Mental musing:
If building an F4 or similar for 4ohm low sensitivity speakers like Maggies the obvious choice appears to build a bridged/balanced configuration.
My question is "If you don't think you need the additional voltage, is it reasonable to drive two sets of output boards from a single 'single ended' front end? Essentially just pour more current through additional output pairs.
And a follow up:
Assuming an appropriate high gain preamp like the BA2018(?) is it reasonable to populate two sets of F4 boards without the input Jfets - 6 output pairs per channel as `crippled' F4s?
As Simon and Garfunkel once sang `Still lurking (and hopefully learning) after all these years'
Mike
If building an F4 or similar for 4ohm low sensitivity speakers like Maggies the obvious choice appears to build a bridged/balanced configuration.
My question is "If you don't think you need the additional voltage, is it reasonable to drive two sets of output boards from a single 'single ended' front end? Essentially just pour more current through additional output pairs.
And a follow up:
Assuming an appropriate high gain preamp like the BA2018(?) is it reasonable to populate two sets of F4 boards without the input Jfets - 6 output pairs per channel as `crippled' F4s?
As Simon and Garfunkel once sang `Still lurking (and hopefully learning) after all these years'
Mike
here we go again .......... What's wrong with the kiss, boy?
first go to https://www.firstwatt.com/prod.html , ogle, stare at goats if you wish (plenty of those to stare at, at linked page)
then spot specific blue letters, pointing to F4 page ........ https://www.firstwatt.com/f4.html
then read, ogle, stare at goats, take your time tio spot link to manual/article/service manual https://www.firstwatt.com/pdf/prod_f4_man.pdf
download it, print 3 copies (one for dining room, one for living room, one for bedroom, one for loo); read, ogle, stare at goats ........ as long you need to spot what's shown on top of page 8, also reading text on same page
Enjoy!
(moral of the story - make regular stereo F4, non crippled, and try driving those maggies; if you have enough SPL , but little strained in bottom - build another regular stereo non crippled one, and connect them one box per channel, parallel mono mode)
first go to https://www.firstwatt.com/prod.html , ogle, stare at goats if you wish (plenty of those to stare at, at linked page)
then spot specific blue letters, pointing to F4 page ........ https://www.firstwatt.com/f4.html
then read, ogle, stare at goats, take your time tio spot link to manual/article/service manual https://www.firstwatt.com/pdf/prod_f4_man.pdf
download it, print 3 copies (one for dining room, one for living room, one for bedroom, one for loo); read, ogle, stare at goats ........ as long you need to spot what's shown on top of page 8, also reading text on same page
Enjoy!
(moral of the story - make regular stereo F4, non crippled, and try driving those maggies; if you have enough SPL , but little strained in bottom - build another regular stereo non crippled one, and connect them one box per channel, parallel mono mode)
I briefly looked at the F4 description. 50W into a Maggie is already silly loud. I think that you should use the F4 as-is.
This site has plenty of amplifiers that can put 100-200W into 4 ohms, but that is only 3-6dB louder.
Ed
This site has plenty of amplifiers that can put 100-200W into 4 ohms, but that is only 3-6dB louder.
Ed
ZM,
I have read these articles and the manual. However, I didn't ask about parallel mono configurations of the standard amplifier. I have seen your schematics for crippled F4 and was hoping to further my understanding of whether in this configuration the number of output pairs could be increased from 3 pairs to 6 pairs. I am aware of (at some level), the Miller effect and the need for a low impedance output from the preamp, but I am a novice (ACA, B1, Bruce Heron tube amp). So, rather than buy instruments and experiment I'd prefer as Newton put it, `to stand on the shoulders of giants'. I am sure given time I can work it out for myself if no one is feeling tall today.
PS. I am familiar with the concept of foreplay. I have cloud-busted as a child but haven't yet succeeded in killing a goat and I am no good at running through walls. I'm not looking for a Pythonesque fish slapping dance.
I have read these articles and the manual. However, I didn't ask about parallel mono configurations of the standard amplifier. I have seen your schematics for crippled F4 and was hoping to further my understanding of whether in this configuration the number of output pairs could be increased from 3 pairs to 6 pairs. I am aware of (at some level), the Miller effect and the need for a low impedance output from the preamp, but I am a novice (ACA, B1, Bruce Heron tube amp). So, rather than buy instruments and experiment I'd prefer as Newton put it, `to stand on the shoulders of giants'. I am sure given time I can work it out for myself if no one is feeling tall today.
PS. I am familiar with the concept of foreplay. I have cloud-busted as a child but haven't yet succeeded in killing a goat and I am no good at running through walls. I'm not looking for a Pythonesque fish slapping dance.
Resolved I think ...BA3 schematic; 6 output pairs shown hanging off single front end.
https://www.diyaudio.com/community/...r-illustrated-build-guide.258301/#post3973243
https://www.diyaudio.com/community/...r-illustrated-build-guide.258301/#post3973243
Hello BeardyWan,
I think the BA-3 poweramp (with its BA-3 inputstage) is very close to the F4. I think the BA-3 is the better amp (especially) for driving maggies...
F4 needs an preamp with a lot of voltage-swing...
And if you want to go more crazy, then build BA-3 - Monoblocks.
But that is my opinion.
Cheers
Dirk 🙂
I think the BA-3 poweramp (with its BA-3 inputstage) is very close to the F4. I think the BA-3 is the better amp (especially) for driving maggies...
F4 needs an preamp with a lot of voltage-swing...
And if you want to go more crazy, then build BA-3 - Monoblocks.
But that is my opinion.
Cheers
Dirk 🙂
what I wrote was for (general) funm and
point is - you asked about personal opinion and experience, I gave you mine - 99% sure that one regular F4 should be more than enough for your Maggies
heck, even Babelfish M25 (OS having one pair of IRFP connected in pure Square Law fashion, vs. 3 pairs of same in F4 (while having source resistors)) should make them happy
Nope. I wouldn't do bridged / balanced. That results in more voltage swing... not current for lower impedance loads. As ZM says... parallel mono might be fun. If one amp doesn't have enough oomph build one more. See page 8
That's what you're doing kinda when running the amp in parallel mono configuration. You're just adding more output transistors for more available current. However, it's still push pull not single ended.
Sure, but crippling your F4 hasn't anything to do with voltage gain. The f4 already has no gain.... crippling still leaves it with no gain. 😉. You might ask ... will your pre-amp be a nice impedance match to the F4 when crippled? Do you need a buffer? Were I in your shoes, I'd just spend the little bit of dough and build the F4 as-is w/o crippling it. The BA-3 could be a wonderful choice also, but if you don't need the gain... F4.
Enjoy building and listening to whatever you choose!
YMMV
Etc. Etc.
Cheers,
Patrick
(Hardly a giant physically or mentally... but a reasonable ZM translator)..
Or, as Murray Gell-Mann used to say, 'if I can look further, it's because I am surrounded by midgets';-)
It's all relative, at least since 1916.
Jan
Since the F4 is very similar to the BA2 output stage (https://firstwatt.com/pdf/art_ba2.pdf) I expect what's described there should generally carry over.
Here's an interesting quote on fewer vs more output devices:
"You can certainly build this amplifier with fewer output devices as mentioned earlier. It will alter the spectral balance slightly – more outputs tends to put a little more emphasis on the bottom end, and fewer tends to brighten the top. At least this is how you will tend to perceive it. I leave it to you to try this if you like, but I think the direction you would want to go is 2-3 pairs, as we already have overkill with 4."
Here's an interesting quote on fewer vs more output devices:
"You can certainly build this amplifier with fewer output devices as mentioned earlier. It will alter the spectral balance slightly – more outputs tends to put a little more emphasis on the bottom end, and fewer tends to brighten the top. At least this is how you will tend to perceive it. I leave it to you to try this if you like, but I think the direction you would want to go is 2-3 pairs, as we already have overkill with 4."