Complete makeover?
Have anyone on this forum thought about completely insert a new analog section instead of modifying the existing Op-Amps?
I have to pay SEK 1200 just to get four OPA627.
Two ideas has emerged in my head, both is to use that the DAC chip actually has balanced output. Modifiction of existing P-3A analog still leaves you with single-ended output.
1) Some balanced preamp design.
Rip off a design by Mr Nelson Pass. Good old Aleph or the new X-series.
2) Inserting an upgrade card.
http://www.lcaudio.dk/com/index.php?page=6
ZAPfilter Mk2
(Don't know more about this card than the website text explains)
Any comments on this?
Have anyone on this forum thought about completely insert a new analog section instead of modifying the existing Op-Amps?
I have to pay SEK 1200 just to get four OPA627.
Two ideas has emerged in my head, both is to use that the DAC chip actually has balanced output. Modifiction of existing P-3A analog still leaves you with single-ended output.
1) Some balanced preamp design.
Rip off a design by Mr Nelson Pass. Good old Aleph or the new X-series.
2) Inserting an upgrade card.
http://www.lcaudio.dk/com/index.php?page=6
ZAPfilter Mk2
(Don't know more about this card than the website text explains)
Any comments on this?
Re: Re: looking for a used P-3A
Mod plans are to make a new powersupply (toroid with mainsfilter), opampchange, diodechange (please advise on which (HEX)FRED to use) and maybe later some capacitorchanges.
Schematics anybody?
I am going to use the P3A as DAC to go to 24/96 for a digitally controlled loudspeakersystem which has DSP 16/44 roomcorrection (Canton Digital 2.1).
Regards,
Arnaud
Duck-Twacy said:
Mod plans are to make a new powersupply (toroid with mainsfilter), opampchange, diodechange (please advise on which (HEX)FRED to use) and maybe later some capacitorchanges.
Schematics anybody?
I am going to use the P3A as DAC to go to 24/96 for a digitally controlled loudspeakersystem which has DSP 16/44 roomcorrection (Canton Digital 2.1).
Regards,
Arnaud
Hi Arnaud,
I posted the schematics of the output stage somewhere on DIYAudio.com (can´t find them right now) but a small search should do it.
I modded mine by changing opamps (OPA627), Caps (panasonic FC bigger size), and the diodes for BYW 27somethinges (must look at home for the exact type).
I use a 60VA toroid with 9VAC.
The difference was quite big (I had an unmodded one to compare) in all areas (bass, highs, room)
William
I posted the schematics of the output stage somewhere on DIYAudio.com (can´t find them right now) but a small search should do it.
I modded mine by changing opamps (OPA627), Caps (panasonic FC bigger size), and the diodes for BYW 27somethinges (must look at home for the exact type).
I use a 60VA toroid with 9VAC.
The difference was quite big (I had an unmodded one to compare) in all areas (bass, highs, room)
William
Hi William,
I already found your schematics, are you sure about the configuration around the second opamp?
Could you please give me the exact partnumber of the diodes?
Does anybody have suggestions for a good type of capacitor to change the 5n6, I want to change all the small filmcaps into Wima FKP2, but in their standard range they do not have this value (5n6 or 5600p). In the datasheet it says that this value is only available upon request, maybe somebody has a source for this value.
Regards,
Arnaud
I already found your schematics, are you sure about the configuration around the second opamp?
Could you please give me the exact partnumber of the diodes?
Does anybody have suggestions for a good type of capacitor to change the 5n6, I want to change all the small filmcaps into Wima FKP2, but in their standard range they do not have this value (5n6 or 5600p). In the datasheet it says that this value is only available upon request, maybe somebody has a source for this value.
Regards,
Arnaud
Hi Arnaud,
I think the schematic is like I´ve drawn it. I don´t really understand it though, but I simulated it to see what it does and it seems to work..
I´ll post the part number as soon as I´m home again (tomorrow)
You could use 4n7 or 6n8 in combination with a different resistor to get the same effect.
William
I think the schematic is like I´ve drawn it. I don´t really understand it though, but I simulated it to see what it does and it seems to work..
I´ll post the part number as soon as I´m home again (tomorrow)
You could use 4n7 or 6n8 in combination with a different resistor to get the same effect.
William
wuffwaff said:
William,
I got my P3A today and opened it up to have a look inside and to check the schematic you posted.
The schematic of my P3A is a little different from what you have drawn. The 20k resistor and the normally closed contact of the mute-relay are connected to ground. The resistor from pin 6 of 2nd opamp to ground (cannot read the value properly in your schematic, but I think it is 47k5 in my P3A) is not connected to pin 6, but from pin 2 to ground. My board says rev. D
When I checked the opamps, I noticed that they were not the original OPA134's. The first opamps were changed into OPA627BP and the second ones were AD797, I changed them to OPA627BP as well. Any comment on that?
Regards,
Arnaud
Hi, I know this is a realy old thread, but I'm hoping someone can help me.
I have a P-3A dac. I was thinking about changing the opamps. I measured the voltage to the current opamps, it's 33vdc, is this normal? Doesn't make sense to me.
In addition, you guys upgraded to the OPA627, what about the AD8610? I heard the AD8610 runs better at lower voltages, say 12V, otherwise it may be harsh. So if I was just going to pull out the old ones and replace with the new, which ones should I invest in?
Thanks
Chris
I have a P-3A dac. I was thinking about changing the opamps. I measured the voltage to the current opamps, it's 33vdc, is this normal? Doesn't make sense to me.
In addition, you guys upgraded to the OPA627, what about the AD8610? I heard the AD8610 runs better at lower voltages, say 12V, otherwise it may be harsh. So if I was just going to pull out the old ones and replace with the new, which ones should I invest in?
Thanks
Chris
I don´t know what exactly you measured but the power supply supplies about +- 12 v when I measured it.
Both 627 and 8610 which I have used elsewhere sound excellent.I don´t think the 8610 sounds aggressive at all with this voltage, in fact I prefer it.8610 is SOIC only so adapter is necessary.You have to carefully snip out the pins of the existing opas and and then desolder them.Then I suggest you use an IC socket so you can swap between various ics which allows for furure upgrades etc.
Now in fact I am not using the P3a but a non-os dac with supereg supply.It beats it quite handily and for a fraction of the price.
Both 627 and 8610 which I have used elsewhere sound excellent.I don´t think the 8610 sounds aggressive at all with this voltage, in fact I prefer it.8610 is SOIC only so adapter is necessary.You have to carefully snip out the pins of the existing opas and and then desolder them.Then I suggest you use an IC socket so you can swap between various ics which allows for furure upgrades etc.
Now in fact I am not using the P3a but a non-os dac with supereg supply.It beats it quite handily and for a fraction of the price.
protos said:
I measured between the +Vs and -Vs pins. So I assume I am getting +-16V. COuld this be because the power supply I have outputs 10VAC? I bought this dac second hand, the previous guy had done some mods to it.
He has already done this for me.
I did a search to firgure out what a non-os dac is. Is it a product offered from pothaudio.com? Seems they have other dacs now. Are you saying it outperforms the P3a?
Sorry to disappoint you guys, but this DAC and upsampler sound horrible! DAC on its own could be used, but only just!
I modified both units 2-3 years ago, and the level of noise and crowded design were the biggest limiting factor. The sound just wasn't right at all. Friend of mine asked me to do something about it... so I did - I built the external power supply, used silver ribbons - a lot! I replaced some capacitors in both DAC and upsampler: used 2200uF FK Black Gates + styrene in analog filtering / buffering.
This external power supply actually did most of improvements.
Needles to say, he is one of many, who once heard NOS with 1541A, will never go back to upsamling. I have 'em waiting in a cue... all quite stunned with NOS DAC sound.
Extreme_Boky
I modified both units 2-3 years ago, and the level of noise and crowded design were the biggest limiting factor. The sound just wasn't right at all. Friend of mine asked me to do something about it... so I did - I built the external power supply, used silver ribbons - a lot! I replaced some capacitors in both DAC and upsampler: used 2200uF FK Black Gates + styrene in analog filtering / buffering.
This external power supply actually did most of improvements.
Needles to say, he is one of many, who once heard NOS with 1541A, will never go back to upsamling. I have 'em waiting in a cue... all quite stunned with NOS DAC sound.
Extreme_Boky
Attachments
I bought some opa627AP's yesterday and had a little try this morning. To be honest, I couldn't tell the difference. I will have to try again as my wife decided to spring clean at the same time
I have heard the difference between the p3a and some expensive cd players (such as simaudio). This was in an acousticaly adjusted room. In my lounge room, I couldn't tell the difference between the p3a and a cheap dvd player (philips q50). I put it down to the acoustics of the room. This would explain why I couldn't tell the difference with the opa627's. Anyone have any opinions/suggestions?
Chris
I have heard the difference between the p3a and some expensive cd players (such as simaudio). This was in an acousticaly adjusted room. In my lounge room, I couldn't tell the difference between the p3a and a cheap dvd player (philips q50). I put it down to the acoustics of the room. This would explain why I couldn't tell the difference with the opa627's. Anyone have any opinions/suggestions?
Chris
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