F5m kit

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#84
KevinHeem said:
how about changes in harmonic distortions
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The output seen by each half of the bridge is of course also halved.
So in general distortion will be lower.

On top of that, even order harmonics cancel.
But that depends on your matching.
In case of the F5X, up to 20dB H2.

Noise will increase by 3dB if random.
Common mode noise will be surpressed.
PSRR will improve if under same power supply.


Patrick
 
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#85
Nelson: Did you consider a pair of SMPS for the F5m rather than the linear supply? Two MeanWell LRS-150-24 24V, 6.5A supplies cost about $42 vs. more than $80 for the linear supply parts.
Being a self proclaimed cheapskate, what was the reason for choosing the linear supply?
 
#87
No, I priced the parts today from DigiKey, Mouser, and Antek. Not including shipping.
  • Antek AS-3220 2x20V $50.00
  • PS PCB ??
  • 12 x 4.7mF 35V D=1" LS=10mm B41231B7478M000 12 x $1.72 = $20.64
  • 2 x 25A 600V bridge rectifiers GBPC2506-BP 2 x $2.68 = $5.36
  • 3 x 10R thermistors 495-76260-nd 3 x $1.82 = $5.46
  • total $81.46
 
#89
Warnings:

There can be noise problems with the switching supplies, as discussed in the "Pass F5m: thread: https://www.diyaudio.com/community/threads/pass-f5m.406472/post-7531709, but with proper grounding the noise can be suppressed to inaudible levels without the need for filters.

There is some concern about speaker damage if one of the two supplies detects current (or voltage) overload and enters "hiccup mode". Simulations indicate that the F5m will not generate excessive output DC voltage in that situation, but I have not tested it one the bench.
 
#91
I did some measurements with and without electrolytics on the output and concluded that it didn't make a lot of difference and potentially created current inrush issues for the SMPS. I also tested using "The Store" SMPS filters and it showed improvements in the spectrum above about 40kHz, but didn't seem to make significant difference in the noise levels in the audible spectrum.
 
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#92
Of course, the biggest cost in all of this is the heatsinks + chassis. Using the "Store" recommendations, least $169 + shipping.

OTOH, both the power supply and the chassis can be used for other amplifier projects, and many of us already have such from previous DIY projects.
 
#93
lhquam said:
Nelson: Did you consider a pair of SMPS for the F5m rather than the linear supply? Two MeanWell LRS-150-24 24V, 6.5A supplies cost about $42 vs. more than $80 for the linear supply parts.
Being a self proclaimed cheapskate, what was the reason for choosing the linear supply?
Click to expand...
Answering my own question, I will make a guess about Nelson's choices both w.r.t. power supplies and front-end circuits for source-follower outputs:
"The DIYer needs to learn about all of the circuits involved end-to-end to make an amplifier".

That is my guess.
 
#95
lhquam said:
"The DIYer needs to learn about all of the circuits involved end-to-end to make an amplifier".
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Who are you quoting here?

EUVL said:
And not just solder, power up, and pray.
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I couldn't disagree more with these statements. I would hazard to guess that the majority of amp builders here in this forum don't completely understand the circuit they're assembling. Should one understand Quantum Mechanics as well before they start their journey into the hobby of amp building? Where does the required understanding of these circuits start and stop?
 
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