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Mac 1500 vs Fisher 500c.

Posted by Michael Samra (D) on November 28, 2016 at 22:42:53

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The 500c and the Mac 1500 are two interesting units.I have six of the 500c and one 800c. The 500c and 800c are all tube units including preamp section while the mac 1500 has a discrete solid state preamp,but the tuner and amplifier stage are tube other than the tuner output stage which has four discrete transistors.
All in all,I much prefer the 1500 as it does everything better IMHO.
Some of the reasons for this is the superior iron,the 12AU7 drivers as opposed to a 12AX7 which are weak by comparison.I say this because on the 500c,there is a slope that develops as you get past 12 o-clock on the volume control and distortion rises dramatically.The 1500 I can take all the way to 4 o-clock on the volume pot and I'm still not clipping and the 1500 is making more power. It also has separate bias pots for the 7591s.
The tuner in the 500c is very good but it also very good in the 1500.What I really love about the 1500 is the fact that it's quiet and that allows you to hear more detail and little nuances that would otherwise over look.
Now keep in the mind that I rebuilt that this unit with new filter caps going up 2.5 times the original values.I also uses Schottkys in the power supply and I did change transistors in the phono section to ones that were more quiet.I changed all coupling caps to k40s and Solen Film and tin foil.Muse caps all thru the bias and emitter circuits.
The main problem with Mac 1500 is the high impedance 10v supply.There is a filter cap that shorts and that will kill the preamp.

Now before you go off on a tangent thinking I'm crazy,I'm working on a circuit for the 500c that will help dramatically..I'm changing the 12AX7 driver to a 7247 or a 6U8a.The feedback also needs tweaking in the 500c because the Sherwood S-8000 runs well with a 12AX7 driving the 7868s but,the iron and feedback are different.When I feel better,I will do more testing on the 500c preamp. Right now tho,this 1500 just gets it in every way.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

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