View Single Post
  #25   Report Post  
Posted to rec.audio.high-end
~misfit~[_3_] ~misfit~[_3_] is offline
external usenet poster
 
Posts: 96
Default Introducing a New Horse to the Stable

On 17/09/2019 11:54 AM, Trevor Wilson wrote:
On 16/09/2019 11:01 pm, ~misfit~ wrote:
On 16/09/2019 9:53 PM, Trevor Wilson wrote:

**Sure. However, make certain the drive circuitry can cope.


I'm not exactly sure of how to do that?


**You need to examine the drive circuitry, the components used and then calculate if those
components can cope with the extra load caused by extra MOSFETs. It will PROBABLY be OK, but I
don't know.


I intend to use the system in my lounge so won't want crazy SPLs, the speakers likely wouldn't
handle that much power anyway. I actually do have two of the toroids but that would make for a
big amplifier case - and surely then I'd need to consider adding *two* more pairs of output
MOSFETs per amplifier?



[ Massively pruned of old quotes because your mod just
couldn't take it any more. --dsr ]




**As Peter has correctly stated, provided you don't need the full continuous power capacity of the
amplifier at all times, then one transformer will likely be plenty. From my perspective, I am a
purist. If I am presented with an amplifier rated at (say) 200 Watts/channel, then that amplifier
needs to be able to deliver 200 Watts/channel INDEFINITELY and, possibly more importantly, it needs
to be able to deliver roughly 40% of it's maximum power without thermal distress. With one
transformer in your amplifier chassis, it would fail such a test. But, your amplifier is not a
commercial item. You can make it anything you want.


I was thinking that, as I don't listen to dubstep or extremely bass-heavy music, using one toroid
and a lot of capacitance (in the region of 20,000 to 50,000 uF per rail) would be enough to
handle transients. If not then I might as well build a pair of monoblocks.


**A worthy consideration.


I've got a few coffee-cup sized Mepco/Electra 14,000 uF / 100v caps but they're not new... I also
have 8 new 10,000 uF / 100v Elna caps that are only about 1/4 of the size.


**The amplifier I presently use has a 5.5kVA (yes, 5,500VA), split wound (one winding for each
channel), double C core power transformer, followed by 92 X 3,300uF filter capacitors.


Wow! Decades ago I used to work with a touring band doing stage lighting and (some) sound mixing
and that's a more capable amplifier power supply than were in some amps we used at medium-sized gigs.

The result
is to ensure that, under full power operation (at any impedance higher than 2 Ohms) ripple is kept
below 100mV. So, discussions of 10,000uF per rail doesn't excite me. It's what I expect to see in a
mass market product from Yamaha or NAD. However, as Peter and I have both suggested, in a high
global NFB amp, such as yours, huge lumps of filter capacitance will not be pivotal to performance.
Placing a decent amount near the output devices will be beneficial though.


Thanks for your input Trevor. It helps me to decide how to go about building my 'franken-amp'.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy little classification
in the DSM"
David Melville

This is not an email and hasn't been checked for viruses by any half-arsed self-promoting software.