TSSA - The Simplest Symmetrical Amplifier - Page 48

Joachim Gerhard · 1st May 2012, 10:30 PM

So you will also use SMS BJT´s, i asume BC850, BC860.

sonnya · 1st May 2012, 10:48 PM

I know that. I could easily remove it from the circuit.

And pass all data on to you.

I do not believe it is a good idea to have bias difference in the parts of the circuit taking care of all the work (i.e. feedback) because that we want to set offset and idle current.

I see no point in building it from my point of view, when this part is not present.

As i have made it, it can always been disabled.

Lazy Cat · 1st May 2012, 10:53 PM

Sonnya you've said that you want the input bias to be independant of output bias setting, because using only master bias trimmers for both, would cause different and uncertain sonic signature, without possibility to find a sweet spot for each of them. With introducing Sziklais in TSSA Basic, bias current in input gain transistors is fixed by Vbe/Rbe, in that way we simply avoid the need of separate bias settings (input bias is fixed in this case) and master bias/offset trimers in pos/neg CCS would be just fine.

You also mentioned that maybe, bacause of better sound, Sziklais will be omitted later, and only cascoded input pair would be present. For this situation your separate bias/offset CCS-s would again be needed to enable independant bias setting for both stages.

Hopefully you find my explanation to be satisfactory, regards Andrej

Joachim Gerhard · 1st May 2012, 10:57 PM

Did i say that i want to remove it ? No !
You and me are the only ones that build this animal. I say that this is such a different toplogy that we really have to study this in detail. Even it´s creator may not understand it 100 %. Art comes before science because intuition is faster then understanding. I think that is where LC is really good at.

sonnya · 1st May 2012, 11:01 PM

Ok, then we got this straighten out!

Lazy Cat · 1st May 2012, 11:02 PM

Quote:

Originally Posted by sonnya

First layout - placement

Back side of PCB will be mainly GND plane.

PCB looks great, Sonnya

Dual layer PCB also enables the SMT parts to be mounted in bottom layer below regular parts mounted on top layer. In that case we have possibility to significanly reduce PCB size, traces lenghts, etc.

sonnya · 1st May 2012, 11:03 PM

I will go to bed.

Joachim Gerhard · 1st May 2012, 11:04 PM

Yes, SMD lends to 3D.

sonnya · 1st May 2012, 11:04 PM

I was afraid than any one would make shorts while soldering them.

Joachim Gerhard · 1st May 2012, 11:08 PM

This amp is for the chosen few. No capabilty - No amp
i think that is fair

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1st May 2012, 10:30 PM	#471
Joachim Gerhard diyAudio Member Join Date: Mar 2009	So you will also use SMS BJT´s, i asume BC850, BC860.

1st May 2012, 10:48 PM	#472
sonnya diyAudio Member Join Date: Oct 2001 Location: Denmark	I know that. I could easily remove it from the circuit. And pass all data on to you. I do not believe it is a good idea to have bias difference in the parts of the circuit taking care of all the work (i.e. feedback) because that we want to set offset and idle current. I see no point in building it from my point of view, when this part is not present. As i have made it, it can always been disabled.

1st May 2012, 10:53 PM	#473
Lazy Cat diyAudio Member Join Date: Sep 2007	Sonnya you've said that you want the input bias to be independant of output bias setting, because using only master bias trimmers for both, would cause different and uncertain sonic signature, without possibility to find a sweet spot for each of them. With introducing Sziklais in TSSA Basic, bias current in input gain transistors is fixed by Vbe/Rbe, in that way we simply avoid the need of separate bias settings (input bias is fixed in this case) and master bias/offset trimers in pos/neg CCS would be just fine. You also mentioned that maybe, bacause of better sound, Sziklais will be omitted later, and only cascoded input pair would be present. For this situation your separate bias/offset CCS-s would again be needed to enable independant bias setting for both stages. Hopefully you find my explanation to be satisfactory, regards Andrej

1st May 2012, 10:57 PM	#474
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Did i say that i want to remove it ? No ! You and me are the only ones that build this animal. I say that this is such a different toplogy that we really have to study this in detail. Even it´s creator may not understand it 100 %. Art comes before science because intuition is faster then understanding. I think that is where LC is really good at.

1st May 2012, 11:01 PM	#475
sonnya diyAudio Member Join Date: Oct 2001 Location: Denmark	Ok, then we got this straighten out!

1st May 2012, 11:04 PM	#478
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Yes, SMD lends to 3D.

1st May 2012, 11:04 PM	#479
sonnya diyAudio Member Join Date: Oct 2001 Location: Denmark	I was afraid than any one would make shorts while soldering them.

1st May 2012, 11:08 PM	#480
Joachim Gerhard diyAudio Member Join Date: Mar 2009	This amp is for the chosen few. No capabilty - No amp i think that is fair