# Matched transistors in Dynahi



## randytsuch

I have almost finished building my dynahi boards, having bought the parts a little while ago, and I see this thread
http://www5.head-fi.org/forums/showthread.php?t=92876

 There are some posts talking about matching/screening transistors.

 Since I did not know about this, I did not do it. But, I want this to be a really good dynahi, so I am wondering how big a deal is it. 

 I don't think I could remove the dual transistors without damaging them, and this point, and I have installed all the transistors that are not mounted to the heatsink.

 I am thinking about just finishing what I have, and maybe in 6 months or so (when I save up some more money), build up another set of boards with matched transistors, and drop them in and try them.

 Any advice would be appreciated.

 Randy


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## amb

You can go ahead and power-up without matching the transistors. Just don't connect your precious headphones until you validate that the DC offset at the output is low enough (less than 10mV would be good). If the transistors are not matched closely enough, the DC servo will fail to correct the offset. In that case, you will need to do some surgery.

 Another point about well matched transistors is that the amp would be most linear (least distortion) even before overall negative feedback loop is applied. This is considered a good thing.


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## chillysalsa

As per amb's suggestion, matching the JFETs can be done using the schematic in the link you mentioned:





 Then,
  Quote:


 For the BJTs, you want to find the best match of the DC current gain (hfe) as well as the Vbe voltage drop, both while the transistor is operating near the intended collector current. 
 

So, how would one go about this? I luckily have a DMM that has PNP/NPN sockets, and a hFE setting, but haven't looked into how to test it yet, but I'm sure the meter can do it. How would one set up a test circuit to test this "at the intended collector current"? 

 To measure Vbe, would this test circuit be useful?




 If so, what values of V1, R1, and R2 would be optimal test values for the dynahi design?


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## amb

Quote:


 To measure Vbe, would this test circuit be useful? 
 

Close, but not quite right because your circuit won't provide forward bias for the transistor. Rather than drawing another diagram, I refer you to this article (courtesy of Elliot Sound Products):

http://sound.westhost.com/project31.htm

 Look in figure 1, which is the most basic hfe tester for an NPN transistor. For PNP, reverse the polarity of the power and the meter. You can use a pot for Rb. When you adjust Rb, the collector current will vary. The hfe is the ratio of the collector current divided by the base current. The meter shown in the diagram will display the collector current, and you can compute the base current by measuring the voltage drop across Rb and use Ohm's Law: current = voltage / resistance. To measure the resistance of Rb you will need to disconnect the power. Also, make sure you start off with Rb turned to maximum resistance and work from there, so that you don't fry the transistor (and the ammeter). If you use 9V DC power, a 1M ohm pot for Rb will probably be a good value to test with.

 As for the designed currents flowing through the various stages of the Dynahi amp, these are my calculations: The input differential stage CCS BJTs (2SA1145/2SC2705) should flow about 2mA. The cascode BJTs (2SC3381/2SC1349) should flow 1mA each. The VAS stage (2SA1145/2SC2705) should flow about 15mA each, and the output stage power BJTs (2SC3421/2SA1358) should flow about 85mA each.

 Note that a small 9V battery isn't going to supply 85mA very well, so a bench power supply would be appropriate for testing those transistors.

 Given this, you can adjust Rb in the Hfe test circuit until you achieve the desired collector current, then do your measurements. You can also measure the Vbe at this time.

 The output transistors should be mounted on a heatsink for hfe measurements at 85mA. Since BJTs have positive temperature coefficient, they're going to warm up under test, and the warmer it gets, the hfe will go up, possibly leading to thermal runaway.

 You could, of course, build the full-boat tester as described in the above web link and enjoy the convenience of switchable ranges and other niceties. Pay special attention to the WARNING paragraph, as it applies to the basic tester as well as the fancy one. If used improperly you could fry the transistor under test.


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## chillysalsa

Well thank you very much!!!

 So basically, using a pot for Rb, turn going from the highest resistance till you read the meter in this figure indicating the value that you quoted for each respective transistor:






 Once that value is set, record the voltage across the Base and Emitter pins to get Vbe. 

 Then calculate as
 hFE = (mA METER) / (Irb)
 where Irb = VRb / Rb while Rb is measured with the power off. 

 With PNP devices measured using the same diagram but with the Emitter and Collector reversed. 

 Is that right?


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## rsaavedra

Could you guys post the range of variation you are getting on the values measured from your pre-matched set of transistors, and then from your matched sets?


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## chillysalsa

Which 2SA1145/2SC2705 are connected to the input differential stage? Is that the set in pairs, or the single ones connected to A/B on the schemeatic?


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## amb

Quote:


  Originally Posted by *chillysalsa* 
_So basically, using a pot for Rb, turn going from the highest resistance till you read the meter in this figure indicating the value that you quoted for each respective transistor.

 Once that value is set, record the voltage across the Base and Emitter pins to get Vbe.

 Then calculate as
 hFE = (mA METER) / (Irb)
 where Irb = VRb / Rb while Rb is measured with the power off_

 

Yup.

  Quote:


 With PNP devices measured using the same diagram but with the Emitter and Collector reversed.
 Is that right? 
 

No, just reverse the power supply polarity and the polarity of the meters.

  Quote:


 Which 2SA1145/2SC2705 are connected to the input differential stage? Is that the set in pairs, or the single ones connected to A/B on the schemeatic? 
 

The single ones, biased by the LEDs. They act as constant current sources for the JFET input differential pairs.

 [edit]
 Oh by the way, as PRR pointed out on headwize, NPN devices are typically going to have 40mV less Vbe than their PNP counterparts. So you won't get perfect Vbe matches. But that's ok, it's much more important to get the hfe matched as closely as possible.


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## randytsuch

Thanks for all the help guys.
 I will sit down, and figure out how I am going to test the transistors now. Since I have not installed the output transistors yet, I can at least test those.
 Will share my results after I get them.

 Randy


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## chillysalsa

I was just about to test them this afternoon, but I wanted to double check the pin-out configurations on all the devices before I put them in the test circuit.

 Unfortunately, the datasheet I looked up from B&D are in Japanese! 

 Anyone know the Collector, Base, and Emitter pin sequences off-hand? Or else I will have to cross-reference the schematic and the board traces for a couple hours to check...


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## dgardner

2sa1145

2sa1349

2sa1358

2sc2705

2sc3381

2sa3421

2sj109

2sk389

 See also:
Gilmore amplifier datasheets page


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## chillysalsa

I must say, HAPPY HAPPY

 JOY JOY






 I finally have a plan of action and everything I need. It looks like all the trans' are the standard pin layouts for their packages. I've been sidetracked today by some other chores, I should have measurements of components for 4 boards by next week maybe...


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## chillysalsa

Ok.. I've just had time to check my J-FET devices for Idss, the results are:

 2SJ109: Part, side 1 (mA), side 2, (using a 9V battery):
 #1 - 8.3, 8.6
 #2 - 10.0, 10.0
 #3 - 10.1, 10.2
 #4 - 10.0, 10.5

 2SK389:
 #1 - 6.9, 7.1
 #2 - 7.4, 7.7
 #3 - 7.9, 7.9
 #4 - 8.9, 9.0

 Hmm... it's difficult to closely match the 2SK's to the 2SJ's... if I make the best matches as above, (1-1, 2-2, etc.) should it be alright?


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## amb

chillysalsa,
 Yeah, it's not surprising that the N-channel devices don't match the P-channels all that well. But that's alright, because each JFET is being "regulated" down to passing only 1mA in the circuit by the BJT CCS. So you should pick the JFETs that have the best match between the two devices within the package, and use the best match you could find for the two CCS BJTs.


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## chillysalsa

Ok.. so I think it's safe to just stick with the JFETs I havce then, and be more discerning with the 2SA1145/2SC2705 matches.

 I've also measured the 2SC3421s, my hFE values were:
 142.2
 157.0
 160.2
 161.3
 161.3
 161.5
 161.6
 167.2
 167.4
 167.5
 167.6
 167.8
 168.2
 169.2
 170.4
 174.5
 177.5


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## amb

Cool, chillysalsa. Now you should measure the 2SA1358s and see if they fall within the same range, and pick the best matches you could. The datasheet of the 2SA1358 says that the hfe range @ 100mA collector current is between 80-160 for the "O" devices, and 120-240 for the "Y" devices. It would appear that you have the "Y" devices, and your measured values do fall between those extremes. Did you test with a collector current of around 85mA?


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## chillysalsa

Yes, I was measuring them at 85mA. And it looks like they are labelled Y on the package for both parts.

 For 2SA1358 I got:

 hFE
 188.1
 192.0
 192.2
 196.1
 200.2
 203.4
 204.5
 204.5
 205.1
 205.2
 205.7
 209.5
 211.3
 213.4
 213.6
 219.0
 244.5

 Pretty far off... but within spec. I guess I will just make the closest matches, lowest 4 with lowest 4, etc. 

 I was going to measure the 705's at 2mA, but my 16V supply and 500K pot don't let it go below 4.5mA for the collector current. Will pick up a 1M pot tomorrow and try to make the low current measurement so I get those in the CCS circuit matched very closely at 2mA.


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## amb

Quote:


  Originally Posted by *chillysalsa* 
_I was going to measure the 705's at 2mA, but my 16V supply and 500K pot don't let it go below 4.5mA for the collector current. Will pick up a 1M pot tomorrow and try to make the low current measurement so I get those in the CCS circuit matched very closely at 2mA._

 

You can also insert another resistor in series with the pot to get into the range that you'd like to measure. Maybe a 470K ohm will do the trick.


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## chillysalsa

Yea, don't have any values above 100K right now. I think I'll just get a couple resistors, it's a lot cheaper than a pot I may never use!


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## chillysalsa

@ 2 mA:

 2SA1145:
 hFE
 127.2
 157.8
 158.2
 160.0
 160.8
 161.0
 169.6
 170.6
 172.0
 191.3
 192.6
 193.1
 760.2

 matching to 2SC2705:
 163.7
 170.9
 177.0
 180.3
 189.3
 193.0

 Ok, at least two pairs there that would be spot-on.

 Same parts @ 15mA:
 2SA1145
 78.5
 80.9
 82.5
 85.7
 86.0
 88.0
 90.6
 70.0
 121.0
 164.6
 581.7
 615600.0
 hmm... a few seem out to lunch here...

 matching to 2SC2705:
 95.0
 94.0
 91.5
 97.8
 95.6
 86.8

 Pretty much within spec. I'll figure out which go best together later. And yes, I had the same # of 705's, but a brain fart caused me to reverse the polarity, and then I shorted a couple by accident so they fried. Oh well, at least these are the cheap ones!


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## Pars

amb (or anyone?)

 Per your suggestions regarding measuring hFE on the BJTs (and this refers to the 2SA1015s and 2SC1815s on a dynalo), I constructed a circuit similar to what was posted. Since I did not have any suitable pots (nor did ratshack), I decided to use a fixed resistor of 220K, giving an Ic value of 10-11mA on the PNPs (2SA1015). Since I know the resistance up front from measuring it, and powering it with 9V from a bench supply, I can more or less assume that when testing in one batch (i.e., one sitting without powering the supply down) that the base current (Ib) will be constant. I will still measure Vb and compute the base current each time unless I see that Vb is holding steady (it seems to be). I will obviously measure Ic for each device and compute the hFE from the measurements.

 Also, since I had already characterized all of these based on Dr. Gilmore's circuit, and have them marked and separated, I should be able to see what correlation they have to those measurements. I picked around 10 mA because the outputs run at 15mA while the second stage runs at 1-2mA (I think)... seemed like a good compromise.

 This seem rational?

 Chris

 [edit: meant Vrb across Rb, not Vb to ground)


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## amb

Quote:


  Originally Posted by *Pars* 
_This seems rational?_

 

Yeah, it's fine. Certainly better than shooting in the dark and not matching them at all.


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## rsaavedra

Quote:


  Originally Posted by *amb* 
_If the transistors are not matched closely enough, the DC servo will fail to correct the offset. In that case, you will need to do some surgery._

 

So from that I gather, if after the DC-adjustments with the trimpots on my Dynahi boards (non-matched transistors) I get a DC offset at the outputs below 10 mv (btw, Kevin indicated it should be within +/- 1mv in post #259 here), then I can assume they were sufficiently matched, and won't have to worry about doing surgery to replace them with carefully matched transistors?


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## Talonz

Quote:


  Originally Posted by *rsaavedra* 
_So from that I gather, if after the DC-adjustments with the trimpots on my Dynahi boards (non-matched transistors) I get a DC offset at the outputs below 10 mv (btw, Kevin indicated it should be within +/- 1mv in post #259 here), then I can assume they were sufficiently matched, and won't have to worry about doing surgery to replace them with carefully matched transistors?_

 

That's what I'm wondering too. It will be much cheaper then getting another $50 in transistors for matching


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## amb

Quote:


  Originally Posted by *rsaavedra* 
_So from that I gather, if after the DC-adjustments with the trimpots on my Dynahi boards (non-matched transistors) I get a DC offset at the outputs below 10 mv (btw, Kevin indicated it should be within +/- 1mv in post #259 here), then I can assume they were sufficiently matched, and won't have to worry about doing surgery to replace them with carefully matched transistors?_

 

The trimpot is used to force the offset back into submission. If the offset is too high without the servo and trimpots, then some transistors (and perhaps the LEDs) are not well matched. Of course by doing the trimpot thing and then adding the servo will bring the offset back in line (and the amp will work ok), it would be more ideal if the devices were better matched in the first place.


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## rsaavedra

Quote:


  Originally Posted by *amb* 
_The trimpot is used to force the offset back into submission. If the offset is too high without the servo and trimpots, then some transistors (and perhaps the LEDs) are not well matched. Of course by doing the trimpot thing and then adding the servo will bring the offset back in line (and the amp will work ok), it would be more ideal if the devices were better matched in the first place._

 

Thanks Amb. Speaking of which, how do you match LEDs? Since those are just a couple per board, I would just need to desolder and replace one if need be. Well, that is, if I can measure their differences while they are still soldered on the board.

 Btw, last DC offsets I measured from my boards were -14.4 and 35.1 mvolts respectively.


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## amb

Quote:


  Originally Posted by *rsaavedra* 
_Thanks Amb. Speaking of which, how do you match LEDs?_

 

Just measure the voltage drop across the LED and find the closest matches.


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## randytsuch

So I finally got around to measuring my 3421. Built up a little circuit, used a lab supply, 1 megohm multi turn pot, and a connector, which I used for a "socket". Then, I figured out my meter can measure it too, so I did it both ways. On the left, are the numbers from my circuit, where the collector current was between 60 and 70.

 155.613826157
 158.6586826160
 138.4615385141
 154.2446043157
 143.0769231146
 145.3846154147
 154.4297719156
 152.4909747154
 156.7346939163

 One other think, for the circuit measurements, I turned the power on, and measured right away. If I leave on power, the transistor will slowly heat up, and the collector current and hfe slowly rises. I was not sure if I should measure a room temp part, or a part that had heated up in the circuit.

 My 1358 measurements, just from the meter
 177
 194
 160
 173
 189
 179
 182
 128
 171

 As you can see, these vary more. The 128 guy is trash, but even then the range is kind of big. I am not sure if this is OK, or if I should buy some more transistors. The transistors themshelves are pretty cheap, but I would have to pay shipping again.

 Randy


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## amb

Quote:


  Originally Posted by *randytsuch* 
_One other think, for the circuit measurements, I turned the power on, and measured right away. If I leave on power, the transistor will slowly heat up, and the collector current and hfe slowly rises. I was not sure if I should measure a room temp part, or a part that had heated up in the circuit._

 

You will get more repeatable and stable measurements if you let the devices warm up. However, the hfe variation due to temperature change should be fairly constant for any given transistor type. So, as long as you measure them using consistent methods then it should be ok.

  Quote:


 My 1358 measurements, just from the meter
 ...
 As you can see, these vary more. The 128 guy is trash, but even then the range is kind of big. I am not sure if this is OK, or if I should buy some more transistors. The transistors themshelves are pretty cheap, but I would have to pay shipping again. 
 

It depends on how a*al retentive you are with wanting as close a match as possible. 
	

	
	
		
		

		
			





 I say go ahead and build the amp and test it before plunking down $$ for more transistors.


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## randytsuch

Quote:


  Originally Posted by *amb* 
_It depends on how a*al retentive you are with wanting as close a match as possible. 
	

	
	
		
		

		
		
	


	




 I say go ahead and build the amp and test it before plunking down $$ for more transistors._

 

Thanks for the response.
 Think is, I am a*al when it comes to this stuff, and once I finish a project, and it is making music, I tend not to want to touch it. So, I ordered some more transistors, will have them by next week. 
 I figured the output transistors, since they must act in concert with each other, would have a bigger effect if they are not matched, so I would like to match them as close as possible. 
 I bought more than I need, and may sell off the excess in matched sets when I am done.

 Randy


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## amb

Quote:


  Originally Posted by *randytsuch* 
_I figured the output transistors, since they must act in concert with each other, would have a bigger effect if they are not matched, so I would like to match them as close as possible._

 

Actually, the output transistors have the benefit of global negative feedback to compensate for mismatchings. The input differential stages, and their constant current source transistors, on the other hand, are much more sensitive to mismatches because they _are_ the very devices responsible for making global negative feedback work.


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## randytsuch

Quote:


  Originally Posted by *amb* 
_Actually, the output transistors have the benefit of global negative feedback to compensate for mismatchings. The input differential stages, and their constant current source transistors, on the other hand, are much more sensitive to mismatches because they are the very devices responsible for making global negative feedback work._

 

Oh great, now I am going to worry about how well the other transistors match up. 
	

	
	
		
		

		
			





 I was also wondering if I could test these other transistors, which are already installed on the board. If I apply a small positive dc voltage to the input (of course nothing will be connected to the output), and measure the outputs from the front end transistors. Then, I could reverse the input leads to apply a negative input voltage, and measure again.
 Is this reasonable?

 Thanks for any advice,
 Randy


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## amb

Quote:


  Originally Posted by *randytsuch* 
_I was also wondering if I could test these other transistors, which are already installed on the board. If I apply a small positive dc voltage to the input (of course nothing will be connected to the output), and measure the outputs from the front end transistors. Then, I could reverse the input leads to apply a negative input voltage, and measure again.
 Is this reasonable?
 Randy_

 

You might as well just power up the amp when you have everything except the DC servo installed, and measure the DC offset at the output. If it's excessive, then check the voltages at various points of the circuit to see if there is any obvious points of asymmetry. Don't forget to short the input to ground when you do this (if you don't have a volume pot connected). With a pot, set the volume to minimum position.


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## chillysalsa

The last devices didn't match so great, so I am ordering a few more:

 2SC3381BL, hfe @ 1mA
 Left sides:
 310.3
 427.2
 575.6
 corresponding right side:
 291.3
 696.0
 575.6


 2SA1349BL @ 1 mA
 Left sides:
 408.9
 445.2
 581.9
 659.4
 corresponding right side:
 449.8
 543.0
 559.8
 679.5

 I couldn't get some of them down to 1 mA, so some measurements were done at 1.5 - 2.5 mA. Even 2.5M ohms wasn't enough in the Rb value to get the collector current down. I'll just assume matching within the same range is better than no matching at all... it at least let me catch one of the 2SC3381BL that was a dud.


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## amb

Quote:


  Originally Posted by *chillysalsa* 
_I couldn't get some of them down to 1 mA, so some measurements were done at 1.5 - 2.5 mA. Even 2.5M ohms wasn't enough in the Rb value to get the collector current down. I'll just assume matching within the same range is better than no matching at all... it at least let me catch one of the 2SC3381BL that was a dud._

 

Yes, that's true.


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## rsaavedra

Quote:


  Originally Posted by *chillysalsa* 
_hFE = (mA METER) / (Irb)
 where Irb = VRb / Rb while Rb is measured with the power off._

 

 Quote:


  Originally Posted by *Pars* 
_I constructed a circuit similar to what was posted. Since I did not have any suitable pots (nor did ratshack), I decided to use a fixed resistor of 220K, giving an Ic value of 10-11mA on the PNPs (2SA1015). Since I know the resistance up front from measuring it, and powering it with 9V from a bench supply, I can more or less assume that when testing in one batch (i.e., one sitting without powering the supply down) that the base current (Ib) will be constant. I will still measure Vb and compute the base current each time unless I see that Vb is holding steady (it seems to be). I will obviously measure Ic for each device and compute the hFE from the measurements._

 

 Quote:


  Originally Posted by *amb* 
_The input differential stages, and their constant current source transistors, on the other hand, are much more sensitive to mismatches because they are the very devices responsible for making global negative feedback work._

 


 Bear with me please, I'm no electronics sage 
	

	
	
		
		

		
		
	


	




 Putting together those quotes above, I understand the critical matching seems to go for 1145 and 2705 (input differential stages? Or do the 1349 and 3381's also belong there?). So in any case, how about the following ultra-cheapo-simple transistor matching procedure:


 1) Fixed Rb, let's say 220K like Pars did

 2) Supply is just a 9V rectangular little battery

 3) I first measure VRb as follows:





 4) Then I measure mA meter as in the image that has been posted already:





 5) Then I compute that transistor's hFE = (mA Meter) / (VRb / Rb)


 After doing that for a bunch of them, I can pick the 1145's with closest hFE's to the corresponding 2705's. Maybe same for 1349's and 3381's.


 Would that be at least better than no matching, or would that ultra-cheapo-simplistic-naive transistor matching procedure be really useless?


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## Pars

Yeah, I think that's right (I was matching for a dynalo, so without the dynahi schematic in front of me, I am just guessing that the tranny #s you gave are correct).

 Amb's suggestion was to match based upon position in the amp at a representative current (Ic) for that position (amb, correct me if I am wrong). So he advocated a pot so you could dial in the resistance (Rb) to give you te appropriate Ic for that amp stage, and then measure the Vrb and Ic for each, calculating the hFE based on that.

 Since I didn't know the exact Ic for each position in a dynalo, I just used ~10mA as a close enough guess (tho some are at 1mA, some at 15mA) to do my measurements at. One transistor I did play around with resistors to give ~1.6mA and ~10mA. The hFEs calc'd out to 240 and 236, respectively, so they weren't moving around alot for changes in Ic (at least for that one).

 The procedure I used was to let the transistor settle briefly, and using two meters at once, read both Vrb and Ic at approximately the same time. Marked each transistor, recorded the numbers and used a spreadsheet to calc hFE when I was done measuring. As had been noted, as the transistor heats up, it will change, so consistency is probably important as far as when you take the measurement. I guess ideally you might also measure transistor temperature?


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## rsaavedra

I see Pars. Well, I only have one meter, could get another similar one since it was just about $15 if I remember well. However I don't have some generic test bench 9V power supply. That's why I would like to use just a simple 9V DC battery despite the low current. I can certainly attach the transistors to a heatsink, but not sure it will heat up much just with such a battery.

 My logic goes that if two transistors are really well matched, they should measure almost identically even in my simple test, right?. Now the reverse I'm not so sure of, which is what I would like to know. If two transistors measuring almost identically in my simple test might still be really off in higher current and temperature conditions. But if they are off already in this simple test, well then those would be bad to use for sure I guess. 

 So the simple test might provide some degree of satisfactory matching. Wonder if that's the case even if done with just one meter powering on and off between measuring voltage and mA. I think I'll get another meter then.


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## rsaavedra

About the Dynahi schematic:
http://members.cruzio.com/~billsiegmund/D2r3.pdf


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## amb

Quote:


  Originally Posted by *Pars* 
_Since I didn't know the exact Ic for each position in a dynalo, I just used ~10mA as a close enough guess_

 

My calculations of the collector currents of the BJTs in the dynalo are: 2mA each for the CCS transistors, 4.3mA for the VAS stage, and about 18mA for each of the output transistors.


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## Pars

Quote:


  Originally Posted by *amb* 
_My calculations of the collector currents of the BJTs in the dynalo are: 2mA each for the CCS transistors, 4.3mA for the VAS stage, and about 18mA for each of the output transistors._

 

Thanks amb. One of these days (years?) I'm going to remember/relearn everything I haven't used in 20 years so I can figure those out myself


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## randytsuch

So, I have assembled both boards now, and tested them.
 Without the pots or opamps, one has 14 mv of offset 
	

	
	
		
		

		
		
	


	




 , but the other has about 90mv of offset 
	

	
	
		
		

		
		
	


	




 .

 Now, I need to look at the second one, and see what is causing that big offset.

 Randy


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## rsaavedra

Quote:


  Originally Posted by *randytsuch* 
_So, I have assembled both boards now, and tested them.
 Without the pots or opamps, one has 14 mv of offset 
	

	
	
		
		

		
		
	


	




 , but the other has about 90mv of offset 
	

	
	
		
		

		
		
	


	




 .

 Now, I need to look at the second one, and see what is causing that big offset.

 Randy_

 

Without any transistor matching, and also without the pots or opamps, one of my boards had -16mv of offset, the other +34mv.


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## dgardner

Looks like MCM is out of stock on the Toshiba 2SC3425. Does anyone have another distributor to recommend? Been matching and baggin transistors all day. I want some more parts for tighter matches.


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## randytsuch

Quote:


  Originally Posted by *dgardner* 
_Looks like MCM is out of stock on the Toshiba 2SC3425. Does anyone have another distributor to recommend? Been matching and baggin transistors all day. I want some more parts for tighter matches._

 

Did you mean the 2SC3421?
 bdent has them. 

 Randy


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## dgardner

yes, the 2sc3421. Funny they are there now. strange how you have to type in the number right....


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## dgardner

Well, I'm done with all the transistor testing for the single BJTs for Gilmore Dynalo and Dynahi designs. Used two precision ammeters. More work to do on the dual transistors and LEDs.

Hfe measurements, then a bagging and sorting operation

 Pretty good set of matches so far. The output transistors for the dynahi could be better. At a buck a pop, I'm not sure how many it makes sense to buy.


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## amb

Quote:


  Originally Posted by *dgardner* 
_Hfe measurements, then a bagging and sorting operation_

 

Very neat! I am impressed.


----------



## chillysalsa

Very organized! I numbered & tagged all my parts with masking tape and threw them back in larger bags to save time now, and frustrate myself later. 
	

	
	
		
		

		
			





 I am waiting for a mouser order and the building will begin over the holiday season.


----------



## dip16amp

Here are my transistor hFE values measured with a DMM that I'm using in my four channels.

 First channel.
 2SA1349: 406, 406
 2SC3381: 281, 281
 2SA1145: 143, 144, 144
 2SC2705: 133, 133, 133
 2SA1358: 146, 146, 146, 146
 2SC3421: 135, 135, 135, 135
 Initial DC offset without the servo was 18 mV. Had to change two 498 ohm resistors to a 497 ohm and a 500 ohm to get the DC offset to 6 mV.

 Second channel.
 2SA1349: 419, 416
 2SC3381: 300, 301
 2SA1145: 145, 147, 147
 2SC2705: 134, 135, 136
 2SA1358: 141, 142, 143, 143
 2SC3421: 133, 133, 133, 134
 Initial DC offset without the servo was 62 mV. Swapped the K389 around and had 68 mV, so I put it back. Swapped the J109 around and had -49 mV. Replaced the J109 with a different one and had 1 mV DC offset.

 Third channel.
 2SA1349: 364, 368
 2SC3381: 290, 292
 2SA1145: 148, 148, 149
 2SC2705: 141, 142, 143
 2SA1358: 146, 147, 149, 149
 2SC3421: 140, 140, 141, 141
 Initial DC offset without the servo was 56 mV. Swapped LEDs until I got -4 mV.

 Fourth channel.
 2SA1349: 364, 369
 2SC3381: 275, 278
 2SA1145: 141, 141, 142
 2SC2705: 130, 131, 132
 2SA1358: 136, 138, 138, 138
 2SC3421: 131, 131, 132, 132
 Initial DC offset without the servo was -38 mV. Swapped LEDs until I got 6 mV.

 The two unbalanced channels has lots of power like my balanced dynalo.


----------



## skyskraper

how many transistors of each did you guys end up buying?


----------



## dip16amp

Quote:


  Originally Posted by *skyskraper* 
_how many transistors of each did you guys end up buying?_

 

I got 50 percent more and was glad that I did to match them fairly close. Since I am building four channels, I bought enough for six channels. This amp certainly has more bass slam than I can believe.


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## dgardner

I bought 50 of each output transistors and got only 16 great matches.
 Enough for a very, very well match dynamite.

  HTML Code:


```
[left]2SC34212SA1358MATCH 120-129 130-139 140-149147.5 148.8 149.6 150-159150.4 157.0157.9-0.57% 159.9 160-169160.7 162.6 162.8 163.0 163.0 163.8 164.4164.5-0.06% 164.9 165.0 165.8 166.3 167.8 168.5 169.1169.00.06% 169.3 169.6 169.8 170-179170.1 170.3 170.4 170.6 170.7 171.6 171.8 172.0 172.7 173.1 174.1 174.1 174.2174.8-0.34% 179.0176.11.62% 179.6 180-189180.3 181.8181.50.17% 182.1183.0-0.49% 183.0 183.5183.30.11% 183.7 184.4184.00.22% 184.5184.8-0.16% 185.3185.7-0.22% 186.0186.4-0.22% 186.9 187.3187.00.16% 188.7 189.1 189.1 190-199190.0 190.3 190.7 190.8 191.0 191.2 191.6 192.7 193.0 193.5193.30.10% 194.0 194.3 195.8 196.4196.30.05% 196.8 197.0 197.0 197.2 198.0 198.6 198.9 200-209202.3 203.9 204.1 205.3205.9-0.29% 208.7 210-219215.8 219.5 220-229 230-239232.5 232.5 240-249243.7 505016[/left]
```


----------



## chillysalsa

Ok, so if you don't have a huge excess of transistors..... and you are trying to match 2SC3421 to 2SA1358... what is the best strategy, considering all the 2SC3421 are rather low HFE compared to the 2SA1358's. 

 I mean, let's say I have about 8 of each and need to make 4 good pairs, should I just take all the highest HFE of 2SC3421 with the lowest HFE values of 2SA1358? 

 Or should I match them so that the AVERGE HFE of 4 2SC3421 and 4 2SA1358 average out to the same? (ie: some high's and lows of each?)

 And does the actual position of the pairs matter in the circuit board, & each respective pair just need to be matched as close as possible? I get the feeling this is the goal...


----------



## dip16amp

Quote:


  Originally Posted by *chillysalsa* 
_Ok, so if you don't have a huge excess of transistors..... and you are trying to match 2SC3421 to 2SA1358... what is the best strategy, considering all the 2SC3421 are rather low HFE compared to the 2SA1358's. 

 I mean, let's say I have about 8 of each and need to make 4 good pairs, should I just take all the highest HFE of 2SC3421 with the lowest HFE values of 2SA1358? 

 Or should I match them so that the AVERGE HFE of 4 2SC3421 and 4 2SA1358 average out to the same? (ie: some high's and lows of each?)

 And does the actual position of the pairs matter in the circuit board, & each respective pair just need to be matched as close as possible? I get the feeling this is the goal..._

 

I just grouped the transistors that are connected in parallel since they have to work together sharing their load. Then I put the groups of high hFE PNP with groups of high hFE NPN in each channel. This weeded out the real high and low oddball trannies.


----------



## intlplby

oops... i got it... bad fuse in the multimeter


----------



## Woody

Quote:


  Originally Posted by *chillysalsa* 
_.....Or should I match them so that the AVERGE HFE of 4 2SC3421 and 4 2SA1358 average out to the same? (ie: some high's and lows of each?)..._

 

This sounds more logical, I've yet to do the exercise but I would have thought it possible to test/measure the effect of combining the transistors in parallel. Use a test circuit, or a semi populated dynahi PCB and measure the hfe of all 4 NPN in parallel and then all 4 PNP ?

 But then again measuring individually and averaging as you suggest should theoretically give the same result ? Anyone ?


----------



## amb

Quote:


  Originally Posted by *Woody* 
_This sounds more logical, I've yet to do the exercise but I would have thought it possible to test/measure the effect of combining the transistors in parallel. Use a test circuit, or a semi populated dynahi PCB and measure the hfe of all 4 NPN in parallel and then all 4 PNP ?

 But then again measuring individually and averaging as you suggest should theoretically give the same result ? Anyone ?_

 

No, it's better to test transistors individually and try to get the best matches throughout rather than find averages. When you have significant variations in hfe between paralleled devices, the amount of current flowing through each one will not be equal. Even though the emitter resistors serve to "equalize" them, the point of matching transistors is to make them as equal as possible without relying solely on the resistors to compensate.


----------



## Syzygies

Quote:


  Originally Posted by *amb* 
_Note that a small 9V battery isn't going to supply 85mA very well, so a bench power supply would be appropriate for testing those transistors._

 

 Quote:


  Originally Posted by *rsaavedra* 
_However I don't have some generic test bench 9V power supply. That's why I would like to use just a simple 9V DC battery despite the low current._

 

Great thread!

 Use 8 NiMh cells? NiMh AA cells have capacities up to 2500 mAh, making 85 mA a "C/30" discharge rate. They also have low internal resistance compared to alkaline batteries. I've seen 6 _amps_ on my multimeter more than once, always indicating an ill-considered circuit at 3am.


----------



## Ozymand

Since there will be such a large quantity of people testing transistors for the Dynahi, has the idea of trading similarly spec'ed transistors came up? I am asking this since I know I will end up one transistor short of a matched set (irregardless of how many I buy.. damn anal-retentiveness). I also understand that there will be variations in the hFE because of different test equipment, test current ranges, etc... but with enough control in place, I think a fair amount of standardization could be done. Food for thought.


----------



## dgardner

Here is an update to the collection of Dynahi amp and Dynahi PS datasheets.

http://www.djgardner.com/headphone/gilmore/datasheets/


----------



## intlplby

do all the transisters need to be matched or just certain ones?

 when matching transistors is it more important for the transistors in the same position on each channel to be matched closely or for all the transistors of the same part number be closely matched oneach channe\


----------



## chillysalsa

The complementary pairs themselves should be matched for hFE values, as follows:

 Group 1- input differential stage CCS BJTs (2SA1145/2SC2705) should flow about 2mA. 

 Group 2- cascode BJTs (2SC3381/2SC1349) should flow 1mA each. 

 Group 3- VAS stage (2SA1145/2SC2705) should flow about 15mA each

 Group 4- output stage power BJTs (2SC3421/2SA1358) should flow about 85mA each.


----------



## dgardner

Group 1 - These two complimentary transistors need to be gain matched very closely to each other. They create the constant current source for the FET. The two 500 ohm resistors and Red LEDs are also part of this important match. Start with a really good match here and the trim pots might not need to be used.

 Group 2 - There is matching inside the dual transistor packages already, but it doesn't hurt to try to get a complimentary match between the 2sk309 and the 2sj109. They are relatively expensive parts, so you can just use what you get here. Likewise it doesn't hurt, but isn't critical, to get a complimentary gain match between the 2sc3381 and the 2sa1349.

 Group 3 - Two ways to consider matching here; parallel match and complimentary match. Most importantly, the 2sa1145 and the 2sc2705 should have complimentary matches. Try for two matched pairs between the compliments. If one close 2sa1145-2sc2705 pair is different from the other close 2sa1145-2sc2705 pair, you are alright since they are load sharing.

 Group 4 - Find four 2sc3421's that are grouped somewhat closely in gain value to each other. Then find four 2sa1358's that are grouped somewhat closely in gain value to each other. Try to match the average gain of the 2sc3421 group to the average gain of the 2sa1358 group. Slight differences in gain will be reflected in slightly different currents through the 20 ohm resistors. Picking closely matched 20 ohm resistors helps, but 1% is probably close enough.


----------



## Woody

My thanks to Amb and DGardner for their contributions in this thread. I was beginning to lose the plot here. Dip16 seemed to have matched his transistors fairly well yet the servo-less offsets initially seemed pretty big, begging the question was it worth matching the transistors at all ! But hopefully that last post from DGardner will help, I'll post back with my results... eventually !


----------



## dgardner

Is it worth matching? Absolutely yes. Keep in mind that the constant current sources can be adjusted with the pots. My biggest error contributor was the 2sj109 and 2sk389 being a lousy match.

 One tip on the pots: If you use them, start with both. Preset the pot wipers to 10k position and stick them both in, perhaps with sockets. Then apply power with the op27 servo *installed*. Look at the initial offset at the amplifier output on a meter using the lowest voltage scale. Lower *one* of the pots and see if it help gets the offset closer to zero. If it goes the offset goes the wrong way, return the pot to the 10K position and try lowering the other one. Don't let the unit warm all the way up during this process. Turn it off after each pot tweak, let it sit a few moments, then hit the power again. Try to get the unit to startup with 10-15mV or less during the first 10 seconds of operation. Remember, the servo starts to work the second you apply power, but it works slowly.

 Work this cycle until you are under 10mv at the moment the unit is first turned on. You should be able to get the initial startup offset under 10mV this way. The servo will be able to control the offset and get it around 1mV or less as the unit warms completely up. Keep in mind that as the unit warms up, all the thermal variables will be moving around in the circuit: some up, some down. Since the servo moves very slowly, it may take a few minutes to stabilize around 1mV. It may not converge in a perfect ramp down to 1mV.

 If your budget is tight, replace the pot that was *not* adjusted with a fixed 10Kohm resistor (or same as the pot) after the tweaking is complete.


----------



## bg4533

Quote:


  Originally Posted by *Ozymand* 
_Since there will be such a large quantity of people testing transistors for the Dynahi, has the idea of trading similarly spec'ed transistors came up? I am asking this since I know I will end up one transistor short of a matched set (irregardless of how many I buy.. damn anal-retentiveness). I also understand that there will be variations in the hFE because of different test equipment, test current ranges, etc... but with enough control in place, I think a fair amount of standardization could be done. Food for thought._

 

Anyone? 

 I would be willing to pay someone who knows what they are doing and has decent equipment the cost of the transistors plus some extra cash for reasonably well matched transistors. It really wouldn't be all that much extra work for someone who was already testing their own and it would help them get better matches. Any volunteers here?


----------



## intlplby

I guess i am lucky then ... MCM totally screwed up and sent me way too many transistors and charged me too much so i got an RMA and i am gonna test them and keep the ones i want and then send the rest back


----------



## ble0t

Well, I measured the hFE for my output transistors, and I'm somewhat dissapointed I guess...

 For the 2SC3421 I have values:

 144 (x3)
 148
 150
 152
 155 (x2)
 157 (x2)
 158
 159
 160
 161
 162
 168

 For the 2SA1358 I have values:

 135
 140
 171
 173
 180
 181
 184
 186
 193
 195
 196
 198
 199
 200
 208
 210

 I have some decent matching within the actual groups, but pretty much no matching between the groups. From reading the beginning of the thread, the best bet in this case is to take the lowest four and match those with the lowest four from the other, correct?

 EDIT: A friend of mine has a DMM with hFE measurement...I am wondering, would this be an accurate way to measure, or is the correct current required for good measurement? Do the DMMs with this feature just give a 'rough estimate'?


----------



## Woody

Quote:


  Originally Posted by *ble0t* 
_Well, I measured the hFE for my output transistors, and I'm somewhat dissapointed I guess...

 ... a DMM with hFE measurement...I am wondering, would this be an accurate way to measure ....'?_

 

I've been putting off this task because I know my results will be just as dissappointing.

 dgardners post seems to be the most informative regarding what to match and how to overcome the compromises. 

 On the issue of using the hfe function on the DMM. The DMM will not be able to measure the hfe at the real world operating current (See amb's earlier post). The implication seems to be that this is significant.

 I think inevitably I'll end up tweaking the DC offset out using the various methods already described and just accept that the chances of it being low as a result of transistor matching alone is nil.


----------



## Woody

Apart from output dc offset, does the higher average hfe on the PNP out transistors, compared with the NPN, have any other consequences ?

 e.g. What ensures a symetrical output signal ? Is this where matching the Vbe of the output transistors comes in ? Along presumably with matching the 20R emitter resistors ?

 Please excuse my ignorance here 
	

	
	
		
		

		
		
	


	




 I'm sure my old electronics tutors, from many years ago I might add, would cry themselves to sleep if they saw me asking these questions now :embarassed: !


----------



## amb

Quote:


  Originally Posted by *Woody* 
_On the issue of using the hfe function on the DMM. The DMM will not be able to measure the hfe at the real world operating current (See amb's earlier post). The implication seems to be that this is significant._

 

This depends on the specific transistors. Some transistors have a really flat hfe vs. Ic curve, and with these, it becomes less of an issue to measure the hfe at the intended operating current. A look at the transistor's datasheet should provide a good clue, if such a graph is included.

 For the output transistors in a dynahi (or other similar amps), it would be nice to have matching hfes for the NPNs and the PNPs for the lowest distortion prior to applying negative feedback, but the feedback does correct for mismatches. How far you want to go with matching is up to you, but in theory it's good to not rely on feedback to correct for gross mismatches. The most critical transistors for minimum DC offset are the input JFETs, the CCS transistors and the LEDs. Get these to match well and you'll be a long way toward a well-behaved amp.


----------



## dgardner

You should be able to see what base current your DMM uses for Hfe testing. It's usually in the microamp range. This might be quite fine for transistors on the front end of the amp that have single digit milliamp collector current.

  Quote:


  Originally Posted by *amb* 
_This depends on the specific transistors. Some transistors have a really flat hfe vs. Ic curve, and with these, it becomes less of an issue to measure the hfe at the intended operating current. A look at the transistor's datasheet should provide a good clue, if such a graph is included.

 For the output transistors in a dynahi (or other similar amps), it would be nice to have matching hfes for the NPNs and the PNPs for the lowest distortion prior to applying negative feedback, but the feedback does correct for mismatches. How far you want to go with matching is up to you, but in theory it's good to not rely on feedback to correct for gross mismatches. The most critical transistors for minimum DC offset are the input JFETs, the CCS transistors and the LEDs. Get these to match well and you'll be a long way toward a well-behaved amp._


----------



## ble0t

I just went and checked out the datasheet of the 2SA1145 to get an idea (it does include a graph of hFE vs Ic) and it does appear to be quite flat all the way out to approx -30mA. So, in this case, using the DMM for measurement might work out just fine...


----------



## Pars

Just for fun (sick, I know), I built up a test jig and ran some Idss measurements on the additional pairs of 2SJ109/2SK389 FETs that I had and came up with these:
  PHP Code:

 2SK389         5V          10V          15V 
1a)          9.40          9.76          9.95 
1b)          9.23          9.59          9.79 

2a)          6.43          6.74          6.96 
2b)          6.49          6.86          7.05 

2SJ109          5V          10V          15V 
1a)          8.60          8.70          8.77 
1b)          9.24          9.32          9.41 

2a)          6.28          6.39          6.49 
2b)          6.61          6.75          6.81  
 ​


It looks like the #2 FET from each pair will be a pretty good match. The #1s might be acceptable also. I noticed that these FETs are available as singles also (I think it is 2SK074 or something like that) and that they are considerably less expensive than the "matched" pairs. Could it possibly be easier to get good matches by getting a bunch of these rather than using the dual packages? Or do these depend upon the thermal characteristics of being packaged together? I would have hoped that for the price they charge for the duals that matching and deviation would be tighter than what I am seeing, as I can't really afford to be buying alot of these in order to get good matches, but they appear to have a large effect on the final performance of the amp in terms of DC offset.


----------



## amb

Pars, the separate versions are 2SK170 (N-channel) and 2SJ74 (P-channel). Since these are not formed on the same substrate you will see much more variations in Idss between units. To get good matches might require a fairly large number of them and a lot of time to test.


----------



## Pars

Amb,

 Thanks. That is what I figured, although I may grab some anyway and see what they are like.

 On a further note, dip16amp mentioned to me that you can just flip the dual packages around, and sure enough, the pinout is symetrical. I also noticed that convention seems to be as far as PCBs go to put the devices facing each other (P vs N channel), which basically matches the #1 device from one device with the #2 device in the other facing package, and vice versa. It might not be a bad idea for PCB design to put two sets of the 3-hole row (3 hole, 4 hole and 3 hole) on the board to facillitate flipping the package around to get the best match. Sounds plausible at least.

 I know this is analog and you're never going to get perfect matches, but every little bit helps within reason.


----------



## rellik

how long did you guys wait for your readings to stabalize? 

 since the values should change while warming up


----------



## Pars

Quote:


  Originally Posted by *rellik* 
_how long did you guys wait for your readings to stabalize? 

 since the values should change while warming up_

 

I'm not sure that mine ever totally stabilized, but I would estimate that I waited about 30-45 seconds each (might have been longer). After you do a few, you should get a baseline for what the current and voltage (Ic and Vrb, respectively) should range at, so wait until it gets into that range and look for signs of stabilization (readings moving more slowly than initial). I was finding if you wait even further, they would start moving again, and you would need to then wait for them to stabilize. Just try to do each approximately the same timewise.


----------



## rellik

how much does bFE or *[size=small]AC[/size]* current gain matter in dynahi transistor matching?

 it would be tricky to do bFE readings, moreso than hFE


----------



## rellik

anyone???

 Edit: the page looped over, my original post is the last on page 4


----------



## amb

rellik, the Hfe matching is important for minimum output DC offset. As for "bfe", it's not even a parameter typically listed on transistor datasheets. I assume you refer to matching the device transconductance curves. While these are desirable to minimize open-loop distortion, in practice it is difficult to do and probably not worth the trouble.


----------



## rellik

ok, thanks

 just trying to see becuase a teacher said if i was matching for bFE was well when i told him i was matching hFE


----------



## steinchen

my favorite national shop carries the trannies for an incredible low price, the most expensive one (2SC3381) for only 1 EUR (~ $1.25) per piece. It is labeled as "SC 3381" and "Japan Transistor". Unfortunately no further information or datasheet linked to the part within the shop.

 Is "SC 3381" the same as "2SC3381" ? If they are the same: are they of lower quality ?


----------



## Woody

I think I'm right in saying that the "2S" is normally left off leaving C3381, but its most likely one and the same.

 One word of caution I ran in to what I believe were fake "TIP" series transistors, a while back. They looked "cheap" externally, no manufacturer marking etc and I was suspicious about the price. Measured hfe was out of spec (Too high) and I cracked the case open to compare die/chip size to a known good original. The die was about 1/3 the size !

 Check here for more info http://sound.westhost.com/counterfeit.htm. 

 I must admit I'm sceptical about the idea of fake transistors, I find it hard to believe that a manufacturing facility that is capable of producing transistors could be bothered to produce fakes, its not exactly a case of a cowboy working from a shed. Maybe a reduced chip/die size is not an indication of a fake, in which case my experience is irrelevant ? 

 I bet I've got you having 2nd thoughts though ? 
	

	
	
		
		

		
			









  Quote:


  Originally Posted by *steinchen* 
_my favorite national shop carries the trannies for an incredible low price, the most expensive one (2SC3381) for only 1 EUR (~ $1.25) per piece. It is labeled as "SC 3381" and "Japan Transistor". Unfortunately no further information or datasheet linked to the part within the shop.

 Is "SC 3381" the same as "2SC3381" ? If they are the same: are they of lower quality ?_


----------



## BrokenEnglish

Quote:


  Originally Posted by *steinchen* 
_Is "SC 3381" the same as "2SC3381" ?_

 

i guess, you're speaking of reichelt.de, steinchen. you may not noticed it, but actually they list the sc3381 under the category "2SC-Transistoren". so these ones indeed should be 2sc3381.


----------



## amb

Answering DigiPete's post from the dynahi PSU thread, which is more appropriate here:

  Quote:


  Originally Posted by *DigiPete* 
_After re-reading that post, matching at the expected Ic seems to be the way to go, though it seems the hfe didn't change too much as a function of Ic._

 

Yes, it's one of the nice things about these particular transistors. Not all transistors are so well behaved, though.

  Quote:


 Would using the amp itself as the test rig for fine tuning work (measure the Ic's in circuit, and swap trannies until the Ic's are matched)? 
 

There is no easy way to do that unless you socket all your transistors, and in some cases the Hfe and Idss are difficult to determine in circuit because of interactions between different parts of the circuit. Much better to do Hfe and Idss measurements on a little solderless plug-style breadboard.


----------



## DigiPete

Quote:


  Originally Posted by *amb* 
_Answering DigiPete's post from the dynahi PSU thread, which is more appropriate here:


 Yes, it's one of the nice things about these particular transistors. Not all transistors are so well behaved, though.


 There is no easy way to do that unless you socket all your transistors, and in some cases the Hfe and Idss are difficult to determine in circuit because of interactions between different parts of the circuit. Much better to do Hfe and Idss measurements on a little solderless plug-style breadboard._

 

Thanks Amb,

 Tried it last night on the plug-style breadboard. I used two 9v in parallel (no power supply yet) and a 1 meg resistor to get 2-2.5 ma readings for Ic. I think I need a second DMM because it was a real pain to hook measure mA, unhook-rehook measure Vrb. Also, talk about a moving target, those Ic mA values just kept changing. 

 Should I repeat the readings @ 16v when I build the powersupply, and use different Ics (4.4 and 16ma) or just stick to the 2.0-2.5 ma?

 I measured 35 2SC1815s hFe (245-306) and 35 2SA1015s hFe(261-298) last night. I can at least get 12 good pairs, 24 pairs.... not likely 
	

	
	
		
		

		
		
	


	




 All part of the learning process 
	

	
	
		
		

		
		
	


	




 Cheers
 Pete


----------



## amb

Quote:


  Originally Posted by *DigiPete* 
_Tried it last night on the plug-style breadboard. I used two 9v in parallel (no power supply yet) and a 1 meg resistor to get 2-2.5 ma readings for Ic. I think I need a second DMM because it was a real pain to hook measure mA, unhook-rehook measure Vrb. Also, talk about a moving target, those Ic mA values just kept changing._

 

Yup. Two meters would definitely be nicer. The Ic will rise as the transistor warms up. So be consistent in when you do your readings. 

  Quote:


 Should I repeat the readings @ 16v when I build the powersupply, and use different Ics (4.4 and 16ma) or just stick to the 2.0-2.5 ma? 
 

It's up to you, how closely do you want them to match.


----------



## DigiPete

Quote:


  Originally Posted by *amb* 
_Yup. Two meters would definitely be nicer. The Ic will rise as the transistor warms up. So be consistent in when you do your readings. 


 It's up to you, how closely do you want them to match._

 

I'll redo the readings once I build the psu and pick up a second DMM.

 Thanks for all your help 
	

	
	
		
		

		
		
	


	




 Pete


----------



## Pars

Rather odd occurance tonight, one that I had not noticed before. I got out my test jig and was going to test some transistors for Mono's discrete buffers. My test jig uses a fixed 220K resistor and I use two DMMs... one to measure Ic and the other for Vrb. I noticed when I hooked the second meter up for the Vrb measurement, that it was reading higher than the supply voltage and Ic shot up considerably (at least according to the meter). I determined that it was the meter connected to measure Vrb that was causing the problem (I could measure Vbe without any problem). Swapping DMMs did nothing. Flipping the lead polarity on the meter for Vrb at least got the Vrb reading where it should be (~8.3V using a 9V supply), but still did effect the Ic reading slightly. I assume that this is an effect from meter loading? I checked and rechecked how I had everything hooked up and it was correct, though different somewhat from how I had previously done it. I also used the second meter to measure the supply voltage while I connected the other to measure Vrb... Vrb reading was wrong (higher than the supply) but the supply voltage stayed constant. One meter is an HP 3268B bench meter... the other a Protec 608. Any thoughts?


----------



## sbelyo

since the 2sk389 and sj109 are becoming a question of availability I thought I would order the seperates (2SK170, 2SJ74) and match The Idss. The way I understand it is this is how you test them:

 Testing a N Channel JFET's IDSS

 connect the gate and source pins. I then connect the negative side of a ~9V power supply to the connected gate and source pins, then connect the negative lead of a milliammeter to the JFET's drain, and finally the positive lead of the milliammeter to the positive supply lead. The JFET saturates at its IDSS level in this situation, and that current value shows up on the milliammeter.

 Testing a P Channel JFET's IDSS

 connect the gate and source pins. Then connect the Positive side of a ~9V power supply to the connected gate and source pins, then connect the Positive lead of a milliammeter to the JFET's drain, and finally the Negative lead of the milliammeter to the Negative supply lead. The JFET saturates at its IDSS level in this situation, and that current value shows up on the milliammeter.

 I just want to know if this is correct? And also by looking at the datasheets for the fets it shows the flat side up with the pins reading 1 2 3 from left to right, Is that with the pins facing you?


----------



## amb

sbelyo, yes your Idss measurement method is ok. If you meter is digital then you don't even need to reverse its polarity for the P-channel (it will read negative current but that's just fine).

 Both the 2SK170 and 2SJ74 have DGS pinout with flat side facing you and leads pointed down. When you insert them on the dynahi pcb note that the holes are oriented DGS-SGD.


----------



## sbelyo

My meter is digital, so I don't have to reverse it.

 I'm a little confused with the orientation on the board using seperates. So if two 2sj47's are side by side, one is flipped opposite of the silkscreen?


----------



## amb

Quote:


  Originally Posted by *sbelyo* 
_I'm a little confused with the orientation on the board using seperates. So if two 2sj*74*'s are side by side, one is flipped opposite of the silkscreen?_

 

Yes.


----------



## sbelyo

Got it.... Thanks amb

 So if you are looking at the board with the output transistors on top, The transistor in the 2SK389 pair furthest away from the output transistors should be flipped. And the transistor in the 2SJ109 pair closest to the output transistors should be flipped

 Right?


----------



## amb

Quote:


  Originally Posted by *sbelyo* 
_So if you are looking at the board with the output transistors on top, The transistor in the 2SK389 pair furthest away from the output transistors should be flipped. And the transistor in the 2SJ109 pair closest to the output transistors should be flipped

 Right?_

 

Yep.


----------



## sbelyo

Cool beans.... Thanks again amb

 I should have my PSU up and running by tomorrow


----------



## sbelyo

I measured all the seperates (2sk170, 2sj74) and I was able to get them all within 0.20 ma of each other. I hope that's close enough


----------



## amb

Quote:


  Originally Posted by *sbelyo* 
_I measured all the seperates (2sk170, 2sj74) and I was able to get them all within 0.20 ma of each other. I hope that's close enough_

 

That's not bad. Some of the 2SK389/2SJ109s don't even match that well.


----------



## sbelyo

I had 2 sets that were dead even. I guess I was just lucky


----------



## Kruemelix

Hello, 

 is it also possible to test the output transistors (1358/3421) at 30mA as they are getting way too hot for my taste at 85mA? The hFE-IC graph is pretty flat in this range. Also, I was unable to do a correct reading at 85mA because the current rose and rose...

 Thomas


----------



## Pars

Quote:


  Originally Posted by *Kruemelix* 
_Hello, 

 is it also possible to test the output transistors (1358/3421) at 30mA as they are getting way too hot for my taste at 85mA? The hFE-IC graph is pretty flat in this range. Also, I was unable to do a correct reading at 85mA because the current rose and rose...

 Thomas_

 

These transistors (alll the Gilmore ones) are typically pretty linear so I wouldn't see why not. Did you have them on a heatsink? I would guess that you might have been pushing thermal runaway territory if not. These should probably be all mounted to the same heatsink and then tested to try to get a reading at approx. the same temperature.


----------



## Kruemelix

Quote:


  Originally Posted by *Pars* 
_These transistors (alll the Gilmore ones) are typically pretty linear so I wouldn't see why not. Did you have them on a heatsink? I would guess that you might have been pushing thermal runaway territory if not. These should probably be all mounted to the same heatsink and then tested to try to get a reading at approx. the same temperature._

 

nope, I just run them for a few seconds at room temperature (I even didn't touch them with my fingers) and repeated the test a second time after a minute or two. Does it make a huge difference whether I test them this way or with a heatsink?


----------



## Pars

Quote:


  Originally Posted by *Kruemelix* 
_nope, I just run them for a few seconds at room temperature (I even didn't touch them with my fingers) and repeated the test a second time after a minute or two. Does it make a huge difference whether I test them this way or with a heatsink?_

 

I would think that if you can repeatedly get a measurement that you feel is the same condition for every transistor, then no, it doesn't matter. If it were me (and I will be there in a bit when I decide to build a dynahi) I would try to make some sort of fixture to mount several transistors to, even if it is just a metal bar/strip or something like that. I was hoping amb or Dan might pop up with their opinions 
	

	
	
		
		

		
		
	


	




.


----------



## amb

Quote:


  Originally Posted by *Pars* 
_I was hoping amb or Dan might pop up with their opinions 
	

	
	
		
		

		
			





._

 

LOL 
	

	
	
		
		

		
		
	


	




 Pars is correct. If you could take a measurement quickly and consistently each time without appreciably heating up the transistor, then you don't need to heatsink it. However, putting them on a heatsink won't hurt either. The key is whatever you do, do the same thing for each one.


----------



## bryerd

I've tried both routes (or really all three of the below).

 1. Tried measuring the current draw on loose transistors (no heat sink). Found that the currents changed rather quickly and could not get an accurate reading by simply counting "1 Mississippi 2 Mississippi...". This was enough to drive me bonkers.

 2. Decided to record the current draw using a stopwatch at 10 seconds, 30 seconds, and after 60 seconds. While the current draw did increase for each successive time, once plotted, the curves for all three time durations were very similar in shape (see attachment). Conclusion: actual time was not that important for matching, but using a stopwatch was very helpful (so was the hold function on my DMM). However, 60 seconds was excessive to wait when measuring numerous transistors, and they get quite hot!

 3. Went back and remeasured with the transistors mounted to a heat sink. All I did was use a clothespin (wooden kind with the spring) to keep the back of the transistor tight against a piece of metal (I used my actual heatsink with a piece of Sil-pad, but a 1/8" thick 1x1" aluminum angle should work too). Upon applying the voltage, the current quickly converged and did not increase or fluctuate at all. No stopwatch was needed, and yet good, repeatable results were obtained within seconds. The clothespin also made it very easy to change transistors as well.

 Good luck,
 Dave


----------



## Pars

Quote:


  Originally Posted by *bryerd* 
_I've tried both routes (or really all three of the below).

 <snip>
 3. Went back and remeasured with the transistors mounted to a heat sink. All I did was use a clothespin (wooden kind with the spring) to keep the back of the transistor tight against a piece of metal (I used my actual heatsink with a piece of Sil-pad, but a 1/8" thick 1x1" aluminum angle should work too). Upon applying the voltage, the current quickly converged and did not increase or fluctuate at all. No stopwatch was needed, and yet good, repeatable results were obtained within seconds. The clothespin also made it very easy to change transistors as well.

 Good luck,
 Dave_

 

Good idea!


----------



## Kruemelix

Hello,

 finally got it to match all the transistors. I checked some of the 1358/3421 a second and third time with the same method quoted above. Around 90% of the transistors were in the +/-1 range, the last 10% in the +/-2 range. IMHO that should be accurate enough. Furthermore I doubt that you will get a much better result with the clothespin method without thermal paste (what's the correct word for?). Can just someone post me a expedient constellation via copy/paste for four boards?

 2SC3421
 134
 136
 137
 138
 139
 139
 140
 141
 141
 142
 143
 143
 143
 144
 144
 144
 144
 144
 144
 145
 145
 145
 147
 147
 148
 150
 151
 151
 151
 153
 154
 154
 154
 154
 154
 155
 155
 156
 156
 156
 158
 159
 160
 161
 161
 162
 166
 169

 2SA1358
 195
 196
 197
 197
 199
 199
 199
 200
 200
 201
 202
 203
 203
 203
 203
 203
 204
 204
 204
 205
 205
 205
 205
 206
 206
 206
 206
 206
 207
 207
 208
 210
 211
 211
 211
 212
 212
 213
 213
 213
 213
 213
 214
 214
 215
 216
 223

 2SA1145
 145
 146
 146
 146
 146
 147
 147
 147
 148
 148
 149
 149
 149
 150
 151
 151,5
 152,5
 153,5
 154,5
 155,5
 167
 170
 172
 173
 173,5
 174
 175,5
 176,5
 177,5
 177,5
 178,5
 179,5
 180,5
 181
 185
 186

 2SC2705
 150,5
 153
 155
 155
 157,5
 158,5
 159
 160
 162
 162
 163
 163
 164,5
 164,5
 165,5
 165,5
 170
 170
 170
 172
 172
 172,5
 173,5
 173,5
 175
 178
 179
 181,5
 181,5
 182,5
 183
 183

 2SC3381
 left-right
 397-397
 409-411
 415-415
 416-415
 420-415
 421-421
 435-433
 447-447
 453-451
 457-453
 533-521
 591-581

 2SA1349
 left-right
 477-474
 477-479
 484-479
 489-494
 493-499
 494-504
 496-499
 511-521
 529-529
 546-551
 574-579
 584-584

 Thanks,

 Thomas


----------



## dip16amp

2SC3421 154, 154, 154, 154
 2SA1358 206, 206, 206, 206
 2SA1145 181, 180.5, 179.5
 2SC2705 182.5, 181.5, 181.5
 2SC3381 397-397
 2SA1349 477-479

 2SC3421 150, 151, 151, 151
 2SA1358 205, 205, 205, 206
 2SA1145 178.5, 177.5, 177.5
 2SC2705 179, 178, 175
 2SC3381 415-415
 2SA1349 496-499

 2SC3421 144, 145, 145, 145
 2SA1358 203, 204, 204, 204
 2SA1145 174, 173.5, 173
 2SC2705 173.5, 173.5, 172.5
 2SC3381 421-421
 2SA1349 529-529

 2SC3421 144, 144, 144, 144
 2SA1358 203, 203, 203, 203
 2SA1145 155.5, 154.5, 153.5
 2SC2705 155, 155, 153
 2SC3381 447-447
 2SA1349 584-584


----------



## DigiPete

Yeah,

 I just did the 15 seconds on a stopwatch (no heatsink) method. 
 It worked just fine, and saves a bit of time not having to mount transistors for the check.

 Pete


  Quote:


  Originally Posted by *bryerd* 
_I've tried both routes (or really all three of the below).

 1. Tried measuring the current draw on loose transistors (no heat sink). Found that the currents changed rather quickly and could not get an accurate reading by simply counting "1 Mississippi 2 Mississippi...". This was enough to drive me bonkers.

 2. Decided to record the current draw using a stopwatch at 10 seconds, 30 seconds, and after 60 seconds. While the current draw did increase for each successive time, once plotted, the curves for all three time durations were very similar in shape (see attachment). Conclusion: actual time was not that important for matching, but using a stopwatch was very helpful (so was the hold function on my DMM). However, 60 seconds was excessive to wait when measuring numerous transistors, and they get quite hot!

 3. Went back and remeasured with the transistors mounted to a heat sink. All I did was use a clothespin (wooden kind with the spring) to keep the back of the transistor tight against a piece of metal (I used my actual heatsink with a piece of Sil-pad, but a 1/8" thick 1x1" aluminum angle should work too). Upon applying the voltage, the current quickly converged and did not increase or fluctuate at all. No stopwatch was needed, and yet good, repeatable results were obtained within seconds. The clothespin also made it very easy to change transistors as well.

 Good luck,
 Dave_


----------



## Kruemelix

Hello,

 I just realized that I measured the 1145/2705 only at 2,5 mA - will this be a problem as they are working at 1 mA and 15 mA?

 Thanks,

 Thomas

 P.S. is dip16amp's suggestion correct this way? Or are there better possibilities?


----------



## Pars

Should be OK as these transistors are quite linear and won't change much at a higher current.

 Dip16amp has built a few of these, and his recommendations seem solid without extensively going thru your list... I don't see any other suggestions anyhow.

 Are you planning on socketing the transitors/FETs? The FETs in particular aren't easy to desolder/remove/swap, so at a minimum I would socket those. Not sure whether you can socket the output transitors or not, but the rest of them I would if it were me doing it. Its educational at the least to try to predict what will happen with offset if you put a certain hFE value in a certain position, and allows you to quickly verify the effects on offset to bring them down as close as possible to 0.0mV without the servos, and without cranking the pots. This will result in an amp that is as linear as possible.


----------



## j4cbo

Hmm...

 I attempted to measure my 2SA1145/2SC2705s, using a fixed 470k resistor and two meters. The collector current ran through an analog VOM, and I simultaneously measured the voltage drop across the resistor with a VTVM. (My test equipment is kinda old.)

 The 2SC2705s wound up in the 110-137 gain range, and the 2SA1145s are all between 151 and 157.

 Did I mess up the measurement somehow?


----------



## amb

Quote:


  Originally Posted by *j4cbo* 
_The 2SC2705s wound up in the 110-137 gain range, and the 2SA1145s are all between 151 and 157._

 

These agree with my own experience with these transistors, the PNP devices seem to have higher Hfe on average. Don't sweat it too much, it's not too bad.


----------



## j4cbo

Quote:


  Originally Posted by *amb* 
_These agree with my own experience with these transistors, the PNP devices seem to have higher Hfe on average. Don't sweat it too much, it's not too bad._

 

Gotcha. Should I match low with low and high with high, or just not bother?

 (I did do a rough match on the LEDs.)

 Next comes the drive transistors, and there's a problem. BDEnt sent me 2SC3421s all in the "Y" gain variety, but all but six of the 2SA1358s are the "O" type. So I've got six pairs of Ys, and another fourteen 2SA1358Os. 

 I'm thinking I'll go through all the 2SA1358Os, do a quick gain test, and pick the highest two. Fortunately I've got the PNP/NPN split difference working on my side in this case.


----------



## j4cbo

Anyone? :/


----------



## Pars

Well, you've got two options: 1) you can send the "O"s back to bdent to have them replaced with "Y"s, or 2) you can try it. I haven't ordered from bdent before (always been lucky... and I do mean LUCKY on gain ranges with mcm), but from what I understand, you really need to call them when you order and make sure they send matched gain ranges. If you can quickly check them and get a baseline idea of where they are at compared to your PNPs (can't remember which is which... SA=PNP/ SC=NPN or the other way around), and they match up OK, I'd probably just go with it. Many of the types there is a considerable difference between the NPN/PNPs in terms of where the gains fall.


----------



## Edwood

Anyone considering building a Dynahi or two, or need lots more parts?

 I'm giving up on the Dynahi (before I even started).

 I bought enough parts to build almost two of them. Right down to the Case, Heatsinks, and all the electronics parts.

 If anyone is interested I'm posting them up for sale. Let's just say my home has to be more than ROHS compliant because of a pregnant wife. 
	

	
	
		
		

		
		
	


	




http://www6.head-fi.org/forums/showthread.php?t=203666

 -Ed


----------



## dhp

Quote:


  Originally Posted by *Edwood* 
_Anyone considering building a Dynahi or two, or need lots more parts?

 I'm giving up on the Dynahi (before I even started).

 I bought enough parts to build almost two of them. Right down to the Case, Heatsinks, and all the electronics parts.

 If anyone is interested I'm posting them up for sale. Let's just say my home has to be more than ROHS compliant because of a pregnant wife. 
	

	
	
		
		

		
		
	


	




http://www6.head-fi.org/forums/showthread.php?t=203666

 -Ed_


----------



## j4cbo

Well, here's what I wound up with for the drive transistors:

 Group 1
 2SA1358Y: 148, 148, 150, 153; spread 5, average 149.75
 2SC3421Y: 148, 148, 148, 149; spread 1, average 148.25

 Group 2
 2SA1358O: 128, 129, 129, 131: spread 3, average 129.25
 2SC3421Y: 128, 130, 132, 133: spread 5, average 130.75

 It's not perfect, but pretty good. Started with 20 of each.


----------



## Mimas

Im building KGSS... For input stage instead of 2SK389(since they aren't available anymore) I have bought 30 pcs of 2SK170 for matching (on the right). Idss looks ok, but transistors themselves look a bit weired comparing to the ones on the left(I have 4 of those).
 Idss(at 9 volt) looks like this:
 for left transistors:
 6,22 (mA)
 6,26
 6,92
 9,95
 And those on the right:
 6,65
 6,8
 6,82
 6,85
 6,93
 7
 7,13
 7,18
 7,49
 7,5
 7,56
 7,63
 7,64
 7,7
 7,74
 7,84
 7,93
 8,13
 8,13
 8,81
 9,15
 9,34
 9,4
 9,45
 9,53
 9,63
 10,25
 10,25
 10,43
 10,73

 Looks ok, but I'am still concerned about them. Did anyone see 2SK170 like those on the right? All pics of s170 i could find on inet look like left ones. Hope those aren't fakes...


----------



## dip16amp

I think they are okay since they all are within BL range of 6-12.
 I've had other components that had different lettering from the same manufacturer. Just different batches.


----------



## luvdunhill

when matching transistors on the Millet diamond buffer, I'm trying to first get h_fe of Q6 == Q7, that part is clear. For Q2,Q3,Q4,Q5 am I trying to get them to all have the same h_fe, or Q2 == Q4 and Q3 == Q5?

 Schematic is here:

http://www.diamondstar.de/dDB_isb_v022_schem.jpg


----------



## MisterX

http://www.diamondstar.de/dDB_partslist.html

  Quote:


 [size=small]*Note 3: hFE matching of BJT transistors*[/size]
 Transistor matching is not a necessity, most probably it doesn't make an audible and just a measurable difference 
 Since we are using bipolar junction transistors (BJT) matching is done by their hFE values. 
 Matching is done within a single channel only, you don't have to match the channels 
 Match input stage Q6 / Q7 (good chances of success) 
 Match current mirror Q2 / Q4 / Q3 / Q5 (medium chances of success) 
 Match output stage Q8a/b / Q9a/b (poor chances of success, little benefit) 
 The small signal transistors used in the input stage and the ccs mirror (2n50xx ... BC5xx) are cheap (~ 5 cent ea.), get about 30 to 50 of each to find decent complementary pairs among them. 
 For the large transistors used in the output stage it's unlikely to get perfect matching pairs, probably npn and pnp types are more or less off each other. Don't get frustrated if the ranges not even overlap, group them as good as possible but don't buy too many surplus. 
 The easiest way matching transistors is to measure their hFE values with a DMM that has a transistor socket and supports this mode. There is a nice transistor matching thread at head-fi.org and a page about BJT transistor matching on my site if you want to read more about this topic.


----------



## luvdunhill

Quote:


  Originally Posted by *MisterX* /img/forum/go_quote.gif 
_http://www.diamondstar.de/dDB_partslist.html_

 

MisterX:

 I don't why that verbiage isn't clear to me 
	

	
	
		
		

		
			





 So, I want Q2 = Q4 = Q3 = Q5?


----------



## steinchen

Quote:


  Originally Posted by *luvdunhill* 
_So, I want Q2 = Q4 = Q3 = Q5?_

 

yes


----------



## Alfiax

I've been preparing for the upcoming set of amps that use the 2sj74 and 2sk170 by trying to match up for Idss and have run into a bit of a problem. I ordered 2sj74-BL from B&D and a mixed assortment of 2sk170 from Futurlec which turned out to be mainly BL with some GR. The 2sj74 tested just fine within their listed range (6-12 mA,) but the ~50 2sk170-BL I got from Futurlec are way out of spec, in the range of 15-16 mA. This is near the center of the V range! 
	

	
	
		
		

		
		
	


	




 I'm trying to figure out what's going on here. I know that these JFETs have a reputation for being off spec, but this seems ridiculous. Is it possible I got re-marked or defective parts, or is this par for the course for these devices?


----------



## Pars

If you are certain that you have the polarities flipped around correctly for matching these (from the 2SJs), I'd send them back as out of spec.


----------



## Alfiax

Yeah, I'm pretty sure the polarities are right. I'm a little loath to send them back as my order did not specify gain class; I'd be in the same position with no ability to complain if these parts were properly labeled as V grade. My big worry is that I got another brand of JFET relabeled as 2sk170. There are lots of rumors but little hard evidence on relabeled parts; while there seems to be a good case for power devices commonly being relabeled i don't see too much about small-signal devices. It would seem like the profit-per-unit would be low enough that it wouldn't be worth it for these, but who knows?


----------



## amb

FWIW, I ordered 25 of each (all BL class) from B&D some time back and was able to get 5 sets of reasonably good 4-way matches (this is for the β22 amp). Maybe I'm lucky...


----------



## operafollower

Hi
 I am going to build KGSS or BH.
 Must I match its transistors (not first FET) like gilmore dynamic too?
 I read headwize so I know KG** must adjust offset with potentiometers.
 It can not adjust If I did not match transistors?


----------



## luvdunhill

hi! would someone be so kind as to compare the method of matching BJTs recommended in this thread (using a variable resistor and two meters) versus grouping by collector voltage (the method is outlined here http://www.diamondstar.de/transistor...ing_bjt.html)?

 Thanks!


----------



## amb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_hi! would someone be so kind as to compare the method of matching BJTs recommended in this thread (using a variable resistor and two meters) versus grouping by collector voltage (the method is outlined here http://www.diamondstar.de/transistor...ing_bjt.html)?_

 

They are essentially doing the same thing, except that in the "grouping by collector voltage" method, you don't actually know what the Hfe of each device is without doing some computation.


----------



## lcp12345

Does your guy know that Dynahi PCB is still available or not? I have email Dan. But, there is no response yet.

 I want to build a Balance Dynhi to drive my KK!


----------



## luvdunhill

delete, wrong thread


----------



## Pars

Quote:


  Originally Posted by *lcp12345* /img/forum/go_quote.gif 
_Does your guy know that Dynahi PCB is still available or not? I have email Dan. But, there is no response yet.

 I want to build a Balance Dynhi to drive my KK!_

 

I know that Dan travels alot. Give him a few days and he should get back to you.


----------



## lcp12345

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_I know that Dan travels alot. Give him a few days and he should get back to you._

 

OIC! 
 Not sure to build a balance Dynahi or β22.


----------



## luvdunhill

so, I'm not sure if my devices are fried, or if there is a conversion problem in my formulae, but here's what I'm getting...

 using a 9v battery supply, that measures right around 9.01 V and a PNP BJT that should be in the 100-200 hfe range. I'm trying to match at 1mA. I get 8.67 V drop across Rb (a 1M pot) and I get 1.004mA through the ammeter, one side which is connected to the emitter, and the other to the negative and the pot. The positive is then connected to the collector and the base to the other side of the pot. After turning things off, I get 10.76k ohm as the value for Rb. So, I calculate 8.67 V / 10760 ohm = .806mA and then hfe = 1.004mA / .806mA = 1.246... ? I also measure hfe using a non-autoranging dmm with hfe support and I got 152. hm... so, I'm a bit confused here. I've double checked all measurements with two meters, and one auto-ranging one. One strange thing, is when I turn the ammeter off, I still get 8.67v drop across Rb, which I didn't really expect. Can anyone give me a hand?

 edit:

 oops, I needed to change the location of the ammeter it seems, not just the polarity.... I think I'm up and running now!

 edit:

 ok, well, it seems to work, as I get get the transistors too hot... problem is, I had to add a series resistor to my pot. well, everything is fine until I try and measure the voltage across the resistor and pot... as soon as I touch my voltmeter across the two in series, my current through the ammeter doubles... ummm... any ideas?

 edit:

 so, the trick here seems to be to take the measurement with the ammeter first, using the pot to set the value to the desired setting. Then, remove the ammeter (short across the probes) and then turn on the voltmeter to test the device. Then remove power from the circuit and turn the voltmeter to the ohm setting to measure Rb. Then don't forget to turn off the voltmeter / ohm meter before turning on the ammeter again and un-shorting the probes. If you have two meters like this, you can get in a nice rhythm for measuring the devices....


----------



## Prenxta

From Figure 1 on the first page. When using the 9v battery to match, is the Emitter connected to ground with out any power to it; or is the negative voltage connected. Assuming it is a NPN BJT.
 Also, would it not be better to use two or three 9v batteries to test under higher voltages?


----------



## Pars

The first figure on the first page is a JFET, not a BJT... assuming you are referring to the second figure posted by chillysalsa, the - terminal of the battery goes to the emitter. 

 The voltage isn't so much of an issue as is the collector current (Ic) that you test at. Depending upon the linearity of the transistors you are testing, you may want to test them at approximately the Ic they will be used at. For the Toshiba transistors used in the Gilmore design, their linearity is so good that it doesn't really matter.


----------



## Prenxta

Thank's.


----------



## Kruemelix

Finally got all the 2SK170 and 2SJ74 for my Dynamight measured, here are the results (all in mA):

 2SK170
 6,6
 6,6
 6,7
 6,8
 6,8
 6,8
 6,8
 6,9
 7
 7
 7
 7,1
 7,1
 7,1
 7,1
 7,1
 7,1
 7,2
 7,4
 7,4
 7,4
 7,4
 7,4
 7,4
 7,5
 7,5
 7,6
 7,6
 7,6
 7,7
 7,7
 7,8
 7,9
 7,9
 7,9
 8
 8,1
 8,1
 8,1
 8,1
 8,2
 8,2
 8,2
 8,5
 8,5

 2SJ74
 7
 7,3
 7,7
 7,7
 7,8
 7,8
 7,8
 7,8
 7,9
 7,9
 7,9
 8,1
 8,1
 8,2
 8,2
 8,3
 8,4
 8,4
 8,8
 8,8
 8,8
 9
 9
 9,2
 9,3
 9,4
 9,4
 9,4
 9,5
 9,5
 9,5
 9,5
 9,7
 9,8
 9,8
 9,9
 10
 10,3
 10,3
 10,4
 10,5
 10,7
 10,7
 10,7
 10,8
 10,9
 11
 11
 11
 11,1

 anything wrong with the following matching?

 ampx: (2SK170 2SK170 / 2SJ74 2SJ74)
 amp1: 7,7 7,7 / 7,7 7,7
 amp2: 7,9 7,9 / 7,9 7,9
 amp3: 8,1 8,1 / 8,1 8,1
 amp4: 8,2 8,2 / 8,2 8,2

 Thomas


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## Pars

Looks perfect. Thermal bonding of the pairs will also help if you can do it.


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## digger945

So is everyone "matched up" now? Anything new to add?


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## jcx

there are actually a few more parameters required to assure matching of "square law" model jfets:
 3 points are the minimum required to define a fit to a parabola

 in practice mask geometry is constant for a particular device # with diffusion concentration/depth being the main batch variables so usually only 2 points are really independent in a single part type

 Vt or gfs0 should really be measured in addition to Idss to match the parts within a diff pair

 to obtain matching between N and P fets is unlikely given the 2:1 difference between N and P doped Si conductivity – “best” compromise with specifically calculated changes to source degeneration and drain resistors with exact N vs P fet parameters would be an interesting study

 practically a place to start would be to select the best match of Vgs at a ids repesentative of the operating point with devices that do match Idss well


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## digger945

That's different.


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## Pars

Thread necromancy FTW! I guess this is the only forum that you can regularly get way with this 
	

	
	
		
		

		
		
	


	




 I am currently building a Dynahi, and apparently wasn't paying close enough attention when more of these were being built and discussed. I am matching the output devices (2SC3421 / 2SA1358) from a mix of a batch I bought from DigiPete (Y grade, with DP's measurements) and some I had myself (O grade). Obviously the O grade aren't going to work.

 What concerns me is the vast difference between NPN and PNP in terms of hfe, with the PNPs typical being considerably higher. Is this normal? In looking at DigiPete's measurements, he was using a 29.35Vrb drop, but had Rb as ~59K ohms for the NPNs, but at 79K ohms for the PNPs to get them around 80mA Ic? I know when I matched output devices for a Dynalo, that Rb was constant for either P or N devices. Seems odd and not correct.

 Example: Kruemelix (sp?) results from post 109, where his highest hfe for NPN is ~169, and lowest hfe for PNP is 199. I see j4cbo had hfe's in the same range for either device type; not sure what gain class and where he got his.


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## FallenAngel

Mine was all over the board as well, especially for a Dynalo.

 It's also a lot easier to simply measure using a cheap DMM that measures Hfe


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## digger945

I had Dan Gardner match me up for mine, I am not sure I could have done it for less, not without buying lots of them.
 He _claimed_ the match was far better than his own, but of course he _would_ say that.


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## digger945

*Copy of his email to me:*


 I can also make sure that the HFE of the PNP’s and NPN’s are close to each other, even though that’s not required. 

 I just checked, and since you are the first, I can supply:



 4 x 2SA1358-Y @ HFE = 153

 4 x 2SA1358-Y @ HFE = 154

 4 x 2SA1358-Y @ HFE = 156

 4 x 2SA1358-Y @ HFE = 158



 4 x 2SC3421-Y @ HFE = 153

 4 x 2SC3421-Y @ HFE = 153

 4 x 2SC3421-Y @ HFE = 153

 4 x 2SC3421-Y @ HFE = 154



 Cream of the crop. Better matching than my first Dynamite. I’m jealous.

 -Dan


*And the following reply to mine was this:*


 Scott:

 Glad to hear you got the parts. If you know anyone else who needs parts, let them know. I have bags and bags just sitting on the shelf “looking for love”.

 -Dan

*Gimme a PM for his shipped quote.*


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## Pars

Quote:


  Originally Posted by *Kruemelix* /img/forum/go_quote.gif 
_<snip>

 2SC3421
 134
 136
 137
 138
 139
 139
 140
 141
 141
 142
 143
 143
 143
 144
 144
 144
 144
 144
 144
 145
 145
 145
 147
 147
 148
 150
 151
 151
 151
 153
 154
 154
 154
 154
 154
 155
 155
 156
 156
 156
 158
 159
 160
 161
 161
 162
 166
 169

 2SA1358
 195
 196
 197
 197
 199
 199
 199
 200
 200
 201
 202
 203
 203
 203
 203
 203
 204
 204
 204
 205
 205
 205
 205
 206
 206
 206
 206
 206
 207
 207
 208
 210
 211
 211
 211
 212
 212
 213
 213
 213
 213
 213
 214
 214
 215
 216
 223

 <snip>_

 

 Quote:


  Originally Posted by *j4cbo* /img/forum/go_quote.gif 
_Well, here's what I wound up with for the drive transistors:

 Group 1
 2SA1358Y: 148, 148, 150, 153; spread 5, average 149.75
 2SC3421Y: 148, 148, 148, 149; spread 1, average 148.25

 Group 2
 2SA1358O: 128, 129, 129, 131: spread 3, average 129.25
 2SC3421Y: 128, 130, 132, 133: spread 5, average 130.75

 It's not perfect, but pretty good. Started with 20 of each._

 

Any other thoughts?

 j4cbo went with a bit lower gain than what is in Kruemelix' mix. I have ~16-20 of each plus 4 "O" grade of each. I haven't measured the "O" grade SA1358s yet, but maybe they will overlap the 3421s. I may pick up another 20 of each in "Y" grade, or maybe just more 3421s to see if I get some that fall higher in the range. I also need to take a look at the SA1145 and SC2705s first in case I wind up needing some of those as well.


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## digger945

I don't know what class of gain 1145/2705's your using, but I've been buying them at Mouser lately. You can get "O's" for $12.50 per 100 pcs. I've had few that were way off.


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## Pars

I didn't even know that Mouser carried these- hehe. I still need to check mine as I probably have enough. I must have been composing your post and hadn't seen your previous one. Good idea; I should just buy some from Dan. If you get a chance, shoot that quote to me via PM.

 Thanks!

 Chris


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## luvdunhill

I dunno, unless they're matched on a heat sink at the proper base current, they won't be all that close I've found. I'd just buy two times as many as you need from Dan in consecutive Hfe units and regroup them yourself. The deal is, most people will just use a hfe meter, which is okay.. it will "work" but the only real way to know if you really have good matching in the output stage is a distortion analyzer after the fact. The temperature is such an important component here, as well as Ib...


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## digger945

True dat.


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## Pars

In matching these myself, I had set up a protoboard that the transistor will fit in with a fixed base resistor. I have one meter measuring Vrb, the other measuring Ic. I use a clothespin to clamp the DUT to a strip of aluminum (heatsink).

 When I apply power, both Vrb and Ic go up pretty quickly. They do stabilize somewhat but never become really stable, at least as long as I have waited.

 I was waiting for Vrb to hit a particular value (which it does within probably 15-20secs of applying power) and reading Ic at that voltage. From what you are saying regarding temp, it sounds like I would be better off waiting for it to stabilize and then grab the readings?

 BTW, my readings are correlating with DigiPete's for the most part (not identical, but very similar).


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## Pars

I just got back to doing this for the output devices since Scott (digger) sent me a few more to play with. I am using a piece of 1" x 1/8" aluminum as the heatsink, with a clothespin, and it seems to be working pretty consistently, and there is a plateau which the devices seem to reach with a couple of minutes.

 I am using a plug-in breadboard with a 100K pot set to ~59K (same value as Digipete used) and noticed something strange. When I was measuring one of the devices I got from Digipete, the Ic was almost half of what it should have been at the test parameters (Vrb 29.35V, Rb of 59K). I also took another meter and measured the input voltage, and at this point it was LESS (26.xx Vdc) than the Vrb. Impossible. Removing the meter measuring Vrb, the input voltage went back to what it should have been, and Ic went from ~45mA back up to 80 something. Even the ammeters on my bench supply showed this fluctuation.

 I guess this is due to meter loading effects? Either of my good DMMs do this (Protek 608 and HP 3468). The Protek will do uA, so, I put it in series to measure Ib, and this seems to be working (Ic is in the correct range).

 Any comments, suggestions?


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