I started building amps many years ago and have gone through a lot of amps. Starting with tube amps and switching to transistor amps , not being satisfied with transistor class AB , went back to tubes. I wasn't until I built a Firstwatt F5 I was satisfied. My next Firstwatt build was the Aleph J. The J has a more relaxed sound and in my opinion more musical ( at least in my system ). My most recent build is the M2X with the Ishikawa input stage. I bought the parts for the Mountain View minus the LEDs. I just can't bring myself to taking this amp out of service long enough to change the input board. I absolutely love this amp. It sounds like music. The top end doesn't have that hifi sizzle ( I cant stand that ) . It just sounds natural. Nelson has done it once again. Can't thank Nelson and the DIY community enough.
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@coolnose, I bought exactly these that @pfarrell links to in his post.
These links are in the quote in my message too.
That looks like a sweet testing setup! Don’t know how it works exactly, but certainly looks really pro!
I used a spare M2X amp board and built an input board test bench out of that so I can test the input boards before they go into the amp. The test generator is just a cheap one that can make sine, triangle and TTL-square from 1 Hz - 250 kHz. The scope is a very old TDS-210 I got cheap on ebay and it does the job and is handy. The lab-supply was also relative cheap. It is nice to have current limiter when you fire up for the first time and that you can slowly increase the voltage and check what happens.
My 328 tester actually gives an "Idss" for J-FETs.
However, it ist much lower than the Idss we typically get when matching J-FETs. I don't find the figure of the 328 meaningful, nor helpful in matching J-FETs.
I guess that is due to the much lower voltage the tester uses than we do in our normal matching (9V or 10V Vds) ...
Regards, Claas
However, it ist much lower than the Idss we typically get when matching J-FETs. I don't find the figure of the 328 meaningful, nor helpful in matching J-FETs.
I guess that is due to the much lower voltage the tester uses than we do in our normal matching (9V or 10V Vds) ...
Regards, Claas
SOT23 jig
I used this to "hold" the SOT23 transistors and made a simple jig with a bread-board proto-typing kit from eBay and used my lab supply.
How many and what match are you looking for? I might be able to assist with matched ones, depending on your requirements for matching? I matched ~50 to make EUVLs UDNeSS amplifier a few months ago.
Peak SOT23 Adapter for Testing Parts on DCA55 DCA75 Model PCA23 Atlas | eBay
***EDIT - mine are the 2sk209-Y, so I'm not sure if you can use those of not.
I used this to "hold" the SOT23 transistors and made a simple jig with a bread-board proto-typing kit from eBay and used my lab supply.
How many and what match are you looking for? I might be able to assist with matched ones, depending on your requirements for matching? I matched ~50 to make EUVLs UDNeSS amplifier a few months ago.
Peak SOT23 Adapter for Testing Parts on DCA55 DCA75 Model PCA23 Atlas | eBay
***EDIT - mine are the 2sk209-Y, so I'm not sure if you can use those of not.
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I was able to test SOT-23-3 parts successfully, by having a PCB with enlarged landing pads for the three leads. I used the eraser end of a wooden pencil, coated with rubber cement, to position and gently press the device onto the PCB. I was testing only one part at a time, I'm not ambidextrous enough to do this to two parts simultaneously!
So many questions.
> Does any one have a jig that can match the 2SK209-GR in black forest?
Peak SOT23 Adapter is a good one.
> Well they should be Idss 3,5mA.
If you looked at the excel sheet, I have given you values from 2mA to 5mA.
But I tested with 3.5mA, and Dirk with 3mA.
So we know those values are reliable.
> Mine are the 2sk209-Y, Y: 1.2~3.0 mA.
You need to pick the ones around 2mA.
I have not tried with 1mA
So I cannot tell you for sure whether it will be stable with those capacitor values I posted.
I would recommend that you match to get 2 pairs, each pair matched to better than 0.1mA.
And difference between the two pairs not > 0.3mA. One pair for each channel.
That way, you can almost use R2 as same value as R1 without trimming, as Dirk did.
He has 2 identical pairs (or a quad), so R11 & R12 are also same value between channels.
If the two pairs differs more than 0.1mA, you need to use the excel sheet to calculate the values of R11,12.
The Idss value can be changed to actual values of your JFETs.
I always order 100 pieces to match to get good yield.
So I suggest you group buy / group match.
Patrick
> Does any one have a jig that can match the 2SK209-GR in black forest?
Peak SOT23 Adapter is a good one.
> Well they should be Idss 3,5mA.
If you looked at the excel sheet, I have given you values from 2mA to 5mA.
But I tested with 3.5mA, and Dirk with 3mA.
So we know those values are reliable.
> Mine are the 2sk209-Y, Y: 1.2~3.0 mA.
You need to pick the ones around 2mA.
I have not tried with 1mA
So I cannot tell you for sure whether it will be stable with those capacitor values I posted.
I would recommend that you match to get 2 pairs, each pair matched to better than 0.1mA.
And difference between the two pairs not > 0.3mA. One pair for each channel.
That way, you can almost use R2 as same value as R1 without trimming, as Dirk did.
He has 2 identical pairs (or a quad), so R11 & R12 are also same value between channels.
If the two pairs differs more than 0.1mA, you need to use the excel sheet to calculate the values of R11,12.
The Idss value can be changed to actual values of your JFETs.
I always order 100 pieces to match to get good yield.
So I suggest you group buy / group match.
Patrick
These are somewhat cheaper, if you are not looking for long life :
SOT23-6L SOT23 To DIP IC Programmer Adapter Chip Test Socket | eBay
(Disclaimer: Have not used them before, so not sure of quality.)
Patrick
SOT23-6L SOT23 To DIP IC Programmer Adapter Chip Test Socket | eBay
(Disclaimer: Have not used them before, so not sure of quality.)
Patrick
M2X - JFet-matching
I test / match my JFets with the PEAK ATLAS DCA75Pro.
For the SMD-JFets (SOT23) I use their adapter named: PCA23.
On the pics you see how small the SMD-JFets are. And some measurements.
Greets
Dirk
I test / match my JFets with the PEAK ATLAS DCA75Pro.
For the SMD-JFets (SOT23) I use their adapter named: PCA23.
On the pics you see how small the SMD-JFets are. And some measurements.
Greets
Dirk
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I reviewed my matching spreadsheet and while most are very close at 1.7-1.85mA - I think I could get you 4-6 and maybe 6-8 in the 1.8-2.1 (starting at the high-end) that are matched within 0.1 per pair.
I used 4 pair matched at 1.7mA for my UDNeSS built, which was spec'd for 2ma or higher as well and they worked great, no issues at all - if my experience means anything at all, but Patrick is the professional and knows specifically what can and can't be used, so take his advice over mine for sure.
Let me know if you want to give them a try and I can send you the spreadsheet for the matches.
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