SX-Amp and NX-Amp

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#1,281
pinnocchio said:
Bonsai,

Do you have some PCBs or gerber for just the speaker protection using SSLR? Something like the PSU from NX but just the speaker protection part?

I want to replace the ones in other projects that I already own for better ones. I have relays for speaker protection... With very high current they could stick and not even disconnect the load.

Thanks
Do
Click to expand...

Yes - on my website there is a layout for an SSLR with just the relay part. Take a look and see - hopefully that is what you are looking for.
 
#1,284
platon.rado said:
Do you think that NX is better than the Bryston ???
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That's what I wrote, yes. As I said, it is a personal opinion

It's not because its got the Bryston logo and the fact that it is a commercial product that it can just be better. Listen to a well build NX and tell me about it afterwards, it will be interesting to know your opinion about it.

Do
 
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#1,286
I was aware of the gain grade matching for Q6,7,12,13,, But overlooked this, when I ordered🙁

I have installed, KSC3503(D) and KSA1381(E)

Looking back in the thread, I see others had a hard time finding matched gain grades for these parts..
I checked Mouser and Digikey, with no luck..

Any suggestions?

Thanks!
 
#1,287
Joel Wesseling said:
I was aware of the gain grade matching for Q6,7,12,13,, But overlooked this, when I ordered🙁

I have installed, KSC3503(D) and KSA1381(E)

Looking back in the thread, I see others had a hard time finding matched gain grades for these parts..
I checked Mouser and Digikey, with no luck..

Any suggestions?

Thanks!
Click to expand...

There is a thread by joshvi in the swap meet forum. He sells genuine pairs of those for a good price. I have bought several and have been very happy.
 
#1,292
Hi Bonsai,

I have few question, technical nature 🙂. I am interested in some things, if you can explain.

Input diamond stage is biased cca 1mA but TIS is biased 28mA. If hfe of TIS devices is 100x, then 0.28mA is needed for base of TIS. Is it OK? Is it to much current taken from input diamond stage? And drivers, 2sa1381/2sc3503, in datasheet SOA for them on 50V at 25°c is 20mA max, but here drivers and TIS go higher than SOA, 30mA? Why?

Thanks.
 
#1,293
jorgovanko said:
................... And drivers, 2sa1381/2sc3503, in datasheet SOA for them on 50V at 25°c is 20mA max, but here drivers and TIS go higher than SOA, 30mA? Why?..............
Click to expand...
You are mis-reading the datasheet.

Look again, there are two plots for DC SOA.
Tc=25°C and Ta=25°C

Ta=25°C is for the device without a heatsink where the Tc becomes so high that the temperature derated power has become 1.2W
When a heastink is fitted and the Tc is held @ 25°C the temperature de-rated factor remains at 1 and the maximum power is 7W.
Both these values are shown in the plot below SOA
"Collector Dissipation,Pc - W vs Ta"
Both these values are also stated in the first table on page1, Absolute maximum Ratings at Ta=25°C

When you hold Tc@25°C and apply the SOA values from the plot you hit the max P @ 70Vce. All Vce below that are limited to the 100mA DC rating.

That 100mApk @ 50Vce also confirms that this is not a Driver device.
Drivers for Power Amplifier require at least 500mApk and preferably around 1500mApk for a 100W amplifier.

100mA devices can be good for pre-driver duty and/or VAS duty.
 
#1,295
A few questions have come up. I have been travelling on business hence the delay

1. AndrewT is right about the SOA derating. Thanks for answering that.
2. I agree that the drivers in the nx-Amp are a bit light. I have built 3 of these Amps (excluding protos) and had no problems. Nevertheless the peak current can be above the rating. I will add a note on the alternatives proposed - I think these are the same ones I refered to in the write up but that needs to be clarified
3. Platon, you can use the PSMN4R4-80PS as long as your total supply rail is less than 80 Volts.
 
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