100W Ultimate Fidelity Amplifier

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#3,401
Alan0354 said:
The reason I ask is because I worked a lot with of transistors ( not in hifi audio amps). I only look at the data sheet and choose one that fits my requirements, one with multiple sources, readily available. But I do notice in hifi world people are very finicky about things that I don't worry about, like brands. That's the reason I ask.
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May be in your non-audio application, small difference does not matter. In audio, small difference may affect overall performance, gives different measurement which may be audible.

Alan0354 said:
I don't mean transistors that have different specs, of cause you need to look at the hfe, fT, power handling, max voltage and current etc. but I am referring to the same transistor ( 2N3055 for example), just different brands. Can they make a difference in sound? Or one transistor sounds better than the other.
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Old 2N3055 (e.g. RCA) has fT less than 1M. Newer ones, slightly more.

Different brand means different machine, different quality control, different quality assurance and in the end, different measured characteristics. Note also that there are many "fake" transistors around these days.

Buy 1000 pieces of brand A, you will get 80% have hfe above 200. Buy 1000 pieces of brand B, you will get nothing above 200.

Alan0354 said:
Yes, I know even the same badge can be a little different. Data sheet only guaranty the minimum spec, transistor can work over the limit, but not guarantied. But there are so many transistors to choose, you can always find one that suit your needs, not by hand pick ones that can perform over the spec.
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That's why amplifier is different. In the old days, may be the difference does not matter because amplifier "technology" is primitive (low expectation from users).

Alan0354 said:
From my experience, transistors don't get old or degrade. They either work or they die.
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Yes, more or less so. What I was saying is that it is the difference in the characteristics (either in tube or transistor) that makes them sound differently. If the measured characteristics is the same, even tube and transistors sound the same. 😀
 
#3,403
Alan0354 said:
Does different transistors make a difference in sound quality? ............
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Probably not change the sound.

But most definitely changed parameters will change the gain and phase margins and WILL require different compensation to return the amplifier to the same stability margins.

If the stability margins are not brought back to the same as the designer intended, then the amplifier WILL perform differently: anything from a sustained oscillation and self destruction to a treble that is rolled off so substantially that the sound is "dead".
 
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#3,404
I just finished populating one more pair of the AX-14. This one uses NJW1381/1032 for the outputs. That makes 5 different versions. In order of build;
AX14 with MJ15003/15004
SX14 with IRFP240/9240
NX14 with MTW32N20E
AX14 IPS only for Slewmaster OPS
AX14 with NJW1381/1302

In an A/B blind test at probably 5W output they sound virtually identical. They may measure slightly different and the SX does clip earlier because it runs on much lower rails but that is louder than I would typically listen to music anyway.

Hope this helps.
 

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#3,406
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#3,417
vargasmongo3435 said:
Is normal man, sometimes we don't see errors till we check many times, I keep working with layout and sometimes I made small mistakes it happens that is why I like it and it keep my mind occupied and learning more every day here is an example, I did this layout a few months ago and I still checking for erratas ones I see is all good then I saved it for later. 😉


Juan
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sir juan,,
this PA protect for ax series sir..?
 
#3,420
short circuit and dc protect on output, 🙂 I'll have to rebuild my ax14 on these PCB since I don't have short circuit protection on my amp, it's always bothered me.

I can't remember is that (DC plus short circuit) protection available n a separate PCB?

Regards
 
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