One question guys.
I´m following the thread to F5 for headphones but I have a question. I have headphone very hard to drive, for example a AKG k340. On this thread Patrick says that if a I need more power, I use a F5 diretly.
Is possible use directly the F5 with a headphone amp? the output impedances are a problem?
I´m following the thread to F5 for headphones but I have a question. I have headphone very hard to drive, for example a AKG k340. On this thread Patrick says that if a I need more power, I use a F5 diretly.
Is possible use directly the F5 with a headphone amp? the output impedances are a problem?
blackdod, what makes you think that k340 are hard to drive?
The spec's sheet says that nominal impedance is 400 Ohms and only 0.63V needed for SPL of 94dB (and that's very loud) - even many OpAmps can do that with ease, let alone F5 headamp. No need to reach for heavy artillery like big F5.
The spec's sheet says that nominal impedance is 400 Ohms and only 0.63V needed for SPL of 94dB (and that's very loud) - even many OpAmps can do that with ease, let alone F5 headamp. No need to reach for heavy artillery like big F5.
They are OK to use in F5. No need to change anything, just take care when adjusting the bias, the gm is higher and the Vgs will be lower (about 2V instead of 4V with HEXFETs) so it might be a bit touchy. Take your time, do it in small steps, let it warm up, and all will be fine.
The 2Sk3497 / 2SJ618 has very high tempco.
That means the bias will increase drastically with temperature at the same Vgs.
So even though I don't like using NTC for bias at all, this is one case that I definitely would.
And I am saying this from experience.
Patrick
That means the bias will increase drastically with temperature at the same Vgs.
So even though I don't like using NTC for bias at all, this is one case that I definitely would.
And I am saying this from experience.
Patrick
That's right. At the same Vgs, Id will almost double from 25 to 100 degrees C. So thermal compensation (NTCs), big heatsinks and patitence in adjusting process are a must.
These issues are discussed in the article, F5 Turbo, which is online at the
First Watt website.
With the 8 devices shown in the schematic, I think 100 watts Class A would
be about it.
The article does discuss some of the issues about scaling the power up,
but I have only identified some potential issues and solutions.
This being a simple amplifier, it is not geared for really high power. Most
designers would opt for a 3 stage design above 100 watts.
😎
First Watt website.
With the 8 devices shown in the schematic, I think 100 watts Class A would
be about it.
The article does discuss some of the issues about scaling the power up,
but I have only identified some potential issues and solutions.
This being a simple amplifier, it is not geared for really high power. Most
designers would opt for a 3 stage design above 100 watts.
😎
The Turbo version... I thought zeepup asked about newer version of standard F5, the one with a pot in JFETs' source circuit.
Id love to build a 80-100watt class a amplifier but these designs use so many matched Fets 🙁 I still running my aleph mini's love them but would like some more power for my new speakers..
the matched fets are the least of the problems. the needed cooling capacity and PSU needs are much more of a problem (Money wise).
F5 turbo V3 monoblocks (5U 400+mm deep dissipante chassis), 2x35VAC 800VA transformer and 100.000uF pr rail PSU. 1 pair matched Jfet's and 4 matched output pairs will do the jobb.
Note: this is for 1 ch only.
F5 turbo V3 monoblocks (5U 400+mm deep dissipante chassis), 2x35VAC 800VA transformer and 100.000uF pr rail PSU. 1 pair matched Jfet's and 4 matched output pairs will do the jobb.
Note: this is for 1 ch only.
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In principle it seems simple but I´m lucky to have some very powerful amplifiers (Beta22, Dynahi...) and I can tell you that it's hard to have a good sound of a K340. You need power.
Also I´m thinking on my Pioneers "old school"collection: Monitor10, SE500, SE505... If I'm not mistaken, on this time (´70), the amps had the headphones output parallel to the output speaker, no?
> but I´m lucky to have some very powerful amplifiers (Beta22, Dynahi...) .....
See :
http://www.diyaudio.com/forums/pass-labs/271926-f5-headamp-5.html#post4374209
Patrick
See :
http://www.diyaudio.com/forums/pass-labs/271926-f5-headamp-5.html#post4374209
Patrick
That's not my experience with them. For the short time I used them, the simple source follower (2sk2013 loaded with 100mA CCS) worked lovely. For the truth's sake, I never drove them to deafening levels...
Hi 'blackdod',
While not having any direct experience with the k340's, the k701s seem to have a requirement for a specific type of amplifier to 'sound good', as they say, and Patrick developed the DAO circuit specifically for the k701s headphones with great success - perhaps your requirement is similar in that it isn't so much about the power levels, but the type of amplifier, even tho it doesn't seem logical
My k701s, for example, sound 'a bit thin' when driven from the F5 (even juma's version) but function perfectly with the DAO-T, my F3 amplifier or ridiculous as it may seem, directly out from my 845 valve amp! - perhaps you might try different amps to see if it suits your needs
I hope you're using really good quality ear protection when racing - I didn't, and suffered all sorts of problems later on and it was a real PIA to get rid of the tinnitus, CPS and the ghastly Meniere's problem
While not having any direct experience with the k340's, the k701s seem to have a requirement for a specific type of amplifier to 'sound good', as they say, and Patrick developed the DAO circuit specifically for the k701s headphones with great success - perhaps your requirement is similar in that it isn't so much about the power levels, but the type of amplifier, even tho it doesn't seem logical
My k701s, for example, sound 'a bit thin' when driven from the F5 (even juma's version) but function perfectly with the DAO-T, my F3 amplifier or ridiculous as it may seem, directly out from my 845 valve amp! - perhaps you might try different amps to see if it suits your needs
I hope you're using really good quality ear protection when racing - I didn't, and suffered all sorts of problems later on and it was a real PIA to get rid of the tinnitus, CPS and the ghastly Meniere's problem
F5 build
Hi guys, i am gathering parts for f5 build. My chassis each side contain two vertical heatsinks so each mosfet will be on its own heatsink. Is it ok ?Or should i joined the two heatsinks together with some flat aluminium sheet?.
Quan
Hi guys, i am gathering parts for f5 build. My chassis each side contain two vertical heatsinks so each mosfet will be on its own heatsink. Is it ok ?Or should i joined the two heatsinks together with some flat aluminium sheet?.
Quan
> My k701s, for example, sound 'a bit thin' when driven from the F5 (even juma's version) but function perfectly with the DAO-T, my F3 amplifier or ridiculous as it may seem, directly out from my 845 valve amp! - perhaps you might try different amps to see if it suits your needs
I can agree to that.
I tried K701 with a 3886 Gainclone before, it sounds lifeless, even though it has a lot more power and damping factor than the DAO-TCS.
On the F5-HA with Fairchild MOSFETs, it has gorgeous treble, but bass is not as tight as the DAO.
There is no scientific explanation, as the F5-HA also has enough Class A power and similar output impedance.
The only major difference is global negative feedback, perhaps.
Patrick
I can agree to that.
I tried K701 with a 3886 Gainclone before, it sounds lifeless, even though it has a lot more power and damping factor than the DAO-TCS.
On the F5-HA with Fairchild MOSFETs, it has gorgeous treble, but bass is not as tight as the DAO.
There is no scientific explanation, as the F5-HA also has enough Class A power and similar output impedance.
The only major difference is global negative feedback, perhaps.
Patrick
Thanks guys.
I´m following the Patrick F5 versión too. 😀
In my experience each headphone needs a specific amp. For example the K701 (I have one) you can use it with a simple Cmoy but the reality is that you need a different amp for the K701 sound good. Don´t you think?
Yes, the "standar F5" can be an overkill project for headphone but based on the above, it is still an option to consider.
I´m following the Patrick F5 versión too. 😀
In my experience each headphone needs a specific amp. For example the K701 (I have one) you can use it with a simple Cmoy but the reality is that you need a different amp for the K701 sound good. Don´t you think?
Yes, the "standar F5" can be an overkill project for headphone but based on the above, it is still an option to consider.