Description: Almost Mint Audio Research D76 75 Watts per channel 6550A Tube Amplifier Selling my audio system of many years, this is one owner All GE 6550A Output Tubes. GE was the acclaimed best power tube for this amplifier because of long life and able to handle higher voltages.Here are the transconductance (Gm) measurements for the 6550A tubes measured with my Heathkit TT1 Tube Tester, calibrated with a 6L6 Bogie tube. This tests tubes at a more realistic 250 Volts instead of 150 like a lot of other testersYou can see that all of these GE 6550A tubes measure like new. because the amplifier sat in a closet for about 40 years V15 11,450 uMhos Left Channel Matched Pair V13 10,700 " Left Channel Matched Pair V14 11,750 " Right Channel Matched Pair V16 11,500 " Right Channel Matched Pair V17 12,300 " Series Regulator New 11,500 umhos: This is a NOS GE 65550A that I have This D-76 was used to drive Quad ESL-57 low distortion speakers. It handles the capacitive load with no problem and sounds great with strings and female voices that I listen to. Also, since I have a Tektronix AA501 Distortion Analyzer and SG505 Low Distortion Oscillator, I have been wanting to measure this amplifier for many years, and here are the results. Remember, distortion specification is less than 0.5% At a low level, both channels less that 0.2% At a louder and more normal listening level they measure about 0.05% This explains the great sound I got from this amp. I really hate to part with it. And I calibrated the AA501 using the method Bob Cordell on his web site. The AA501 reads about 5% high, not enough to affect my readings. Issues Both Left and Right Terminal Blocks have broken spacer tabs. Does not affect speaker wire spade lug installation. Even Skyfi sells amps like this. Small scratch less than 1 inch on rear chassis. Pictures are as follows: Front Panel Heathkit Tube Tester Reading. Multiply by 5 to get actual Gm Top Inside Rear Inside Model Number AA501 Residual Distortion .0028% AA501 Calibration. Should read 1.002%, and it reads 1.007% Left Channel Distortion .05% Right Channel Distortion .05% Left Terminal Block, Broken Spacer Tabs. Does not affect speaker wires Right Terminal Block Broken Spacer Tabs. Does not affect speaker wires Rear Chassis Scratch, about 1 inch long Shipping will be Fedex for 53 pounds
Price: 2025 USD
Location: Fairport, New York
End Time: 2024-11-11T03:39:27.000Z
Shipping Cost: 0 USD
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Item Specifics
All returns accepted: ReturnsNotAccepted
Brand: Audio Research
Type: Tube Amplifier
Model: D76
MPN: D-76
