I'll try since I just went through this with my Baby Bluesbreaker this afternoon.
100 power rating of KT66 is 24 watts. Power(watts)=Voltage(volts)*Current(amps) - (remember to convert milli-amps to amps)
Now, it depends on your amp, and how close to the edge you want to run your tubes. I'm running Shuguang KT66s and they sound better running hotter.
Normally, you'd run the KT66s around 60% of the 24 watt max, or 14.4 watts (24*.60). If you want to run them hotter, 70% is 16.8 watts, and 80% is 19.2 watts.
Pick what you're comfortable with and what sounds best in the amp.
I biased my amp (since Lou recently installed a bias pot) so that it runs at 425V and 43 mA. That gives me (425)(0.043)=18.275watts or 76%.
I had a pair of Gold Lions that ran fairly hot - I could not set the bias where they ran at less than about 55mA. I pulled them and am now running the Shuguangs since they seem to run better in this amp.
If I did this wrong, someone please tell me soon. KT66s are not cheap.
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