tscharma wrote some while ago:
I just started my listening test of my pair of MOSFETs JLH 10W Class A amplifiers....
. oooohhhhhhfffffffffffff the sound stage is soooooooooooooooooo much better than my original BJT version..
I was chocked realy... I'm really really very euforic on this one.. it's so nice to have that 'virtual live performance quality' .. the soundstage covers allmost my whole back wall...
after several days of simulating, buying parts, blowing MOSFETs, failing soldering iron, discussing the circuit, again simulating alll night, measureing on scope, optimizing, again simulating, again blowing MOSFETs, again buying parts... .. but it was worth while..
The only problem I have now is that I can't say ' well it must be the MOSFET output stage being so superoir' .. because I used different parts, and gain sturcture.... so many factor have changed that I can't claim the MOSFETs must be the reason why it is so much better... I also spend far more time optimizing on this one that on my BJT version..
I will attache the circuit I have used for my version. I sound very very good, soundstage is fabulous, tembre sound good, but I thinks that more difficultto judge....
Thanks Millwood for the inspiration!
I just started my listening test of my pair of MOSFETs JLH 10W Class A amplifiers....
. oooohhhhhhfffffffffffff the sound stage is soooooooooooooooooo much better than my original BJT version..
I was chocked realy... I'm really really very euforic on this one.. it's so nice to have that 'virtual live performance quality' .. the soundstage covers allmost my whole back wall...
after several days of simulating, buying parts, blowing MOSFETs, failing soldering iron, discussing the circuit, again simulating alll night, measureing on scope, optimizing, again simulating, again blowing MOSFETs, again buying parts... .. but it was worth while..
The only problem I have now is that I can't say ' well it must be the MOSFET output stage being so superoir' .. because I used different parts, and gain sturcture.... so many factor have changed that I can't claim the MOSFETs must be the reason why it is so much better... I also spend far more time optimizing on this one that on my BJT version..
I will attache the circuit I have used for my version. I sound very very good, soundstage is fabulous, tembre sound good, but I thinks that more difficultto judge....
Thanks Millwood for the inspiration!
Re: Some pics of mine proto
...Nice work!!!
What is the brand mark of the yellow plastic cap?...i think i have some of this!!
Dragance007 said:
...Nice work!!!What is the brand mark of the yellow plastic cap?...i think i have some of this!!
Re: Re: Some pics of mine proto
ERO I think.
Tube_Dude said:
What is the brand mark of the yellow plastic cap?...i think i have some of this!!
ERO I think.
Re: Some pics of mine proto
nice work. I wish I could make pcbs as nice as yours, 🙂
One question: do you get turn-on inrush on the MOSFETs? you can check the voltage on the source resistors at turn on and let us know. Mine has large turn-on inrush current and I am not sure if it is inherient to the design or my implementation of it.
Dragance007 said:
nice work. I wish I could make pcbs as nice as yours, 🙂
One question: do you get turn-on inrush on the MOSFETs? you can check the voltage on the source resistors at turn on and let us know. Mine has large turn-on inrush current and I am not sure if it is inherient to the design or my implementation of it.
Re: Re: Some pics of mine proto
If you are using a output cap...that inrush current at turn-on is the charge of the big output cap...😉millwood said:
dragance,
that is really neat - well done.
It would be interesting to see the schematic.
I am planning to do a mosfet version and I am hoping that the sound will be a little more dynamic than BJT's. Could tell us a little about the differences in sound with this new amp. Do you find there is more life and dynamics in this one ?
mike
that is really neat - well done.
It would be interesting to see the schematic.
I am planning to do a mosfet version and I am hoping that the sound will be a little more dynamic than BJT's. Could tell us a little about the differences in sound with this new amp. Do you find there is more life and dynamics in this one ?
mike
Re: Re: Re: Some pics of mine proto
a little bit more complicated than that. the inrush current is large indepdent of: size of the cap (470uf vs. 3300uf I have tried), with or without a load attached, single rail vs. dual rail operation (thus no cap at all).
and the kicker is that it is the same for the upper output transistor than it is for the lower output transistor.
On thermal stability: I quickly simulated a 1v Vgs drop on the upper mosfet. the corresponding increase in Iq is 20%. and for 0.1v Vgs drop, the Iq increase is 2%.
empirically, I have had no problemw ith irf devices (540 + 240). But it is a little hard to get fairchild fdp mosfets to work stably.
Tube_Dude said:
a little bit more complicated than that. the inrush current is large indepdent of: size of the cap (470uf vs. 3300uf I have tried), with or without a load attached, single rail vs. dual rail operation (thus no cap at all).
and the kicker is that it is the same for the upper output transistor than it is for the lower output transistor.
On thermal stability: I quickly simulated a 1v Vgs drop on the upper mosfet. the corresponding increase in Iq is 20%. and for 0.1v Vgs drop, the Iq increase is 2%.
empirically, I have had no problemw ith irf devices (540 + 240). But it is a little hard to get fairchild fdp mosfets to work stably.
the basic schematic is on page 29, post 421. there have been some (minor) changes to it but that should get you started.
enjoy.
enjoy.
millwood said:
Thanks!
Do this experience...disconnect the output cap...and without a load see if the inrush current are gone!!
I bet ...Yes!!😉
Hi everyone.
There is inrush current. I didn't have much time for cheking the circuit or else. I was very exited about the sound of this project. The components on the board are cheap and old, but correct value. I can say that is sounds very warm 😎 We tried the board on some JBL studio monitors 15" they 're big as house and this small board gave a pretty big sound on them. We were amazed. Realy interesting 🙂
The heet sink is way to small...you can see on foto that one isolator(left) is meltet...we were so caried away with music...the kid got boiled...both IRF are dead now 🙂
Input cap...sorry i don't know were i got it. It is 1micro MKT.
I make boards with pen and acid...primitive but working metod.
Well .. just wana say again. Maybe the amp is cheap but the sound is very good 🙂
Good work tschrama, millwood and oll the rest good involved 🙂
There is inrush current. I didn't have much time for cheking the circuit or else. I was very exited about the sound of this project. The components on the board are cheap and old, but correct value. I can say that is sounds very warm 😎 We tried the board on some JBL studio monitors 15" they 're big as house and this small board gave a pretty big sound on them. We were amazed. Realy interesting 🙂
The heet sink is way to small...you can see on foto that one isolator(left) is meltet...we were so caried away with music...the kid got boiled...both IRF are dead now 🙂
Input cap...sorry i don't know were i got it. It is 1micro MKT.
I make boards with pen and acid...primitive but working metod.
Well .. just wana say again. Maybe the amp is cheap but the sound is very good 🙂
Good work tschrama, millwood and oll the rest good involved 🙂
pcb and circuit
I am interested in the pcb and layout. I always use hard wiring but this is a lot of effort. I guess more people are interested in this pcb because it is small and neat. Could it somehow be organized that some dozens of these boards are ordered and sold to some people on this forum? Besides that I am interested in the final circuit (or modifications with respect to post 421 for that matter).
I am interested in the pcb and layout. I always use hard wiring but this is a lot of effort. I guess more people are interested in this pcb because it is small and neat. Could it somehow be organized that some dozens of these boards are ordered and sold to some people on this forum? Besides that I am interested in the final circuit (or modifications with respect to post 421 for that matter).
it is not post 421
Only minor changes with respect to post 421's schematic? For a start there is no output cap anymore, so this is a symmetrical powered version! Not a detail I would say.
Only minor changes with respect to post 421's schematic? For a start there is no output cap anymore, so this is a symmetrical powered version! Not a detail I would say.
Re: it is not post 421
I think the big cap in the photo next to the terminals is the output cap. I am not sure if others changes have been made, tho.
personally, the biggest I have done to post 421 is to use a mosfet driver and run it at 40-50ma iq.
by the way, the same schematic can run in rual rails, assuming of course that you can some resistors (the bootstrap resistors).
rmgvs said:
I think the big cap in the photo next to the terminals is the output cap. I am not sure if others changes have been made, tho.
personally, the biggest I have done to post 421 is to use a mosfet driver and run it at 40-50ma iq.
by the way, the same schematic can run in rual rails, assuming of course that you can some resistors (the bootstrap resistors).
right
Millwood,
I guess you are right about the output cap. Following the tracks at the soldering side of the pcb this seems plausible. Maybe I just wanted to see a DC-version.
Millwood,
I guess you are right about the output cap. Following the tracks at the soldering side of the pcb this seems plausible. Maybe I just wanted to see a DC-version.
you can run a DC version out of this particular PCB as well, if you just short the cap termianals and apply two rails (against, use new resistors).
the Iq on the driver is determined by the emitter resistor on the driver and the type of transistors in the output. Once you have that determined, you just need to drop enough voltage on the bootstrap resistors to maintain the DC offset.
the two other grounding points in the scehmatic, the decoupling cap for the input stage and the feedback cap, aren't really important with regards to where they go.
just a word of caution for those of you wanting to do cap-less with the mosfet: the DC voltage does drift more than on the bjt version. over a long period of time (5 - 8 hours), mine drifts about 100mv, vs. about 10mv on the bjt version.
the Iq on the driver is determined by the emitter resistor on the driver and the type of transistors in the output. Once you have that determined, you just need to drop enough voltage on the bootstrap resistors to maintain the DC offset.
the two other grounding points in the scehmatic, the decoupling cap for the input stage and the feedback cap, aren't really important with regards to where they go.
just a word of caution for those of you wanting to do cap-less with the mosfet: the DC voltage does drift more than on the bjt version. over a long period of time (5 - 8 hours), mine drifts about 100mv, vs. about 10mv on the bjt version.
There is no changes made to the schematic tscharma attached. If anyone is intrested i will post PCB layout tomorow in JPG format. I guess no one here uses Tango V2.11 , PCB editor 20 years old 🙂