can i use 50kohm resistor instead of 47kohm and 20kohm instead of 22kohm and what is the effect of this part substitution?
https://docs.google.com/spreadsheets/d/14s2xhW8gYww6wosUlQOb7nHIz30J3MtAXlK9fdEq8QQ/edit?usp=sharing
Just updated it since some components are no longer stocked and retrofitted some from the FE BOM
Just updated it since some components are no longer stocked and retrofitted some from the FE BOM
Has anybody experienced this?
Assembled two identical boards. Myref rev C. Pcb was designed by a friend, it was posted already here a long while ago by jlester. First board fires up w/o problem. 2nd board goes to DC protect. I checked the amp output and the DMM alternates between full + and - rails. Op-amp and lm3886 rails are good.
Whats's wierd is that I tried desoldering every resistor around the two ICs for checking, and without replacing anything, the board powers up fine. The next morning it goes DC protect mode again. Tried desoldering the Main IC unsuccessfully, then powered up and again it was working. Reflowed the main ic then retired for the night. And this morning, the same problem. I already tried cleaning up the flux.
Any hints please. TIA
Assembled two identical boards. Myref rev C. Pcb was designed by a friend, it was posted already here a long while ago by jlester. First board fires up w/o problem. 2nd board goes to DC protect. I checked the amp output and the DMM alternates between full + and - rails. Op-amp and lm3886 rails are good.
Whats's wierd is that I tried desoldering every resistor around the two ICs for checking, and without replacing anything, the board powers up fine. The next morning it goes DC protect mode again. Tried desoldering the Main IC unsuccessfully, then powered up and again it was working. Reflowed the main ic then retired for the night. And this morning, the same problem. I already tried cleaning up the flux.
Any hints please. TIA
Has anybody experienced this?
Assembled two identical boards. Myref rev C. Pcb was designed by a friend, it was posted already here a long while ago by jlester. First board fires up w/o problem. 2nd board goes to DC protect. I checked the amp output and the DMM alternates between full + and - rails. Op-amp and lm3886 rails are good.
Whats's wierd is that I tried desoldering every resistor around the two ICs for checking, and without replacing anything, the board powers up fine. The next morning it goes DC protect mode again. Tried desoldering the Main IC unsuccessfully, then powered up and again it was working. Reflowed the main ic then retired for the night. And this morning, the same problem. I already tried cleaning up the flux.
Any hints please. TIA
Assembled two identical boards. Myref rev C. Pcb was designed by a friend, it was posted already here a long while ago by jlester. First board fires up w/o problem. 2nd board goes to DC protect. I checked the amp output and the DMM alternates between full + and - rails. Op-amp and lm3886 rails are good.
Whats's wierd is that I tried desoldering every resistor around the two ICs for checking, and without replacing anything, the board powers up fine. The next morning it goes DC protect mode again. Tried desoldering the Main IC unsuccessfully, then powered up and again it was working. Reflowed the main ic then retired for the night. And this morning, the same problem. I already tried cleaning up the flux.
Any hints please. TIA
Update :
Tried replacing the op-amp. It worked again on the third IC. Then went back and inserted the 1st and 2nd. It worked. ��. Blasted the whole board with contact cleaner before leaving for work. Will test again tonight. Next pair of boards will definitely be direct-soldered.
PS : lacquer thinner is not so good as flux remover. Effective but I think it eats the glossy layer of the solder mask.
Tried replacing the op-amp. It worked again on the third IC. Then went back and inserted the 1st and 2nd. It worked. ��. Blasted the whole board with contact cleaner before leaving for work. Will test again tonight. Next pair of boards will definitely be direct-soldered.
PS : lacquer thinner is not so good as flux remover. Effective but I think it eats the glossy layer of the solder mask.
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Can someone please help me update BoM?
I used Dario's 2.0 version from last year (post #1966), but I had to change 5 items.
MyRef Rev C (NOT Checked!) - Google Sheets
I have some doubts about Q1. Did I choose an equivalent?
Thanks!
I used Dario's 2.0 version from last year (post #1966), but I had to change 5 items.
MyRef Rev C (NOT Checked!) - Google Sheets
I have some doubts about Q1. Did I choose an equivalent?
Thanks!
MyRef Rev C Troubles
I've been using my MyRef Rev C (Linuxguru board + kit) for nearly a year now without trouble. The other day it went silent.
I opened it up and found that R11/1R had become open on both channels. I replaced them, powered it up on the bench, checked for offset voltage on both channels (around 7-8 mV) and connected the amp back in the chain since it was on without any obvious issues for more than one hour on the bench. On powering it up, I'm greeted by a loud continuous noise on both speakers.
Opened up once more and found the same resistors R11 had blown again. Same replaced and offsets are normal. Supplies to both opamp and 3886 are also normal.
I'm afraid to connect it back till I know what more to check.
Any advice, please?
I've been using my MyRef Rev C (Linuxguru board + kit) for nearly a year now without trouble. The other day it went silent.
I opened it up and found that R11/1R had become open on both channels. I replaced them, powered it up on the bench, checked for offset voltage on both channels (around 7-8 mV) and connected the amp back in the chain since it was on without any obvious issues for more than one hour on the bench. On powering it up, I'm greeted by a loud continuous noise on both speakers.
Opened up once more and found the same resistors R11 had blown again. Same replaced and offsets are normal. Supplies to both opamp and 3886 are also normal.
I'm afraid to connect it back till I know what more to check.
Any advice, please?
I'd suspect that the opamps in both channels blew, probably as a result of a mains spike or similar. You can replace the LM318 with a TL071 for a sanity check - if it works with modest offset with a TL071, then the LM318 is suspect (By any chance, is it an LF01 hybrid discrete opamp?)
It's also worth checking your source, especially the trafo and grounding.
For me, the fact that offset is ok on the output after replacement says that th lm318 is ok..
What is not Ok is the source. It seems to create a common offset on the input! That is that burns the R11
What is not Ok is the source. It seems to create a common offset on the input! That is that burns the R11
I'm using TI's LM318, not the discrete LF01.
I have spare TL071. I'll try it. Thanks for the advice.
The same chain works fine with my other power amp. But in any case let me check the output of my buffer. Thanks for the pointer.
It happens for my amp too, twice but always only on L-channel.. there is no differences between L & R channel except CL-60. I installed CL-60 only on R channel while the L channel does not
Hi,
What's best value for a power transformer for a stereo system Rev C for 4-ohm speakers?
I plan on buying a transformer from Antek.
I've been searching this thread but cannot find a definitive answer.
Thank you for your help - z
What's best value for a power transformer for a stereo system Rev C for 4-ohm speakers?
I plan on buying a transformer from Antek.
I've been searching this thread but cannot find a definitive answer.
Thank you for your help - z
you may want to have a look at the "My_Ref Fremen Edition - Build thread and tutorial" thread. 😉
In short, for 4 Ohm speaker it's better to stay on the low side with supply voltage, say 18 ~ 22 Vac (on the lowest end you may need to adjust the protection circuit, as there may be problem driving the relay; over ~20Vac it should work without changes).
Power rating should be around 300VA or more, as usual. More is better (within limits: up to 500 ~ 600 VA may be reasonable, even more is likely overkill).
Choose a transformer which has good "regulation". Usually it's expressed in form of % of nominal voltage (the lesser the better).
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Resurrecting an oldie here...
I originally built the MyRef RevC over 10 years ago, and finally got it off the plywood into a proper case about 5 years ago. But it still didn't sound great for some reason. A year ago I finally got a proper preamp to pair with my MyRef RevC, and have (finally) been loving it ever since. Turns out it just needed a little bit of time controls to sound great.
So yesterday I was at a local audiophile gathering, and the host had a pair of the new Magnepan LRSs. They sounded amazing for $650. And it made me wonder if the MyRef would be capable of driving them. Anyone have experience driving the LRS with the My Ref RevC or other versions of the MyRef? Mine is a single-chassis stereo configuration using 1 Antek AN-2225 (25V output, 200VA) toroidal per channel for power transformers.
I originally built the MyRef RevC over 10 years ago, and finally got it off the plywood into a proper case about 5 years ago. But it still didn't sound great for some reason. A year ago I finally got a proper preamp to pair with my MyRef RevC, and have (finally) been loving it ever since. Turns out it just needed a little bit of time controls to sound great.
So yesterday I was at a local audiophile gathering, and the host had a pair of the new Magnepan LRSs. They sounded amazing for $650. And it made me wonder if the MyRef would be capable of driving them. Anyone have experience driving the LRS with the My Ref RevC or other versions of the MyRef? Mine is a single-chassis stereo configuration using 1 Antek AN-2225 (25V output, 200VA) toroidal per channel for power transformers.