Well, looks like I am in the clear and will install today. FWIW, the Amazon seller for this was called honestyparts. Thanks for the help. I just removed my Noble pot and it was a disaster inside. Nothing I wanted to think about still being in there. Which makes me wonder more about bypassing the balance control. Can anyone tell me how to bridge the 8 contacts on that?
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Good news!
Now you have work to do
I am of no help about your balance control, I would think a look at the schematic, and a bit of confirming with a meter would give you the answer you are looking for.
Looks like hifiengine has the schematic, and an owners manual for the L10. Free download, but you will need to create an account.
Best of luck,
~C
First of all, that is insane that AI will even try to do that and draw that nicely. Second, just wanted to post my results here and thank everyone for their help. I am going to recap this while its open, but for now I have functional volume control it appears, (not tested yet)
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Hey folks. I went and ordered some KA series Nichicon Caps to replace the 6x100uf and 2x3300uf. I got them yesterday and put them in last night. Have not tested the unit yet, was leaving that for the long weekend. Any thoughts on my choice for the filter caps? They are not snap in like the originals, and smaller, but I went with em anyways. They have very low ripple current. I couldn't find any snap ins in 3300uf anyways.
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Yes, I don't think I can edit it anymore. Listening to it now!
Hey folks, really enjoying this preamp at the moment the way I have it now, but it is making me want to keep going on it. I ordered the replacement resistors to lower crosstalk as described here, post number 57 https://forums.phxaudiotape.com/threads/upgrading-the-acurus-pre.8852/page-3
After this I may attempt the transformer upgrade. I have a couple questions about the upgrade.
1. I see it is a Triad Transformer. Does anyone know the model?
2. The soft diode upgrade. What would be a suitable part?
3. I have just put it 2 UKA series 3300uf caps in. How high would make sense to go up on these? 6800?
Thanks!
@mondialfan
Edit: I think this is the transformer? https://www.ebay.com/itm/225015818977
After this I may attempt the transformer upgrade. I have a couple questions about the upgrade.
1. I see it is a Triad Transformer. Does anyone know the model?
2. The soft diode upgrade. What would be a suitable part?
3. I have just put it 2 UKA series 3300uf caps in. How high would make sense to go up on these? 6800?
Thanks!
@mondialfan
Edit: I think this is the transformer? https://www.ebay.com/itm/225015818977
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KNielsen
Well-Known Member
This transformer in the link will do or similar. Be aware that you need to drill in the PCB for the Triad to fit.
As for the e.caps at the PSU, 8200uf seams to be the limit in the builds I've done with a 10VA transformer. You'll be just fine with 6800uf as well.
Personally I would search for a snap-in cap with 10mm lead spacing, as you'll easily get much better ripple performance from these then with standard radial caps you selected now at C8/C9.
As for the diodes I've used SBYV27-200-E3/73 to replace the original 1A type.
The resistor change is quite easy, just compare the L10 schematic with the newer LS11/RL11 schematic:
In the L10; Remove R5, change R23 to 22.1Kohm, change R22 to 3.32Komh.
If you look at the Aragon-series they use 12Kohm/1.76Kohm. The ratio is about the same but you'll expand the bandwidth to about -3db @1.2MHz, no oscillations in the build I have.
A constant current source might come in handy, and can be soldered to the main PCB with some added drilling. Replacing R12/13 with a LED reference source with 992/1845 and some P2P will do perfect. Set for around 260μA pr rail.
Hope this helps
As for the e.caps at the PSU, 8200uf seams to be the limit in the builds I've done with a 10VA transformer. You'll be just fine with 6800uf as well.
Personally I would search for a snap-in cap with 10mm lead spacing, as you'll easily get much better ripple performance from these then with standard radial caps you selected now at C8/C9.
As for the diodes I've used SBYV27-200-E3/73 to replace the original 1A type.
The resistor change is quite easy, just compare the L10 schematic with the newer LS11/RL11 schematic:
In the L10; Remove R5, change R23 to 22.1Kohm, change R22 to 3.32Komh.
If you look at the Aragon-series they use 12Kohm/1.76Kohm. The ratio is about the same but you'll expand the bandwidth to about -3db @1.2MHz, no oscillations in the build I have.
A constant current source might come in handy, and can be soldered to the main PCB with some added drilling. Replacing R12/13 with a LED reference source with 992/1845 and some P2P will do perfect. Set for around 260μA pr rail.
Hope this helps
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First, thanks so much for your responses. I have come to realize my mistake on the 3300's. This part above that I quoted, I do not understand. I do see the changes that mondialfan has made with the custom boards, but do not understand these instructions, does this require a board? Any more insight would be appreciated here. Thanks again!
KNielsen
Well-Known Member
I did custom boards after seeing Mondialfan's work. But you can do this mod without adding PCB's and still make it look almost original in the original PCB.
To show you a current source, look at Q3/Q4, D1-D4, R8/R9 and R15 in the Aragon 28K schematic attached.
This is your constant current sources.
Mondialfan replaced D1-D4 with single LED diodes pr rail, as do I.
I'm in Italy right now on holiday, and cannot remember the LED diodes I chose on top of my head, but;
To calculate the current:
(Vf of the diode - Vdrop of the transistor) / resistor = Current
Example (260μA target): a LED diode with a forward voltage (Vf) of 2V, a transistor with a Vdrop of typical 0.7V and we have 1.3V left.
1.3V / 5Kohm = 260μA.
The 5Kohm is R8/R9 in the 28K-schematic.
The numbers are just an example and may vary depending on components chosen!
R15 sets the current through the LED's or diodes if used. If a 20mA type LED-diode is used I normally target a 3mA for a long healthy life of the LED....
You just measure the voltage across this resistor to calculate the current passing through the LED's.
If you just want to follow the 28K-schematic with the 4x 1N4148, then R8/R9 should not be 3.92Kohm, but more something like ±3.16Kohm to get you in the ballpark of 260μA for the L10.
The Vf of the two diodes combined sets the value for calculating.
Try building a CCS on a breadboard to experiment. It's fun stuff
EDIT: do not overdo the CCS. Keep it within reason, like 250-270μA pr rail or you'll have excessive currents later on in the circuit
To show you a current source, look at Q3/Q4, D1-D4, R8/R9 and R15 in the Aragon 28K schematic attached.
This is your constant current sources.
Mondialfan replaced D1-D4 with single LED diodes pr rail, as do I.
I'm in Italy right now on holiday, and cannot remember the LED diodes I chose on top of my head, but;
To calculate the current:
(Vf of the diode - Vdrop of the transistor) / resistor = Current
Example (260μA target): a LED diode with a forward voltage (Vf) of 2V, a transistor with a Vdrop of typical 0.7V and we have 1.3V left.
1.3V / 5Kohm = 260μA.
The 5Kohm is R8/R9 in the 28K-schematic.
The numbers are just an example and may vary depending on components chosen!
R15 sets the current through the LED's or diodes if used. If a 20mA type LED-diode is used I normally target a 3mA for a long healthy life of the LED....
You just measure the voltage across this resistor to calculate the current passing through the LED's.
If you just want to follow the 28K-schematic with the 4x 1N4148, then R8/R9 should not be 3.92Kohm, but more something like ±3.16Kohm to get you in the ballpark of 260μA for the L10.
The Vf of the two diodes combined sets the value for calculating.
Try building a CCS on a breadboard to experiment. It's fun stuff
EDIT: do not overdo the CCS. Keep it within reason, like 250-270μA pr rail or you'll have excessive currents later on in the circuit
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Hey there, thanks for the response from vacation! This current source stuff is beyond my understanding at this point. I am a basic tinkerer with a desoldering station.I did custom boards after seeing Mondialfan's work. But you can do this mod without adding PCB's and still make it look almost original in the original PCB.
To show you a current source, look at Q3/Q4, D1-D4, R8/R9 and R15 in the Aragon 28K schematic attached.
This is your constant current sources.
Mondialfan replaced D1-D4 with single LED diodes pr rail, as do I.
I'm in Italy right now on holiday, and cannot remember the LED diodes I chose on top of my head, but;
To calculate the current:
(Vf of the diode - Vdrop of the transistor) / resistor = Current
Example (260μA target): a LED diode with a forward voltage (Vf) of 2V, a transistor with a Vdrop of typical 0.7V and we have 1.3V left.
1.3V / 5Kohm = 260μA.
The 5Kohm is R8/R9 in the 28K-schematic.
The numbers are just an example and may vary depending on components chosen!
R15 sets the current through the LED's or diodes if used. If a 20mA type LED-diode is used I normally target a 3mA for a long healthy life of the LED....
You just measure the voltage across this resistor to calculate the current passing through the LED's.
If you just want to follow the 28K-schematic with the 4x 1N4148, then R8/R9 should not be 3.92Kohm, but more something like ±3.16Kohm to get you in the ballpark of 260μA for the L10.
The Vf of the two diodes combined sets the value for calculating.
Try building a CCS on a breadboard to experiment. It's fun stuff
EDIT: do not overdo the CCS. Keep it within reason, like 250-270μA pr rail or you'll have excessive currents later on in the circuit
Is it necessary to do this current source stuff if doing the power supply change, or is that something I can plan out and do later?
I chose these diodes BTW and had basically just ordered them when I got your post. Would these work? I was very focused on the "soft" aspect of them per mondials notes. These show a 500ns trr. and from some reading , to me that meant soft/fast haha.
I will take a look at the 28K schematic and try to see the similarities and differences.
Thanks so much!
Thank You, next project once complete I will have to go for the current source upgrade.You don't need the current sources, but I thought you should know these are often added when a L10/L11/RL11 is reworked
The FR207 diodes will work and the packedsize is spot on. You should have no problems installing these.
Best regards
KNielsen
Well-Known Member
I'll be home in about 24hours, I'm on a long drive through Germany. I'll check if I have some photos to back you up later
Well, I think I figured it out. I had to open up the board holes slightly and carefully to get the pins in there. Th PS is now in and soldered. Are there any modifications that need to be done, jumpers or anything. I am thinking that it is kind of plug any play, but please let m know if i am wrong on that.I'll be home in about 24hours, I'm on a long drive through Germany. I'll check if I have some photos to back you up later
Also, I bought a couple of .1 uf film caps for the 8200's that I put in, not sure if that is overkill or not, but they were cheap enough