Linuxguru gave you great advice. From watching other people have similar problems I am betting you have issues with LM318. Hopefully thats all. Do you know how to check if LM3886 is in contact with sink? Put DMM on the tab of LM3886 and also on the heatsink. If you have any resistance at all this is a bad thing. 0 resistance is obviously very bad. We are looking for no reading. Just using the mica sheet is not good enough. You must use a shoulder washer as well because the bolt will touch the tab and short it to the heatsink without the shoulder washer.
Uriah
PS HEY LINUXGURU do you still have more boards? I have had a few requests for boards and want to know if I can send people to you.
Uriah
PS HEY LINUXGURU do you still have more boards? I have had a few requests for boards and want to know if I can send people to you.
So, its okay usually in test mode to have no isolation to heatsink. Problem comes when heatsink touches just about anything else. If it comes in contact with ground for split second she is burnt. So keep that sink on cardboard and also you may want to try to insert some insulation between board and sink so that they can not touch as this might make a resistor leg or blob of solder or simply copper on side of board touch sink.
Swap your LM318 for the one from the other channel if both channels have not had problems.
Uriah
Swap your LM318 for the one from the other channel if both channels have not had problems.
Uriah
Yup, some 30+ version 1.3 bare boards left, both Chinese and locally-made ones. You're welcome to refer interested people here - I can always source more boards with about 2-4 weeks lead time if there's sufficient interest.
Yup, this worked... the led glows, relay clicks and the dc offset is about 8mV. So, that means the LM318 is gone. I haven't played music through it, but I'm sure the rest is ok.
I checked digikey and mouser, niether have LM318.
Anybody know of a quick source for these?
Thanks for the help guys!
Funky - sorry about the dead LM318N. This is the first I've supplied that has died, but it does happen on occasion. Before looking for a new one, clean out its leads with a razorblade and test it again - it may just be oxidized leads.
I think you'll be happier with a TI LM318P, although it has a different sonic signature. Check at Radio Shack and Frys (if there's one at Seattle), otherwise get it from EBay, preferably from a US seller - it should run about $1 in volume, maybe a few dollars in pairs.
Edit: Maybe the X-Ray screening at Mumbai Airport for overseas cargo isn't friendly for sensitive semiconductors like opamps, etc. - just a guess. I'll know for sure if there are more failures like these in the kits shipped to the US.
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I tried to seach but could not find useful info, can you elaborate on what you mean?
Texas Instruments makes several second-source versions of the LM318 op-amp. The best is probably the LM318J CERDIP version, but the current production is probably the LM318P plastic DIP8 only.
The internal equivalent schematic of the TI LM318P is very similar to the NatSemi LM318N, but there subtle differences in audible sonics when used in a MyRef. IMHO, the TI part has more full-bodied mids and slightly de-emphasized lows, compared the NatSemi part, which is more flat and neutral - this is mostly a matter of subjective perception.
The TI LM318P is also better built, with thicker tinned pins compared to the plated pins of the NatSemi LM318N.
Awesome Amp
Well i finished my first ever chip amp i was eager to here it as this would also be a first.
I switched it on expecting to hear hiss/hum etc however it was dead quiet i assumed it was not working,not until connected to my system and sat back listening to ELO( out of the blue, lp.) a big smile appeared on my face .
One of the reasons i made this was to compare it to my tube amp ,,,,i have given the tube amp to my son !
This amp is fantastic clarity/detail ,i now understand why people rate this so highly. A big thanks to all involved john
Well i finished my first ever chip amp i was eager to here it as this would also be a first.
I switched it on expecting to hear hiss/hum etc however it was dead quiet i assumed it was not working,not until connected to my system and sat back listening to ELO( out of the blue, lp.) a big smile appeared on my face .
One of the reasons i made this was to compare it to my tube amp ,,,,i have given the tube amp to my son !
This amp is fantastic clarity/detail ,i now understand why people rate this so highly. A big thanks to all involved john
I was never one to put much stock in burning in electronics but I recently built the last Rev C go around with the ultimate BOM and I found that it really made a difference. The amp did sound clear and crisp at first turn on, then a little odd (nasally)for about the next 10 hours, I changed through several different speakers and they all sounded similarly odd which pointed to the amp. Finally left the damn thing on to run for a few days and with about 20 hours on the clock things changed greatly for the better. Great amp.
PJN
PJN
I dont recall anyone testing this before as we have all been told to stick exactly to this OPAMP. Glad you compared and thanks for sharing.
Also good to hear from you recent builders!!
Uriah
Hi All,
Following Linuxguru's recommendation I picked up and tried the TI 318P's in my build. While it's impossible to do a true side to side comparison the change did seem to warm up the amp a bit. Vocals seem a little richer for want of a better word. Soundstage, imaging, and detail remain the same (excellent). It's a bit of a bitch changing them out, but well worth the small expense to try out a completely reversible mod.
PJN
Following Linuxguru's recommendation I picked up and tried the TI 318P's in my build. While it's impossible to do a true side to side comparison the change did seem to warm up the amp a bit. Vocals seem a little richer for want of a better word. Soundstage, imaging, and detail remain the same (excellent). It's a bit of a bitch changing them out, but well worth the small expense to try out a completely reversible mod.
PJN
For any of you who participated in the most recent group buy of the "Ultimate BOM" and are bothered by a slight metallic edge or treble brightness, I suggest you try Dario's recommeded switch of R1 and R4 from the Dale metal films supplied in the kit to KOA SPR3 carbon film. The result is smoother highs and a bit more flesh to the mids, with no loss of detail.
You might also want to try a Sonicap for C13. See the "New MyRef C" thread for a more detailed analysis of cap trials.
Peace,
Tom E
You might also want to try a Sonicap for C13. See the "New MyRef C" thread for a more detailed analysis of cap trials.
Peace,
Tom E
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