Mr Pass answered that question in the very first post, matching would not be required for most applications.
Right. I saw that. And in that post he lists 3 different types of VFETs without distinguishing which one the build is going to require or perhaps more precisely which one is going to be optimal for the build. So my question wasn't really about matching, although personally I will buy matched VFETs just to be safe. My question is which of the two VFETs that seem to be available is it better to buy. Since they cost $180/pair I would like to make sure I'm ordering the right ones.
My attitude is more aligned with Post #63.
The idea that differently speced parts are interchangeable with no consequence requires more experience/knowledge than this newbie is comfortable with yet. But I will trust in Pass and flip a coin ;-).
The idea that differently speced parts are interchangeable with no consequence requires more experience/knowledge than this newbie is comfortable with yet. But I will trust in Pass and flip a coin ;-).
Hi Paul.
One small factor is the mounting arrangement, 51's have connections from the top, away from the heat sink, so are very easy to directly mount to a heat sink. 180's have connections on the heat sink mounting side, this makes them easier to mount onto a 'T' section heat connecting piece via a PCB if that is how it's proposed. (As it was with some lower power device arrangements). This latter method is possibly not the option to be used (I have no prior knowledge) here as the connections on the 180's are splayed out and pierced with a hole at their ends. (This could be snipped off I suppose).
Won't effect the sound but could be a factor for some people. Personally having both parts available I prefer the first, (for better heat transfer reasons) and will just connect the devices to the PCB via small leads.
One small factor is the mounting arrangement, 51's have connections from the top, away from the heat sink, so are very easy to directly mount to a heat sink. 180's have connections on the heat sink mounting side, this makes them easier to mount onto a 'T' section heat connecting piece via a PCB if that is how it's proposed. (As it was with some lower power device arrangements). This latter method is possibly not the option to be used (I have no prior knowledge) here as the connections on the 180's are splayed out and pierced with a hole at their ends. (This could be snipped off I suppose).
Won't effect the sound but could be a factor for some people. Personally having both parts available I prefer the first, (for better heat transfer reasons) and will just connect the devices to the PCB via small leads.
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Thanks. That is great input and a deciding factor for me. The 51's would definitely be easier to work with. I'll be ordering a pair of those unless something has changed and people think more than two might be needed?
I think it comes down to money, As the supply of VFets like other now obsolete parts dwindles they can become very expensive or impossible to get. Designs can change and grow so who knows, also if one were to pop and "Let the smoke out" whilst building, or later in use, it would be a shame that the amp becomes useless. As this amp will hopefully become
"My Precious" My PRECIOUS!!!! - YouTube
I have invested in a few spares too.
Good point. I bought a second pair of roughly matched THF-51S. That makes for quite an investment an amp I know nothing about and might not be able to build LOL. But I'm loving the F6 I just completed and I may have caught the DIY bug!
do not worry, there is always Plethora of Choice
whatever Papa is going to make, I'm certainly going to make my version, much more complicated and much worse sounding
whatever Papa is going to make, I'm certainly going to make my version, much more complicated and much worse sounding
Zen Mod, "whatever Papa is going to make, I'm certainly going to make my version, much more complicated and much worse sounding"
With shiny green LEDs?
With shiny green LEDs?
Just wondering...I bought one pair of TH51s that were tested as ZM outlines in beginning of Sissy thread with VGS of -1.8 and -1.6 @ 19 V 1.8A.
Besides that I have (4) TH51s I bought from from Watanabe before he was doing any matching. Haven’t tested any yet...sort of consider these extras.
If I wanted the option of two stereo amps, after I finish my Bi-amp crossover, would a “Rough Matched” pair be pretty much the same as the tested pair I already have on hand?
Besides that I have (4) TH51s I bought from from Watanabe before he was doing any matching. Haven’t tested any yet...sort of consider these extras.
If I wanted the option of two stereo amps, after I finish my Bi-amp crossover, would a “Rough Matched” pair be pretty much the same as the tested pair I already have on hand?
I don't think matching Vgs will give exact matches. I think matching of curves is necessary for exact matches.
I have built a few amps with SITs and none of my SITs were exact matches for Vgs nor were they curve traced. The distortion figures ended up different between channels but the amps still sound great.
So don't worry. Just build and enjoy.🙂
I have built a few amps with SITs and none of my SITs were exact matches for Vgs nor were they curve traced. The distortion figures ended up different between channels but the amps still sound great.
So don't worry. Just build and enjoy.🙂
I have gone through a population of 2SK182ES of varying lot codes, and there is
a decent level or performance matching when you actually put them into circuits,
bias them up and measure the distortion vs output. The most picky application is
Common source without degeneration, and about 90% of these are good matches
when you bias them for same Vds at a given current.
Worst example was a piece that had obviously low gain. It still worked, but was
out of the pack curve-wise. Not that it would necessarily sound bad, but you would
likely want another like it.
For Common Drain applications, it's easier yet, since the load degeneration will
make them more similar.
I'm setting up a rig for easier batch testing, so I'll let you know what I get, but
I don't think there's much cause for concern.
a decent level or performance matching when you actually put them into circuits,
bias them up and measure the distortion vs output. The most picky application is
Common source without degeneration, and about 90% of these are good matches
when you bias them for same Vds at a given current.
Worst example was a piece that had obviously low gain. It still worked, but was
out of the pack curve-wise. Not that it would necessarily sound bad, but you would
likely want another like it.
For Common Drain applications, it's easier yet, since the load degeneration will
make them more similar.
I'm setting up a rig for easier batch testing, so I'll let you know what I get, but
I don't think there's much cause for concern.
Thankyou Ben and Pa
I think this helps calm my compulsion to buy more SITs (no guarantee)
I need to find time to set up my own test rig just to see how the other (4) TH51s VGS compare.
I think this helps calm my compulsion to buy more SITs (no guarantee)
I need to find time to set up my own test rig just to see how the other (4) TH51s VGS compare.
Please Mr. Pass
could be possible sharing with Diyers Tokin DUT rig schematicso we can verify all important parameters in the same conditions ?
We can then write as well observations about different SIT 's batches 🙂
The first example project under preparation is an amplifier simple enough to serve
as the test rig. This week is launch of DIY Sony VFETs, so I'll put the documentation
together next week.
as the test rig. This week is launch of DIY Sony VFETs, so I'll put the documentation
together next week.