kcin
Well-Known Member
Hi,
I'm new to this group and Mac equipment it's great to see a helpful group dedicated to the marque.
I must admit I was never a much of a Mac fan until I was converted this past fall by acquiring a vintage Mc225. After some updates it has to have one of the best presentations I've ever heard on my quad ESL's. I've tried and have on hand the Marantz 8b, Citation II, quad II, Dynaco MkIII....the only one that works better may be the Futterman H3.
So now that I've got the bug I acquired a pair of Mc30's that are in pretty good condition. Trouble is that they are slightly different in topology. One has a separate tap off the xfrmr for bias and one does not. Additionally,the one with the separate tap has a couple of extra caps in place (.047mfd) and some of the voltage divider resistors around the splitter are of different values.
The other amp has the odd arrangement of bias through a dropping resistor only off the HV...this one I can find schematics for on the web ...the other I cannot. I've changed the bias rectifier , a weird looking thing that looked like a paper cap, to bring the bias voltage up... It was off by more by half! I changed the electrolytics as well.
Any sense of what's going on with the additional circuitry of the Mc30 with the separate tap ( access to a schematic) or more importantly is there significant enough difference between the two to result in audible performance issues? I'm waitng on a few parts that are off spec and will fire them up on the system and report back.
Thanks for any help.
Nick :scratch2:
I'm new to this group and Mac equipment it's great to see a helpful group dedicated to the marque.
I must admit I was never a much of a Mac fan until I was converted this past fall by acquiring a vintage Mc225. After some updates it has to have one of the best presentations I've ever heard on my quad ESL's. I've tried and have on hand the Marantz 8b, Citation II, quad II, Dynaco MkIII....the only one that works better may be the Futterman H3.
So now that I've got the bug I acquired a pair of Mc30's that are in pretty good condition. Trouble is that they are slightly different in topology. One has a separate tap off the xfrmr for bias and one does not. Additionally,the one with the separate tap has a couple of extra caps in place (.047mfd) and some of the voltage divider resistors around the splitter are of different values.
The other amp has the odd arrangement of bias through a dropping resistor only off the HV...this one I can find schematics for on the web ...the other I cannot. I've changed the bias rectifier , a weird looking thing that looked like a paper cap, to bring the bias voltage up... It was off by more by half! I changed the electrolytics as well.
Any sense of what's going on with the additional circuitry of the Mc30 with the separate tap ( access to a schematic) or more importantly is there significant enough difference between the two to result in audible performance issues? I'm waitng on a few parts that are off spec and will fire them up on the system and report back.
Thanks for any help.
Nick :scratch2:
