Ipanema said:Hi Roly3055 ,
I just complete one channel of blameless amplifier. Would like to know how you mirror one channel to get two channel side by side on eagle?
r!sc!,
Your input and decoupling caps sharing the same ground, will it generate hum?
Thanks.
Is it advisable to add electrolytic capacitor 100-220uF parallel to 100nF decoupling capacitor and separate grounds with 10 ohm res.,
Mr. Leach:
"I have seen some circuits in which the values of the decoupling capacitors are far too small. When I first started designing the Low TIM amplifier, I used a single 0.1 uF capacitor to decouple each power supply rail at the points where they connect to the circuit boards, i.e. in place of C21 through C24. I used that value because I had seen it used in so many other circuits. In taking measurements on the amplifier, I found a very large AC signal would appear on the power supply rails when I tested the amplifier at high frequencies. At 1 MHz, the AC signal on the rails had the same amplitude as the amplifier output signal. When I removed the 0.1 uF decoupling capacitors, the AC signals on the rails would almost disappear. Replacing the 0.1 uF capacitors with 10 uF capacitors eliminated the problem. I settled on 100 uF capacitors to be on the safe side."
Hi r!sc!,
Actually I’m wrong, which is good! J You swapped the - + voltage rails, I see it now.
With your present layout your input and output are too close, is wise to have some distance between them. R9, R10 and R15 must be ½ watt. Provide more space around Q4 for air cooling or place for heatsink. C4 and C6 didn’t like heat too. Rest is very good.
Pozdrav!
Actually I’m wrong, which is good! J You swapped the - + voltage rails, I see it now.
With your present layout your input and output are too close, is wise to have some distance between them. R9, R10 and R15 must be ½ watt. Provide more space around Q4 for air cooling or place for heatsink. C4 and C6 didn’t like heat too. Rest is very good.
Pozdrav!
Hi r!sc!
I think you have done an excellent job on this PCB. I have recently gone through the same process, starting with Rod Elliott's original PCB and spending a few hours tidying things up. Your's looks a lot better than mine BTW.
I like what you did around VR1, the original was ugly. Also your earthing scheme looks better. I do think it would be nicer if the power feeds for the first 2 stages come of the main feed just once, closer to the original. That being said, it probably won't make any difference.
I have built an ESP P3A which is quite a compressed layout and the gap between the output and input shouldn't be an issue.
You have D1 on the silkscreen as a diode but it is really a led. I notice Rod did the same thing. On such a nice layout I think you should put on a led symbol.
I found reversing Q5 and R11 improved the track layout but obviously upset the Q5 and Q6 symmetry.
C4 and C6 need to be close to the transistors and if you use polystyrenes you could move the pads closer together.
It will be interesting if adding C8 and C9 make any difference.
Regards
I think you have done an excellent job on this PCB. I have recently gone through the same process, starting with Rod Elliott's original PCB and spending a few hours tidying things up. Your's looks a lot better than mine BTW.
I like what you did around VR1, the original was ugly. Also your earthing scheme looks better. I do think it would be nicer if the power feeds for the first 2 stages come of the main feed just once, closer to the original. That being said, it probably won't make any difference.
I have built an ESP P3A which is quite a compressed layout and the gap between the output and input shouldn't be an issue.
You have D1 on the silkscreen as a diode but it is really a led. I notice Rod did the same thing. On such a nice layout I think you should put on a led symbol.
I found reversing Q5 and R11 improved the track layout but obviously upset the Q5 and Q6 symmetry.
C4 and C6 need to be close to the transistors and if you use polystyrenes you could move the pads closer together.
It will be interesting if adding C8 and C9 make any difference.
Regards
Hi Greg Erskine,
Pls explain how you will move C4 and C6 closer to transistors???
We all know that any, I mean any capacitor don’t like heat and take another look at pcb. Capacitors are stick to transistors!?!
Possible solution is soldering under the board, or at least 5mm far from Q4 and Q6?
r!sc!, scrap 10 ohm resistor to ground; we talk about ESP amp, not AKSA one.
C7 must go to power ground, not signal ground.
C8 and C9 can’t do any harm, so I’m for them.
Best regards,
Chicco
Pls explain how you will move C4 and C6 closer to transistors???
We all know that any, I mean any capacitor don’t like heat and take another look at pcb. Capacitors are stick to transistors!?!
Possible solution is soldering under the board, or at least 5mm far from Q4 and Q6?
r!sc!, scrap 10 ohm resistor to ground; we talk about ESP amp, not AKSA one.
C7 must go to power ground, not signal ground.
C8 and C9 can’t do any harm, so I’m for them.
Best regards,
Chicco
hi chicco_36,
Sorry if I didn't explain myself properly. When I said, "C4 and C6 need to be close to the transistors" I was meaning, leave them where they are, don't move them further away. Sticking them under the board as you suggested, directly on the transistor pads would be good IMO if you like having components underneath, some people don't.
I had the impression that polystyrenes or ceramics were not sensitive to temperature like electrolytics, but I could be wrong. Next time I have the lid off my P3A I'll check the two transistors and capactiors because I think the caps were actually touching the transistor.
Lots of amps have a resistor between grounds. From memory Rod Elliott never does. Six of one, half dozen of the other?
Regards C8 and C9 - I always wondered why Rod doesn't use them, so it will be interesting to find out what improvement results.
Regards
Sorry if I didn't explain myself properly. When I said, "C4 and C6 need to be close to the transistors" I was meaning, leave them where they are, don't move them further away. Sticking them under the board as you suggested, directly on the transistor pads would be good IMO if you like having components underneath, some people don't.
I had the impression that polystyrenes or ceramics were not sensitive to temperature like electrolytics, but I could be wrong. Next time I have the lid off my P3A I'll check the two transistors and capactiors because I think the caps were actually touching the transistor.
Lots of amps have a resistor between grounds. From memory Rod Elliott never does. Six of one, half dozen of the other?
Regards C8 and C9 - I always wondered why Rod doesn't use them, so it will be interesting to find out what improvement results.
Regards
Hi Chicco_36,
I'll fully agree with you on that! I like to use multiple 'nude' capacitors, to spread the ESR heating and in an open ventilated chassis! I've seen too many 'cooking' chassis where the caps 'fall over' sonically after just 400 hrs. Electro.... springs to mind, sounds great while it lasts because ESR is lower at high temp. Fry an egg on the case while it goes downhill before your eyes.
Cheers,
Greg
I'll fully agree with you on that! I like to use multiple 'nude' capacitors, to spread the ESR heating and in an open ventilated chassis! I've seen too many 'cooking' chassis where the caps 'fall over' sonically after just 400 hrs. Electro.... springs to mind, sounds great while it lasts because ESR is lower at high temp. Fry an egg on the case while it goes downhill before your eyes.
Cheers,
Greg
chicco_36 said:Cats didn't like water, caps also.
I wash my cat from time to time and it doesn't seem overly concerned, so are there some types of caps that are heat tollerant.
It's obvious that electro caps have a problem with heat, that's why they have a rating i.e. 85 or 105 degress, but do ceramics or smd caps for example dry out? The caps, C4 and C6, we were specifically talking about are 100pF.
I wonder what the average life of an DIY amp is, and is it less than the average life of an electro cap.
thanks
to complete the circle...
P88 Preamp PCB Layout. Made by: Vinko (Pinco) and Boban (r!sc!).
P88 Preamp PCB Layout. Made by: Vinko (Pinco) and Boban (r!sc!).
An externally hosted image should be here but it was not working when we last tested it.
Hi Greg,
Maybe for you or me diy amps last from one idea to another, but some people have their diy amps made 20 years ago and still have them in constant use. Ceramic caps do know to dry out, but main concern is that when they are exposed to heat they change characteristics. Be wise and keep them far from heat. Think on the sound, not just reliability…
New thought about capacitors:
Caps like heat, like humans – radiation.
After my third beer I will try to be wiser, or I will come here with some stupid idea, who knows…
Chicco
Maybe for you or me diy amps last from one idea to another, but some people have their diy amps made 20 years ago and still have them in constant use. Ceramic caps do know to dry out, but main concern is that when they are exposed to heat they change characteristics. Be wise and keep them far from heat. Think on the sound, not just reliability…
New thought about capacitors:
Caps like heat, like humans – radiation.
After my third beer I will try to be wiser, or I will come here with some stupid idea, who knows…
Chicco
Hi Chico,
Bit early in the day for a beer (10.18am Sunday) but yes often wiser by the third and lost the plot by the fifth!
PS capacitor ESR heating from inside is the issue especially in BASS amps (subs,etc..) and open ventilated chassis. If you see my amps they usually have open mesh look with 40% open like a tube amp. Multiple paralleled C's spreads the centres of ESR heating. 'nude' is always good - except fat ladies!
The bass will go soft with C ageing but it's a lot like the brake pedal in a car - it's goes down slowly that you don't notice the decline until someone else tells you your brakes need adjusting or your bass is soft.
Cheers,
greg
Bit early in the day for a beer (10.18am Sunday) but yes often wiser by the third and lost the plot by the fifth!
PS capacitor ESR heating from inside is the issue especially in BASS amps (subs,etc..) and open ventilated chassis. If you see my amps they usually have open mesh look with 40% open like a tube amp. Multiple paralleled C's spreads the centres of ESR heating. 'nude' is always good - except fat ladies!
The bass will go soft with C ageing but it's a lot like the brake pedal in a car - it's goes down slowly that you don't notice the decline until someone else tells you your brakes need adjusting or your bass is soft.
Cheers,
greg
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