I was reading something on those speakers the other day, and it said they needed a lot of power. My speakers are the exact opposite, they're around the 100db sensitivity mark and 8 ohms. Could the pm66 be biased into class a up to around 15 watts before the class ab "kick in"? That's all my speakers need to go really loud!
If it can, it will be good 'cos I like class a sound.
Lee.
If it can, it will be good 'cos I like class a sound.
Lee.
Thomo said:
I'd say cut your losses and buy a class A amp from the start. The Marantz can't be biased very high AT ALL on the standard flimsy heatsinks, as Brent found out. 15W would surely blow it up in minutes.
Can you confirm, Brent?
Simon
It would most certainly self detonate.
A second TX in the PM66KI makes a world of difference to the power and sound, give it a whirl.
The ATC do need a bit of beef behind them (50W - 300W). TBH I barely have to turn it higher than I did with my 89db missions, and thanks to the quality of them they deliver good bass at low volumes.
Brent
A second TX in the PM66KI makes a world of difference to the power and sound, give it a whirl.
The ATC do need a bit of beef behind them (50W - 300W). TBH I barely have to turn it higher than I did with my 89db missions, and thanks to the quality of them they deliver good bass at low volumes.
Brent
Hi. Will it be ok to add the PM66KI toroid and the PM6010KI toroid? They look the same except the 6010 version has a copper shield around it.
Lee.
Lee.
Thomo said:
While we are at it !!!!
Brent, what is the overall size of your 'double' transformer ?
Andy
poynton said:
I have not measured the transformers for their physical size, the VA is approx 450 ~ 500VA.
Brent
Hi guys
Finally got round to doing more mods on the 66KI at the weekend.
In went the 10uF BG AC's in place of the FK's a la Brent, also replaced the bias trim pots with 25 turn precision jobbies, set idle voltage to 18mV and took out the choke, varistor and caps across L/N etc. that I had put in copying Ray's CD63 filtering mods.
Overall a MASSIVE difference!
Loads more detail, attack and realism. Dynamics have come back with a vengeance, so Brent was absolutely right about the choke killing dynamics, the choke made everything seem so flat and lifeless. I did it at the same time as some mods on the CDP so I wasn't sure what had done it. A lesson learned - don't do too many mods at once.
I bought a dead 66SE off eBay hoping it was the fuse resistor. Turned out there was a big hole burnt in the board and then case was a mess.
However, there is a big beefy transformer (copper shielded) and I wondered..............
Brent has two trannies, so maybe I could use the two together.....
What you think guys?
Jim (very happy with his amp now.....) 😀
PS. Next up will be the Alps Blue motorised volume pot and the diodes replacing the bridge
Finally got round to doing more mods on the 66KI at the weekend.
In went the 10uF BG AC's in place of the FK's a la Brent, also replaced the bias trim pots with 25 turn precision jobbies, set idle voltage to 18mV and took out the choke, varistor and caps across L/N etc. that I had put in copying Ray's CD63 filtering mods.
Overall a MASSIVE difference!
Loads more detail, attack and realism. Dynamics have come back with a vengeance, so Brent was absolutely right about the choke killing dynamics, the choke made everything seem so flat and lifeless. I did it at the same time as some mods on the CDP so I wasn't sure what had done it. A lesson learned - don't do too many mods at once.
I bought a dead 66SE off eBay hoping it was the fuse resistor. Turned out there was a big hole burnt in the board and then case was a mess.
However, there is a big beefy transformer (copper shielded) and I wondered..............
Brent has two trannies, so maybe I could use the two together.....
What you think guys?
Jim (very happy with his amp now.....) 😀
PS. Next up will be the Alps Blue motorised volume pot and the diodes replacing the bridge
Hi Jim
Good work indeed 😉
Did you mean you bought another 66KI, if so fitting the second tx transforms the amp into something much more special. The delivery of bass and vocals is superb.
Did you set both channels bias up to 18mV once it was warmed up. If so you need to let the amp go cold and monitor them. You really want to make sure the idle for both channels is pretty much identical so that both channels sound the same.
You can also run the idle higher than that. You are 18mV = 70mA.
Set it to 22mV = 110mA. The heatsinks will be fine but remember to check both channels bias from cold, let them settle for 10-15 mins. If one channel is much higher then knock it back quickly. The reason I say this is because once the heat has got into the sink it takes ages for it to settle back. Then always test from cold.
Brent
Good work indeed 😉
Did you mean you bought another 66KI, if so fitting the second tx transforms the amp into something much more special. The delivery of bass and vocals is superb.
Did you set both channels bias up to 18mV once it was warmed up. If so you need to let the amp go cold and monitor them. You really want to make sure the idle for both channels is pretty much identical so that both channels sound the same.
You can also run the idle higher than that. You are 18mV = 70mA.
Set it to 22mV = 110mA. The heatsinks will be fine but remember to check both channels bias from cold, let them settle for 10-15 mins. If one channel is much higher then knock it back quickly. The reason I say this is because once the heat has got into the sink it takes ages for it to settle back. Then always test from cold.
Brent
rowemeister said:
Hi Brent
No it was an SE, so it doesn't have a toroid.
Yes I started the bias adjustment from cold and watched it go up.
Once well warmed up it was a bit weird, adjusting the voltage to 18mV and a couple of minutes later it had changed. Took about half an hour of tiny adjust, let it settle, tweak, settle, etc.
The only thing I didn't do is let it go cold, but I'll check when i get chance.
Do you reckon the SE TX will be OK in the KI?
Cheers
Jim
Yes it takes ages to get bias to settle when you are tweeking it up. It's the extra heat generated that effects the bias current. eg you are changing it with the pot and the heat is effecting the HFE of the transistor on the heatsink. Small adjustments are needed.
Don't use the SE tx with the KI tx its not the same voltage or current (never mind they both offer a different sound).
Brent
Don't use the SE tx with the KI tx its not the same voltage or current (never mind they both offer a different sound).
Brent
OK guys thanks for the advice.
Will stick with the one Tx for now.
Will up the bias voltage again when I do the volume pot and replace the bridge. Left it at 18mV until I saw the heating effect and it seems fine, so I'll go a bit more and see how that goes.
I could use the heatsinks from the SE on the inside of the existing ones to help with cooling, though, couldn't I?
I'd also like to wire the cd input through in my gold plated silver wire but am unsure where to take it from/ to.
Brent I know you did this, could you please advise where from, to etc?
Thanks mate.
Jim
Will stick with the one Tx for now.
Will up the bias voltage again when I do the volume pot and replace the bridge. Left it at 18mV until I saw the heating effect and it seems fine, so I'll go a bit more and see how that goes.
I could use the heatsinks from the SE on the inside of the existing ones to help with cooling, though, couldn't I?
I'd also like to wire the cd input through in my gold plated silver wire but am unsure where to take it from/ to.
Brent I know you did this, could you please advise where from, to etc?
Thanks mate.
Jim
jimh0612 said:
Presumed it's from the input RCA to the mainboard, but that would mean no other inputs would be available if I bypass the source direct switch, right?
I'd still like to use the tuner input, but am not as bothered at this stage about improving its signal quality.
Is this possible with your mod Brent?
Jim
The source select switch is on the input pcb, it is really easy to meter out the tracks from the rca to the switch. The end connector of that pcb is also labled so you can meter back from that to the switch.
Brent
Brent
rowemeister said:
D'oh!!
Obvious really at that end!!
How about source direct at the other end?
I wouldn't want to bother with balance, so I need to figure that one out as well.
Thanks mate.
Jim
All you need to do is run the wire from the source select switch out pins direct to the pot and from the pot to the input on the main pcb (which is also labled). Everthing is then bypassed 😉
Make sure you run the gnd to the pcb from the pot also.
Brent
Make sure you run the gnd to the pcb from the pot also.
Brent