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Old 9th July 2012, 10:02 PM   #81
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I can understand why bf862 sounds good but not sure why changing the bipolar would make much difference. Or are you saying you used those parts because that is what you had on hand?
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Old 9th July 2012, 10:29 PM   #82
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2n4401 sounds clearly better to me than bc550c, more detail especially. But then again it depends on the rest of your system.

I ve experiment with bjt s in this position also with salas shunt and i does influence the sound to a certain degree. it is a reference for the current setting after all.
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Old 9th July 2012, 11:28 PM   #83
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Originally Posted by pidesd View Post
2n4401 sounds clearly better to me than bc550c, more detail especially. But then again it depends on the rest of your system.

I ve experiment with bjt s in this position also with salas shunt and i does influence the sound to a certain degree. it is a reference for the current setting after all.
are you talking about amp made by Camp Amp schematic ?

that (sole ) bjt is bootstrapped with 1KuF ;

there is no way you can hear difference between ZTX , BC , 2N or even BD139 in that position

toss it , and use pot instead , all you'll have is just different biasing ....... while that 1KuF is there , it will be hardly any change in sound

Q3 is there simply to maintain 0V65 across R1+R3
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Old 9th July 2012, 11:34 PM   #84
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yes that is the amp, CLC psu though.

i swear to god i hear a difference.

but now you hust put a little doubt in my head...

Last edited by pidesd; 9th July 2012 at 11:39 PM.
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Old 9th July 2012, 11:41 PM   #85
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if you're not setting same bias (and that is hardly , without pot in that area ) , then you'll hear difference ........

again - induced by bias amount change , not difference in bjt type
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Last edited by Zen Mod; 9th July 2012 at 11:50 PM.
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Old 9th July 2012, 11:47 PM   #86
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But is this a teaching tool or is it an amp you could listen to for a few years? I would love to know from some of the builders how it sounds into full range drivers (reviews).
I would like to know if it could beat my current class-D demo board for an ADAU1592 with diy power supply to drive my Fostex full range speakers (all subjective I know).

One thing that I think would encourage more people to "jump in the pool", If the parts to populate the PCB are provided. To my everlasting shame I have purchased some
PCB’s I have never populated, and will most likely never do so. However I am happy to say that I have built every kit I have ever purchased (mostly headphone amps)
where the parts to populate the PCB were provided. This is what Glass Jar Audio does.
Leve
Many good points here. I've listened to it a bit, but now that amp camp is over :

-I have to work a lot due to neglecting my real job preparing for the event.
- We organizers gave up our PCB's so more people could participate (they were begging to come! ). Then the amps all went home with people. I did listen to them on various systems though, and they do have that Pass sweet sound for sure. They seemed happier with full range drivers.

And yes we are not only ordering boards, once we clear up the PCB/schematic discrepancy, but we'll have it bundled with parts so it can be built up easily and quickly. We've already proven it can be built in half a day. Ours took a bit longer for most people due to the chassis requiring cleaning and polishing.

There are going to be a lot of happy newbies making amps.

The amazing thing to me is how easy and cheap it is to use the SMPS. Of course lots of people could propose such a thing, but Papa is in the position to bless the concept, and make it work and we all then believe him. And sure it seems obvious now, but great ideas always do after the fact!

Last edited by Variac; 10th July 2012 at 12:15 AM.
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Old 9th July 2012, 11:59 PM   #87
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Originally Posted by Zen Mod View Post
if you're not setting same bias (and that is hardly , without pot in that area ) , then you'll hear difference ........

again - induced by bias amount change , not difference in bjt type
you have a good point that bias should effect the sound...but that much? i dont know...

2n4401: 0.55V
bc550c: 0.65V

can a lesser bias sound better?
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Old 10th July 2012, 12:20 AM   #88
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difference between 0V55 and 0V65 is bias difference between 478mA and 565mA ..... so , around 16% increase

which one will be better to your ears ......... well - those are your ears
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Old 10th July 2012, 01:36 AM   #89
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ok but...can an ugly old turkey (post 51) even recognize sound?

no seriously i might just be crazy but i prefer not to admit it publicly

i ll begin by building another channel first, that might help my cause...

P.S. isnt bias around 1 A...?
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Old 10th July 2012, 01:59 AM   #90
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The amazing thing to me is how easy and cheap it is to use the SMPS. Of course lots of people could propose such a thing, but Papa is in the position to bless the concept, and make it work and we all then believe him. And sure it seems obvious now, but great ideas always do after the fact!
Yeah I was suggesting this years ago now, and everyone laughed at the suggestion like I was on drugs or something. I just might have convinced Nelson though.
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