Hi guys,
Bought an Levinson ML3 amp for sentimental reasons I think. I had a schematic for it but lost it in my latest move to another house.
Mailed with the original designer Tom Colangelo in 2003 about a conversion from 120V to 220V. He told me that he lost all his paperwork about these old MLAS models in 1989 due to tornado. Due to the age of 40 years of this amp and it's completely original it could be a candidate for some maintenance.
Maybe somebody has the service manual of schematics of the ML3. Any help is welcome of course.
This one has been converted to 220 AC already.
Bought an Levinson ML3 amp for sentimental reasons I think. I had a schematic for it but lost it in my latest move to another house.
Mailed with the original designer Tom Colangelo in 2003 about a conversion from 120V to 220V. He told me that he lost all his paperwork about these old MLAS models in 1989 due to tornado. Due to the age of 40 years of this amp and it's completely original it could be a candidate for some maintenance.
Maybe somebody has the service manual of schematics of the ML3. Any help is welcome of course.
This one has been converted to 220 AC already.
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Great you have them all three!
The one with a 18000uf silver Callins filtercaps.
The one with the 33000uf Spragues and the one with the 36000uf Spragues.
Single and double fuseholders.
The ones with and without dampingswitches.
Ones with the added four smaller blue Sprague filtercaps for the predriverstage.
On my lost schematics MLAS added the Series I to III.
Do you have any info for me maybe?
The one with a 18000uf silver Callins filtercaps.
The one with the 33000uf Spragues and the one with the 36000uf Spragues.
Single and double fuseholders.
The ones with and without dampingswitches.
Ones with the added four smaller blue Sprague filtercaps for the predriverstage.
On my lost schematics MLAS added the Series I to III.
Do you have any info for me maybe?
Just another question.
The MLAS specified emitter voltage over the .56 Ohm emitterresistors is 47mV
With 10 pair powertransistors per channel with a load of 4 Ohm I get 5.6 Watts of Class A per channel.
The ML-3 has huge heatsinks (although rather short fins) and I wonder if this biassetting can be safely increased with a maximum of 45 degrees Celcius value roomtemperature 20 degrees. Or are their other parameters to consider?
The MLAS specified emitter voltage over the .56 Ohm emitterresistors is 47mV
With 10 pair powertransistors per channel with a load of 4 Ohm I get 5.6 Watts of Class A per channel.
The ML-3 has huge heatsinks (although rather short fins) and I wonder if this biassetting can be safely increased with a maximum of 45 degrees Celcius value roomtemperature 20 degrees. Or are their other parameters to consider?
I read a technical paper from Nelson Pass where he stated and showed that Class A enrichment lowers all kind of distortion.
It was called 'Leaving Class A' and he stated:
"Higher bias doesn’t just move the Class A transition to higher ground – it has a profound influence on the amplifier at all power levels. It lowers the distortion at low levels as well as high levels, as seen in the distortion vs power curves for an amplifier with the bias set at different levels.¨
Then he showed this graph:
So I thought what the heck lets give it a try.
I will be very careful of course. Have experience with the one turn biastrimmers in my Threshold SA/1.
Will first check the bias after the unit heats up with an hour and then check for the current biassetting with several emitterresistors and adjust it if necessary.
I will use an energymeter to check the AC intake
Then I will check the temperature and when the heatsinks permit it I can slowly raise the bias while still carefully monitor the AC intake of course.
Easy does it and patience are the keys.
Thanks for the supportive remark. I luckily also the have Threshold 'Standard Amplifier Bias Procedure' as a reference.
Would a heatsink temperature of 25 degrees Celcius increase over the surrounding temperature be a good reference point you think?
Any other considerations?
Okay that would be around 48 degrees Celcius I believe.
Thank you very much for the advice.
To be sure I just check if you didn't confuse this stereo ML3 with the monaural Levinson ML2 which you are very much aquinted with.Being that it's Class A, I would go with the warmest temperature you can leave your hands on.
