I recently acquired two Macintosh 75 watt monos. (from family) They are about 40 years old but have been in storage for most of that time. This tech is new to me and I don't know exactly how I can feed a signal into them. I looked on line at mac preamps and was floored by sticker shock. I want to use them for a PA for my son. (guitar,piano and mics) He is using a Yamaha solid state mixer. The input on the Mac is labeled .5 volt. This is the only input and it is an unbalanced rca connection. How can I put this stuff together. What do I have to do with the mixer output. I don't want to blow anything up. Any help from experience out there?
pre-amp for a macintosh 75 watt mono amp
- Thread starter jim pavs
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SlyFoxx
Glossless
Re: pre-amp for a macintosh 75 watt mono amp
If they have been idle that long I doubt they will work at all as the filter caps have probably dried out. But if that's not the case just plug in the mixer, choose an audio source (I'd plug in a CD player or mp3 player) and s-l-o-w-l-y bring up the master and see what's what.
If they have been idle that long I doubt they will work at all as the filter caps have probably dried out. But if that's not the case just plug in the mixer, choose an audio source (I'd plug in a CD player or mp3 player) and s-l-o-w-l-y bring up the master and see what's what.
Re: pre-amp for a macintosh 75 watt mono amp
Serious disappointment! plugged them in. One of the kt88 tubes didn't even light up. No sound, not even a touch of static. Maybe I can get a professional or hobbyist to look them over. thanks
Serious disappointment! plugged them in. One of the kt88 tubes didn't even light up. No sound, not even a touch of static. Maybe I can get a professional or hobbyist to look them over. thanks
Jeffblue
Well-known member
Re: pre-amp for a macintosh 75 watt mono amp
I agree with Darg1911, sell them as they are to someone who knows how or knows someone who can repair them. Hopefully you didn't pay too much for them. If you decide to keep them, use them for high end stereo audio because after they are brought back to life, you won't believe your ears. If you are not an audiophile, just let them go.
I agree with Darg1911, sell them as they are to someone who knows how or knows someone who can repair them. Hopefully you didn't pay too much for them. If you decide to keep them, use them for high end stereo audio because after they are brought back to life, you won't believe your ears. If you are not an audiophile, just let them go.
TwilightOdyssey
Darkness on the edge of Tone
Re: pre-amp for a macintosh 75 watt mono amp
Macs are not suitable for using in a PA type of situation; they are hifi. Connect a good source and preamp, connect them to decent speakers, and enjoy music to a level you have never experienced before.
For a decent preamp, I would use conrad-johnson, Audio Research, or Krell. My home hifi is an Audio Research preamp, Krell power amp, and Sonos Faber loudspeakers with Audioquest, Lyra Constellation and Kimber Select cables.
Macs are not suitable for using in a PA type of situation; they are hifi. Connect a good source and preamp, connect them to decent speakers, and enjoy music to a level you have never experienced before.
For a decent preamp, I would use conrad-johnson, Audio Research, or Krell. My home hifi is an Audio Research preamp, Krell power amp, and Sonos Faber loudspeakers with Audioquest, Lyra Constellation and Kimber Select cables.
L
Little Pigbacon
Guest
Re: pre-amp for a macintosh 75 watt mono amp
I’ll go out on a limb and say something tubed and balanced from Audio Research, like an LS-25, would be a great match.
I’ll go out on a limb and say something tubed and balanced from Audio Research, like an LS-25, would be a great match.
TwilightOdyssey
Darkness on the edge of Tone
Re: pre-amp for a macintosh 75 watt mono amp
You could also go with something like a Creek or Arcam intergrated amp and use the preamp outs just to get started.
Valve preamps need a lot of surrounding space for ventilation. If that's an issue, a solid state model would be preferable. Personally, I prefer hybrid setups (valve preamp, solid state power amp). Mac amps are not known for being very precise.
You could also go with something like a Creek or Arcam intergrated amp and use the preamp outs just to get started.
Re: pre-amp for a macintosh 75 watt mono amp
+1 to what others have said. I doubt the Macs were designed to be hauled around and take the abuse of pro PA gear. Sell them and get the proper tool for the job.
FYI (if you really want to use these), I have a Dynaco SCA-35 and had no issues running a Mesa Studio preamp into it. Just need some 1/4" to RCA conversion jacks. I don't use this amp for guitar now (went back to hi-fi use), but it got the job done. You could do the same thing with pedals instead of the Mesa, just make sure they have a good level / volume control.
+1 to what others have said. I doubt the Macs were designed to be hauled around and take the abuse of pro PA gear. Sell them and get the proper tool for the job.
FYI (if you really want to use these), I have a Dynaco SCA-35 and had no issues running a Mesa Studio preamp into it. Just need some 1/4" to RCA conversion jacks. I don't use this amp for guitar now (went back to hi-fi use), but it got the job done. You could do the same thing with pedals instead of the Mesa, just make sure they have a good level / volume control.
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