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Wow! - Thank you so much for your reply. And there I was thinking the NAD was pretty good.
It did have new psu caps fitted about 12 months back, and I drive it from a valve preamp fed into the 'Lab In' input of the power amp section, - so for me, it is just a power amplifier.
Any ways I shall get my order for the P3A boards sent today then think about what components to use, - power/driver transistors etc.
Please don't go any where, I think I may be posting a bit more in the future.
Thanks.
Kind Regards
Roy.
It did have new psu caps fitted about 12 months back, and I drive it from a valve preamp fed into the 'Lab In' input of the power amp section, - so for me, it is just a power amplifier.
Any ways I shall get my order for the P3A boards sent today then think about what components to use, - power/driver transistors etc.
Please don't go any where, I think I may be posting a bit more in the future.
Thanks.
Kind Regards
Roy.
Hi Roy, I'm new to this thread but have been playing around with the P3A for about a year now. Until recently I a built up version in a nice chassis was a permanent fixture in my living room, and a second board is set up as a test fixture on my workbench.
I can tell you that the choice of VAS transistor and Cdom have the biggest impact on sound quality, to my ears. I would substitute a KSA1381 for the BD140 specified at Q4 and reduce C4 from 100p to 68p.
I can tell you that the choice of VAS transistor and Cdom have the biggest impact on sound quality, to my ears. I would substitute a KSA1381 for the BD140 specified at Q4 and reduce C4 from 100p to 68p.
Agree
Even you can reduce miller cap and add lead compensation (like AKSA 55 style) to increase the slew rate.
I've also been following this thread for many years and have always enjoyed it. I particularly enjoy your comments regarding the various amps that have been on your workbench over this time as you repair them and often improve upon. A great source of insight into what makes for a sucessful amp. And I really like your kindly attitude....so I thank you Sakis very much and keep posting.
Hey guy's,
Thanks for the advice, I will take it all on board and it will probably make more sense to me when I am compliling my component list.
Ive ordered my boards and already received my user name and password for the build instructions.
What would be the recomended outputs for it nowadays?
Regards to all
Roy
Thanks for the advice, I will take it all on board and it will probably make more sense to me when I am compliling my component list.
Ive ordered my boards and already received my user name and password for the build instructions.
What would be the recomended outputs for it nowadays?
Regards to all
Roy
Hi Mr Sakis,
I Just found these whilst looking for transistors ...
MJL1302A/MJL3281A audio transistors - Boards | Kits | Components | Modules | Tools
Must I assume these to be fakes and avoid?
Regards
Roy
I Just found these whilst looking for transistors ...
MJL1302A/MJL3281A audio transistors - Boards | Kits | Components | Modules | Tools
Must I assume these to be fakes and avoid?
Regards
Roy
I could not say for real There is no original picture of the product what is there is animation so i can actually not tell .
As about miller cap on the Vas changes are to be made after verification and also will depend on the overall choice of VAS and set up and semis ..I dont find it wise to jump into a choice from a suggestion without having the proper tools to verify your choice . In such a case 100pf is a move to the safe side .
P3A is very tolerant in choice of outputs it will start working even with TIp 3055-2955 1943 and 5200 is also a nice choice ...
@kimbo
thank you for your kind words i wish i had more time to upload more things ( actually i upload plenty in the web page but this is in Greek)It is interesting though to tell that uploading those stories has a lot of fun since includes often historical data often hard to collect , repair procedures , hard to find failure modes and so on ...
Kind regards
Sakis
As about miller cap on the Vas changes are to be made after verification and also will depend on the overall choice of VAS and set up and semis ..I dont find it wise to jump into a choice from a suggestion without having the proper tools to verify your choice . In such a case 100pf is a move to the safe side .
P3A is very tolerant in choice of outputs it will start working even with TIp 3055-2955 1943 and 5200 is also a nice choice ...
@kimbo
thank you for your kind words i wish i had more time to upload more things ( actually i upload plenty in the web page but this is in Greek)It is interesting though to tell that uploading those stories has a lot of fun since includes often historical data often hard to collect , repair procedures , hard to find failure modes and so on ...
Kind regards
Sakis
Ah...the voice of long experience.
You can actually fry your amp and speakers with too small a cap. If you intend only to "listen with your ears" to verify adequate compensation, you will literally get burned sooner or later. Without a scope (analog is actually best for this) you can't see the little instabilities of wriggling sinewaves and other spurious effects when you check out square wave edges, clipping etc.
Amplifier response drifts also with temperature and age. What is stable now, may become more stable or it may burst into full amplitude oscillation some time later unless you make sure it leaves the bench clean - free of problems, regardless of how wonderful instabilities may sound. A couple of quotes from DestroyerX suggesting "These are the good ones" may be ok for someone with his experience and skills to tweak but for most of us, we probably would not recognize a stability problem soon enough to save the amplifier.
As Sakis said, 100 pF is a safe bet to begin with - only reduce if you have a means of checking what happens at a range of frequencies and output levels and dropping from 100 to 68pF for example, is a drastic change. Note that if you are cloning P3a from the general schematic shown on the website - It isn't quite the same as the P3a design you find on the ESP forum when you buy Rod's PCBs so you can't really be sure you have the current P3a circuit or layout but it's safe enough and fun trying with what you see there.
Hi All,
I must be honest here. I really know very little about miller caps, VAS and Cdom etc., so I will stick to the normal build components (initialy at least) to ensure a working amp at the end.
One thing I have noticed on the schematic on the esp secure site is the change of resistor values on the signal input.
I have a 300VA transformer that has 2 x 30v secondaries which I hope will be okay to use and I am on the look out for a nice case (black) with heat sinks both sides.
Mr Sakis, I will go with your recommendation for the outputs and use 2SA1943 & 2SC5200.
Regards
Roy.
I must be honest here. I really know very little about miller caps, VAS and Cdom etc., so I will stick to the normal build components (initialy at least) to ensure a working amp at the end.
One thing I have noticed on the schematic on the esp secure site is the change of resistor values on the signal input.
I have a 300VA transformer that has 2 x 30v secondaries which I hope will be okay to use and I am on the look out for a nice case (black) with heat sinks both sides.
Mr Sakis, I will go with your recommendation for the outputs and use 2SA1943 & 2SC5200.
Regards
Roy.
To be honest, you'll need to deviate from Rod's component recommendations to get the best performance from the P3A. There is a large sonic improvement going from the BD140 to something like a KSA1381.
You'll be fine with that transformer; however, at those rail voltages, I would be inclined to use something more robust like the MJL4302 (and compliment) rather than those outputs you mention.
You'll be fine with that transformer; however, at those rail voltages, I would be inclined to use something more robust like the MJL4302 (and compliment) rather than those outputs you mention.
Mr Sakis,
Is there any particular reason why you have used two emitter resistors in parallel as opposed to the single one specified?
Would there be a benifit in using carbon resistors for the build? Im sure I read somewhere that carbon resistors dont sound as clinical as metal film. - any thoughts?
What is a zobel network for? - I notice some use a coil in parallel with a resistor and others use a capacitor in series with a resistor. What difference does this make?
Sorry for all the questions - just curious.
Hi Ranchu, Wow! Those MJL4302's sure arn't cheap at around £15 each.
Regards
Roy
Is there any particular reason why you have used two emitter resistors in parallel as opposed to the single one specified?
Would there be a benifit in using carbon resistors for the build? Im sure I read somewhere that carbon resistors dont sound as clinical as metal film. - any thoughts?
What is a zobel network for? - I notice some use a coil in parallel with a resistor and others use a capacitor in series with a resistor. What difference does this make?
Sorry for all the questions - just curious.
Hi Ranchu, Wow! Those MJL4302's sure arn't cheap at around £15 each.
Regards
Roy
that is a method of justifying a using resistor that adds distortion compared to a more linear component.
The Output Zobel is an R+C connecting the Output to audio ground.
An output Thiele network is a combination of R+C and a R||L.
Invented by Neville Thiele. It is used to help stabilise an amplifier.
Dr Cherry did a paper expanding on Thiele's work. Dig it out. It is worth memorising.
The R||L does not help to stabilise the amplifier. It helps to isolate the load and the cables from the amplifier.
Combining the R||L and the R+C does both, helping to stabilise the amplifier and helping to isolate the external side from the internal side.
An output Thiele network is a combination of R+C and a R||L.
Invented by Neville Thiele. It is used to help stabilise an amplifier.
Dr Cherry did a paper expanding on Thiele's work. Dig it out. It is worth memorising.
The R||L does not help to stabilise the amplifier. It helps to isolate the load and the cables from the amplifier.
Combining the R||L and the R+C does both, helping to stabilise the amplifier and helping to isolate the external side from the internal side.
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Hi Thimios
Their headquarters are in Montreal and they operate in 42 countries. I should point out that I've never ordered from them, but they could be worth investigating.
So would 2SA1943 & 2SC5200 be totally not suitable at all, or would I just not have to drive them so hard?
While waiting for my boards to arrive Ive been looking around for some kind of enclosure for my P3A. When I (hopefully) finish it, it will take pride of place in my music room so I'm after something smart for it. But guess what? I don't seem to be able find anywhere suitable to purchase one from. There seems to be a distinct shortage of enclosure supplies in the UK.
Does anyone have any suggestions please?
Regards
Roy.
While waiting for my boards to arrive Ive been looking around for some kind of enclosure for my P3A. When I (hopefully) finish it, it will take pride of place in my music room so I'm after something smart for it. But guess what? I don't seem to be able find anywhere suitable to purchase one from. There seems to be a distinct shortage of enclosure supplies in the UK.
Does anyone have any suggestions please?
Regards
Roy.