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Old 7th May 2012, 07:03 AM   #511
sonnya is offline sonnya  Denmark
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actually, for example the bc860, bc856, mmbt5401 shares the same pinout. So i do not think it is a problem
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Old 7th May 2012, 09:06 AM   #512
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Started to build the first version of the TSSA (the schematic in post #1).

I got an -2.5V on the output without any load. I was to tired to troubleshoot so Im going to finish it tonight. Has anyone done schematic #1 successfully? This thread is to long to follow... =)

Nice work guys


The amp:
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Old 7th May 2012, 09:41 AM   #513
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Hi McDaisy

Look to post #19, #20 Sonnya's work.

Also Gerhard did it.

Two trimmers serves to set the bias (output drain current) and output offset to zero. Sch is so simple that by rotating trimmers you should get linear readout change of these two values accordingly.
-2,5 V at the output simply means the offset is not finnaly set. Probably trimmer value should be changed if you reach the end position before zero output.
TSSA is a nice amp case of practicing electronics and gaining new experiences.

Regards, Andrej
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Old 7th May 2012, 09:45 AM   #514
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Quote:
Originally Posted by Jay View Post
Have you tried various transistor for the input stage? How do you choose your transistor? I found that in TSSA this transistor matters a lot. Usually I still can use my standard 2N5401 for prototyping but here it is not possible at all. Yes, low noise transistors work better but I was surprised that the difference is so big. Attached is a simulated comparison between BC557C/547C and 2N5401/5551. Actually the 2N5401 doesn't work at all even with 0.1V input while BC557 can give THD of 0.002% at 60W output
This is probably only the case in simulation or did you practically tested that 2N5401/5551 are not suitable.

Otherwise BC550/560 are very good for audio, best performance, low noise, at 1-10 mA bias (collector current).
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Old 7th May 2012, 10:16 AM   #515
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Lazy Cat View Post
This is probably only the case in simulation or did you practically tested that 2N5401/5551 are not suitable.

Otherwise BC550/560 are very good for audio, best performance, low noise, at 1-10 mA bias (collector current).
Only simulation (the fft is fine but distortion is not: it is not sinewave at the output). But with such a simulation result of course I don't want to use 2N5401.

I used BC550/560 actually. Even BC550 is not as good as BC557 (almost tho) in simulation. My original concern was: if transistor change can change the simulated result significantly, then it will be difficult to control the real result without real measurement and tweaking. No wonder someone got -2.5V at the output

Quote:
Originally Posted by Lazy Cat View Post
TSSA is a nice amp case of practicing electronics and gaining new experiences.
Actually after giving up the 3-stage SSA, my intention with 2-stage SSA (or TSSA) was to learn and understand the circuit before working with 4-stage ones. But it seems 2-stage has some benefits, especially it can be used for high power version.

Anyhow, I don't understand the added complexity by the new current source etc. I saw only little improvement on simulation. I'm interested to build the sizklai ouput version but with IRF610/9610 . Any circuit that sound good, yet? Otherwise I will just wait
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Old 7th May 2012, 10:38 AM   #516
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Quote:
Originally Posted by Lazy Cat View Post
Hi McDaisy

Look to post #19, #20 Sonnya's work.

Also Gerhard did it.

Two trimmers serves to set the bias (output drain current) and output offset to zero. Sch is so simple that by rotating trimmers you should get linear readout change of these two values accordingly.
-2,5 V at the output simply means the offset is not finnaly set. Probably trimmer value should be changed if you reach the end position before zero output.
TSSA is a nice amp case of practicing electronics and gaining new experiences.

Regards, Andrej

Hi Lazy Cat!

Thanks for the quick reply... Ill check it out tonight. But I still think something is wrong. Its because Im using smps and it got hot really really quick so I disconnected it until I find the fault...

If this amp sound good Im going to build one with smps and double amps in each channel to make it balanced
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Old 7th May 2012, 10:38 AM   #517
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Quote:
Originally Posted by Jay View Post
My original concern was: if transistor change can change the simulated result significantly, then it will be difficult to control the real result without real measurement and tweaking. No wonder someone got -2.5V at the output
Not related to BCs but rather to N-P ch Vgs threshold difference.

Quote:
Originally Posted by Jay View Post
Any circuit that sound good, yet? Otherwise I will just wait
It depends on stage's complexity-optimization level and DIY-er skils. Try TSSA Basic from post #1 and be surprised. All more complex versions discussed, like TSSA Basic 1.5, should perform much better.
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Old 7th May 2012, 10:44 AM   #518
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Quote:
Originally Posted by McDaisy View Post
Hi Lazy Cat!

Thanks for the quick reply... Ill check it out tonight. But I still think something is wrong. Its because Im using smps and it got hot really really quick so I disconnected it until I find the fault...

If this amp sound good Im going to build one with smps and double amps in each channel to make it balanced
Gerhard explained it in post:

Quote:
Originally Posted by Joachim Gerhard View Post
I build the super simple version of post one. It worked right away. I made some additions and changes. I run it on plus-minus 35V with 500 Ohm resistors instead of trimmers. I runs quite hot that way but i can stilll toutch the cooling profile so it must be around 55 Celsius.
I added a low pass filter at 3MHz -3dB. This amp is very fast and with the filter the square wave is clean. I have cap multipliers in the PSU. That way the amp is dead quiet on my 95dB sensitive speakers.
The sound is a bit lighter then with my power buffer ( see MPP ). By adjusting the gain in the preamp and using a warmer sounding cable i got it going. I have to listen more but the amp is very transparent.
... and continued in following posts.
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Old 7th May 2012, 11:05 AM   #519
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Originally Posted by Lazy Cat View Post
Gerhard explained it in post:



... and continued in following posts.

Thanks! Good reading. Ill come back with my result

As Gerard, Im doing this for studiyng purpose...
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Old 7th May 2012, 01:54 PM   #520
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Lazy Cat View Post
Try TSSA Basic from post #1 and be surprised.
How much WATT can you get at THD of no more than 0.1% with the vanilla circuit, and with the V1.5?

Last edited by Jay; 7th May 2012 at 02:13 PM.
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