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In Reply to: Re: AirTight ATM 2 Amplifier Help posted by who on August 2, 2005 at 14:30:09:
Many thanks for your reply. Should each valve be set to the middle of the meter or just numbers 2 and 4 that have the word "bias" on the adjuster? (Sorry I'm a bit dim on this!)Thanks
Follow Ups:
Hi Clennard,You turn the Bias (#2 and #4) to approximately set the overall bias to the middle area, and then you turn the Balance (#1 and #3) to give each tube the exact & equal bias level.
You use the front meter to monitor this procedure. It should take no more than a minute when you are familiar with it.
Be careful and insulate your screwdriver with some kind of tape because you COULD touch the amp interior in this process.
Please experiment with the bias level to your liking, but no lower than 3 dots from the bias “bubble”, where distortion appears.
I use Magnepan speaker, so the bass is still pretty fast at the lower bias setting.
Some people think this amp does not sound like a typical tube amp, and I agree. It has strong bass and does not roll off the treble.
For your reference, I use Telefunken 12AX7 and 12AU7, GE 12BH7, Electro-Harmonix KT88 and 6550.
You could also use Electro-Harmonix 12AX7/12AU7/12BH7 for a lot more bass and treble at a cost of a little more graininess.
I believe this amp was rated Stereophile class A 10-12 years ago.I hope this helps.
Regards,
-who (my real name :) after the English translation)
Who,
I have an AirTight ATM-2 also and love it. I'm using TungSol 6550, RCA 12AX7, and RCA 12AU7. I've also got a set of the Siemens (ECC82 and ECC83) that I'm gonna test in the next few months. Have you done any modifications to the speaker wire posts and the power cable? The originals look pretty cheap. I'm wondering if replacing those with something a little more high quality will improve sound. And if so, is it a pretty involved process?
Hi Winston,I keep my all stock. I have no doubt that the speaker wire posts and the power cable modifications could change the sound, but the ROI (return on investment) could be low:
- It is impossible to do A/B test to know for sure if they make any difference
- It could decrease the resale value
- I am too lazyI prefer reversible tweaks like the tube rolling that you plan to do. I do like different sound from time to time and have tried 211 and 845 monoblocks.
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