) case - lower than JFet buffer
Hello,
simple question, my F4 is done and working, unfortunately the output of my Audio Research SP9 doesn't really take all the juice out of it but a solid state preamp is in the near future plans, in the meantime I am running the F4 and I can tell it doesn't get that hot at all, actually just warm, since I have not much space and I need to somehow arrange the huge thing somewhere what happens if I partially obstruct some of the vents on the top of the case by stacking the TV screen on top of it, maybe a third of the vents will be obstructed and, by the way, I don't run it for long nor at high volumes
Grazie
simple question, my F4 is done and working, unfortunately the output of my Audio Research SP9 doesn't really take all the juice out of it but a solid state preamp is in the near future plans, in the meantime I am running the F4 and I can tell it doesn't get that hot at all, actually just warm, since I have not much space and I need to somehow arrange the huge thing somewhere what happens if I partially obstruct some of the vents on the top of the case by stacking the TV screen on top of it, maybe a third of the vents will be obstructed and, by the way, I don't run it for long nor at high volumes
Grazie
No need. Greedy Boyz understand.I think it will be perfectly fine. Warm heatsink means approximately 36 -40 °C. Temperature of PS components inside case will be about 30 – 33 °C (transformer 40 -50 °C). Obstructing one third of top cover vents will increase inside temp by max 5 °C and outside heatsinks by 2 -3 °C.
The volume doesn't affect the temperature significantly.
Have you tried measuring the temperature at various points on the heatsinks, (in particular, at where the output mosfets are mounted) after full warm up of the amp? Then try covering some vents and see how the temp measurements change.
Have you tried measuring the temperature at various points on the heatsinks, (in particular, at where the output mosfets are mounted) after full warm up of the amp? Then try covering some vents and see how the temp measurements change.
I first ran my baby on a speaker-stand (because I could) and it was getting just cozy-warm (45° or so). Later on I put it in a sideboard (with open front +rear), and a couple cm space on the sides and plenty space above, and it went up to 55° heatsinks…
You could lower the bias to have it dissipate a little less, but at the price of less precision—see 6L6 build guide, https://www.diyaudio.com/community/...ng-the-pass-f4-amplifier.234355/#post-3467561 scroll down…, where he shows how his F4 behaved at various biasses…
But the best and safest method is to make sure airflow is not impeded. If nothing else helps, go for a ZM-babysitter https://www.diyaudio.com/community/threads/babysitter-for-papas-koan.186554/
Add this to feel like a king: https://www.diyaudio.com/community/...-temperature-controlled-analog-no-pwm.336346/
You could lower the bias to have it dissipate a little less, but at the price of less precision—see 6L6 build guide, https://www.diyaudio.com/community/...ng-the-pass-f4-amplifier.234355/#post-3467561 scroll down…, where he shows how his F4 behaved at various biasses…
But the best and safest method is to make sure airflow is not impeded. If nothing else helps, go for a ZM-babysitter https://www.diyaudio.com/community/threads/babysitter-for-papas-koan.186554/
Add this to feel like a king: https://www.diyaudio.com/community/...-temperature-controlled-analog-no-pwm.336346/
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Ahah the rush and the heat (not the F4's, the Mediterranean is quite hot...) made me forget to post the question "would it run too hot if I obstruct a third to half of the top vents?" but the answer is already there.
I have no way to measure temperature but I can keep a hand on the heatsinks for how long as I want.
Once I have the BA-3 preamp done I will ask the person in charge to check the bias again
Grazie
I have no way to measure temperature but I can keep a hand on the heatsinks for how long as I want.
Once I have the BA-3 preamp done I will ask the person in charge to check the bias again
Grazie
You are Greedy Boy enough to do it yourself. As long as you have a DMM. Set to DC volts, just measure voltage drop across any of the source resistors and voila, we can do the maths.
Standard should be approx 0V2/200mV, meaning a bias/Iq of 0A4 per device.
Question, how do one turns a dual mono F4 into a mono as to take the whole 50W out of it?
This is the reason why I ask, as of now with my Audio Research SP9 and its 20something db output I don't like the sound pressure, not just a matter of pressure but it sound thin if you know what I mean, I maybe got used to the "coloured" sound of the KT88 but at the end of the day it lacks in power, the cheapest way to overtake this limitation is to upgrade the pre with some more gain and that will probably happen in the fall, the parts for a BA-3 are almost there (still have to get transformers, case, plugs, potentiometer...), I guess that with 5-6db more it all should fall back in place but, just in case, should I want to run the F4 in mono (before I ask to the guy who built it for me), what it takes to make the switch?
Grazie
This is the reason why I ask, as of now with my Audio Research SP9 and its 20something db output I don't like the sound pressure, not just a matter of pressure but it sound thin if you know what I mean, I maybe got used to the "coloured" sound of the KT88 but at the end of the day it lacks in power, the cheapest way to overtake this limitation is to upgrade the pre with some more gain and that will probably happen in the fall, the parts for a BA-3 are almost there (still have to get transformers, case, plugs, potentiometer...), I guess that with 5-6db more it all should fall back in place but, just in case, should I want to run the F4 in mono (before I ask to the guy who built it for me), what it takes to make the switch?
Grazie
Yes it does, not as much as with the tubes, with the other amp I barely went past 11h on the volume knob, to have that kind of pressure I have to go almost all the way up with the F4 but mostly it feels like missing as if there is not enough juice for the speakers (90db JBL L220 with old big white woofers).
I love the JBL but they are quite big, I don't mean to sell them (yet) but I'd some day like to get bookshelves and for sure I'd need more power (friend might sell his SF Electa Amator, if it happens...) so was wondering if first stage (F4 plus BA-3 preamp running at 30v) won't make it I could ask the person who made the F4 for me to build another one and run the two in mono as to have enough power for even an upcoming smaller and less efficient speaker.
p.s. asking as a friend is coming off the US and might ask him to bring me the boards and the MOSFETS in case I decide
I am not listening to it much, I am quite busy in summer but with some bad weather in the last couple weeks (I live and work in a summer destination) I have been using it a bit, yes, anemic describes it, I have the KT88 amp on a table and so very much tempted to switch again while the BA-3 project comes to life (again, with about 30v off the PSU it should be 6+ db higher in gain than my AR and, yes, might sell it but will keep for the phono stage)
point is, which is written numerous times for F4 - that's "sort of" Chameleon amp ....... meaning - intrinsic THD levels of F4 itself are so low, that any THD contribution from preceding stage (preamp) is dominant
what you hear with AR + F4 combo is result of AR sound nature, not F4 itself
if you prefer AR + KT88 combo more, nothing wrong with that , but you must know that resulting sound is combination of sound signatures of that preamp and that amp combined
conclusion
- find appropriate SE preamp, you'll have decent combo with F4 and 25W/8R
-find appropriate Bal preamp, you'll have decent combo with F4 and 100W/8R
what you hear with AR + F4 combo is result of AR sound nature, not F4 itself
if you prefer AR + KT88 combo more, nothing wrong with that , but you must know that resulting sound is combination of sound signatures of that preamp and that amp combined
conclusion
- find appropriate SE preamp, you'll have decent combo with F4 and 25W/8R
-find appropriate Bal preamp, you'll have decent combo with F4 and 100W/8R
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It is not really matter of what I prefer, the AR I bought as a great deal and it came handy with the phono stage, the KT88 came later and I liked the sound of the duo even tho my JBL L220 are not really what I'd call a clinical speaker to give subtle details as to tell how the combo sound, at least not in my environment and didn't bother to look up for it.
I wanted to upgrade the quality and to try solid state sound and that's why the F4 but it won't make so much sense to couple such a thing with a preamp which is in the 30 years old range so a new preamp was on the bucket list and in fact the BA-3 is on the build, I got boards, most of the passive components, the two PSUs and next month I plan to get transformers, volume pot, plugs etc and with the extra gain from that preamp I am sure the F4 would almost do its possible best.
Just in case the 25W won't still be enough to give the push to the big white woofers I might then think to add, in the next future, another F4 and to use the two bridged, I will check the manual to find out how to achieve that, if it takes some hardware mods to get in in whose case it will have to go back to the guy who built it.
Grazie e buona domenica
I wanted to upgrade the quality and to try solid state sound and that's why the F4 but it won't make so much sense to couple such a thing with a preamp which is in the 30 years old range so a new preamp was on the bucket list and in fact the BA-3 is on the build, I got boards, most of the passive components, the two PSUs and next month I plan to get transformers, volume pot, plugs etc and with the extra gain from that preamp I am sure the F4 would almost do its possible best.
Just in case the 25W won't still be enough to give the push to the big white woofers I might then think to add, in the next future, another F4 and to use the two bridged, I will check the manual to find out how to achieve that, if it takes some hardware mods to get in in whose case it will have to go back to the guy who built it.
Grazie e buona domenica
there is no right or wrong - outside your own liking and preferences
what I wrote is merely trying to explain why you're hearing what you hear, to help you understand, so easier to make choices in future
nature of sound is always combination of specific natures of all components in link
and, F4 is practically not having any significant amount of specific nature, thus anything preceding it will dominate final result
what I wrote is merely trying to explain why you're hearing what you hear, to help you understand, so easier to make choices in future
nature of sound is always combination of specific natures of all components in link
and, F4 is practically not having any significant amount of specific nature, thus anything preceding it will dominate final result