Description
Up for you consideration is a PAIR of what I am calling Yamaha M-60M Monoblock power amplifiers. They in good to fair used physical condition, functionally fully working and upgraded. I have upgraded a couple of stock Yamaha M-60 Stereo power amplifiers to Monoblocks. So, you need both of these for a stereo set-up. Both are part of this auction. I did the following to convert these into monoblocs. Set voltages 10% higher for additional power/ headroom.Upgraded Audio outputs to 230v/ 16A devices that are used in the Krell/Dagostino Relentless amplifier. The OEMs are 140v devices. I kept both Sanken outputs to keep the Yammy sonic signature.Old capacitors in the signal path upgraded to Nichicon Muse. Other caps checked to make sure they were in spec.Base current and output current to the output stage has been doubled. Each monoblocs now has Eight output devices plus eight Regulators for a total of 16 power transistors per monobloc.Bias for lower heat operation is set at 2 watts pure Class A. ie it runs on 2 watts pure class A all the time.The standard Auto class A is fully functional. And raises this between 15-25 watts pure class A if you desire to heat up your room. With this setting please do not stack anything on top of the mono-blocks to impede cooling.Used the second (un-used) RCA input to be capacitor coupled. So you can now use the R input as DC coupled, and the L input as AC coupled. Furthermore, you can use this to daisy chain more amplifiers by putting signal into the R input, and getting an AC coupled signal out from the L RCA.Both Monoblocs were designed the same in terms of both have the Right channel configured as the Master, driving the left channel in parallel, thus you will only see right channel inputs and outputs in both units. Gold plated speaker posts installed. All Speaker A, B and C are user selectable as stock. (For normal operation, keep A + B engaged)New LEDs installed to replace worn out lamps. Meters calibrated.Voltage set at 110v at the rear, you may set it to 120v if you wish, to have the amplifier run cooler, however you will lose about 20watts of power at 8 ohms. I have used larger outputs to be able to run at higher voltages, and as long as you keep the amplifiers cool, there is no harm. I would not recommend leaving the amplifiers on for extended periods of time. It just reduces the life of the product. Condition:Mixed bag, both units are used and vintage, so they are not MINT. However, they are quite presentable.One of the units has some dents underneath, but not visible unless you turn it upside down. In the rear it has some cracked glass on the edges, not very visible unless to take a flashlight and look. Id say they are in fair condition overall. Some scratches commiserate with age are present. Glue issue mitigated, new caps in audio path. Good for another 20 years. This been fully tested, bias is set. Class-A bias confirmed. I tested full power into 4 ohms and prior to clipping gave me more than 400 watts into 4 ohms (one combined channel driven, ie one monoblock). At 8 ohms, it pumps out over 200 watts before clipping. (closer to 245watts) Essentially, I have parallel bridged both channels. Doubled the outputs from stock. The amplifier is now more stable into lower impedances. UPGRADED speaker posts on this unit. The are 5 way Banana binding posts. The OEM could only accept bare wire. You can now use Banana jacks, spades, inserts and bare wire. Sounds amazing, soft, delicate, detailed, most importantly, because of an upgrade I did (will share details with the new owner) the sound is warm and less steely, especially in the mids. Please see all photos and ask questions if in doubt!
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