Air Tight ATM-300 - Bias procedure - Alex

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Air Tight ATM-300 - Bias procedure

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Hello all,
I've purchased a second hand Air Tight ATM-300 amplifier.
The original tubes are Electro Harmonix 300B and on the boxes are written: 48mA and 61mA respectively.
I've tested the bias through the dedicated knob and the reading was the same for the two channels.
Then, I've switched-off the amp and installed a brand new MATCHED pair Electro Harmonix GOLD grid(47mA both tubes).
After some time, I've tested the bias and the reading was different for each channel.
I've listened to the music and the left channel was louder than the right channel.
With my multimeter and a tone of 315Hz from a CD player, the readings measured at the speaker terminals were 0,34V(L) and 0,12V(R), a big difference.
Please, owners of the ATM-300 help me! Is there any potentiometer inside the amp that must be set when replacing 300B tubes?
I thank you in advance for your support.
Best regards,
Alex

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Topic - Air Tight ATM-300 - Bias procedure - Alex 11:11:59 04/01/07 (1)

Re: Air Tight ATM-300 - Bias procedure - cjfrbw 17:15:01 04/01/07 (0)

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