Okay Bonsai, clearly something is amiss.
"mail them to me" - Your offer is well appreciated, thank you. I will first take another look at all the removed semiconductors, also I want to check all traces and the remaining parts..
Cheers!
You have two amplifier boards that behave similarly (badly). So there could be the same mistake in the build of both boards or some common element is faulty. That could be the power supply or the chassis - wiring, heatsink insulation for the transistors, etc. If you carefully check the resistor values and transistor types in both boards and find no issues then look at the common elements for problems.
NX amplifier build update
Hi Bonsai I have tested my amplifier module both one I have to say perfect there was no issues at all it worked like a charm very important think was that its is very quite no hum no hiss I can say excellent design from Bonsai.
Tested both power amp modules and worked very good now just waiting for same gain grade driver transistors to come.Will post the update here.
Also bonsai I have used a soft start module before the toroidal transformer but when I use soft start module the muting option on the PSU have some issues like it will not discharge fast but very slowly.Any issue to use softstart module with the NX psu ?
Hi Bonsai I have tested my amplifier module both one I have to say perfect there was no issues at all it worked like a charm very important think was that its is very quite no hum no hiss I can say excellent design from Bonsai.
Tested both power amp modules and worked very good now just waiting for same gain grade driver transistors to come.Will post the update here.
Also bonsai I have used a soft start module before the toroidal transformer but when I use soft start module the muting option on the PSU have some issues like it will not discharge fast but very slowly.Any issue to use softstart module with the NX psu ?
Attachments
Hi guys,
I wanna know if I could use my smps500r power supply I have laying around. I bought the +- 50v version from connex and made a l15d class D amp with it. One of the l15d failed after a month and I am looking for a better solution.
ps. The ljm l15d pcb bought from aliexpress wasn't of good quality. I should have bought from the recommended sellers...
I wanna know if I could use my smps500r power supply I have laying around. I bought the +- 50v version from connex and made a l15d class D amp with it. One of the l15d failed after a month and I am looking for a better solution.
ps. The ljm l15d pcb bought from aliexpress wasn't of good quality. I should have bought from the recommended sellers...
Spyros abs, What is the wattage rating of your PSU?
Also important is that it is free from any HF noise SMD ripple (applies to any SMPS for audio work).
Also important is that it is free from any HF noise SMD ripple (applies to any SMPS for audio work).
The psu is rated 500w and designed for audio :
http://www.connexelectronic.com/documents/SMPS500R.pdf
http://www.connexelectronic.com/documents/SMPS500R.pdf
Wow - looks like a nice PSU!
I think this should work very well with your nx-Amp
How much was it BTW, if you don't mind me asking?
I think this should work very well with your nx-Amp
How much was it BTW, if you don't mind me asking?
Hi Andrew, I am going to build this amp coming winter. It has been referred to me by Struth on DIYAudio.com.
My question is if I could exchange the 10Volt Zeners with these:
https://www.hypexshop.com/DetailServlet?detailID=2014
Ofcourse positive and negative ones. I think this will do much with the sound quality because this is very clean!
Any changes need to be made if I put these on instead of the zeners?
Thanks!
Sjoerd
My question is if I could exchange the 10Volt Zeners with these:
https://www.hypexshop.com/DetailServlet?detailID=2014
Ofcourse positive and negative ones. I think this will do much with the sound quality because this is very clean!
Any changes need to be made if I put these on instead of the zeners?
Thanks!
Sjoerd
Somewhat late with a reply This is as far as I have got today.
Metal film is slightly better for noise.
Metal oxide is slightly better for overload tolerance.
Tempco of metal film is generally lower.
At the very low levels of resistance used in the NX noise is not a problem.
Overload should not be a problem provided the 2k7 resistors have a voltage rating >>40Vpk
That just leaves Tempco.
Metal film are available from 5ppm/C to 100ppm/C
Metal oxide are generally 50ppm/C to 300ppm/C
If both were 100ppm/C, there would be no difference in using either in this amplifier.
But, I have two concerns.
@ 100W into 8ohms the peak voltage across the feedback is around 40Vpk
The resistors are paralleled and then series connected to the lower NFB.
This gives a dissipation of ~1.4W for the group, i.e. 280mW for each 2k7.
That will change the resistance of the upper feedback leg.
I would use 10 resistors 5 on top and 5 on the bottom soldered to the protruding leads. That gets dissipation down to 140mW for the typical 600mW resistors that I use.
The second concern is the use of paralleled resistors for the 5off 2k7 = 540r
This exposes each resistor to peak output voltage. Some resistors are rated @ 50V, these low voltage resistors must be avoided. Those that are >=100V rated will be OK.
A solution would be to use a series pair of 1k3 for an effective 2k6 giving 520r as the upper NFB leg. This would also use 10 resistors and result in the 140mW dissipation as well as allowing any voltage rating.
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A 230:34Vac 5% regulation transformer will overvoltage 50V smoothing capacitors. 63V caps are the correct and safe voltage rating. The sch shows 220uF 63Vdc.
Output voltage = Primary supply voltage / transformer rated voltage * secondary rated voltage * (1 plus regulation)
Apply sqrt(2) to get the peak voltage and then subtract 1.2V for the dual rectifiers.
eg. supply 239Vac, transformer 230:34Vac 5% regulation gives
239/230*34*1.05*sqrt(2) - 1.2 = 51.26Vdc at the smoothing capacitors.
In the UK where maximum supply is 253Vac and most transformers are 230:35+35Vac the maximum smoothing capacitor voltage can be as high as 56Vdc
post481
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spare components for NX build
I have placed an order with Farnell, for the following
a114et
a115et
a144et
c114et
c115et
c144et
10uF 25V 1206 X5R
bat54w
2n7002
10V Zener 500mW
4.7V Zener 500mW
4r7 1W 2512 1% thick film
Go to swapmeet, if you need some of these to complete an NX build.
http://www.diyaudio.com/forums/swap-meet/281305-nx-amplifier-components.html#post4489713
I have placed an order with Farnell, for the following
a114et
a115et
a144et
c114et
c115et
c144et
10uF 25V 1206 X5R
bat54w
2n7002
10V Zener 500mW
4.7V Zener 500mW
4r7 1W 2512 1% thick film
Go to swapmeet, if you need some of these to complete an NX build.
http://www.diyaudio.com/forums/swap-meet/281305-nx-amplifier-components.html#post4489713
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I changed my filter caps to 63v 22000uf because the rails were right at +/- 50v with no load and the 50v caps worried me. I'm using a 34-0, 34-0 Antek transformer.
NX amplifier build update
Hi All,
At last I have successfully placed everything inside my cabin.As I dont have much to do as the cabinet was fully set to fix all parts.Just connected to two way car speaker directly played some song via my ipod.As this is in testing mode. I can hear very detailed fantastic sound with excellent sound stage.Still I have not connected my main speakers.So after connecting my main speakers I can provide a complete update.Still it awesome amp is very quite.I am updating the pictures of the amp.
Hi All,
At last I have successfully placed everything inside my cabin.As I dont have much to do as the cabinet was fully set to fix all parts.Just connected to two way car speaker directly played some song via my ipod.As this is in testing mode. I can hear very detailed fantastic sound with excellent sound stage.Still I have not connected my main speakers.So after connecting my main speakers I can provide a complete update.Still it awesome amp is very quite.I am updating the pictures of the amp.
Attachments
