2SK2013/2SJ313 will make a very good F5-HA (I've made a few using them).
Consider using GR grade 2SK170/2SJ74 for the input JFET if you have them, and increase the gate stopper of the MOSFET from 2k to 2k7 if you want perfect square wave from your scope.
Good to know. Any other tips? Like bias current? Does it require running at 300mA to sound better?
Interesting that gate stoppers are higher as only 220R used on F5 Juma - big difference there.
The F5 based amplifiers are all push pull topology.
The maximum output current in ClassA is just under double the output stage bias current.
If you set the output stage bias to 100mA then the maximum ClassA output current is just under 200mApk
Does your Receiver require more than that?
If not, then I don't see any advantage to increasing it to 600mApk.
The maximum output current in ClassA is just under double the output stage bias current.
If you set the output stage bias to 100mA then the maximum ClassA output current is just under 200mApk
Does your Receiver require more than that?
If not, then I don't see any advantage to increasing it to 600mApk.
It was just some assessment from Juma that the SK2013/SJ313 sounds better under heavy bias of 400mA. Of course I prefer lower bias and I think in case of 50ohm headphones 150mA was recommended.
I would expect the peak transient current to a pair of 50ohm headphones to never exceed 100mApk.
On that basis a bias of around 50mA to 60mA would keep the amplifier in ClassA for all audio signals.
Whether the amplifier performance varies significantly by changing the bias a bit, or a lot, while always remaining in ClassA is not something I am qualified to comment on.
I just run them at 150mA bias, sound good enough for me.
I did measure the THD under load with different bias level. With low impedance load (say, 30R), the THD is lower under higher bias level. With 300R load, the difference is negligible.
Cwtim01,
Did you just use the standard Euvl amp layout but substituted the MOSFETs and change gate stoppers to 2.7k? Any other mods? I will try it out on the new Prasi PCBs once those arrive. Now I am glad I have several sets to play with. It will be good to AB the two MOSFETs side by side.
Did you just use the standard Euvl amp layout but substituted the MOSFETs and change gate stoppers to 2.7k? Any other mods? I will try it out on the new Prasi PCBs once those arrive. Now I am glad I have several sets to play with. It will be good to AB the two MOSFETs side by side.
First build is the official v1 PCB from XEN Audio, others are based on PCB I made myself where the amp layout is strongly inspired by the official PCB (so I'm not going to share it here).
IMHO, if you want to get good results, better stick with the Vero layout from post #1, but it's your call.
IMHO, if you want to get good results, better stick with the Vero layout from post #1, but it's your call.
since someone asked , here are the gerbersIf someone does decide to take it further (stereo and PSU), here is what I would use, as it has a amenable concept for a central PSU and left and right channels on the left and right of afore said PSU with a nice central star ground. and most importantly, all through-hole things for diy friendliness.
It is also a better layout compared to my earlier layout whose PCB's are being manufactured in China as i write here😱. Cheers to the spirit of DIY!!
reg
Prasi
Any suggestion if I am using the IRF MOSFET as shown in the vero board scheme, and not the FQP as described in the F5 V1.4 PDF?
Regards,
I have been aked by PM :
(1) Is Xen Audio selling matched sets 2SK170/2SJ174?
NO. We don't sell components.
We only support our own projects by providing PCBs, and sometimes optional Q-Sets.
(2) Is Xen Audio selling machined heatsinks for TO92 pairs?
Also only as part of projects.
(3) Is Xen Audio selling headamp kits, boards, or other components?
Only as GBs, as no time to entertain individual requests.
If you wish to join, there is a GB for F5-HA still open.
Only PCB set.
For Q-Set you can ask Cloud85.
We might have more time when one of us retires, will take quite a while.
Patrick
(1) Is Xen Audio selling matched sets 2SK170/2SJ174?
NO. We don't sell components.
We only support our own projects by providing PCBs, and sometimes optional Q-Sets.
(2) Is Xen Audio selling machined heatsinks for TO92 pairs?
Also only as part of projects.
(3) Is Xen Audio selling headamp kits, boards, or other components?
Only as GBs, as no time to entertain individual requests.
If you wish to join, there is a GB for F5-HA still open.
Only PCB set.
For Q-Set you can ask Cloud85.
We might have more time when one of us retires, will take quite a while.
Patrick
Matched Q's here:
http://www.diyaudio.com/forums/vend...uding-some-very-rare-toshiba-transistors.html
I could not find the F5 HA GB thread - do you have link?
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The GB is within this very thead --> look here: http://www.diyaudio.com/forums/pass-labs/271926-f5-headamp-81.html#post4844356
I have not tried the IRF on the F5-HA so don't really have much to say.
Most of their datasheet parameters are at the same ballpark, so I think you can safely replace one with another without much adaptations (the Vgs required for the IRF is slightly lower, but there is already a trimmer to cope).
An externally hosted image should be here but it was not working when we last tested it.
Finally got my own version of the F5-HA boards.. they are 54x68mm, so should fit on the side sinks of 2107 just fine.
I did them with the current limit transistors and only through hole components.. Will start building as soon as i get transistors which i just ordered.
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Q21 and Q22 are the current limiter transistors, as included in the original layout(not vero layout), but there as SMD. They (and four resistors) are not needed for function, and is just optional.
I'm thinking if i should grab a 2107 case, myself or if i shall build in the 2109 case i already have had sitting for a year (which was supposed to be used for another project).
I'm thinking if i should grab a 2107 case, myself or if i shall build in the 2109 case i already have had sitting for a year (which was supposed to be used for another project).
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Possibly the mo' bettah version with CCS's? or following full size F5 with Zetex's?