This project was my own decision. I could have made an amplifier using somebody else's design, but when I (and all the other diyaudio members) did the design myself, I can get more credits for that.
This project is on hold at the moment, because I'm doing my practical training at the moment. But when I get back to school, I'm hoping to finish the amp.
I've seen the overture design guide and got some hints from that, thanks! I'll also check the other link you posted.
This project is on hold at the moment, because I'm doing my practical training at the moment. But when I get back to school, I'm hoping to finish the amp.
I've seen the overture design guide and got some hints from that, thanks! I'll also check the other link you posted.
Hi, had a quick look at your layout:-
I would suggest;
1. C10 and C9 need to be closer to the amplifer ideally they should be right next to the power pins as they provide the high frequency decoupling. The longer the trace to the pin the more inductance there is in the way of the the amplifer drawing power from the capacitor. This can lead to instability in the amplifer.
2. R10 and R9 the output zoble resistors should really be 1W parts . You will probably get away with it playing music but if you put a 20KHz test tone in the resistor will burn out.
3. I would recomend seperating the ground (0v) conections from the input and output and taking them seperately back to the connector. This is so that the high current returns from the output do not interact with the low current returns from the input.
4. Generally the smaller a circuit is the better it works so I would try to pack the bits a bit closer together. The traces will pick up less noise from the environment that way. (don't go mad but it looks like you could easly take some of the space out)
Regards,
Andrew
I would suggest;
1. C10 and C9 need to be closer to the amplifer ideally they should be right next to the power pins as they provide the high frequency decoupling. The longer the trace to the pin the more inductance there is in the way of the the amplifer drawing power from the capacitor. This can lead to instability in the amplifer.
2. R10 and R9 the output zoble resistors should really be 1W parts . You will probably get away with it playing music but if you put a 20KHz test tone in the resistor will burn out.
3. I would recomend seperating the ground (0v) conections from the input and output and taking them seperately back to the connector. This is so that the high current returns from the output do not interact with the low current returns from the input.
4. Generally the smaller a circuit is the better it works so I would try to pack the bits a bit closer together. The traces will pick up less noise from the environment that way. (don't go mad but it looks like you could easly take some of the space out)
Regards,
Andrew
I've been planning to use my fellow countryman's schematic in my own project but maybe with few alterations to make it suit my needs better.
I'm trying to fit the whole amp (including the power supply and others) inside an old ATX-power supply case, so the space very limited.
And what about those 220uF electrolytics in the voltage rails? What are they used for and will I need them? I'll be placing power supply filtering caps (probably 4700uF per rail) very close to chip i.e. in the same pcb.
And should there be any changes made to the component values if I'm going hook up my 50k Alps rk27 as a volume controller?
What is the purpose of the 1M resistor (and the 2,2k in series with it) in the input? I'm trying make the design a little more compact, so I'm wondering if these are too important to be left out of design.danielwritesbac said:
I'm trying to fit the whole amp (including the power supply and others) inside an old ATX-power supply case, so the space very limited.
And what about those 220uF electrolytics in the voltage rails? What are they used for and will I need them? I'll be placing power supply filtering caps (probably 4700uF per rail) very close to chip i.e. in the same pcb.
And should there be any changes made to the component values if I'm going hook up my 50k Alps rk27 as a volume controller?
Hi,
If you have the main bulk storage capacitors on the same PCB you can reduce the size of the local decoupling to a minimum of 10uF per rail. These should be placed as close as possible after the 100nF decoupling capacitors. The 4700uF capacitors can then be placed upto say 10cm from the power pins with no problems.
As I don't have the schematic you are refering to so these are the most likely reason for the components you have mentioned. The 1M resistor will be to provide a DC path to ground after the AC coupling capacitor. The 2.2K is probably an input filter in combination with a capacitor to ground.
Regards,
Andrew
If you have the main bulk storage capacitors on the same PCB you can reduce the size of the local decoupling to a minimum of 10uF per rail. These should be placed as close as possible after the 100nF decoupling capacitors. The 4700uF capacitors can then be placed upto say 10cm from the power pins with no problems.
As I don't have the schematic you are refering to so these are the most likely reason for the components you have mentioned. The 1M resistor will be to provide a DC path to ground after the AC coupling capacitor. The 2.2K is probably an input filter in combination with a capacitor to ground.
Regards,
Andrew
I am referring to Nenola's schematic (the topic of this thread) shown in the post #53. The 1M resistor is placed before the AC coupling capacitor, so that is unlikely the reason for the resistor. As far as I know, (I have basic knowledge of electronics and op-amp circuits) those two resistors act only as voltage divider in the input. They lower the gain and increase the input impedance. A pretty useless function IMHO.gfiandy said:
no, they are there to sink any leakage current through the blocking cap to ground.
Similarly there is often a resistor fitted after the DC blocking cap on the source equipment.
These ensure that after the ground of the interconnect contacts, the line is at the same DC voltage and minimises the risk of high voltage pulses going through your system if you hot plug.
Once the interconnect is fitted, they play virtually no part in modifying/conditioning the audio signal.
Similarly there is often a resistor fitted after the DC blocking cap on the source equipment.
These ensure that after the ground of the interconnect contacts, the line is at the same DC voltage and minimises the risk of high voltage pulses going through your system if you hot plug.
Once the interconnect is fitted, they play virtually no part in modifying/conditioning the audio signal.
I just tried this amp for the first time and it.... didn't work!
Everything is like it should be, but I'm getting only loud noise from output. Without input signal, at least the other channel gives 25 volts.
I'm absolutely sure, that my layout sucks, and I'll redo it soon.
Also thinking about using some more simple schematic, maybe some for the 1875 chip in the other thread?
Everything is like it should be, but I'm getting only loud noise from output. Without input signal, at least the other channel gives 25 volts.
I'm absolutely sure, that my layout sucks, and I'll redo it soon.
Also thinking about using some more simple schematic, maybe some for the 1875 chip in the other thread?
25V output with no input? If that is DC that channel is probably blown.
Check the input of the working channel for DC. Check your grounding scheme to make sure you have not constructed a ground loop that produces hum.
And post pictures that show what you did. Somebody might be able to spot something and help you there.
Check the input of the working channel for DC. Check your grounding scheme to make sure you have not constructed a ground loop that produces hum.
And post pictures that show what you did. Somebody might be able to spot something and help you there.
This project isn't dead and the thread has been quite silent for a while. I kinda forgot this whole thing when I got my other amplifier project "ready". After that I didn't have such big need for this amp and also I've been quite busy with my studies.
I still have the boards and components, so maybe one day I'll start this project again and try to make it work this time. I have the PCBs but I'm sure that they could be better.
ps. how can I find out if the chip is blown? shortcut somewhere?
I still have the boards and components, so maybe one day I'll start this project again and try to make it work this time. I have the PCBs but I'm sure that they could be better.
ps. how can I find out if the chip is blown? shortcut somewhere?
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