LM3886
Most likely you killed the LM3886. They are suposed to have output protection, but I killed one also. Never figured out how.
George
Most likely you killed the LM3886. They are suposed to have output protection, but I killed one also. Never figured out how.
George
Re: Padding Down Preamp Output
I haven't tried this, so you will have to check for loop stability (oscillations) and check for clipping on the LM318.
Looking at the rev3 schematic, right channel, the overall gain is set by the R7,12K resistor divided by the R10, 390 resistor. So if you changed R7 down to 8K you would lose about 10db gain.
You now could be dissipating close to .2W in this resistor, R7, so use at least a half watt resistor.
Let us know if it works and what it does to the sound.
groch said:
I haven't tried this, so you will have to check for loop stability (oscillations) and check for clipping on the LM318.
Looking at the rev3 schematic, right channel, the overall gain is set by the R7,12K resistor divided by the R10, 390 resistor. So if you changed R7 down to 8K you would lose about 10db gain.
You now could be dissipating close to .2W in this resistor, R7, so use at least a half watt resistor.
Let us know if it works and what it does to the sound.
psmithmx, great looking amp.
I was lucky when I had carelessly hardwired one of my out put channels to the PS capacitor (not Mauro's or Brian's board) and it nearly killed my speakers. Measured 37VDC across the speaker output. I thought one of the LM3886 chip would be fried too, but after correcting the wiring, it was working fine. Tough little critter.
Wish I could suggest something, but with some luck, it may not be as bad as it seems.
I was lucky when I had carelessly hardwired one of my out put channels to the PS capacitor (not Mauro's or Brian's board) and it nearly killed my speakers. Measured 37VDC across the speaker output. I thought one of the LM3886 chip would be fried too, but after correcting the wiring, it was working fine. Tough little critter.
Wish I could suggest something, but with some luck, it may not be as bad as it seems.
Re: Killed my RevC
One thing I would suspect is the speaker protection transistors. Check all your power traces especially those to the LM3886,Sp circuit, and LM318.
SmellOfPoo said:Stupid me ...Last night I wanted to measure TSPs of some woofers, didnt notice that I accidentdly shorted my RevC´s outputs.
So I wondered why there was no sound, and now my beloved gem is dead. When powering it up, the relays don´t ´switch. Nothing inside looks fried. Any idea what could be faulty ? Help me, please
One thing I would suspect is the speaker protection transistors. Check all your power traces especially those to the LM3886,Sp circuit, and LM318.
Hi groch & safetyman,
Thanks for the compliments. Groch, it is actually a 19 inch case, similar to that being used in laboratory test equipment (rack mounted equipment). Had to modify it to look more like a high quality amp, than lab test equipment. 🙂
Thanks for the compliments. Groch, it is actually a 19 inch case, similar to that being used in laboratory test equipment (rack mounted equipment). Had to modify it to look more like a high quality amp, than lab test equipment. 🙂
Hi guys, my amp is getting a bit better as the caps burn in still...
But I noticed something last night on checking DC output again...
the one channel seems inverted to the other one.... in other words the one gives +2.5mv and the other -3.2mv....
I took care to make sure I put the poles of the meter on the outputs in the same orientation.
How do I fix this?
But I noticed something last night on checking DC output again...
the one channel seems inverted to the other one.... in other words the one gives +2.5mv and the other -3.2mv....
I took care to make sure I put the poles of the meter on the outputs in the same orientation.
How do I fix this?
Hi Nordic.
this is very common. you need not worry about it. it is very normal. wait till you start messing with a class A and you think you have set the amp up, and when you think it is ready it warms up and then you have -70mv, 🙄 you start all over again.
I got you some WIMA MKS 10mm pitch. i will post this at some stage
this is very common. you need not worry about it. it is very normal. wait till you start messing with a class A and you think you have set the amp up, and when you think it is ready it warms up and then you have -70mv, 🙄 you start all over again.
I got you some WIMA MKS 10mm pitch. i will post this at some stage
Nordic said:
well - I would say DC offset this low is very good - nothing to fix...😎
( I have run amps in past with much higher levels of DC offset and I never noticed any ill effect. )
mike
Hi Rudi - you just beat me !...🙂
I just finished mine last night...giving it a little time to settle before any serious listening; but if first impressions mean anything, it is going to be stunning. Powering a pair off a 25V 400VA transformer...plenty.
Just wanted to give a big thanks to mauro and the twistedpear crew for doing all this!
Happy holidays and happy listening
--Scott
Just wanted to give a big thanks to mauro and the twistedpear crew for doing all this!
Happy holidays and happy listening
--Scott
Congratulations Scott! If its anything like mine it sounds great from the first moment it turns on. It appears its a pretty robust kit, at list through the building stage.
Post a photo of it if your get a chance to add to the Penasa MyRev collection.
George
Post a photo of it if your get a chance to add to the Penasa MyRev collection.
George
Well i have the X-Calibre (the MINI with a V8 engine 
) running and first impressions.
Very, VERY Clean. Soundstaging is very good. all over. AWESOME very close to being there, just thought I would let you all know 😀
you can do the REF-A and REF-C on this board.
Regulated or Zener supply for the LM318
I will take this to another thread as soon as i have done the burn-in Thing
) running and first impressions.Very, VERY Clean. Soundstaging is very good. all over. AWESOME very close to being there, just thought I would let you all know 😀
you can do the REF-A and REF-C on this board.
Regulated or Zener supply for the LM318
I will take this to another thread as soon as i have done the burn-in Thing
Attachments
rudi said:
Wow only almost there? Thats too bad... 😉 Good luck with your amp. Looks like an interesting project.
Russ White said:
Hi Russ. Yeah I am working on the concept of time warping and actually being there. but alas it would not be through a HIFI set 😉
well all i can say is that this layout is a tweakers dream. you can almost do all configurations on it, and best of all it sounds VERY GOOD, you just got to dail in the flavour you want.
MINIMUM LOAD?
hi there!!
....and congratulation, as everybody say,it seems to be a VERY VERY good design,and i am tempted to use it but....
i don't find information on the minimum load (impedance) it can support ?
ps:my speakers are line array with a dc resistance at about 2 ohms
hi there!!
....and congratulation, as everybody say,it seems to be a VERY VERY good design,and i am tempted to use it but....
i don't find information on the minimum load (impedance) it can support ?
ps:my speakers are line array with a dc resistance at about 2 ohms
Hi Hobby1
you will be able to drive it, i have driven some full range ribbons of 1.2ohm but only at a fairly low level - i have to add that it was actually a acceptable listening level . after that it clips terribly. ( the only thing i have against the amp)
you will be able to drive it, i have driven some full range ribbons of 1.2ohm but only at a fairly low level - i have to add that it was actually a acceptable listening level . after that it clips terribly. ( the only thing i have against the amp)
hi there
Rudi,thanks for reply!
but if you,or someone else can give me some number ,i much appreciate ....
because,according to what you say it seems that the limits are not too far
greets
fred
Rudi,thanks for reply!
but if you,or someone else can give me some number ,i much appreciate ....
because,according to what you say it seems that the limits are not too far
greets
fred
hobby1. lets put it this way. if your speakers are more than say 92db and you do not tend to play it extremely load you will be OK
I would also recommend that you drop the rail voltage a bit if you are using only a very load load. Try a 22V transformer, which should drop you to about 30V rails. Should give you a little more room before SPIKE/clipping.
I think really, though, that thisd may not ber the best amp for your load. It will work, but not a good long term match up, as the LM3886 really isn't meant for loads below 4ohm.
I think really, though, that thisd may not ber the best amp for your load. It will work, but not a good long term match up, as the LM3886 really isn't meant for loads below 4ohm.
Brian was restating what has been said many times; the My Reference is not meant for loads lower than 4ohms.
It is rated at 40W into 8 ohms and 56W into 8 ohms.
If you overdrive it, it will clip, as any amplifier will.
This is not the fault of the amplifier, but of the user.
It is necessary to match the power output and load handling capability of the amplifier to the power demands and loading requirements that it has to meet.
Audie.
It is rated at 40W into 8 ohms and 56W into 8 ohms.
If you overdrive it, it will clip, as any amplifier will.
This is not the fault of the amplifier, but of the user.
It is necessary to match the power output and load handling capability of the amplifier to the power demands and loading requirements that it has to meet.
Audie.