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Old 15th June 2013, 12:23 AM   #61
kp93300 is offline kp93300  Malaysia
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Hi PMI,
thanks for these helpful suggestions------ that is what i am after .
I am collecting the parts now.
cheers
kp93300
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Old 9th November 2013, 03:14 AM   #62
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by PMI View Post
I started with ceramic Miller caps and later changed them to silver mica.
Interesting - can you remember, were they the same value ? Did you use npo/cog ceramic (good) or something else (baaaad) ? did you hear a difference between them ?
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Old 9th November 2013, 06:20 AM   #63
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As said one of the P3A i made was constructed with """anything i can find parts "" that will be 3055-2955 outs 139-140 drivers and classic ceramics of 100pf equally the Ltp and current source was also anything available '

Both measuring and listening was by far worst distortion and bandwidth figures had a difference of at least 30% worst .

At that point the race was against a pcb that had properly matched LTP and mica caps that should be like 5-6 years ago later on with better choice of parts , matched drivers and a better VAs things got even more better than the """"anything i have """"project

Kind regards Sakis

The intention of the project was to know first hand what a poor choice of parts can do to a known amplifier .-
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Old 9th November 2013, 02:05 PM   #64
Bigun is offline Bigun  Canada
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I see. Well, I guess my question was really about the possibility of identifying the effect of only one change

I believe there has developed an allergic reaction by people to use of ceramic because of historical use of poor ceramic, especially by cheap manufacturers. They did not use the excellent npo/cog types. These types have better performance than many other types of capacitors but are still shunned by some people. So the question is still specifically about this ceramic.

I noticed you changed your username Sakis :-)
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Old 9th November 2013, 02:14 PM   #65
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yes about the name ... Its better for Google to find me easier ....

As about the rest ..i am sorry to say that is almost a year now that i didn't produce a new pcb for the P3A or tested any goodies like the degeneration and a few others i have in mind ..

Sorry for that but god i am so busy that i come to work 6 days a week something like 9.00 and go from the lab often after 12.00 midnight ...

Too much work ...

Kind regards
Sakis
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Old 9th November 2013, 04:11 PM   #66
Bigun is offline Bigun  Canada
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No such thing as too much work when you are self-employed, it is a good sign for your bank manager and then you can buy some fine wine

I am still very attracted to this amplifier and perhaps I should be the one to make a new pcb. I will include some goodies if I do this. Would this amplifier be a candidate for my home theatre ? could it really compete with the SKA GB150 from Greg Ball ? it might be interesting for me to find out.
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Old 9th November 2013, 04:52 PM   #67
PMI is offline PMI  United States
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Quote:
Originally Posted by Bigun View Post
I am still very attracted to this amplifier and perhaps I should be the one to make a new pcb. I will include some goodies if I do this.
Same here. Mostly I just lurk here, but I would be interested in seeing what you come up with.

I built mine using the boards from the ESP web site, and I made some of the changes that were suggested by Sakis. Some are not very easy using the original boards, like on-board caps which are much larger than the board can easily accomodate.

A really good HT setup usually needs a combination of good sound in the normal audio range, in combination with good bass response, and extended dynamic range. Not sure if all that can be accomplished simultaneously with this circuit.

There was also an interesting note about CCS in the first post, which might be relevant for higher voltage and power, not sure...

@Sakis:
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Old 9th November 2013, 05:11 PM   #68
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Quote:
Originally Posted by Bigun View Post
I believe there has developed an allergic reaction by people to use of ceramic because of historical use of poor ceramic, especially by cheap manufacturers. They did not use the excellent npo/cog types. These types have better performance than many other types of capacitors but are still shunned by some people. So the question is still specifically about this ceramic.
I used 100pF multilayer ceramic NP0 for both input shunt and Miller cap and must say that I was not disappointed, they sound excellent and they are cheap (I bought 30pcs).
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Old 9th November 2013, 05:18 PM   #69
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by PMI View Post
I built mine using the boards from the ESP web site, and I made some of the changes that were suggested by Sakis. Some are not very easy using the original boards, like on-board caps which are much larger than the board can easily accomodate.

A really good HT setup usually needs a combination of good sound in the normal audio range, in combination with good bass response, and extended dynamic range. Not sure if all that can be accomplished simultaneously with this circuit.
I figure that on-board caps only need to be large enough to capture the audio return current at 1kHz and above because if you design properly, the wiring resistance back to the PSU should be much lower impedance than your speaker cables - so bass is not limited by where the large caps are. At higher frequencies you have to have adequate rail decoupling to minimize any issues with inductance - but even then that's likely not an issue except well up in the treble or higher.

I am planning to use the GB150 (my TGM7 is a variant - waiting for my revised PCB) for HT so the P3A would be a surprise winner if it were better suited. However, perhaps if I build a P3A variant and it didn't go into my HT I would very likely still find a good home for it.

Ivan - thanks for sharing your experience, it matches mine, but I do feel we are in the minority of opinion here !
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Old 9th November 2013, 05:32 PM   #70
PMI is offline PMI  United States
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Originally Posted by ivanlukic View Post
I used 100pF multilayer ceramic NP0 for both input shunt and Miller cap and must say that I was not disappointed, they sound excellent and they are cheap (I bought 30pcs).
I tried both. I could not tell much difference, but I did not use the same higher grade and higher precision silver mica caps that Sakis recommends. I also did not have the same kind of VAS transistor, so the advantage of Silver Mica might not have been apparent.
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