AudioNervosa
Systemic Development => Amplification and Preamplification => Topic started by: S Clark on October 23, 2020, 07:34:24 PM
-
I finally got an old Moscode 300 amp back to George Kaye for repair. He's come up with a way to double the number of mosfets for supposedly a magical and mystical improvement- at a price that isn't crazy. Anyone here know what doubling the number of mosfets would effectively do?
-
Scott,
I believe that a company called Magnetec in the UK at one point was able to put two of the Hitachi style power MOSFET die in one case to effectively make two in one. That would drop the device output impedance in half and allow greater output drive current capability.
It would also double the input capacitance of the MOSFET device, so mods to the driver stage might be needed.
A friend uses them in his power amp design and he started with the Hitachi devices years ago like Hafler used in the DH200 amps.
-
... That would drop the device output impedance in half and allow greater output drive current capability.
It would also double the input capacitance of the MOSFET device, so mods to the driver stage might be needed...
... so, more headroom, more open and spacious???
-
Probably more bass control or lower extension with more current drive. With no driver stage change, might roll off the top end.
-
Does the double Mosfet mod change the output power?
-
... That would drop the device output impedance in half and allow greater output drive current capability.
It would also double the input capacitance of the MOSFET device, so mods to the driver stage might be needed...
... so, more headroom, more open and spacious???
Maybe. Are you able to hear one before mod ? Hard to say the outcome.
charles
-
Does the double Mosfet mod change the output power?
The double MOSFETs should give more output power to low impedance loads if the power supply can handle the extra current required.
-
Well, when George gets back to me, hopefully before I leave this planet, I'll pass along what he says about it. This old amp has been sitting too long, and needed to be junked or repaired, so inquiring about an upgrade was also a motivation to get him to respond to my repair request. I also sent him a pair of 17 000 uF caps that can be strapped to the original power caps. It will be interesting to see how he responds.
-
Maybe. Are you able to hear one before mod ? Hard to say the outcome.
charles
Well honestly, I haven't heard it in 7-8 years as I replaced it with a Moscode 401HR that had some upgrades. It's been driving my GR LS9's ever since.
-
I have to say, over the years my Moscode 600 made 3 trips to George for upgrades and I was always very happy with the results.
-
George Kaye responded to questions about the double mosfet upgrade: "Deeper soundstage, better bass control, increased damping factor, more power into low impedance (4 ohms or less) speakers." Seems like Rich pretty well nailed it in his response. My LS9's are moderately efficient, but have high back EMF that requires some power to keep under control. It will be interesting to see if the old Moscode 300 can work as well or better than it's younger, more powerful cousin, the HR401.
-
I sent my old Moscode 300 to George Kaye last October... and just got it back today with a list of mods as long as your arm. And I gotta say, as of the first hour or so, it sounds pretty darn good. Which is a miracle.
UPS made it a personal challenge to try to break it into a thousand pieces. The box was wet, one corner torn badly 5-6 inches, crushed in the center, another corner crushed 3-4" -- even the UPS driver was embarrasses and walked me though how to best word a claim.
But I had expected it to be handled by lower primates, so it was double boxed with a 2" layer of styrofoam between boxes. The inner box had a plywood bottom, and inch of styrofoam surrounding everything. The inner amp was wrapped in 3" of bubble wrap.....
And so it's playing magnificently in my small system. I'll let it go a bit, then move it into my big system. Honestly I haven't heard it in years, but it sure seems clearer and more detailed than I remember. Bass control is also noticeably excellent.
Wasn't cheap, but so far so good. :thumb:
-
I sent my old Moscode 300 to George Kaye last October... and just got it back today with a list of mods as long as your arm. And I gotta say, as of the first hour or so, it sounds pretty darn good. Which is a miracle.
UPS made it a personal challenge to try to break it into a thousand pieces. The box was wet, one corner torn badly 5-6 inches, crushed in the center, another corner crushed 3-4" -- even the UPS driver was embarrasses and walked me though how to best word a claim.
But I had expected it to be handled by lower primates, so it was double boxed with a 2" layer of styrofoam between boxes. The inner box had a plywood bottom, and inch of styrofoam surrounding everything. The inner amp was wrapped in 3" of bubble wrap.....
And so it's playing magnificently in my small system. I'll let it go a bit, then move it into my big system. Honestly I haven't heard it in years, but it sure seems clearer and more detailed than I remember. Bass control is also noticeably excellent.
Wasn't cheap, but so far so good. :thumb:
:thumb:
I've always heard good things about GK!
-
I sent my old Moscode 300 to George Kaye last October... and just got it back today with a list of mods as long as your arm. And I gotta say, as of the first hour or so, it sounds pretty darn good. Which is a miracle.
UPS made it a personal challenge to try to break it into a thousand pieces. The box was wet, one corner torn badly 5-6 inches, crushed in the center, another corner crushed 3-4" -- even the UPS driver was embarrasses and walked me though how to best word a claim.
But I had expected it to be handled by lower primates, so it was double boxed with a 2" layer of styrofoam between boxes. The inner box had a plywood bottom, and inch of styrofoam surrounding everything. The inner amp was wrapped in 3" of bubble wrap.....
And so it's playing magnificently in my small system. I'll let it go a bit, then move it into my big system. Honestly I haven't heard it in years, but it sure seems clearer and more detailed than I remember. Bass control is also noticeably excellent.
Wasn't cheap, but so far so good. :thumb:
Ya know, Scott. You’ve got a way with words :lol: 🦍 🦍
-
:thumb:
I've always heard good things about GK!
I have to say that so far I'm impressed with the sound. Just don't expect George to get in any hurry to work on stuff. I suspect that he works for a day, then takes off two. I know he took 3 weeks on the amp before mine.
But the time and money will be well worth it, I suspect.
-
Ya know, Scott. You’ve got a way with words :lol: 🦍 🦍
Sometimes. Kinda like my arthritis, it comes and goes.
-
My Moscode 600 made three trips to George's shop for upgrades over the years. It always came back sounding significantly better, and while quality was always the hallmark of his work, speed was never really on the table. Luckily it was never my only amp, so I was not high and dry while the Moscode was in the shop. That made the wait a little easier to deal with,
But then, good things are always worth waiting for. 8)
-
Scott,
Glad the upgrade worked out for the MOSCODE amp! :D
-
and while quality was always the hallmark of his work, speed was never really on the table.
When George emailed to say that the amp was finished, he also said he wanted to hang on to it for another 4-5 days to continue to listen, burn in, and adjust. Got to say, this is admirable in a world where turnaround is king. Most shops would simply want to get it out the door. So I've got to agree that George takes pride in the sound of his gear. And like you, not having this amp did not deprive me of music.
-
:thumb:
I've always heard good things about GK!
I have to say that so far I'm impressed with the sound. Just don't expect George to get in any hurry to work on stuff. I suspect that he works for a day, then takes off two. I know he took 3 weeks on the amp before mine.
But the time and money will be well worth it, I suspect.
George is a lot like the rest of the "olde garde" I think. We work because we love what we do and enjoy the reality of making another's experience as good as possible. Old guys are slow, by definition. We have already run the race and we are taking cool down laps...
-
:thumb:
I've always heard good things about GK!
I have to say that so far I'm impressed with the sound. Just don't expect George to get in any hurry to work on stuff. I suspect that he works for a day, then takes off two. I know he took 3 weeks on the amp before mine.
But the time and money will be well worth it, I suspect.
George is a lot like the rest of the "olde garde" I think. We work because we love what we do and enjoy the reality of making another's experience as good as possible. Old guys are slow, by definition. We have already run the race and we are taking cool down laps...
Nah, George took his time 30 years ago when brought my amp to him in the early 90s. Can't blame his age, it's just the way he is. But he always took great pride in what he did and his work showed that, so I was always willing to put up with the wait.
-
I will second the motion re:GK. He can be quirky as all hell. One call he's very snippy and impatient, the next call he's your long lost pal! :shock: My used Moscode 600 was completely revamped by George a good number of years ago when I first got it. (2011...?) It took forever, but it sounds great and will drive a pair of cinder blocks! :lol:
A "lifetime" amp in my opinion.
SN
-
It should be a step forward knowing the reputation of George.
charles
-
It's been 7 months since I put the Moscode 300 in my system to compare to the Moscode 401HR.
This was one of those repair it or junk it decisions. But when George Kaye described a "double" mosfet option, I decided to gamble the extra bucks on upgrades, and the "in for a penny, in for a pound" decision. This led to much more investment than planned, a frustrating relationship with George (sloths move faster), and a real question about whether investing $$ in a "backup" amp was wise. I still don't know it was wise, but I have absolutely no regrets about the investment.
The short version is that the old 300 is still driving my LS9's. It's not that it's better than the 401HR, but months and months later, the 401 HR is still sitting on the shelf not hooked up. Now some of that is related to my listening habits-- I'll go through slumps where I don't put on an lp for weeks. But the truth is, this amp has precision, soundstage, and BALLS that it didn't have before. The 401 HR still goes into service in the main system, but I'll change it out occasionally. And when I do, the little 300 stays longer that expected.
When I picked up the 401, it was because I was chasing the first of three amps to come up used/cheap. I was looking for a Dodd 120, or a McCormack 500, or the 401HR... all recommended by guys that had the same speakers that I had. At the time I was using the old 300, and it didn't quite have the control and nuance I was looking for to match with such huge speakers. The 401 came in at a deal, and I never looked back. Much later I had hooked up the 300 to find it motor boating (not tube related). Gary D had fixed it before, but this time he just wasn't able to work reliably. The amp sat... and sat... and there was no one willing to look at it in Texas.
But now... this little amp is glorious. I'd really have to say that it serves as well as it's bigger cousin. George has delivered on all of his promises that I had suspected were a bit of hype.
If you are looking for an amp with power, used 300's are out there in the $400-500 range. Add another $700 and George can make it something special.
I've always been skeptical of spending more on upgrades than the equipment cost. Dueland caps are probably amazing, but I'm not the guy to put $3000 into a $2000 speaker. But in this case, it was money well spent. :thumb:
-
I felt the same way about the upgrades George did to my Moscode 600.
Glad to hear it worked out for you. :thumb:
-
I felt the same way about the upgrades George did to my Moscode 600.
Glad to hear it worked out for you. :thumb:
At the time George did mine, he had just finished putting the double die Mosfets in a 600. If you still have yours, it's an upgrade worth thinking about.
I wanted to wait to follow up on this story. With amps, it usually takes a while for me to really form an opinion other than first impressions. It usually comes down to whether the amp stays in the system for an extended time. In this case, the 300 has really stepped up.
-
I felt the same way about the upgrades George did to my Moscode 600.
Glad to hear it worked out for you. :thumb:
At the time George did mine, he had just finished putting the double die Mosfets in a 600. If you still have yours, it's an upgrade worth thinking about.
I wanted to wait to follow up on this story. With amps, it usually takes a while for me to really form an opinion other than first impressions. It usually comes down to whether the amp stays in the system for an extended time. In this case, the 300 has really stepped up.
Thanks, I'll have to look up the specifics.
-
Did George take his meds??
-
Did George take his meds??
He must have, although he took his sweet time getting my repair and mods done.