Upgrading the Acurus Pre
- Thread starter mondialfan
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Well the Coherence is a helluva pre so the fact the modded Acurus is in the same ballpark as it is a good thing to hear. I'm really partial to the Acurus pre's for the price the build quality and design are hard to beat.
125 - 129dB RANGE!!!
WTH man you are close to breaking windows.
125 - 129dB RANGE!!!
WTH man you are close to breaking windows.
Yep, damn close....
Yeah, I'm getting pretty attached to that Coherence....
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- Joined
- Jan 14, 2011
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- 74,912
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- Tagline
- Halfbiass...Electron Herder and Backass Woof
Put her thru some paces last night. Pretty good sounding stock. I think I will leave it in long enough to make some small upgrades to the Yamaha pre that I've been running then pull the Acurus for the full monty that you had done to yours Lee. I'll see if Mondialfan might sell me some of those little PCB's so I can do the upgrade myself. Looking like the Acurus will be a keeper for sure. Cheap and good, my favorite!
Yeah, I had the C-200 as well and I recapped it but it wasn't anything to write home about. I have had a number of preamps in my time, Pioneer C20, Spec 1, Horneshop The Truth, Harmon Kardon, Denon, and more. I've found Yamaha to be my favorite by far, now this Acurus is on par, could be better but it is close. If upgrades are like Lee is hearing, I could be done on the SS side. Still wanna try a tube pre with a WOPL yet.
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I haven't been on the forum in a while but read thru this thread and thought I'd mention that I have an RL11 that Kevin upgraded a few years ago. He outfitted mine with an outboard power supply and I've told many people that it's likely the LAST piece of audio gear that I'd ever sell. I've swapped in other preamps here and there and always come back to my modded RL11.
If I'm not mistaken, the guy Kevin originally built it for tried to buy it back a year or 2 ago. Kevin would likely remember better than me. I've got another RL in the box, just in case! I'm feeding my Aragon 8008bb amps with this thing. I think the Acurus power supplies and the 10V+ output just man-handles whatever you have. Love it!!!
If I'm not mistaken, the guy Kevin originally built it for tried to buy it back a year or 2 ago. Kevin would likely remember better than me. I've got another RL in the box, just in case! I'm feeding my Aragon 8008bb amps with this thing. I think the Acurus power supplies and the 10V+ output just man-handles whatever you have. Love it!!!
Sorry I haven't logged in for quite a while so just reading this now. The L10 is mostly the same as the LS11. The L10 uses Noble volume & balance pots and the L10 also uses the J72/K147 Jfet pairs in the outputs versus the later k389/j109 paralleled Jfet pairs. My preference if I'm going without a remote is for the L10 as I much prefer the Noble pots. IMO The build quality of the Noble pots is a lot better than the Alps blue velvet.
The LS11/RL11 will have lower residual noise stock than the L10. IIRC the stock L10 measured about 30 - 35uV of residual noise and the LS11/RL11 are around 16 - 18uV. This can be rectified in the L10 by installing the same value resistors in the feedback positions. Remove R23 L-Ch & R24 R-Ch and install 22.1k metal films in place of the 36.5k resistors. Also install 3.32k metal films in the R22 location. The gain will remain the same but you'll now have the same < 20uV residual noise as the later models. While you're at it remove the R5 resistor and leave it out. Replace the R4 1k ohm resistors with 100r metal films too.
Pay particular attention to the through hole connections on the two large primary power supply caps. One of those connections passes from the bottom of the board to the top of the board through one of those holes and the pads are notorious for opening up after you pull the extremely tight snap-in caps out of the board. Your symptoms will be no sound when you power it back up and one of the DC rails missing...... You should ohm it out throughly before putting the board back into the chassis for reassembly. I've had a lot of people that have contacted me with dead pre's after trying to upgrade them and more often than not that connection was the culprit.
I'm out of the custom current source pcb's that I had made to drop in. Truth be told I don't think the little boards were worth the trouble over dead bugging the parts into the board. I can put the parts into the stock board (it does require drilling some holes with a small wire gauge bit) and from the top you'd be hard pressed to know the parts weren't put there by the factory.
The LS11/RL11 will have lower residual noise stock than the L10. IIRC the stock L10 measured about 30 - 35uV of residual noise and the LS11/RL11 are around 16 - 18uV. This can be rectified in the L10 by installing the same value resistors in the feedback positions. Remove R23 L-Ch & R24 R-Ch and install 22.1k metal films in place of the 36.5k resistors. Also install 3.32k metal films in the R22 location. The gain will remain the same but you'll now have the same < 20uV residual noise as the later models. While you're at it remove the R5 resistor and leave it out. Replace the R4 1k ohm resistors with 100r metal films too.
Pay particular attention to the through hole connections on the two large primary power supply caps. One of those connections passes from the bottom of the board to the top of the board through one of those holes and the pads are notorious for opening up after you pull the extremely tight snap-in caps out of the board. Your symptoms will be no sound when you power it back up and one of the DC rails missing...... You should ohm it out throughly before putting the board back into the chassis for reassembly. I've had a lot of people that have contacted me with dead pre's after trying to upgrade them and more often than not that connection was the culprit.
I'm out of the custom current source pcb's that I had made to drop in. Truth be told I don't think the little boards were worth the trouble over dead bugging the parts into the board. I can put the parts into the stock board (it does require drilling some holes with a small wire gauge bit) and from the top you'd be hard pressed to know the parts weren't put there by the factory.
Thanks for the reply Kevin. When I went in to change some of the resistors that you also changed in Lee's R11 I did find out that the circuit was different. I think I only changed out 2 then stopped there as many positions did not match up.
I ended up getting the bigger Xformer in, as well as PS and rail caps changed out though, so was good overall. Sometime I may go back in and finish up the work. I didn't do anything in the area where you installed the secondary boards. Couple questions:
1. For R5, take it out and place nothing, or drop in a jumper in it's place?
2. Replace R4 with 100 ohm resistor?
Thank you,
Scott
I ended up getting the bigger Xformer in, as well as PS and rail caps changed out though, so was good overall. Sometime I may go back in and finish up the work. I didn't do anything in the area where you installed the secondary boards. Couple questions:
1. For R5, take it out and place nothing, or drop in a jumper in it's place?
2. Replace R4 with 100 ohm resistor?
Thank you,
Scott
The L10 & ls11 are numbered differently and laid out a bit differently but its mostly the same circuit. Once you put the two schematics side by side you'll see what I mean.
1) Remove R5 and leave it out, installing a jumper will be a permanent signal mute.
2) Yes replace the 1k with a 100r (ohm). L10 & RL/LS11 schematics all show 1k here however in practice the factory installed 100r in LS11/RL11.
1) Remove R5 and leave it out, installing a jumper will be a permanent signal mute.
2) Yes replace the 1k with a 100r (ohm). L10 & RL/LS11 schematics all show 1k here however in practice the factory installed 100r in LS11/RL11.
Kevin have yet another question for you. I have all parts now to go in and update per your suggestions but the schematic I found shows the R23 and R24 are 36.5k and 47.5K respectively, for each channel. Do I need to replace both of these with 22.1K resistors, or just the R23's of each channel. I've attached the L10 schematic that I found on the net.
"Remove R23 L-Ch & R24 R-Ch and install 22.1k metal films in place of the 36.5k resistors"
"Remove R23 L-Ch & R24 R-Ch and install 22.1k metal films in place of the 36.5k resistors"
