Here is the latest update.
ROWEMEISTERS - MARANTZ PM66 KI MODS 2006/07
PSU
• FITTED SECOND KI TX (NOW RUNNING 2) VA approx 500VA
• REPLACED BRIDGE RECTIFIER (D801) WITH 4X MBR20 20A SCHOTTKY DIODES
• REPLACED C801 C802 WITH 56V 22000uF SILMICS
• REPLACED C717 C718 C719 WITH 50V 1000uF BLACK GATE STD TYPE
• MOVED Q801 Q802 ONTO HEATSINK
• FITTED 100nF , 10nF AND 1 OHM 3W RES ACROSS C801 C803 (snubber)
INPUT
• FITTED QUALITY RCA TO CD INPUT
• REPLACED C701 C702 WITH 50V 10uF BLACK GATE AC TYPE
• REPLACED C705 C706 WITH 16V 100uF BLACK GATE N TYPE
• REPLACED C709 C710 WITH 100pF SILVER MICA 1% TOL
OUTPUT
• REPLACED C751 C752 WITH 25V 100uF ELNA CEREFINE (ON BIAS CIRCUIT)
• REPLACED R755 R756 WITH 2K 24 TURN PRECISION POT (ON BIAS CIRCUIT)
• REPLACED C753 C754 C755 C756 WITH 120pF SILVER MICA 1% TOL
• REPLACED INTERNAL OUTPUT WIRE WITH CABLE TALK MONITOR 2
• UPGRADED WITH UBER HEATSINKS
• ADJUSTED OUTPUT IDLE FROM 14mV (70mA) to 30mV (150mA)
NOTE – VOLTAGE TO OUTPUT IS NOW 46V (WAS 38V) THEREFORE THE OUTPUT WATTAGE SHOULD BE 80W INTO 8 ohm AND 100W INTO 4 ohm.
OTHER
• FITTED CHASSIS AND LID WITH DAMPING MATERIAL
• UNIT SITS ON OAK CONE FEET
WEIGHT – 12.62 KGS
Brent
ROWEMEISTERS - MARANTZ PM66 KI MODS 2006/07
PSU
• FITTED SECOND KI TX (NOW RUNNING 2) VA approx 500VA
• REPLACED BRIDGE RECTIFIER (D801) WITH 4X MBR20 20A SCHOTTKY DIODES
• REPLACED C801 C802 WITH 56V 22000uF SILMICS
• REPLACED C717 C718 C719 WITH 50V 1000uF BLACK GATE STD TYPE
• MOVED Q801 Q802 ONTO HEATSINK
• FITTED 100nF , 10nF AND 1 OHM 3W RES ACROSS C801 C803 (snubber)
INPUT
• FITTED QUALITY RCA TO CD INPUT
• REPLACED C701 C702 WITH 50V 10uF BLACK GATE AC TYPE
• REPLACED C705 C706 WITH 16V 100uF BLACK GATE N TYPE
• REPLACED C709 C710 WITH 100pF SILVER MICA 1% TOL
OUTPUT
• REPLACED C751 C752 WITH 25V 100uF ELNA CEREFINE (ON BIAS CIRCUIT)
• REPLACED R755 R756 WITH 2K 24 TURN PRECISION POT (ON BIAS CIRCUIT)
• REPLACED C753 C754 C755 C756 WITH 120pF SILVER MICA 1% TOL
• REPLACED INTERNAL OUTPUT WIRE WITH CABLE TALK MONITOR 2
• UPGRADED WITH UBER HEATSINKS
• ADJUSTED OUTPUT IDLE FROM 14mV (70mA) to 30mV (150mA)
NOTE – VOLTAGE TO OUTPUT IS NOW 46V (WAS 38V) THEREFORE THE OUTPUT WATTAGE SHOULD BE 80W INTO 8 ohm AND 100W INTO 4 ohm.
OTHER
• FITTED CHASSIS AND LID WITH DAMPING MATERIAL
• UNIT SITS ON OAK CONE FEET
WEIGHT – 12.62 KGS
Brent
Ran amp quite hard last night and all is good. The amp now runs at a warmer level without the heatsink getting too hot. The treble defo has more attack with the bass appearing to be tighter. This could be due to the higher idle current and or the heatsinks. The heatsinks are dead to ringing.
Here are a few pics of the sinks in situe
Brent
Here are a few pics of the sinks in situe
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Brent
Well I'm basing it on the PM17 for now until I have proper proof.
The PM17 is rated at 100W into 4ohm with a voltage of 44V.
Yes my TX and caps are larger so maybe the output is more.
At the moment I am running the standard output transistors on the heatsink (100W max) to make sure everything is ok.
Brent
The PM17 is rated at 100W into 4ohm with a voltage of 44V.
Yes my TX and caps are larger so maybe the output is more.
At the moment I am running the standard output transistors on the heatsink (100W max) to make sure everything is ok.
Brent
Thanks for the update list Brent it looks like C701,C702 are now BG AC but were FK on the last list.
Did you find any difference as I've done the FK mod?
Also when you do the Schottky bridge mod does it matter which way the bridge is orientated?
(Obviously the polarity of the diodes forming the bridge is important or it wouldn't be a bridge!!!)
On the normal heatsink how high would you suggest taking the bias setting? (I know I'd have to check temperature anyway but you have a hell of a lot more experience than me
)
Lots of questions I know but I thought I'd get it all out of the way in one go!
Thanks for your help
Jim
Did you find any difference as I've done the FK mod?
Also when you do the Schottky bridge mod does it matter which way the bridge is orientated?
(Obviously the polarity of the diodes forming the bridge is important or it wouldn't be a bridge!!!)
On the normal heatsink how high would you suggest taking the bias setting? (I know I'd have to check temperature anyway but you have a hell of a lot more experience than me
)Lots of questions I know but I thought I'd get it all out of the way in one go!
Thanks for your help
Jim
Hi Jim
I find the AC caps much better than the FK, they are more natural sounding. I have tried various plastic etc caps and non came close to these. I believe a small fortune would have to be spent to better them. I use them on the output of my cd player too. Use the FK on a 12 or 5v rail in your cd player,I find the FK are hard to beat here.
Idle current, don't go above 20mV (100mA). I originally had mine set to 25mv and after about half an hours listening at an avarage volume the heatsinks were cooking. The lower idle voltage its set too pushed the minimum temp up and when driven harder they got too hot for comfort. If I hadn't got the large caps fitted I would have bolted another heat sink to the inside of the original ones. I do think the original heat sink is very good at dissipating heat, but of course the higher idle current pushes the boundries.
For the bridge it is quite straight forward. As long as the diodes are the correct way round you can't go wrong. The original bridge runs very warm in the 66 but my 4 TO220 package items run fairly cool.
Brent
I find the AC caps much better than the FK, they are more natural sounding. I have tried various plastic etc caps and non came close to these. I believe a small fortune would have to be spent to better them. I use them on the output of my cd player too. Use the FK on a 12 or 5v rail in your cd player,I find the FK are hard to beat here.
Idle current, don't go above 20mV (100mA). I originally had mine set to 25mv and after about half an hours listening at an avarage volume the heatsinks were cooking. The lower idle voltage its set too pushed the minimum temp up and when driven harder they got too hot for comfort. If I hadn't got the large caps fitted I would have bolted another heat sink to the inside of the original ones. I do think the original heat sink is very good at dissipating heat, but of course the higher idle current pushes the boundries.
For the bridge it is quite straight forward. As long as the diodes are the correct way round you can't go wrong. The original bridge runs very warm in the 66 but my 4 TO220 package items run fairly cool.
Brent
Hi
The diodes made very little difference but the difference was positive, they helped with timing. The main reason for changing them was to allow higher current handling with all my other mods.
I have not changed the pot yet, it is a Alps in it but I know there are better ones out there. I don't want to loose the remote control function of it either. There is probs a way of fitting the motor to a new one too.
Have you swapped the vol pot in yours, if so what too and what difference was there.
Brent
The diodes made very little difference but the difference was positive, they helped with timing. The main reason for changing them was to allow higher current handling with all my other mods.
I have not changed the pot yet, it is a Alps in it but I know there are better ones out there. I don't want to loose the remote control function of it either. There is probs a way of fitting the motor to a new one too.
Have you swapped the vol pot in yours, if so what too and what difference was there.
Brent
Alps Blue is pretty standard and has very good tracking (I use one in my preamp). The 66 was probably too cheap to use this part though. Check! You can get a motorised version of Alps Blue. There might even be better ones out there, but it's just a pot at the end of the day and channel balance is the most important thing.
Simon
Simon
My 20k log Alps Blue keeps the image pretty much central right down to the tiniest level. The previous cheap log pot or previous 10k linear Vishay (expensive) couldn't do that at all!
No surprise the attenuaters help with the balance as (most) pots are rubbish at the start of the range, aren't they?
No surprise the attenuaters help with the balance as (most) pots are rubbish at the start of the range, aren't they?
The standard pot standard cheapo stuff. I replaced mine with a 50k Alps Black.
I attached it with solid silver wire, bypassing the little pcb as the pot is massive. The sound improved in all areas, bags more detail.
The best pot I have used was a Noble, removed from my old (awful) Audiolab 8000a. Should've kept that and put in something else!
Don't know if they're available in motorised versions though.
Lee.
I attached it with solid silver wire, bypassing the little pcb as the pot is massive. The sound improved in all areas, bags more detail.
The best pot I have used was a Noble, removed from my old (awful) Audiolab 8000a. Should've kept that and put in something else!
Don't know if they're available in motorised versions though.
Lee.
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