Hey all,
I'm about to replace the linear PSU of my ClassT (Truepath) amp with a SMPS and I was thinking of building something entirely "different" with the left over parts.
These include a 3U case (no heatsinks - but can be attached on the sides), a rectifier board (upgraded with these diodes and 4 x 10000uF, 100V Epcos Sikorel caps), the matching softstart module and last but not least a beefy Amplimo 800VA, 2x40V AC transformer.
The Sikorels will, most probably, not be enough but I can live with buying bulk caps as well (even if they're of lesser quality).
Anyway, I'm looking for a SS amp that would work with the aforementioned PSU. As a minimum I'd like to be able to get my hands on PCBs and a detailed BOM for the amp (a kit would be a plus but not a requirement).
I would very much like to build an F5 since I read only good comments about it, it's a fairly easy build with PCBs and kits but, unfortunately, my rails are too high (~56V DC) and, moreover, the F5's power is too low for my loudspeakers.
Speaking of which, I'm listening through a pair of ATC SCM-40s which sound great but are not what you'd call "easy to drive".
I'd say 100W @ 8Ohms are a minimum. This puts any "pure" Class A amp out of the picture, I suppose. As much as I like it I wouldn't be able to afford 2x100 watts of it - not only in terms of build cost but also everyday use (see: power consumption).
So, I'm open to suggestions...
Some other design of Mr. Pass which would work well with 56V rails?
A Krell clone (KSA50?) perhaps? [Don't underestimate the "Look mom, I own a Krell"-factor!]
A Leach clone?
Concerning the latter, I found a really interesting post of AndrewT on a Leach clone thread:
That 3rd option in specific seems a very attractive solution.
A tried and tested design, with positive feedback from users, more than enough power to handle my speakers and the benefits of class A at moderate listening levels.
Any input would be appreciated!
Don't hesitate to recommend an amp I haven't mentioned here if you think it's worth a look.
Cheers! 🙂
I'm about to replace the linear PSU of my ClassT (Truepath) amp with a SMPS and I was thinking of building something entirely "different" with the left over parts.
These include a 3U case (no heatsinks - but can be attached on the sides), a rectifier board (upgraded with these diodes and 4 x 10000uF, 100V Epcos Sikorel caps), the matching softstart module and last but not least a beefy Amplimo 800VA, 2x40V AC transformer.
The Sikorels will, most probably, not be enough but I can live with buying bulk caps as well (even if they're of lesser quality).
Anyway, I'm looking for a SS amp that would work with the aforementioned PSU. As a minimum I'd like to be able to get my hands on PCBs and a detailed BOM for the amp (a kit would be a plus but not a requirement).
I would very much like to build an F5 since I read only good comments about it, it's a fairly easy build with PCBs and kits but, unfortunately, my rails are too high (~56V DC) and, moreover, the F5's power is too low for my loudspeakers.
Speaking of which, I'm listening through a pair of ATC SCM-40s which sound great but are not what you'd call "easy to drive".
I'd say 100W @ 8Ohms are a minimum. This puts any "pure" Class A amp out of the picture, I suppose. As much as I like it I wouldn't be able to afford 2x100 watts of it - not only in terms of build cost but also everyday use (see: power consumption).
So, I'm open to suggestions...
Some other design of Mr. Pass which would work well with 56V rails?
A Krell clone (KSA50?) perhaps? [Don't underestimate the "Look mom, I own a Krell"-factor!]
A Leach clone?
Concerning the latter, I found a really interesting post of AndrewT on a Leach clone thread:
That 3rd option in specific seems a very attractive solution.
A tried and tested design, with positive feedback from users, more than enough power to handle my speakers and the benefits of class A at moderate listening levels.
Any input would be appreciated!
Don't hesitate to recommend an amp I haven't mentioned here if you think it's worth a look.
Cheers! 🙂
Last edited:
Thanks Tom.
I do need a proper lab PS so I'll keep your suggestion in mind!
ATM I'm leaning towards the Leach.
I do need a proper lab PS so I'll keep your suggestion in mind!
ATM I'm leaning towards the Leach.
A lab PS has regulators.
At low output voltages, these regulators would run VERY hot.
Instead they use multi-tapped transformers that automatically relay switch in more turns as one asks for more voltage. My +-30Vdc @ <=3A would require enormous heatsinks if it did not incorporate that special transformer.
At low output voltages, these regulators would run VERY hot.
Instead they use multi-tapped transformers that automatically relay switch in more turns as one asks for more voltage. My +-30Vdc @ <=3A would require enormous heatsinks if it did not incorporate that special transformer.
Andrew, did you have time to finish your Leach?
Other than PSU and heatsinks, how much would you estimate PCBs and parts cost?
Other than PSU and heatsinks, how much would you estimate PCBs and parts cost?
Thanks Andrew,
I went through some of your older posts. Very informative.
The amp might not be "the best in the world" (as is popular in thread titles nowadays ;p ) but I suppose it's a good and proven design to start with.
Other than the Leach, is there another "popular" amp (JLH, Pass, Krell ?) that'd work with 40V AC rails?
I went through some of your older posts. Very informative.
The amp might not be "the best in the world" (as is popular in thread titles nowadays ;p ) but I suppose it's a good and proven design to start with.
Other than the Leach, is there another "popular" amp (JLH, Pass, Krell ?) that'd work with 40V AC rails?
Cviller's boards give you the option of a beef'ed-up F5, but I'm not sure what the max rails would be. I'm sure they're far from the 56Vs DC I have on my PSU.
A standard F5 runs 1.3A from +-25Vdc.
That gives the heatsink a dissipation load of 1.3 * [25+25] = 65W/channel.
This allows ~2.6Apk of ClassA into 8r0 for a maximum ClassA output of ~2.5^2 * 8 / 2 = 25W into 8r0.
If one cascades the F5 to use say, +-35V and wants maximum ClassA into 8r0 then the output bias goes up to ~1.9A.
The heatsink dissipation load goes to 1.9 * [35+35] = 133W/channel.
This allows a maximum ClassA of ~55W into 8r0
I would take that as the maximum a paralleled F5 output stage could reliably manage.
Any more than +-35Vdc and you are aiming for a 3pair or more output stage.
That gives the heatsink a dissipation load of 1.3 * [25+25] = 65W/channel.
This allows ~2.6Apk of ClassA into 8r0 for a maximum ClassA output of ~2.5^2 * 8 / 2 = 25W into 8r0.
If one cascades the F5 to use say, +-35V and wants maximum ClassA into 8r0 then the output bias goes up to ~1.9A.
The heatsink dissipation load goes to 1.9 * [35+35] = 133W/channel.
This allows a maximum ClassA of ~55W into 8r0
I would take that as the maximum a paralleled F5 output stage could reliably manage.
Any more than +-35Vdc and you are aiming for a 3pair or more output stage.
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