KSC2690A and KSA1220A

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In the original thread question, distortion of the 2690 vs the 3503 was called into question.

What I am showing is the datasheet curve of gain vs Ic for the 2690A on the left and my measurement of a 3503E on the right. The measured 3503E curve has some noise. The base current is uA and the cables and fixture are unshielded and unguarded. This measurement deserves shielding and guarding.

If you bias the 2690A at 30mA and Ic swings 60mA p-p, the gain of the 2690A will change by 50% (or possibly more, LOG curve difficult to read) p-p while the 3503E biased at 10mA and swinging 20mA p-p will experience a gain change of 4% p-p. If the 3503E current swings 10 mA p-p, the gain change is less than 1%.

If the 2690A is biased at 30 mA and only swings 10mA p-p, then possibly the linearity is very good. I would want to see the curve plotted with better resolution. 90% of the datasheet curve is useless white space.

It will depend on how much p-p current you want to get out of the 2690A as to whether it is more linear than the 3503.

This is just my musing of a linearity comparison of the two parts.

In a practical EF3, the VAS current, and the pre- driver current vary only a relatively small amount compared to the standing current and the overall current gain is probably about 10 000, So I think the issue is something else.

I will try s few other models and report back.
 
I need to spend time understanding how the models work, but I did find for you to try out. I am so juvenile I have to look at Bob's book in order to figure out how to attach the symbol to the model.
*********************************************************************
* (C) Copyright TOSHIBA CORPORATION 2016
* Date :05/08/2016
* File Name :TTC004B.lib
* Part Number :TTC004B
* Parameter Ver. :Ver.1
* Simulator :pSpice
* Model Call Name :TTC004B
* TNOM :25 degree
* Pin Assign :1=Collector 2=Base 3=Emitter
*********************************************************************
.SUBCKT TTC004B 1 2 3
Q1 1 2 3 3 TTC004B_BJT
.MODEL TTC004B_BJT NPN(
+ LEVEL = 1
+ TNOM = 25
+ IS = 1.374e-013
+ BF = 137.2
+ NF = 1
+ VAF = 11.95
+ IKF = 0.5057
+ ISE = 8.098e-013
+ NE = 1.8
+ BR = 35.11
+ NR = 1
+ VAR = 1000
+ IKR = 10
+ ISC = 1.916e-011
+ NC = 1.5
+ NK = 0.55
+ RE = 0.115
+ RB = 0.885
+ RC = 0.0709
+ CJE = 5.78E-011
+ VJE = 0.75
+ MJE = 0.33
+ CJC = 2.89E-011
+ VJC = 0.75
+ MJC = 0.33
+ FC = 0.5
+ TF = 1.545E-009
+ XTF = 1
+ VTF = 1
+ ITF = 1
+ PTF = 0
+ TR = 0
+ EG = 1.11
+ XTB = 1.4
+ XTI = 6.467)
.ENDS

*********************************************************************
* (C) Copyright TOSHIBA CORPORATION 2016
* Date :21/08/2016
* File Name :TTA004B.lib
* Part Number :TTA004B
* Parameter Ver. :Ver.2
* Simulator :pSpice
* Model Call Name :TTA004B
* TNOM :25 degree
* Pin Assign :1=Collector 2=Base 3=Emitter
*********************************************************************
.SUBCKT TTA004B 1 2 3
Q1 1 2 3 3 TTA004B_BJT
.MODEL TTA004B_BJT PNP(
+ LEVEL = 1
+ TNOM = 25
+ IS = 7.5e-014
+ BF = 190
+ IKF = 0.47
+ ISE = 5e-011
+ NE = 2.4
+ NK = 0.63
+ XTB = 1
+ XTI = 2
+ TRC1 = 0.003
+ NF = 1
+ VAF = 6.8
+ VAR = 50
+ BR = 6
+ IKR = 5
+ ISC = 1.0e-21
+ NR = 1.015
+ NC = 1
+ RB = 4
+ RC = 0.125
+ RE = 0.05
+ CJC = 4.09E-011
+ MJC = 0.33
+ VJC = 0.75
+ CJE = 1e-11
+ MJE = 0.33
+ VJE = 0.75
+ EG = 1.11
+ TR = 1E-009
+ TF = 1.59E-009)
.ENDS
 
Last edited:
+- 70 V rails...
So, probably not for indoors? Or, what room is this for?
That sort affects transistor availaibity.
So, not for house?
Need application specs lashed down tighter.
I'd like 4 times tighter on application spec, because that will make finding the transistors easier.
The do-all are in short supply.
 
Last edited:
Sorry, I was concentrating on less words and wiped out the meaning in the process.

Had meant to say that with targeted sizes, you could use the smd parts for the home size or the high-current parts for the nightclub size, and perhaps avoid to126 availability problems entirely.

One measure is convenient: if the room size is half, then it needs half the power voltage at the amplifier. They could use different size transistors.
 
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The SOT223 are very easy to use and to heatsink. I actually prefer them over TO126. I am pretty good at placing SMD 0805 and larger and SOT23 but not as neat as Syn08 who’ solder jobs on SMD look as good as a machine job.

You need a fine tipped soldering iron and a few pairs of tweezers.

:)
 
With smt, it really comes down to practice. I can not see myself using sot-223 as to-126 replacements, you need copper area to cool a sot-223, so the pcb area needed for a HS can be wasted, so the apparent gain with sot-223 is erased with copper area for cooling, its all about trade offs.
I do not see any sot-223 parts with the same specs as a 2sc3503/a1381.
 
www.hifisonix.com
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Here’s how you do it
 

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www.hifisonix.com
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If you cascode the VAS you can get around the Cob problem by using a small signal transistor for the bottom half of the cascode

Bob Cordell covered this IIRC somewhere - so the loss of these very high performance, high voltage transistors will have to be addressed through new circuit techniques most likely.
 
I worked on a old Yamaha P-2200 power amp recently, they used a cascode VAS, even back then.
If you look at what Toshiba makes in TH these days, it isn't very much, but there must be a big enough market for them to continue making the TTA/TTC004B parts available. We shall see the fallout of Fairchild parts with On taking over. So far it is not as bad as I thought it might be, thinking it would be the same as when they took over the Sanyo semi ops.
 
If you cascode the VAS you can get around the Cob problem by using a small signal transistor for the bottom half of the cascode

Bob Cordell covered this IIRC somewhere - so the loss of these very high performance, high voltage transistors will have to be addressed through new circuit techniques most likely.


...or stockpile the parts that you like. I bought 500 pcs of 1381E 6 years ago but not as many of the 3503E. Not that I need as many of the 3503E. I can probably match every one of the 3503E with one of the 500 pcs of 1381E parts.

How many amplifiers do you think you may build over the next X years? Which is more annoying, redesigning or stockpiling?
 
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