Hello MOrten,
Please reserve 2 boards for me.
I made some suggestions and I didn't tell right. I mean that You put perhaps 2kOhms from the 24v to the bases of Q3 and Q4 to give Q5 more Current than the small basecurrents of Q3 and Q4.
I Think You can take the two 1yf as I suggested but You need the fixation of the voltage between the bases of
Q9 and Q10 perpaps with 220 yf as in the original mf a1.
This should be an advantage because the feedbacksignal goes through Filmcaps instead of elcos.
Sorry , I have still no simulationprogram
With regards
Please reserve 2 boards for me.
I made some suggestions and I didn't tell right. I mean that You put perhaps 2kOhms from the 24v to the bases of Q3 and Q4 to give Q5 more Current than the small basecurrents of Q3 and Q4.
I Think You can take the two 1yf as I suggested but You need the fixation of the voltage between the bases of
Q9 and Q10 perpaps with 220 yf as in the original mf a1.
This should be an advantage because the feedbacksignal goes through Filmcaps instead of elcos.
Sorry , I have still no simulationprogram
With regards
Micro-Cap 12
has been freeware for some time now!
The market is almost filled with really great simulators. How about TINA, for example?
The IPS of the original uses BC184/BC214, you use BC337/BC237; is it for a reason? Will BC650/BC560 be as good?
Yes Morten, there is an ulterior motive in this selection - and if possible you should select and mate exactly this type.
Although all AF transistors of this Siemens / Philips series are similar and it could perhaps also work safely with BC556B /546B at this point - but whether the unusual type of frequency response compensation (acting on the input capacitance and with it) will only become apparent at the end.
But now you're going the whole hog Morten!
😎
greetings,
HBt.
Although all AF transistors of this Siemens / Philips series are similar and it could perhaps also work safely with BC556B /546B at this point - but whether the unusual type of frequency response compensation (acting on the input capacitance and with it) will only become apparent at the end.
But now you're going the whole hog Morten!
😎
greetings,
HBt.
Is there any advantage of using the old 3055/2955 instead of newer ones? I have plenty of 2SA/2SC types with better specs, but are there disadvantages with using those?
If we use the TIP xxxx, we make sure that the simulated frequency response compensation (i.e. the stability/ oscillation tendency) works.
What types are these exactly? The only (critical) point is that we form a classic darlington with the drivers (the BD xxx)!
The credo here is:
try it out, but I don't expect an improvement in overall performance.
The situation is completely different with the competing idea from ZenMod (with the likeness of Pippi Longstocking), which benefits enormously from modern power transistors, the 3/4 + 3/4 amp doesn't care about that. If it does not cause any damage (instabilities) and is thermally up to the task, then "fire away".
#
I still have to ask for a lot of patience, it will be some time before I get to the construction.
greetings,
HBt.
Here is a list of BP power transistors. You'll see the ones that I have will have a number in the QTY column. More or less up to date.
Might be it is too late as you have already got the board that looks so beautiful.
I want to input another idea.
There is a topology called "Transnova". It is equivalent to common emitter output stage that A1 has, but with conventional bias setup. One of the benefits with a conventional Vbe multiplier is that it can work into deep class B region without THD spike. Thus, you don't have to bias it heavily at the first place. The drawback is you need a floating power supply. I am not sure if you can overcome this with a simple bootstrap.
Here, I believe, is the original paper.
https://forums.melaudia.net/attachment.php?aid=43792
I want to input another idea.
There is a topology called "Transnova". It is equivalent to common emitter output stage that A1 has, but with conventional bias setup. One of the benefits with a conventional Vbe multiplier is that it can work into deep class B region without THD spike. Thus, you don't have to bias it heavily at the first place. The drawback is you need a floating power supply. I am not sure if you can overcome this with a simple bootstrap.
Here, I believe, is the original paper.
https://forums.melaudia.net/attachment.php?aid=43792
I cannot directly understand the TRANSNOVA insertion. I do not yet recognize a connection with the MF-A1 and its derivatives.
#
The current model (version 2023) uses the inexpensive and robust TIP35 & TIP36 pair. In this model, it is mainly the completely undersized mains transformer that is cooking!
#
The current model (version 2023) uses the inexpensive and robust TIP35 & TIP36 pair. In this model, it is mainly the completely undersized mains transformer that is cooking!
BC327/BC337 are the least noisy of that bunch. Better than the always returning BC550/BC560.
The first stage, the differential amplifier with its current mirror, is precisely selected, paired and symmetrical. You can estimate 60 minutes for this work step!
Reference points
BC3x7
HFE 343
BC5x0
HFE 442
vs.
Cob 3pF (4pF) & Cib 8pF (10pF), ft 200MHz (250MHz), F -> 2dB
I cannot find a noise figure for the BC3x7 type in the old Siemens data books. Whether there will be noticeable noise with a 500µA IC, I doubt it. I have more cuffs before the frequency response compensation, you never know beforehand whether everything is stable, especially not with this concept ... we'll see!
HBt.
tbc
Reference points
BC3x7
HFE 343
BC5x0
HFE 442
Cob 12pF (8pF) & Cib 60pF, ft 200MHz (170MHz), F -> ?
vs.
Cob 3pF (4pF) & Cib 8pF (10pF), ft 200MHz (250MHz), F -> 2dB
I cannot find a noise figure for the BC3x7 type in the old Siemens data books. Whether there will be noticeable noise with a 500µA IC, I doubt it. I have more cuffs before the frequency response compensation, you never know beforehand whether everything is stable, especially not with this concept ... we'll see!
HBt.
tbc