Ok, so just buying KSC3505DSTU will be fine with the KSA1381ESTU I already have? Or are you saying the 2SA3503E will work fine with the KSA1381ESTU?
The prior post from @kolakidd sort of implies matching may matter, or am I missing some key point here?
TTC004BQ and TTA004BQ also are available and sounds like they may be adequate substitutes for 2sa1381e/2sc3503E?
The prior post from @kolakidd sort of implies matching may matter, or am I missing some key point here?
TTC004BQ and TTA004BQ also are available and sounds like they may be adequate substitutes for 2sa1381e/2sc3503E?
Speaking from memory and I'm old... what looks good might not be right as we saw oscillations from one to another that were not anticipated by the sheets. In fact some of the them looked perfect, but when subs were made, we had less than stable results. This isn't in reference to any one circuit, but if memory serves, test.
Fair, I'm out of my league here. Lots of info and not everything is lining up. I'll wait till the group buy purchase so I have access to the BOM and other build guide docs. I suspect things will line up for me then. Thank you!
I suggest those interested in making changes go to page 1 and send PMs. I think they did a very good job of most questions in the docs, some of which are only available after buying the boards. IMHO this is the best high output amp you can get for under 15k.
Full disclosure, I was a small part of the testing team.
It's the one thing, I feel, I gave back for all the help I was given when starting up. Stu & JJ esp, but so many more were there.
Frankly, this is the best, most researched amp, with the best docs, of any I have seen in DIY.
Full disclosure, I was a small part of the testing team.
It's the one thing, I feel, I gave back for all the help I was given when starting up. Stu & JJ esp, but so many more were there.
Frankly, this is the best, most researched amp, with the best docs, of any I have seen in DIY.
All good points @thompsontechs . I'm getting ahead of myself by reading the latest threads posts before I even buy the boards and get access to the full documentation. I'm clearly asking noob dodo questions so I'll try and avoid that going forward. Thank you!
Oh damn, birdbox pointed out in my table I mixed up vbe and hfe rows for:
KSA1381
KSC3503
How closely do Q106 and Q105 need to be matched, if at all? Apologies, I am just confused by the list I referenced and recent comments.
KSA1381
KSC3503
How closely do Q106 and Q105 need to be matched, if at all? Apologies, I am just confused by the list I referenced and recent comments.
Q105/106 is not that important. There will always be some Vbe difference between the junction at PNP Vs NPN. You might succeed in finding pairs that match Vbe quite good between polarity if your are really into this matter. As for the HFE, the D vs E-versions shows same figures in the batch I have as posted here in post #3780, approx 85 vs 120...
The differential pair is the most important to match if I understand the schematic correctly.
My tech English is s**t so I might screw up the terms, but hope its helpful🙂
Regards
The differential pair is the most important to match if I understand the schematic correctly.
My tech English is s**t so I might screw up the terms, but hope its helpful🙂
Regards
The team purchased many 2SC3503E from Rochester. Most of us have an abundant supply of all the transistors listed in the BOM. Even ones that are o longer available.
My advice is PM @fireanimal and ask him what you'd like. The only other thing I would say is don't mess us around if you ask for something its assumed that you want them. Don't ask then never respond or finish the correspondence on the subject.
My advice is PM @fireanimal and ask him what you'd like. The only other thing I would say is don't mess us around if you ask for something its assumed that you want them. Don't ask then never respond or finish the correspondence on the subject.
I don't really agree with that.
Mismatched HFE values lead to unbalanced gain between the transistors that handle the positive and negative halves of the audio signal. This imbalance will cause increased distortion as the asymmetric amplification can skew the waveform of the output signal.
Imagine that the amplifier had no negative feedback the positive and negative half's of the waveform would be very different.
So your asking the negative feedback to fix the issue.
This is generally not a problem with an amplifier like the wolverine at low frequencies but as the frequency increases, the effectiveness of negative feedback (Loop gain) diminishes due to phase shifts and timing delays within the feedback loop. The loop gain, which is the product of feedback factor and the amplifier gain, decrease with frequency. When the loop gain falls, the amplifier’s ability to correct errors (like those caused by the mismatched HFE) diminishes. This effect is more pronounced at higher frequencies where the amount of loop gain may not be enough to adjust the distortions and imbalances effectively.
Having said all that. I wouldn't get to concerned if you can match them as the amplifier will still preform very well.
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This is true for stages that cut-off (the driver and output stages in the Wolverine), and becomes less true for stages that run in class A (the pre-driver and earlier stages).stuartmp said:
Because the pre-driver stage does not cut-off, the NPN and PNP both load the VAS for the entire cycle. The pre-driver's Hfe attenuates the non-linear current drawn by the driver. The effects of Hfe mismatch in the pre-driver will be small.
Since I like to point out what my amplifier does better - I run both the pre-driver and driver stages in class A. This has the lowest possible sensitivity to Hfe mismatch (while still having a class AB output stage). Minimizing distortion in the EF3 matters more when the global feedback is moderate.
Ed
Ok Guys,
Just for a bit of fun here is a quick THD measurement for you:
Just for a bit of fun here is a quick THD measurement for you: