I still have the hum as mentioned in the previous thread I started.
Can anyone comment on this :-
The light bulbs dim when a source is connected to the input. I can get output from an MP3 player and it sounds very nice (apart from the hum
)
But when I put a passive pre-amp in betweenmsource and de-lite the light bulbs go out and I get no sound.
I am wondering whether R4 (1 ohm resistor) Is causing problems. I am using a wirewound 3W. I think that NP used the same 1ohm resistor as he used in the power supply and as this has to dissipate about 20W.
The 3W resistor gets quite hot, but has not failed. I have some high power alu cased 1ohm resistors. Is it likely that the 3W is not man enough for the circuit?
Can anyone comment on this :-
The light bulbs dim when a source is connected to the input. I can get output from an MP3 player and it sounds very nice (apart from the hum
)But when I put a passive pre-amp in betweenmsource and de-lite the light bulbs go out and I get no sound.
I am wondering whether R4 (1 ohm resistor) Is causing problems. I am using a wirewound 3W. I think that NP used the same 1ohm resistor as he used in the power supply and as this has to dissipate about 20W.
The 3W resistor gets quite hot, but has not failed. I have some high power alu cased 1ohm resistors. Is it likely that the 3W is not man enough for the circuit?
Improved De-Lite schematic
R4 is the 3W resistor I mentioned above.
An externally hosted image should be here but it was not working when we last tested it.
R4 is the 3W resistor I mentioned above.
Nothing to show in pics. I have built the thing as per the schematic.
This may help?
Version 2
The first effort works, but with the high distortion, it's hard not to want to monkey with it. After you have basked in the glow of accomplishment and light bulbs for a while, perhaps you will feel ready for a little more effort.
In this case, that means a couple more parts. Placing a power resistor on the Source of the Mosfet will lower the gain and distortion. After a little testing, I settled on a 1 ohm power resistor, as seen in the schematic of Figure 5. Frugal guy that I am, I used the same resistor as in the power supply.
This may help?
Version 2
The first effort works, but with the high distortion, it's hard not to want to monkey with it. After you have basked in the glow of accomplishment and light bulbs for a while, perhaps you will feel ready for a little more effort.
In this case, that means a couple more parts. Placing a power resistor on the Source of the Mosfet will lower the gain and distortion. After a little testing, I settled on a 1 ohm power resistor, as seen in the schematic of Figure 5. Frugal guy that I am, I used the same resistor as in the power supply.
well - something is obviously wrong ;
either some part , or your implementation
I can't be sure what's the culprit , without proper information
Ok Zen mod. I can post pics, but I did this before about 2 years ago, but no one had any idea about the problem I had then i.e that it didn't work, light bulbs did not light. I was using the IXYS 6N Fets.
I have now rebuilt the modules using IXYS 20N Fets and have some success as outlined in my first post.
I have had someone check the modules and they agree that all parts are connected as on the schematic.
The light bulbs used are 300W 130v.
I have now rebuilt the modules using IXYS 20N Fets and have some success as outlined in my first post.
I have had someone check the modules and they agree that all parts are connected as on the schematic.
The light bulbs used are 300W 130v.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I still have the hum as mentioned in the previous thread I started.
Can anyone comment on this :-
The light bulbs dim when a source is connected to the input. I can get output from an MP3 player and it sounds very nice (apart from the hum
But when I put a passive pre-amp in betweenmsource and de-lite the light bulbs go out and I get no sound.
I am wondering whether R4 (1 ohm resistor) Is causing problems. I am using a wirewound 3W. I think that NP used the same 1ohm resistor as he used in the power supply and as this has to dissipate about 20W.
The 3W resistor gets quite hot, but has not failed. I have some high power alu cased 1ohm resistors. Is it likely that the 3W is not man enough for the circuit?
It depends at what voltage the amp is connected , but I think 3W for R4 is too low . I still use 30W for example .
For the hum , if they are 2 separated power supply arrangement , it should be seen how the ground are connected . It is better ( imo ) to connect the 2 channels together at the output of the amp . A bad ground "scheme" could produce hum .
For the fact that the amp dim when connectin a source , check the input capacitor also .
s
Edit : For a decent s/n ratio I needed 150.000 uF / channel . 96dB speakers , it is dead quiet .
Last edited:
OK , check if you can , what is the current draw of one channel ;
If it is 1.6Amp then R4 is still doing a good job .
At the input cap , you may want to apply some resistance to ground to control the charge .Say 47K.
UPDATE:-
Well I think I have finally cracked it. Having had the situation of the light bulb staying lit when using an MP3 player (albeit it would dull - less volts?), but getting sound out, but no sound when connected to a Pre-Amp. The bulb would go out completely.
I made a new module. The first positive thing was that when it was all connected and I held the phono lead it buzzed as it was being grounded. This did not happen before. Connected a CD player to the pre-amp and bingo. The light bulb on that channel stays as bright as the other one (which is not currently connected) and looks like it should in the pic in the article by Mr Pass.
I did initally try a 15 Ohm resistor in place of the bulb (this is still on the heatsink). It worked but the resistor (high power alu clad) got blisteringly hot after a very short time.
I have also replaced the 1 Ohm resistor with a high power alu clad one and this gets mildly warm. The 3W wirewound ones I initally used got very hot.
There is still some hum, but much less. May move the PS to another box.
Now I can work on getting it finished.....Finally!
An externally hosted image should be here but it was not working when we last tested it.
Well I think I have finally cracked it. Having had the situation of the light bulb staying lit when using an MP3 player (albeit it would dull - less volts?), but getting sound out, but no sound when connected to a Pre-Amp. The bulb would go out completely.
I made a new module. The first positive thing was that when it was all connected and I held the phono lead it buzzed as it was being grounded. This did not happen before. Connected a CD player to the pre-amp and bingo. The light bulb on that channel stays as bright as the other one (which is not currently connected) and looks like it should in the pic in the article by Mr Pass.
I did initally try a 15 Ohm resistor in place of the bulb (this is still on the heatsink). It worked but the resistor (high power alu clad) got blisteringly hot after a very short time.
I have also replaced the 1 Ohm resistor with a high power alu clad one and this gets mildly warm. The 3W wirewound ones I initally used got very hot.
There is still some hum, but much less. May move the PS to another box.
Now I can work on getting it finished.....Finally!
I said in post 7 that I had made new modules using the 20N FETs.
In the light of Nelson's comments I would like to know if the schematic in FIG 5 (The Improved Circuit) makes a proper working amplifier :-
QUOTE: You want to be sure that your circuit
corresponds to the more finished version.
If you are literally building the circuit posted at the beginning of this thread,
then you are missing some elements. This was a simplified intermediate
schematic for tutorial purposes. You want to be sure that your circuit
corresponds to the more finished version.
Please Mr Pass, don't leave me in the lurch
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