This time I wanted an amp that will combine qualities of my F5 (made with k2013/j313) with a certain seductive gentlenes that comes with good tube amps (member p18 recently made a nice amp with 6C33C that inspired me). Comparatively, I wanted something like F3 but with more control, more gain, more power and insensitiveness to characteristics of source and speakers.
I worked for a few months on it and tried a number of ideas (best candidates were a circlotron with LU1014 and a single rail version of F5 with BJTs at input and Laterals at output) but the buck stopped here:
I chose single rail PS becouse it enables using the benign reactive component at the output that makes "sound tailoring" possible.
Transformer is 500VA (2 x 40V AC, one secandary per channel). Cap. multiplier provides smooth and fast source of power (1.5mV ripple at 1.3A). 10mf ELKOs are Siemens Sikorel, bypass are MKC in PS and MKP in direct signal path.
Q1 provides high Zin and Low Z feedback point. Q2 gives all the voltage gain (OLG is about 50dB), it runs on about 7.5mA and that's more than enough to drive a pair of Laterals in push-pull Source follower topology (there are jumpers over Source resistors which are taken off when setting the bias with P2 ; P1 sets the half of the PS voltage at the output).
Here is the 90kHz square wave at the output loaded with Epos 5M (two way, bass reflex, 4 Ohm speaker). CRO was set at 5V/div vertical and 2uSec/div horizontal:
Projekat: SVAJA - diayudio.rs
Schematic :
Version 2.0 - post #180
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I worked for a few months on it and tried a number of ideas (best candidates were a circlotron with LU1014 and a single rail version of F5 with BJTs at input and Laterals at output) but the buck stopped here:
An externally hosted image should be here but it was not working when we last tested it.
I chose single rail PS becouse it enables using the benign reactive component at the output that makes "sound tailoring" possible.
Transformer is 500VA (2 x 40V AC, one secandary per channel). Cap. multiplier provides smooth and fast source of power (1.5mV ripple at 1.3A). 10mf ELKOs are Siemens Sikorel, bypass are MKC in PS and MKP in direct signal path.
Q1 provides high Zin and Low Z feedback point. Q2 gives all the voltage gain (OLG is about 50dB), it runs on about 7.5mA and that's more than enough to drive a pair of Laterals in push-pull Source follower topology (there are jumpers over Source resistors which are taken off when setting the bias with P2 ; P1 sets the half of the PS voltage at the output).
Here is the 90kHz square wave at the output loaded with Epos 5M (two way, bass reflex, 4 Ohm speaker). CRO was set at 5V/div vertical and 2uSec/div horizontal:
An externally hosted image should be here but it was not working when we last tested it.
Construction looks like this:An externally hosted image should be here but it was not working when we last tested it.
and the rest of the pictures are here:Projekat: SVAJA - diayudio.rs
Schematic :
Version 2.0 - post #180
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Juma
Wow that's some response. Interesting arrangement of your Q2 stage (to me anyway). Thanks for sharing, got me thinking of a few different circuits which just might benefit from a similar configuration.
Thanks
-Tony
Wow that's some response. Interesting arrangement of your Q2 stage (to me anyway). Thanks for sharing, got me thinking of a few different circuits which just might benefit from a similar configuration.
Thanks
-Tony
Nice to see something different... you might even say a bit of lateral thinking even 🙂
At the risk of sounding picky, 7.5 ma just sounds rather a lot to feed through a standard preset wiper for long term (many years) reliability. Fixed resistors maybe ?
And I can tell you now how this amp will sound... wonderful!!!
At the risk of sounding picky, 7.5 ma just sounds rather a lot to feed through a standard preset wiper for long term (many years) reliability. Fixed resistors maybe ?
And I can tell you now how this amp will sound... wonderful!!!
Great work, I like this 'le retro' circuit, can I suggest to put outputs on pcb in future. I expect many diyers will build this amp. Nice way to use laterals.
Regards
Regards
Actually it's a very common way to make a Vas stage. It's just that I carefully trimmed it (bootstrap configuration and emitter degeneration) to achieve the ammount of gain (about 50dB OLG) that gave the sonic result that I like the best.
Thanks Mile (and all the other guys) 🙂
There is a PCB under the aluminum profile where the MOSFETs are mounted. This way it was easy to test different front stages.
It is nice to see more designs with lateral mosfets. Great work
The only thing I would have done different is put the transformer at the front of the case away from signal wires. I am not sugeesting it would make a difference to the end result but that is how I like to do things.
The only thing I would have done different is put the transformer at the front of the case away from signal wires. I am not sugeesting it would make a difference to the end result but that is how I like to do things.
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Juma,
I have a pair of Toshiba laterals, which Ii bought some 15 years back for a elektor circuit and never completed. I also have a 35-0-35v transformer, for which I am looking for a project. Your idea seems a perfect fit. Do you have PCB layout, which you can share?
Thanks.
I have a pair of Toshiba laterals, which Ii bought some 15 years back for a elektor circuit and never completed. I also have a 35-0-35v transformer, for which I am looking for a project. Your idea seems a perfect fit. Do you have PCB layout, which you can share?
Thanks.
Anliva, which Toshiba laterals do you have?
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As for PCBs, if you look at the pics you'll see that I make my PCBs by hand and according to my needs. I don't know if it will suit your needs, but here it is (copper/bottom view, 80 x 44 mm).
There are things to consider, to name some of them: most of bypass caps are soldered on the bottom side of the PCB, there are three 3k6 resistors in parallel instead of one 1k2/1W, MOSFET's gates are in the middle, between S and D, there are two GND wires that go to star groung, etc... You'll have to be very carefull if you want to use this PCB, this is not a layout made for beginners 😉
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Since you asked me, I went and looked at the laterals with a magnifying glass. I am sorry they are not Toshiba, but Hitachi and the parts are 2SK1058/2SJ162.
I am looking at this as a long shot for now. Will keep you views in mind, if I do the PCB.
Regards
I didn't know that Hitachi made the plastic packaged Laterals, before they sold off/shut down that part of the business.
Ofcourse, the Hitachi plastic parts were available easily for a long time and they were very good replacements (in most cases) for the static sensitive erstwhile metal parts.
I've seen plastic FET's with the Hitachi logo... not sure when Renesas took over but this is from 1999 and is Hitachi,
http://www.datasheetcatalog.org/datasheet/HitachiSemiconductor/mXyzruwz.pdf
http://www.datasheetcatalog.org/datasheet/HitachiSemiconductor/mXyzruwz.pdf
I finally managed to lay my hands on 2SJ74BL to get going with Juma's F5 with 2SK2013/2SJ313 and just then Juma comes up with this other masterpiece. I happen to have all the components for this amp including the Hitachi Laterals but I'll hold it and go ahead with Juma's Toshiba F5.
Juma can I guess the sonic character of this amp compared to the Toshiba F5? This amp is more lush in the mid, subtler/smoother in the highs with the sound-stage a bit more forward. More relaxed overall presentation.
Toshiba F5 is more detailed throughout the spectrum with the Bass a tad bit tighter.
Just my guess but I'd like to hear your reactions. Thanks.
Juma can I guess the sonic character of this amp compared to the Toshiba F5? This amp is more lush in the mid, subtler/smoother in the highs with the sound-stage a bit more forward. More relaxed overall presentation.
Toshiba F5 is more detailed throughout the spectrum with the Bass a tad bit tighter.
Just my guess but I'd like to hear your reactions. Thanks.
Wow, Sam ! That's some review ! 😀
F5 with k2013/j313 is, as I already said, the end of the road when it comes to 20W cl. A amps (that's my opinion).
But this time I wanted something that doesn't have to be perfect in every possible aspect, but it has to be always pretty and attractive without being wrong.
For example: listening to MP3 through F5 is not a pleasent experience, with this amp it's far more enjoyable. Not all our sound sources are perfect, I use the amp to listen to TV and FM tuner too - and I want to enjoy it too. 🙂
F5 with k2013/j313 is, as I already said, the end of the road when it comes to 20W cl. A amps (that's my opinion).
But this time I wanted something that doesn't have to be perfect in every possible aspect, but it has to be always pretty and attractive without being wrong.
For example: listening to MP3 through F5 is not a pleasent experience, with this amp it's far more enjoyable. Not all our sound sources are perfect, I use the amp to listen to TV and FM tuner too - and I want to enjoy it too. 🙂
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