SX-Amp and NX-Amp

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#2,082
carbondated,

Have you downloaded the latest sx-Amplifier doc from the website (V2.10)?

There is no BC847 in the sx-Amp.

The BC547C devices may be difficult to get because a lot of semi vendors are moving away from TO-92 devices to SMD (SOT23 for example). In the first post some alternative types are listed that you can use.

C1 and C2 are 1206 devices - one filters the offset adjustment - that's the one near the 15 ohm resistor - and the other decouples the bias controller around Q3. These are very easy to solder - use a pair of fine tipped tweezers and a fine tipped soldering iron.
 
#2,088
Therer are none 847 in that amp 🙂 Its probably a typo.
The BOM says Q3= bc847 but the schematic says Q3=bc547... The schematic is correct.
You can use bc550 instead of bc547
and bc560 instead of bc557

The 550/560 are lower noise versions of the other.
Best of luck building that great amp.
 
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#2,090
I agree that having the two amps together is confusing, but to be honest I did not expect the interest in them to be that high. Its too late to separate them out now or to start new threads - it will just create more confusion.

I'll update the sx-Amp BOM - thanks for catching that - appreciate it.
 
#2,092
Bonsai said:
I agree that having the two amps together is confusing, but to be honest I did not expect the interest in them to be that high. Its too late to separate them out now or to start new threads - it will just create more confusion.

I'll update the sx-Amp BOM - thanks for catching that - appreciate it.
Click to expand...

Then the only solution is to specify the type of amplifier from any post them here🙂
 
#2,093
I encourage builders to download the relevant articles for the amps - my errors obviously don't help, but I believe most of them are cleared up now. That's the reference that should be used.

I think about 100+ of each amp have been build so far (V1 and V2).

Make sure BTW you always get V2 boards!
 
#2,095
My nx it works great from the first time and it sounds much better than my old amp. I have used transistors KSA992, KSC1845, KSA1142Y, KSC2682Y, TTA004B, TTC004B, NJW1308G and NJW3281G. I had to use heat shrink tubing and silicone paste for KSA992 and KSC1845. I also managed to buy the body of the old Sony looks good and I am very happy, I like vintage. Now I needs to do preamp and fit it to the body. I want to make a simple version of The Ovation preamp but I do not see diagram 0dB Buffer in doc.
 

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#2,097
tjbox said:
My nx it works great from the first time and it sounds much better than my old amp. I have used transistors KSA992, KSC1845, KSA1142Y, KSC2682Y, TTA004B, TTC004B, NJW1308G and NJW3281G. I had to use heat shrink tubing and silicone paste for KSA992 and KSC1845. I also managed to buy the body of the old Sony looks good and I am very happy, I like vintage. Now I needs to do preamp and fit it to the body. I want to make a simple version of The Ovation preamp but I do not see diagram 0dB Buffer in doc.
Click to expand...

Very nice! Glad you like the sound!

🙂
 
#2,098
Progress report on the SX build,
Jims boards, parts from Mouser/CPC/Farnell/RS Components and Joshvi. Aliexpress case.

I now have the SX working.. I tested the amps on heatsinks yesterday and wired it all into the open case today as a lash up. I have been listening for a few hours and it is very good. Everything worked straight away and it was a doddle to set up the 1.4A and zero. The offset pot on one is close to the end of its travel so I will investigate this but there is no need to modify much as when warmed up the offset is about 3mV. The offset drift when warming up is only a few mV. Even with this quick connecting up there is no noise or hum, in fact I couldn’t tell they were connected to the speakers!

There is plenty of volume and the clarity and speed are excellent, the bass is very articulate and accurate. A most impressive little amplifier, and a lovely project to build.

Thank you Bonsai it does exactly what you said on the tin.

I used BC550c/560c and matched them carefully, and thanks to Joshvi for the driver pairs.
here is a picture of what I am listening to now.

I bought two PS boards from Jims and for the transformers I stole the old transformers out of the JLHs so I have a dual mono set up. They turned out to be 180VA each. Question; would it be preferable to get a single large transformer of say 400VA or more with twin secondaries to feed each side or stick with the two as they are?


Thanks again Bonsai a smashing amp and thanks to the other contributors for their tips.
YdIvr7V.jpg
 
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