triibies, please consider putting the PSU components on the board itself, i'm currently building an amp which uses this method(the Fetzilla) and i love it. It will make the board slightly longer, but as most heatsinks are at least 300mm deep it should be on little concern, especially with an SMD design.
Here is another idea for increasing phase margin. Bootstraped collectors will decrease miller effect on feedback input. If there is anyone willing to try this solution please note that input transistors should be rated for higher voltage. There follows first modified schematic by bootstrap only, and second my upgrade of original crescendo.
Very nice and clean, one question, what is the power of your Toric? Mine's 680VA and I must bootstrap it otherwise it blows the mains fuse ever ytime 😛
Hi pmk can you email me a copy of the original crescendo article
Best Regards
Tom Ferguson
email "tomferguson610@hotmail.co.uk"
Best Regards
Tom Ferguson
email "tomferguson610@hotmail.co.uk"
Hi Esperado, I had a look at the schematic on your site (sorry, my non-english is not very good)!! Is this the most up-to-date schematic for the Crescendo? I actually some 2sk135 and 2sj50 and would like to build this amp (with no hum etc of course!)
Much appreciated
Barney
Much appreciated
Barney
Could anyone please tell me the reason why the MJE340/350 trannies are 'better' than the original BF469/470? Of course, they are much beefier in terms of maximum specs. But, as far as I see it, even the originals are operating well within their specs. Me, at least, never had a faulty Crescendo, due to broken BF's (I used BF871/872 - same price, then, but higher voltage). So, what's the benefit for the Crescendo from the MJE's?
Best regards!
Best regards!
In terms of Ic and Ptot the MJE's by far are superior, compared to BF471/472, Vceo is equal, but in terms of hFE the BF's are better. But I can't find fT and Cre specs for the MJE's? fT for the BF's is 60 MHz, Cre is 2 pF. I think that the Crescendo would benefit exactly from these two specs if they were superior.
Best regards!
Best regards!
..a new variant of an Elektor Crescendo:
PCB: 160mm*100mm
Heatsink: SK85-150 oder MARSTON-938SP
Power: ALF08N16/ALF08P16 or variants
Driver: current KSA1381 & KSC3503 (choise of: MJE340/350) or variants
Voltage Rail: +/-60VDC up to 75VDC
PCB: 160mm*100mm
Heatsink: SK85-150 oder MARSTON-938SP
Power: ALF08N16/ALF08P16 or variants
Driver: current KSA1381 & KSC3503 (choise of: MJE340/350) or variants
Voltage Rail: +/-60VDC up to 75VDC
Last edited:
Well, looks fine!
Would you please post the schematics of your amp? Thx in advance!
Best regards!
Would you please post the schematics of your amp? Thx in advance!
Best regards!
Hi,
please pardon me for reviving this dusty rusty old thread!
As mentioned here, my stereo Crescendo presents some hum, even with no preamp connected to it. Not that much, not disturbing at all, it is audible only if you poke your head into the woofers. But it could do better, couldn't it?
I've shown some images of my build here. You see that I've provided a central ground right between the large electrolytics. Literally everything returns to this, both taps of the power transformers' secondaries, speaker ground (separate for both channels), input gnd (dito), signal gnd (dito), just everything. R10 is present on both PCBs, so no earth loop should be expected. The case is connected to protective earth of the power cord and also loosely connected (via two diodes in antiparrallel and a 0.1 µF cap) to the gnd star. Alle jacks are well insulated form the case.
Today I saw HumNSmoke's solution here. Could I really expect to get rid of the hum if I'd provide two separate gnd stars, one for each channel? And why?
Best regards!
please pardon me for reviving this dusty rusty old thread!
As mentioned here, my stereo Crescendo presents some hum, even with no preamp connected to it. Not that much, not disturbing at all, it is audible only if you poke your head into the woofers. But it could do better, couldn't it?
I've shown some images of my build here. You see that I've provided a central ground right between the large electrolytics. Literally everything returns to this, both taps of the power transformers' secondaries, speaker ground (separate for both channels), input gnd (dito), signal gnd (dito), just everything. R10 is present on both PCBs, so no earth loop should be expected. The case is connected to protective earth of the power cord and also loosely connected (via two diodes in antiparrallel and a 0.1 µF cap) to the gnd star. Alle jacks are well insulated form the case.
Today I saw HumNSmoke's solution here. Could I really expect to get rid of the hum if I'd provide two separate gnd stars, one for each channel? And why?
Best regards!
Hi man
This is how I did. The remaining hum was the mechanical one from the transformers. My concern when I did this was I lowen the peak power from the power supply by a factor 2.
And later I also balanced the inputs, for no worry any more with long wires from the preamp.
Is your hum here from the life begin of the amp, or later ? If later, maybe some recap could help. I'd also take care to provide very good isolation between transformers and case (and between tranfos themselves), because I believe the rubber washers (both top and bottom) are far too thin after all those years: have a look at my HugeMac isolation recipe.
But in fact, I would have never got rid of the hum without the help of guys here.
This is how I did. The remaining hum was the mechanical one from the transformers. My concern when I did this was I lowen the peak power from the power supply by a factor 2.
And later I also balanced the inputs, for no worry any more with long wires from the preamp.
Is your hum here from the life begin of the amp, or later ? If later, maybe some recap could help. I'd also take care to provide very good isolation between transformers and case (and between tranfos themselves), because I believe the rubber washers (both top and bottom) are far too thin after all those years: have a look at my HugeMac isolation recipe.
But in fact, I would have never got rid of the hum without the help of guys here.
Last edited:
Why have you left copper on top layer where mosfets go ?
This means you will need to insulate heat sink from pcb.
I usually make a new part with no copper on top layer.
I would like to share some playworks. Close to original, but with additional places for plastic power transistor packages. Also places for compensation caps, as spice shows unconditional stability with few more pickofarads. All there in attachment, if some mistakes please write it here.
This amp is real legend, it deserves more buildings 🙂
This amp is real legend, it deserves more buildings 🙂
Thanks, very appreciated!
Which plastic FETs do you recommend to replace these 2SK135/2SJ50 originals?
Best regards!
Which plastic FETs do you recommend to replace these 2SK135/2SJ50 originals?
Best regards!