Upgrading the Acurus Pre

[mondialfan]

Unfortunately the L10 board silk screen has errors. There are multiple R24's.

Find R23A in the middle of the L channel circuitry it's sitting right next to a mica cap. It should be 36.5k if you're on the right resistor. Now look at the same location in the center of the R channel circuitry and you'll see R24B it should also be a 36.5k. That resistor should've been marked R23B but the board designer f'd up.

Those are the two resistors you're replacing.

Now if you look towards the rear of the board near the output RCAs you'll see an R24A & R24B right next to each other. Do not mess with these.

 

[Gibsonian]

Unfortunately the L10 board silk screen has errors. There are multiple R24's.

Find R23A in the middle of the L channel circuitry it's sitting right next to a mica cap. It should be 36.5k if you're on the right resistor. Now look at the same location in the center of the R channel circuitry and you'll see R24B it should also be a 36.5k. That resistor should've been marked R23B but the board designer f'd up.

Those are the two resistors you're replacing.

Now if you look towards the rear of the board near the output RCAs you'll see an R24A & R24B right next to each other. Do not mess with these.

Got it now, thanks alot for your help on this!

 

[laatsch55]

Second that, thanks MDF!!

 

[Gibsonian]

All recommend changes made, and it works! Might even sound better. Thanks again for your help Kevin. L10, modified is a keeper

 

[mondialfan]

All recommend changes made, and it works! Might even sound better. Thanks again for your help Kevin. L10, modified is a keeper

Excellent news!
Enjoy it...

 

[Ultron09]

Hi Kevin, I've owned an Acurus LS-11 and I'm not a DYI person so wondering if you're still doing the Acurus mods. I'd like to explore improving the performance of mine.

 

[mondialfan]

Hi Kevin, I've owned an Acurus LS-11 and I'm not a DYI person so wondering if you're still doing the Acurus mods. I'd like to explore improving the performance of mine.

Yes I am still performing the Acurus & Aragon work. I've taken a break from audio work this summer due to some traveling and house projects that I have going on. I expect to resume audio work either late Sept or early Oct. I have a few people that have been waiting to send me their gear.

 

[J!m]

Any upgrades for the original D2A? I found an upgrade path for the existing converter chips but implementation is rather complex… plus the alignment of the bits after upgrade is necessary.

Anyway, I was just asking as I may want to upgrade the D2A and someone with experience would be required.

I’m happy to share what I’ve learned if you like.

 

[mondialfan]

Hi Jim,

I seem to remember you talking about your D2A work. We spoke via email a few years back about the power supplies I designed for Aragon components. I haven't dabbled with the D2A. Not that its not a good design for its time, but digital has come so far since the early 90's that its hard for me to put much energy into upgrading those older pieces. I looked at the later D2A2 several years ago but the sealed UltraAnalog module used in those was prone to failure over time and the only drop-in replacement I ever saw was built by Sonic Frontiers and was pricey, like $350 for the module.

 

[Gepetto]

Old digital is just old digital...

 

[J!m]

Okay! Nice to have you here.

After we spoke, Joe (Gepetto) and I also spoke about the PS upgrade. I settled on two lab power supplies in a 2u (1u if they’d fit) box- one for analogue (47k) and one for digital (D2A).

But the converter chips used are socketed, and the spec sheet shows they were designed to allow adjustment of the first four bits. Aragon adjusts only the first (which is required) but not the remaining theee. Sony, in one (possibly more) of their ES players used these same chips but did adjust all four bits.

I figured a daughter board could plug into the chip socket and have the four but trim posts etc on this board. I spoke with Wyn Palmer about this (he used to design ICs and now builds world class circuits around various chips) and he wasn’t interested.

But if you pull the spec sheet on the chips you can see the suggested implementation, with four trim pots per chip. The analogue output could certainly be improved upon, probably with an outright replacement. Fortunately the digital and analogue sections do not share a board. I think they should not share a power supply either...

But today I’m working on an eBay special DAC. Old as well but newer than the D2A. It’s a simple op amp output and I have three replacement sets to “roll” in.