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Old 14th May 2002, 11:43 AM   #1
protos is offline protos  Greece
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Default Mods for perpetual technologies dac?

Has anyone attempted to mod the p3a dac from perpetual tecnologies? I understand certain mods are offered for a fee by Modwright. This includes changing the opa134pa for opa627ap and various cap and resistor replacements for more exotic types.
I was wondering if it was worth attempting it on my own and if other members could give any advice .
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Old 21st February 2003, 08:16 PM   #2
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Hello Protos,

Ive just received my P-3A and had a short look inside. I think its not that difficult to modify as most parts can be reached very easy.
What I will do is along the lines of the Modwright mods.

Change the opamps for OPA627
Change the caps for Panasonic FC and maybe change the 1000uF to 2200uF
Change the resistors near the opamps with dales or holcos
Change the standard power supply with a nice 9VAC toroid (65VA)
Change the diodes for some FREDs

Ill take some pictures when I do the mods.

But first I will listen a bit more, first impressions are not that good but I think (hope) some running in will better this. Im using it with my Marantz CD10 (LClock, AD845, OPA2107, OPA627, Pan FC etc.) and at the moment its only marginally better in a few ways.

I tried a Chord DAC64 a few weeks ago and this really blew the Marantz away in every aspect and I hope the P-3A will do the same.

Has anybody tried the P-1A? Tests are generally very good but I also found some very negative reviews on the web.

william
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Old 24th February 2003, 10:04 AM   #3
protos is offline protos  Greece
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Hi Wuffwaff
Well in the end I changed to opa 627 and hexfreds.This was a few months ago.I feel the 627 upgrade was really worthwhile since it fleshed out the sound and evened out a bit of the midrange forwardness of the old opamps.More dynamics too.The hexfreds were bit more subtle giving probably better dynamics and timing.However it is hard to say exactly the extent because you can't A/B with your previous set-up can you?I think the 627s is a must upgrade though. I have got a set of standard BGs for the whole of the P-3 and I am probably goig to put them in at some stage although I think they won't make a big difference.I am using the monolithic PS but I guess you can use the much cheaper alternative of a good trafo. I also use the P1a with usually good results .It gives a smoother presentation more "analog" like as they say.However with the mods the P3 is quite strong on its own now and the P1a might not be worth the extra money depending on your point of view.In some cases it could sound a little too smooth if you know what I mean.Depends on the recording and system you have.Sometimes it gives a more rich deeper soundstage while the modded P3 is more upfront and punchy. I know it is hard but maybe you can audition one in your system.
I am using a Teac Vrds-25 superclock/ps and it has been op-amped with AD ? from LC .(I don't know because somebody did it for me when I didn't have the knowledge to do it myself). I think the P3 sounds quite a bit better with respect to almost everything.I don't know if changing the resistors and film caps in the P3 is really worth it.Maybe you should try it (I have the impression you are more experienced than me) and give some feedback.
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Old 1st March 2003, 03:06 PM   #4
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Hello Protos,

thanks for the info. Just came back from a week in Sweden and the DAC has improved over this week so Ill wait a bit more before I change anything. The sound is quite good now but somehow a bit "slow" if you know what I mean.

After reading your answer I think the first mods will be the opamps and the caps (have them lying around).

I have also ordered a new transformer.

Can you tell me the difference between the standard and upgraded powersupply?

william
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Old 22nd March 2003, 05:44 AM   #5
teetee is offline teetee  United States
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Smile mod p3a

Hello protos,

I am going to mod the p3a too. Can you tell me what vaule did you choose for FRED Diodes? 4A 600V? 6A 1200? 8A? 12A ?

thanks
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Old 22nd March 2003, 09:08 AM   #6
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Default mods P-3A

just a little progress report,


changed the OPA134 for 627 and changed the two caps for the opamps power supply from muse 470uF to panasonic FC 680uF.

Didnt touch anything else cause I want to wait until my transformers arrive.

Sound has improved by the opamp change but not that much. It sound a bit better now than the modified CD10 now (especially in the highs it sounds more naturall and room and placement are a bit better).

Bought a second one (488 incl. 2 years waranty) for my upstairs stereo and I will leave this unmodified to see if all the mods really work.

william
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Old 24th March 2003, 09:28 AM   #7
protos is offline protos  Greece
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The 627s need some breaking in of course, they sound a little bit heavy at first.. I recently changed the caps around the op-amp supply (can;t be sure without schematic -have you found one?) where there are two nichicon muse 220uf green caps (are you sure 470uf?) with two BG FK 220uf and BG standard caps for the rest (47uf mostly) and sound seems to have more authority in bottom end and perhaps more dynamic.The FK's were four times the size of the muse so were a tight fit. I am thinking of changing the main power caps but it is going to be too tight I think with the BG's.
My freds are 8A .
Desoldering plated thru boards is a bit of a hassle for me -can't seem to suck all the solder from the hole so then I have to redrill them.
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Old 24th March 2003, 06:26 PM   #8
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Protos,

youre right. They were 220/25V and now 470/25V Panasonics.
Yes desoldering is a bit troublesome. I cut all the little feet of the poor OPA134 before getting them out..........

Im still waiting for the transformer to arrive so nothing new here.

When really modifying the thing I think it would be convenient to take it out of the case and into a bigger one with more space for power supplies etc.

william
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Old 24th March 2003, 06:48 PM   #9
Raj1 is offline Raj1  United Kingdom
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Default de-soldering

Hi,

Try adding a few drops of a no-clean liquid flux to the de-soldering wick before use, I find that this helps to suck up almost all the solder from a hole. If you have already tried to de-solder a joint, then wait for it to cool down and re-solder it before trying this.


Thanks
Raj
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Old 24th March 2003, 10:17 PM   #10
teetee is offline teetee  United States
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Smile mod p3a

Here is my plan, replace Opa 134 with Opa 627BP,replace some Fred diodes, replace 47uf,100uf,220uf Capacitors with BG Capacitors. Replace digital input resistor(SMD) 110 Ohms with Caddock MK132 resistor and some resistors around the Opa amp. Protos, what cap did you use around the Opa amp 627?
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