Well for starters, it still works.
I can sit for hours and just listen and think, this works!
I'm using it to drive my Falcon kit LS3/5A speakers and it is great sound.
Big soundstage in my near listening setup.
I think they are a great match.
And the F4 keeps working.
Knock on wood [my forehead]
I can sit for hours and just listen and think, this works!
I'm using it to drive my Falcon kit LS3/5A speakers and it is great sound.
Big soundstage in my near listening setup.
I think they are a great match.
And the F4 keeps working.
Knock on wood [my forehead]
Very good to hear. Congrats again! The laidback sound of the F4 is, well, something to remember and never to forget 
Very good to hear. Congrats again! The laidback sound of the F4 is, well, something to remember and never to forget
I think that if the F4 sounds "laidback", then it's gotta be the preamp driving it or the speakers after it that needs to be examined.
IME, the F4 driven with a capable preamp (BA-3 FE in my case), is a very nice sounding amp with detail and impact second to none and responds well with the adjustment of the H2 and H3 profile of the preamp driving it. IOW, transparent in a sense.
Laidback doesn’t have to be negative. I found the sound of the BA-3 with BA-2 OS relaxed and effortless, but that doesn’t exclude dynamics and impactfulness. Maybe laidback is the wrong word, though I have seen others describe it like that too.
Whatever the term: it sounds great.
Whatever the term: it sounds great.
I agree with Andy. "Laid back" yet very present is what I hear.
Only have one preamp at present, but have started on a BA-3 Preamp.
Looking forward to putting it into my system.
Only have one preamp at present, but have started on a BA-3 Preamp.
Looking forward to putting it into my system.
The BA-3 FE will rock the show with the F4.
What PSU will you be using, and what voltage? I am wondering how much vPP seing you are planning on.
Regards,
Andy
What PSU will you be using, and what voltage? I am wondering how much vPP seing you are planning on.
Regards,
Andy
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Yes!
Since I dialed in the H2 and H3 in my BA-3 that suits my system, my BA2018 and ACP+ linestage preamps are just for display. Sounds very nice driving my M2X as well, and hopefully will match well with the Token SIT amp when the design comes out from Mr. Pass. I still have not built a case for my BA-3 FE up to now but it is very quiet anyway.
Just a thought, have you tried the Muses volume control in your BA-3? I highly recommend it to try if you are looking for a great sounding attenuator. Cheers!
Cool to hear you are happy, Amanda!
I too considered the Muses, but abandoned it at the time because of it’s price. It is on my long term list.
I am curious as to what power supply you use for the BA-3 pre? Also, what method did you use to set H2/H3?
I bought an old 334A, but seems it’s state was worse than advertised. So I am considering recapping it, or trying REW.
PS: your speakers look awesome!
Regards,
Andy
I too considered the Muses, but abandoned it at the time because of it’s price. It is on my long term list.
I am curious as to what power supply you use for the BA-3 pre? Also, what method did you use to set H2/H3?
I bought an old 334A, but seems it’s state was worse than advertised. So I am considering recapping it, or trying REW.
PS: your speakers look awesome!
Regards,
Andy
Out of the three, only the BA-3 FE has the stock voltage swing to drive the F4 to full / approx full output. I would think the ACP and the WLS paired with the F4 might sound a bit flat and boring compared to the BA-3, but that might depend on what is connected downstream. It is possibly one of the best pairings too, as it was chosen by Papa to drive the BA-2 OS.
That said, I am very happy with the sound of the ACP+ on my apple (!!!) headphones. Might have to consider an upgrade…
After having built a scaled down version of the F4 for headphone duty (see https://www.diyaudio.com/community/...ass-f4-amplifier.234355/page-102#post-6281443) it's now time to build a full scale version for my stereo.
I have a full set of curve traced IR irfp240/9240, and I'd like to match the P-channel transconductance to the N-channel by using appropriate source resistors. On page 233 of Designing Audio Power Amplifiers, Bob Cordell suggests 0R15 for the N-channel device and 0R22 for the P-channel device, which I'd like to use as a starting point.
Ideally, I'd like to measure the respective transconductance with the parts I have on hands. Following https://www.firstwatt.com/pdf/art_mos_test.pdf I have drawn the attached circuit.
At a given bias point mimicking operating conditions in the F4, the transconductance should be gm=(Vac/R)/Vin and so by keeping all other parameters identical between N and P measurements, a gm match is achievable by selecting R accordingly, right?
I have a full set of curve traced IR irfp240/9240, and I'd like to match the P-channel transconductance to the N-channel by using appropriate source resistors. On page 233 of Designing Audio Power Amplifiers, Bob Cordell suggests 0R15 for the N-channel device and 0R22 for the P-channel device, which I'd like to use as a starting point.
Ideally, I'd like to measure the respective transconductance with the parts I have on hands. Following https://www.firstwatt.com/pdf/art_mos_test.pdf I have drawn the attached circuit.
At a given bias point mimicking operating conditions in the F4, the transconductance should be gm=(Vac/R)/Vin and so by keeping all other parameters identical between N and P measurements, a gm match is achievable by selecting R accordingly, right?
Attachments
TL431 is TL431 is TL431 ??? 🙄
While waiting for the ACA-Mini boards to show up in the store, I'm building a pair of F4's. 😆
Problem is, I can't find a 'just TL431'. I have TL431CLP, TL431ACZT and TL431BVLPRAG. Are there any difference in functionality or quality, or is it just a matter of manufacturer being clever?
While waiting for the ACA-Mini boards to show up in the store, I'm building a pair of F4's. 😆
Problem is, I can't find a 'just TL431'. I have TL431CLP, TL431ACZT and TL431BVLPRAG. Are there any difference in functionality or quality, or is it just a matter of manufacturer being clever?
Attachments
Not very familiar with the new interface yet, look up my posts here and following discussion, there is an explanation and links to what you need.
here:https://www.diyaudio.com/community/threads/f4-power-amplifier.97540/post-6360536
here:https://www.diyaudio.com/community/threads/f4-power-amplifier.97540/post-6360536
Good morning and happy Sunday everybody,
my F4 is under construction, I didn't feel like engaging in such a build as a first attempt and as such a skilled tech is doing it for me, we went for a dual mono construction, the case is there, the black one with 10mm front panel (the Dissipante 4U if I recall correct), boards with the MOSFETS are there, if I am correct two by 300VA transformers, two by four capacitors arrays (which seem to be, after the case, the most expensive part of the build) are also on the way so what is left is just smaller parts and, of course, tuning.
My question being, what else might be worth adding to the original project on a dual mono config? I don't want the bump on my speakers, he said he'd rather have the output signal "clean" and that the bomb won't do any harm to the speakers (he did modify an old Adcom GFA 535 for me by replacing caps and removing whatever not necessary off the signal path but I don't like the bump on switching off, no big deal there as I won't sell the amp but I won't want it on the F4), he suggested we might use relais if bump is there; also I read about soft starts but he said for such low power it won't add any protection.
What would you suggest as final details before it gets too late in the build?
Grazie
p.s. still wondering if my AR SP9 + F4 would do a good job on my vintage JBL L220, I know, Watts is not everything but many suggest triple digit wattage to power the old JBL :-|
my F4 is under construction, I didn't feel like engaging in such a build as a first attempt and as such a skilled tech is doing it for me, we went for a dual mono construction, the case is there, the black one with 10mm front panel (the Dissipante 4U if I recall correct), boards with the MOSFETS are there, if I am correct two by 300VA transformers, two by four capacitors arrays (which seem to be, after the case, the most expensive part of the build) are also on the way so what is left is just smaller parts and, of course, tuning.
My question being, what else might be worth adding to the original project on a dual mono config? I don't want the bump on my speakers, he said he'd rather have the output signal "clean" and that the bomb won't do any harm to the speakers (he did modify an old Adcom GFA 535 for me by replacing caps and removing whatever not necessary off the signal path but I don't like the bump on switching off, no big deal there as I won't sell the amp but I won't want it on the F4), he suggested we might use relais if bump is there; also I read about soft starts but he said for such low power it won't add any protection.
What would you suggest as final details before it gets too late in the build?
Grazie
p.s. still wondering if my AR SP9 + F4 would do a good job on my vintage JBL L220, I know, Watts is not everything but many suggest triple digit wattage to power the old JBL :-|
I'm bringing up my F4 build on the variac and a dim-bulb to bias, and I'm getting no voltage across the source or gate resistors, regardless of P1 movement. Either channel. I can adjust DC-offset with P2. Dim bulb is dim, because clearly three's no current passing through these front ends. Power supply is working fine V+, V- is correct at the amp boards.
First thought: I'm not setting up the biasing properly. I have no input signal and no dummy load on the outs. This is correct procedure, yes?
Second thought: Something in the combination of the TL431and the JFETs. I used that which came with the DIY store's F4/BA3 kit, and matched quad Toshibas, 8-11ma.
Third thought: Turns out the C1-C4 I bought were biPolar, not polarized. I used the "long leg positive" rule of thumb when stuffing them. I wouldn't think this should matter, but more knowledgeable of you might enlighten me differently.
Any advice for sussing this out?
First thought: I'm not setting up the biasing properly. I have no input signal and no dummy load on the outs. This is correct procedure, yes?
Second thought: Something in the combination of the TL431and the JFETs. I used that which came with the DIY store's F4/BA3 kit, and matched quad Toshibas, 8-11ma.
Third thought: Turns out the C1-C4 I bought were biPolar, not polarized. I used the "long leg positive" rule of thumb when stuffing them. I wouldn't think this should matter, but more knowledgeable of you might enlighten me differently.
Any advice for sussing this out?
post your reference schmtc (or link to)
bulb tester only for initial - no biased - state
remove bulb tester, or - as soon you start increasing bias, amp is going in voltage starving
you'll need to alter few resistors , nothing more
but schmtc first, to avoid broken phones game
bulb tester only for initial - no biased - state
remove bulb tester, or - as soon you start increasing bias, amp is going in voltage starving
you'll need to alter few resistors , nothing more
but schmtc first, to avoid broken phones game