Yes, long time ago - their inherent non-linearity makes them usable only as a CCS or as a voltage regulators, maybe cascoding devices.
IME, those are sub-optimal parts to use as amplifying devices in audio - maybe in guitar amps or in PA amps or in designs with a lot of NFB...
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luckily , I'm not an emg .... ing... img.... wtf! not even good at math
(now - you'll say that toobz aren't good for audio
)
Different bias voltage and you'd have to swap the 0.47 for 1 Ohm.
The F4 has less than unity gain, not very practicle for a headphone amp, imSo.
The F4 has less than unity gain, not very practicle for a headphone amp, imSo.
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I thought low gain was preferable for HP amps, with a standard 2V in out its pretty loud. Besides I crank it up full all of the time so best to keep gain low😉
Would changeing the bias voltage be a simple adustment of the pot and maybe adjacent resitor that sets the Vref of the TL431?
Would changeing the bias voltage be a simple adustment of the pot and maybe adjacent resitor that sets the Vref of the TL431?
With some minor adjustments (as Jacco mentioned) it would be great. OTOH, when it comes to power-buffer for low Z headphones (but not lower than 25 Ohms) EUVL's DAO is my favourite ...
Well IRF9610 is used in the front end of Aleph 3/30 etc, so they can't be too bad.
But I take your point, the toshiba devices are much more linear according to the data sheets.
Maybe I should also try the toshibas in the front end of my Aleph 30.
I also like the look of 2sj407, not sure if there is a complementary N channel version though.
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I prefer laterals in common-drain topology, like here.
I tried F5 with old Hitachi laterals (k135/j50) and it didn't sound bad, it was different from original F5 but not better...
I would not do that - you'd need a lot of current through that LTP and it doesn't seem like a good idea at all, especially in context of the amp as a whole.
Best upgrade would be to turn your Aleph into Aleph-J (Toshiba JFETs at the input.)
> The F4 has less than unity gain, not very practical for a headphone amp, imSo.
My DAO Follower also has unity gain.
All those who built it loved it, especially if you have low impedance phones.
Much easier to build than a down-versioned F4, may I add.
Patrick
My DAO Follower also has unity gain.
All those who built it loved it, especially if you have low impedance phones.
Much easier to build than a down-versioned F4, may I add.
Patrick
Thanks. I have one of those too (ie Aleph J).
I have been away for a while, and I can see my enthusiasm is getting the better of me.
I will definitely be giving these mosfets a go in my F5.
How about using these on the burning amps 1 and 2 to replace irf610.
Do they really need to be biased high? How about 50mA or 100mA
I understand you want to bias them high on the F5 output stage, but do you really need to bias them that high in a circuit such as BA2.
The other option is to throw a power Jfet in that position, however that is an expensive option.
Do they really need to be biased high? How about 50mA or 100mA
I understand you want to bias them high on the F5 output stage, but do you really need to bias them that high in a circuit such as BA2.
The other option is to throw a power Jfet in that position, however that is an expensive option.
Looking good prakit 
You should be fine with that heatsink, just use white heat-transfer paste more liberaly 😉
You should be fine with that heatsink, just use white heat-transfer paste more liberaly 😉
To follow up my attempt to try this a line amp...
I supplied each channel with a set Jung's super regulator set at +/-23V as seem the attached picture. I've been listening to the line amp for a week now. This version of F5 with a pair of k2013/j313 indeed makes a very good lineamp.
I tried varying the bias of the output Mosfets up to 450mA where the regulators seemed running out of steam(the heatsink for the pass devices became very hot). It did sound better at higher bias but the dc drift at the output was getting bigger too. I settled at 250mA where it sounded good and the dc stability was good too.
This circuit should make a very good sounding headphone amp too.
Anything I can do to minimize the dc drift at higher bias?
Regards
I supplied each channel with a set Jung's super regulator set at +/-23V as seem the attached picture. I've been listening to the line amp for a week now. This version of F5 with a pair of k2013/j313 indeed makes a very good lineamp.
I tried varying the bias of the output Mosfets up to 450mA where the regulators seemed running out of steam(the heatsink for the pass devices became very hot). It did sound better at higher bias but the dc drift at the output was getting bigger too. I settled at 250mA where it sounded good and the dc stability was good too.
This circuit should make a very good sounding headphone amp too.
Anything I can do to minimize the dc drift at higher bias?
Regards
Attachments
Of course, the most simple, but very effective thing to do is to add NTC resistors (like in F5). They are changing their resistance with temperature thus keeping the current through MOSFETs and DC offset constant.
Btw, great build
I tried the other option and put two SSR100 instead of irf610
......sounds more liquid!
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