Exicon Fets
I just used the exicon mosfets 'cos they were sold in maplin and they were in the circuit diagram (which does have one or two printing errors).
I have found this amp does have a good sound, also, it seems to be inherently stable. The PCB I designed for it are BAD because it was one of the first amps I have built. Another thing (maybe cos of my PCBs) it runs ok at +-37V but I have had problems running it at +-50V, it runs ok but when pushed, sounds nasty, I think it clips with MASSIVE harmonics.
I have not yet found the truth about the 'short-circuit' proof or 'thermal shut down' property of these mosfets
I have built a mid-sized crescendo from about 1982 elecktor and I just couldn't stop the damn thing from oscillating, many FETs when to silicon heaven, having said that, I am now listening to my millennium crescendo, which seems to be well mannered and rugged.
I just used the exicon mosfets 'cos they were sold in maplin and they were in the circuit diagram (which does have one or two printing errors).
I have found this amp does have a good sound, also, it seems to be inherently stable. The PCB I designed for it are BAD because it was one of the first amps I have built. Another thing (maybe cos of my PCBs) it runs ok at +-37V but I have had problems running it at +-50V, it runs ok but when pushed, sounds nasty, I think it clips with MASSIVE harmonics.
I have not yet found the truth about the 'short-circuit' proof or 'thermal shut down' property of these mosfets
I have built a mid-sized crescendo from about 1982 elecktor and I just couldn't stop the damn thing from oscillating, many FETs when to silicon heaven
, having said that, I am now listening to my millennium crescendo, which seems to be well mannered and rugged.
2SK134/2SJ49 Inverted Darlington non NFB Power Amplifier looks fairly simple, all the other parts are available.
Regards
James
Regards
James
Hello,
Sorry to bring up this old thread!
I was wondering if anyone had pairs of 2SK134, 2SJ49's ?
I need them to repair my Sanyo P55 Amp.
Also, this amp looks like its 'watercooled' with a heat pipe and lots of fins, and when in use it crackles a little as if it has not much water in it. I know this sounds daft but has anyone successfully filled one back up?!?
Many thanks,
James
Sorry to bring up this old thread!
I was wondering if anyone had pairs of 2SK134, 2SJ49's ?
I need them to repair my Sanyo P55 Amp.
Also, this amp looks like its 'watercooled' with a heat pipe and lots of fins, and when in use it crackles a little as if it has not much water in it. I know this sounds daft but has anyone successfully filled one back up?!?
Many thanks,
James
What!?
Non NFB Power Amplifier my aunt Fanny....... There is a conventional feed loop around the voltage gain stage and current feedback around the four mosfet output stage. Which of these two feedback loops (actually three if consider the negative and positive output devices) is the non NFB part? If you are going to lie about circuit, it should at least be to an audio reviewer in the process of selling expensive amplifiers based the latest trendy market buzz word. At least they didn't call it single ended. I would not even attempt to build this without gate resistors for the mosfets.......
Non NFB Power Amplifier my aunt Fanny....... There is a conventional feed loop around the voltage gain stage and current feedback around the four mosfet output stage. Which of these two feedback loops (actually three if consider the negative and positive output devices) is the non NFB part? If you are going to lie about circuit, it should at least be to an audio reviewer in the process of selling expensive amplifiers based the latest trendy market buzz word. At least they didn't call it single ended. I would not even attempt to build this without gate resistors for the mosfets.......
I think he's got it.
You are right ...... it's drawn a little strange and I thought the 430 resistor was the resistor to ground in the feedback network. It actually the degeneration for jfets and the 5.1K the collector load for BJTs. Never assume a simple circuit is as simple as the first glance. I should know better and stand rightfully chastised. Thank you for your tact.
You are right ...... it's drawn a little strange and I thought the 430 resistor was the resistor to ground in the feedback network. It actually the degeneration for jfets and the 5.1K the collector load for BJTs. Never assume a simple circuit is as simple as the first glance. I should know better and stand rightfully chastised. Thank you for your tact.
I have found this schematics from a site of flowchart software !!! 
http://novagraph.com/examples/mosfet.html
E.T.I. Audio Project P.104
what E.T.I. is it ?
http://novagraph.com/examples/mosfet.html
E.T.I. Audio Project P.104
what E.T.I. is it ?
Hi everybody!
I see that it is a quite long time when was the last post placed but after all I will ask - I would need an big help with setting up of the amp which is using 2sj49/2sk134.
I have the Quadral Vulkan's Mk II "activepacket" called Quadral PA04. I had some problems with one of the two PA04 amplifiers few weeks ago and I had it repaired at a professional service person (there was something interrupted in the power supply but it's now fixed).
In addition, doing the repair we thought it might be useful to also check the quiescent current settings for both the amplifiers and see whether it matches the specifications given in a circuit diagram I also have (see here). I think the circuit diagram shows the bass amplifier from the PA04 packet but I am not sure. However, it says that the voltage should be between 1,2 and 1,5 mV at the emitter resistor. It was quite surprising to see that in real life it was about 30 mV and, in addition, it differed for each amplifier
(e.g. the other bass amplifier had more than that and the midrange and treble amplifiers also give different voltage). Moreover the serviceman says that the value of 1,2-2,5 mV at the emitter resistor is too low because the quescent current should be about 180-200 mA (hence 40-45 mV at the emitter resistor).
As a result, I have the PA04 packet with different quiescent currents for each amplifier and with a circuit diagram telling me something which doesn't seem to be correct and I'm lost.
Could anybady count from the circuit diagram what are the correct quiescent currents for the bass, midrange and treble amplifiers for the PA04? As soon as I know the values I will have my amps serviced accordingly.
Bass amp has two pairs of 2sj49/2sk134, middle and treble amps has one pair of 2sj49/2sk134 each.
The 2sk134 datasheet is for example here
Could anybody please help me?
Thanks a lot in advance!
I see that it is a quite long time when was the last post placed but after all I will ask - I would need an big help with setting up of the amp which is using 2sj49/2sk134.
I have the Quadral Vulkan's Mk II "activepacket" called Quadral PA04. I had some problems with one of the two PA04 amplifiers few weeks ago and I had it repaired at a professional service person (there was something interrupted in the power supply but it's now fixed).
In addition, doing the repair we thought it might be useful to also check the quiescent current settings for both the amplifiers and see whether it matches the specifications given in a circuit diagram I also have (see here). I think the circuit diagram shows the bass amplifier from the PA04 packet but I am not sure. However, it says that the voltage should be between 1,2 and 1,5 mV at the emitter resistor. It was quite surprising to see that in real life it was about 30 mV and, in addition, it differed for each amplifier
(e.g. the other bass amplifier had more than that and the midrange and treble amplifiers also give different voltage). Moreover the serviceman says that the value of 1,2-2,5 mV at the emitter resistor is too low because the quescent current should be about 180-200 mA (hence 40-45 mV at the emitter resistor).
As a result, I have the PA04 packet with different quiescent currents for each amplifier and with a circuit diagram telling me something which doesn't seem to be correct and I'm lost.
Could anybady count from the circuit diagram what are the correct quiescent currents for the bass, midrange and treble amplifiers for the PA04? As soon as I know the values I will have my amps serviced accordingly.
Bass amp has two pairs of 2sj49/2sk134, middle and treble amps has one pair of 2sj49/2sk134 each.
The 2sk134 datasheet is for example here
Could anybody please help me?
Thanks a lot in advance!
Brownlow said:
Erno Borbely designed a 60 watt design which used these devices ,for David Hafler. He improved it somewhat and THE AUDIO AMATEUR Magazine published the circuit with an article written by Borbely. A circuit board was also available. AUDIOXPRESS.COM still offers the board with a copy of the original article. I built two of these units and was quite satisfied with the sound.