An alternative approach, is to draw a new PCB to accomodate 6 deep on one PCB in the 5U400, or even 8 deep since there are in fact a total of 16 predrilled FET mounting holes in the sinks.
But such a PCB would maybe have to be several layers, since the size can only be increased lengthwise.
Is that a bad or good idea, anyone? It is an idea that has been lurking in the back of my head for some time.
Cheers,
Andy
But such a PCB would maybe have to be several layers, since the size can only be increased lengthwise.
Is that a bad or good idea, anyone? It is an idea that has been lurking in the back of my head for some time.
Cheers,
Andy
And if you can do it, so can I, apparently.
Need to make changes to compensate increased capacitance with 8 deep?
I have doubts...
after my lovely Aleph J, now I'm assembling a new BA3 (complementary output with 1.0 ohm source resistors).
My set up is dual mono, two transformers (2x24Vac 400VA each) two rectifiers stations CRC (564.000uF each), two soft start circuitry and two speaker protection boards 🙂.
Now, I'm wondering, what would be the benefit doubling the output devices, whether such output stage actually constitutes an advantage as compared with a standard (6 devices) output stage, heat sinks permitting?
I appreciate every comment and feedback.
Thank you
after my lovely Aleph J, now I'm assembling a new BA3 (complementary output with 1.0 ohm source resistors).
My set up is dual mono, two transformers (2x24Vac 400VA each) two rectifiers stations CRC (564.000uF each), two soft start circuitry and two speaker protection boards 🙂.
Now, I'm wondering, what would be the benefit doubling the output devices, whether such output stage actually constitutes an advantage as compared with a standard (6 devices) output stage, heat sinks permitting?
I appreciate every comment and feedback.
Thank you
to bergy #786
Hello bergy,
the question is: Do you need that much of drive capability? current?
Low ohm-ic loudspeaker? Power hungry loudspeaker with low efficiency (dB/W/m)?
Or is it -like many DIYers - let's go big...?
Cheers
Dirk 😀
Hello bergy,
the question is: Do you need that much of drive capability? current?
Low ohm-ic loudspeaker? Power hungry loudspeaker with low efficiency (dB/W/m)?
Or is it -like many DIYers - let's go big...?
Cheers
Dirk 😀
In general you should get an amp with more control, especially in the LF’s, and more authority (citing Papa). Citing ZM, you may also get a bit less detail. And the devices will have to run at a lower IQ per device, which may also have an effect. I am contemplating the same build for my BA-3 iteration (see thread BA-3 revisited), but that project is on halt as I have decided to go for high efficiency speakers and singled ended class A instead - for now.
If you do this, I would think going for huge sinks to maximize bias current per device, is recommended. Meaning trying to get close to the 300 watts total dissipation as described in the manual.
Like ZM and Cubicincher say, it really comes down to what you are going to connect to it downstream.
Also, don’t underestimate Papas words about using prescribed parts in the front end. That means JFETs with 10mA IDSS and Toshiba MOSFETs. I can also recommend you push the FE bias high, and experiment with that. Just remember to sink the MOSFETs properly. Of all the (few) meaningful things I have done with my BA-3, maximizing FE bias had had the most dramatic effect, next to high OS IQ of course.
PS: I am a GH, so primarily listen to ZM and Dirk 🙂
Good luck!
Andy
If you do this, I would think going for huge sinks to maximize bias current per device, is recommended. Meaning trying to get close to the 300 watts total dissipation as described in the manual.
Like ZM and Cubicincher say, it really comes down to what you are going to connect to it downstream.
Also, don’t underestimate Papas words about using prescribed parts in the front end. That means JFETs with 10mA IDSS and Toshiba MOSFETs. I can also recommend you push the FE bias high, and experiment with that. Just remember to sink the MOSFETs properly. Of all the (few) meaningful things I have done with my BA-3, maximizing FE bias had had the most dramatic effect, next to high OS IQ of course.
PS: I am a GH, so primarily listen to ZM and Dirk 🙂
Good luck!
Andy
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As you already have an Aleph J and planning on dual mono - why not go all the way and build balanced monoblocks with 24 devices each and retire.
Yes, yes, a perfect idea. And when you find an available chassis for 300-350
Watts dissipation, please - I mean really please - do share
Watts dissipation, please - I mean really please - do share
Thank you all guys 
I'm also building a biamp 6-24 crossover that will be driven by an excelent BA 2018 linestage. The Aleph J is intended to drive mid-high section and the BA3 the bass bin, (under 500Hz one reflex Altec 416-8C).
By this scenario it seems that the power is not a matter, but I have experienced that especially in low section, usually a big solid state amplifier offers the best performance, I was using a Krell KSA80...
I'm also building a biamp 6-24 crossover that will be driven by an excelent BA 2018 linestage. The Aleph J is intended to drive mid-high section and the BA3 the bass bin, (under 500Hz one reflex Altec 416-8C).
By this scenario it seems that the power is not a matter, but I have experienced that especially in low section, usually a big solid state amplifier offers the best performance, I was using a Krell KSA80...
Aleph J on top, J Zen for bottom oomph a solution? Xtra xconductance offered by IRFP150 ommphing it up a bit perhaps?
Thank you all guys
I'm also building a biamp 6-24 crossover that will be driven by an excelent BA 2018 linestage. The Aleph J is intended to drive mid-high section and the BA3 the bass bin, (under 500Hz one reflex Altec 416-8C).
By this scenario it seems that the power is not a matter, but I have experienced that especially in low section, usually a big solid state amplifier offers the best performance, I was using a Krell KSA80...
One thing I have thought a bit about, is that a well built BA-3, adjusted for some sugar, have a beautiful midrange and soft and reasonably extended highs. So might be a bit too good an amp to use only for lows, or overkill to use another expression. Many Krells, after KSA-50 (maybe the 80 is an exception, I really dunno), use a modest amounts of feedback and deliver huge amounts of bass (wham, bam, thank you Dan!), but many times at the cost of some glare. So if you like the bass of the Krell, may I suggest you also consider a Vanilla F5 dual mono, or an F5 Turbo (without diodes should suffice). Parts for the BA-3, at least for balanced monoblocks, makes for efficient emptying of dollars from your pockets. The F5 and F5T strike me as less expensive, and with less unobtanium parts (J113 and K2013).
Another alternative, and the most obvious, is to try the BA-3 you are assembling with 3 pairs per side and see how it goes. If ZM sez your Altecs need no more, my guess is he is right - as always. Then adjust for minimal distortion and I am pretty sure you’ll have all the oomph you’ll ever need.
Regards,
Andy
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Why 1R? Store MOSFETs should take 0R5, though not always very well matched. Will give you more power 🙂 If you need it.
Thanks guys,
all your suggestions are really interesting to me.
Andy, you were spot on, I really really love bass performance provided by old Krell amplifiers, capacities that I never found in any other amp.
About Altec, the 416-8C (ferrite magnet) is a bit different than the most popular 416 alnico magnets, that I think Zen is referring, the 8C can easily eat many Watt and deliver beautiful controlled deep bass (if well drived).
PS
What you mean with "F5T (without diodes should suffice)" and what is Vanilla F5?
Vanilla i just another way of saying «plain» or «original». Simply an F5, like ZM sez two MOSFETs per channel. It’s feedback and high damping factor should give you bass along the lines of Krell, but I dunno if it gives you what you want or not. The F5T is the F5 Turbo. It can be built without using the diodes in parallel with the source resistors, and this will give you 50 watts and quite a few amps. With diodes you will kick Krells *** I would think, but realiability may become an issue as these amps have a tendency to blow up if built wrong. Most of the other alternatives in Papas DIY lineup are a bit more forgiving.
That said, I love the bass of the BA-3. it is quite massive, with great impact, but also naturally soft. Meaning a bass guitar sounds like a bass guitar, and not as dry as a synthesizer. No cyborg dry and hard bass, just lovely massive and naturally soft. Like,, i’ll skip the analogy. With BA-3 you get the power and swing of push pull, but without the sometimes unnatural characteristics of feedback. Worth a shot. I used it to drive current sucking speakers with crossovers, and it did a good job. Should kick *** with your drivers in biamp config.
The 1R source resistance was originally intended for 6 deep config and less precariously matched MOSFETs handed out at BAF. Meaning more and less matched devices having to share the current, needing more source resistance to share it well. If you have store MOSFETs, and will only use 6 MOSFETs per sink (3 pairs) these are intended for this exact output stage (F4 is the same), and as such matched to bias evenly and work stable with 0R47 source resistance
if you reread Papas BA-2 article, he sez if you reduce amount of devices by half, you can half the source resistance too. Though many choose not to, the circuit can take it fine. Itsallinmyhead uses 0R22, absolutely fearless but also a result a precarious matching.That said, I have experienced some poor matching from the store wrt these MOSFETs, but nothing to worry about unless you are a perfectionist 🙂 At best the devices bias within 3% of each other (very good), at worst 19% (not so good, but nothing to cry over either). So depends on the batch you get. (If you matched them Papa, please disregard and assume it to be the cause of a GH brainfart/F40 error (the error being 40cm from the circuit
)In other words, if you dare it and need the power, use 0R47. If you don’t need the extra power and want to play it safe, use a higher value.
Regards,
Andy
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