Hi,
have you checked for any mistakes?
Did you use the standard schematic?
What PSU have you used?
have you checked for any mistakes?
Did you use the standard schematic?
What PSU have you used?
Hi Andrew,
Thanks for the reply.
I use p3a schematic from esp site.
I've checked and double checked the pcb.
my friend'd checked it also
Power supply dual EI transformer (160VA each, 22V CT 22V) with
4 X 4,700 uf nichicon gold tune.
I've check my amp with friend's scope,
I found no trace of oscillation,
normal square wave (100 hz, 1,10, 15lhz) on low level and high level signal.
I measured around 19V AC @8R before clipping
imo, the amplifier works fine.
What I found as a nuisance is the treble quality.
ear piercing, metallic shrill, hard and grainy.
Other P3a please share your opinion about its sound.
rgds,
Thanks for the reply.
I use p3a schematic from esp site.
I've checked and double checked the pcb.
my friend'd checked it also
Power supply dual EI transformer (160VA each, 22V CT 22V) with
4 X 4,700 uf nichicon gold tune.
I've check my amp with friend's scope,
I found no trace of oscillation,
normal square wave (100 hz, 1,10, 15lhz) on low level and high level signal.
I measured around 19V AC @8R before clipping
imo, the amplifier works fine.
What I found as a nuisance is the treble quality.
ear piercing, metallic shrill, hard and grainy.
Other P3a please share your opinion about its sound.
rgds,
hi dexter,
What amp are you comparing your P3A to?
What speakers are you using?
I wouldn't say a P3A sounds bad at all. IMHO, it sounds on par with (or a little better) than gainclones and many other DIY amps.
OTOH, if you are used to, and like, the sound of commercial amps like a Yamaha I have, you could be "surprised" at the increase in top end detail.
regards
What amp are you comparing your P3A to?
What speakers are you using?
I wouldn't say a P3A sounds bad at all. IMHO, it sounds on par with (or a little better) than gainclones and many other DIY amps.
OTOH, if you are used to, and like, the sound of commercial amps like a Yamaha I have, you could be "surprised" at the increase in top end detail.
regards
hi Greg,
I don't really mind lots of treble as long as it's clean and smooth but my p3a, hig h freq sounds is not, it's piercing and etched.
Female vocal sibilance reproduced like a nail on chalk board
IMO, yamaha amplifier sounds bright, but not as bright as p3a.
Comparison amplifier:
Gain clone Lm 1875 actually this chip amplifier sound s not too bad, its big brother (3875) sounds kinda similar to p3a.
Leach Amplifier, very clean treble, but bass 's lean.
ETI 466 200 watt amplifier, my favourite, muscle amplifier with (quite) good details.
Speaker :
Celestion SL 600
DIY kit Gemini using dynaudio drivers
Source:
Cheap DVd player+ AA DAC
Pre amplifier:
Maramtz 7 clone and Conrad Johnson clone.
Yamaha Receiver pre amplifier section.
rgds.
I don't really mind lots of treble as long as it's clean and smooth but my p3a, hig h freq sounds is not, it's piercing and etched.
Female vocal sibilance reproduced like a nail on chalk board
IMO, yamaha amplifier sounds bright, but not as bright as p3a.
Comparison amplifier:
Gain clone Lm 1875 actually this chip amplifier sound s not too bad, its big brother (3875) sounds kinda similar to p3a.
Leach Amplifier, very clean treble, but bass 's lean.
ETI 466 200 watt amplifier, my favourite, muscle amplifier with (quite) good details.
Speaker :
Celestion SL 600
DIY kit Gemini using dynaudio drivers
Source:
Cheap DVd player+ AA DAC
Pre amplifier:
Maramtz 7 clone and Conrad Johnson clone.
Yamaha Receiver pre amplifier section.
rgds.
hi dexter,
Sounds like you have done enough comparisons to come to your own conclusion. 😉
I'm finding as I "improve" my system sibilance becomes more of an issue on some recordings. I haven't come to any conclusion other than, if I listen to recordings with sibilance on my computer (with headphones) the sibilance is still there. Also, listening to conversations on trains, I can sometimes hear sibilance between elderly ladies and even some male commuters. So it seems to me that sibilance is a natural (and annoying) occurence.
You mention the ETI 466, are you in Australia (or Sydney) by any chance? If so, you could borrow my P3A for comparison.
regards
Sounds like you have done enough comparisons to come to your own conclusion. 😉
I'm finding as I "improve" my system sibilance becomes more of an issue on some recordings. I haven't come to any conclusion other than, if I listen to recordings with sibilance on my computer (with headphones) the sibilance is still there. Also, listening to conversations on trains, I can sometimes hear sibilance between elderly ladies and even some male commuters. So it seems to me that sibilance is a natural (and annoying) occurence.
You mention the ETI 466, are you in Australia (or Sydney) by any chance? If so, you could borrow my P3A for comparison.
regards
Hi,
I wonder if the low supply voltage is causing some stage to draw insufficient current and thus failing to bias itself properly?
Have you checked the currents through each of the stages to see how they compare to the standard P3a when on the normal voltage supplies?
I wonder if the low supply voltage is causing some stage to draw insufficient current and thus failing to bias itself properly?
Have you checked the currents through each of the stages to see how they compare to the standard P3a when on the normal voltage supplies?
Greg,
Many thanks for your very kind and generous offers.
Unfortunately, I don't live in the Oz.
what is your take on your p3a,
can you describe your component pick, any special recipe?
Andrew,
Thanks for the suggestion.
I'll put 50V ct transformer and measure around.
Hopefully, that's the problem all along.
warmest rgds,
Many thanks for your very kind and generous offers.
Unfortunately, I don't live in the Oz.
what is your take on your p3a,
can you describe your component pick, any special recipe?
Andrew,
Thanks for the suggestion.
I'll put 50V ct transformer and measure around.
Hopefully, that's the problem all along.
warmest rgds,
hi dexter,
I built my P3A (Rod's PCB) at the same time as I was building my AKSA 55, so I used Toshiba 2SC5200/2SA1943 output transistors, I replaced ceramic caps with polystrene. The PSU is actually a AKSA 55 PSU, 2 x 25-0-25 160VAC toriods, 4,700uF filter caps between each rail.
To my ears the P3A wasn't as good as the AKSA 55, so I hardly ever use it. Having said that, it certainly wasn't disgraced, just not quite as good. I would put it on par with my other DIY amps.
Unfortunately, I find it difficult to describe what I'm hearing so I won't embarrase myself. 😱
regards
I built my P3A (Rod's PCB) at the same time as I was building my AKSA 55, so I used Toshiba 2SC5200/2SA1943 output transistors, I replaced ceramic caps with polystrene. The PSU is actually a AKSA 55 PSU, 2 x 25-0-25 160VAC toriods, 4,700uF filter caps between each rail.
To my ears the P3A wasn't as good as the AKSA 55, so I hardly ever use it. Having said that, it certainly wasn't disgraced, just not quite as good. I would put it on par with my other DIY amps.
Unfortunately, I find it difficult to describe what I'm hearing so I won't embarrase myself. 😱
regards
Hi,
In some duties polystyrene are nearly unbeatable. Similarly ceramic are the best one can get for particuler duties.
The result is that ceramic and polystyrene are often not interchangable.
Without being comprehensive, I would suggest a few rules to help select approriate locations.
To pass audio - polystyrene. Decoupling and feedback through the audio stage.
To pass Radio frequency - ceramic. RF input filter.
Constant voltage across cap - ceramic is permissible in an audio amp eg. bypass across the V+ to V- .
For attenuation to continue way beyond the audio spectrum (two to three decades), consider if low K or NP0 (=C0G) ceramic is suitable/permissible.
why? Where?
In some duties polystyrene are nearly unbeatable. Similarly ceramic are the best one can get for particuler duties.
The result is that ceramic and polystyrene are often not interchangable.
Without being comprehensive, I would suggest a few rules to help select approriate locations.
To pass audio - polystyrene. Decoupling and feedback through the audio stage.
To pass Radio frequency - ceramic. RF input filter.
Constant voltage across cap - ceramic is permissible in an audio amp eg. bypass across the V+ to V- .
For attenuation to continue way beyond the audio spectrum (two to three decades), consider if low K or NP0 (=C0G) ceramic is suitable/permissible.
AndrewT said:
Hi Andrew,
Referring to the P3A schematic here http://sound.westhost.com/project3a.htm I replaced C4 and C6.
regards
Attachments
Hi,
C4 definately requires to operate as a feedback cap to past the 0db gain frequency of the open loop amplifier. I think C6 also operates out to this frequency. We are in the region of 5MHz to 20MHz here. I suspect that even small polystryrenes are starting to struggle with this (they are usually rolled).
A low inductance cap is essential for C4, a stacked film type may produce good results or maybe a silvered mica.
C4 definately requires to operate as a feedback cap to past the 0db gain frequency of the open loop amplifier. I think C6 also operates out to this frequency. We are in the region of 5MHz to 20MHz here. I suspect that even small polystryrenes are starting to struggle with this (they are usually rolled).
A low inductance cap is essential for C4, a stacked film type may produce good results or maybe a silvered mica.
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