Marantz PM66 KI tweeks

Point to point sounds good. You're a braver man than I am 😉

Brent's told me I need to hardwire the connections from mech to pcb. I don't fancy doing that but I think there's no choice. Also my remote's stopped working because the front panel connector is getting monged. A wire bridge temporarily fixed this but it stopped working again, presumably due to another connection going that was needed to use the remote. It's a nightmare really. But it's worth the hassle for the sound it can make.

Sorry about the OT.
 
Hi Simon

Yeah its the brave bit that's making me hesitate cos its gonna take some thinking to get it right........ try it all together dry.. fiddle about.. try it again... fiddle about some more....etc.....

I just think that for the same brainpower and effort I can move forward more quickly with the individual regs etc, which I know you had amazing success with.

Coax hardwiring seems to be much favoured by bobwire and others. I think he suggested making the wires to the mech PCB about 4" to allow for disassembly.

OT again so back to the PM66KI....

Next for me after the CD mods will be Schottky bridge mod, bigger output trannies then BG AC's on the input and then the pot.

Gonna need to do something with those Missions to get the benefit though. Since I got the Grado's it's been like lifting another heavy veil off the sound, like removing DC blocking caps and muting trannies at the same time. Trouble is, now the speakers sound like they're under a duvet by comparison.

Like you and Brent were saying on the CD63 thread, once you get the modding bug you just can't stop cos you know there's still more listening pleasure to come......

Good luck getting going again..
 
Volume pot upgrade

Fancy an Alps Blue Beauty motorised for my 66KI and wondered how it would compare with Brent's new pot (which is non- motorised).

Also have done the same mains filtering mod as in Ray's CD63 list, i.e. varistor S20K250 on mains terminals on pcb, common-mode choke 2x7.7MH 0.7A across live/neutral after power switch and 2xY-class caps 4.7n/250v across mains before and after filter.

This seems to have killed dynamics a little, but I can't be sure this was the mod that did it as I made a number of changes at once DUH!- noob and keen at the time.

Is this filtering really necessary on the amp?

I can understand the need on a CDP with low-level signals being polluted but on reflection maybe not in the amp.

I read somewhere about mains impedance or something similar.

Opinions please??

Jim
 
Now then I don't know how familiar you are but we build mains filters and they are all passive, I have spent the last two years looking at mains filters and every time found inline filter (coils) killed dynamics. VDRs (MOVS/varistors) also wear out, use transient diodes instead.

Passive filters are best as they do not add impeadance.

Pot wise I picked the one I did based on other reviews on forums etc.

Brent
 
jimh0612 said:
Hi Simon

Apart from channel balance, do you feel there are any improvements sonically?

Jim

Hi Jim,

Yes, but only subtle ones. Before the Alps I used a cheap 10k log pot, and before that a Vishay linear taper. The first two were rubbish as volume controls and all three (when L-R was ok!) made music. The Alps Blue does seem to give a little more music, however. I think it's a 20k this time.

Simon
 
Hi Brent. Good to see you're keeping busy. Have you compared your amp to any standard commercial amps?

I still have a ki amp in bits on the shelf (maybe 2), just haven't got around to sorting it yet! I suppose I should really.

Lee.
 
Hi Lee

I have compared it to a PM17KI and I can honestly say mine beat it on every single aspect apart from power as they are approx the same. Bass was lower and more controlled, treble extension was better and crisper. Mid range my PM66 competely out performed it. The distortion levels are very low on my amp now.

I have also listened to a £12500 Naim system running ATC speakers with Simon and it never blew me away, apart from the impressive volume levels it was not really any better than my system in terms of overall performance.

Simon will tell you how well it performs on the power hungry ATC.

Brent
 
rowemeister said:
Simon will tell you how well it performs on the power hungry ATC.

It drives the ATC SCM40s readily, with no signs of stress. Basslines are very controlled, full and detailed. The tone and smoothness is terrific. I also heard it cranked and the amp delivered the needed current, that's for sure! It was smooth and dynamic up to VERY high levels (in Brent's small room).

It shows that this amp can really perform when properly modified, much like the CD63/7 range.

Simon