I rarely listen to classical music, but tonight I dug out a classical remaster of some of the greatest Queen songs. I honestly didn't know how low my amp goes, there was a huge ground floor apartment that I didn't even know was there, and it reached these depths effortlessly. These Wonfor Class A amps ooze scale and size of sound window, one year on and my amp still takes me by surprise and impresses me.
Well i've been listening to this little amp for the last five hours or so and its quite exceptional !
Would have carried on but someone wants to watch TV.......doh.
Although I only have the one channel of the TOCA built, i would say that at low to medium levels, this gets 90% there.
One of the great things about these SECA amps is the ability to sounds rich and full, even at low levels and this one doesn't disappoint.
Considering the TOCA cost several K over 20 years ago and is much more complex, thats some performance for an amp thats very simple and costs under £400 to build.
A big thanks to Colin for making these boards available.
Your right mate, I'm hoping ............??????,,,,,,....... To have the mother 40 Watter spinning tunes by Wednesday, I'll just set it out on a bread board first, as I'm still working out case, or probably my own bespoke creation. After this I plan to tackle the DIY one you have just built but using the two power supply boards.... Then I plan to just listen to music for a while ;-)
Your right mate, I'm hoping ............??????,,,,,,....... To have the mother 40 Watter spinning tunes by Wednesday, I'll just set it out on a bread board first, as I'm still working out case, or probably my own bespoke creation. After this I plan to tackle the DIY one you have just built but using the two power supply boards.... Then I plan to just listen to music for a while ;-)
I've got the amp and PSU boards sitting here. I need to pull my finger out and place an order with Farnell.
Important! Before I make any more comments on the A-Class kit it should be noted that I am a good friend of Colin the designer and I may be a little biased.
So I have built both the Amp and Tracking Power Supply boards and they have been mounted on their heatsinks but are not yet in their cases which I have to make.
I disabled the Thump Buster circuit removing diode D7 - I have not experienced any switch on problems.
The amps are set to have a bias of 1.5 amps by adjusting the voltage across R11 or R12(the .1R resistor) to be 150 mV. The temperature is settling at about 50 degrees C, the ambient room temp is about 26-27 C.
So how does it sound - in a nutshell, bloody marvellous! OK so some context is required. My system has changed recently and now is Windows 7 / XXHE, Uptone Regen USB device, iFi iDSD micro, Kondo M77 clone, PassDIY F5 mono blocks into Infinity RS3a speakers. The latter are not particularly easy to drive but the F5s manage very well.
The SECA amps (I tend to build mono blocks) sound as good as the F5s in all areas and better them in the bass where the SECA seems to go lower and is tighter, better defined. Low level detail abounds throughout the spectrum and to say that it is easy to listen to is a bit of an understatement.
Anybody hearing my system may think it is a little 'slippers and pipe' but it suits me.
Once I have made the cases and installed the amps I will take some photos - just want to make sure the mains police don't visit me! At that point people would be welcome to come to Farham and have a listen.
Just to reiterate my first point I cannot pretend to be un-biased about the kit.
Glad your happy. When I first heard my Iridium the first thing I noticed was also much deeper bass, but it wasn't simply hearing the next bass note down, it was the fact that the floor of the music has fallen away and there is a whole basement apartment beneath you, and you are now hearing the deepest notes on the recording , and effortlessly.
I have made this batch with a higher density Cu so we can run the driver if required at a high bias this will increase the Bandwidth to over 1MHz. The circuit has been designed to run current in A Class in the driver stage with a standing current of 10mA but now it can be pushed to 30mA see table.
Important! Before I make any more comments on the A-Class kit it should be noted that I am a good friend of Colin the designer and I may be a little biased.
So I have built both the Amp and Tracking Power Supply boards and they have been mounted on their heatsinks but are not yet in their cases which I have to make.
I disabled the Thump Buster circuit removing diode D7 - I have not experienced any switch on problems.
The amps are set to have a bias of 1.5 amps by adjusting the voltage across R11 or R12(the .1R resistor) to be 150 mV. The temperature is settling at about 50 degrees C, the ambient room temp is about 26-27 C.
So how does it sound - in a nutshell, bloody marvellous! OK so some context is required. My system has changed recently and now is Windows 7 / XXHE, Uptone Regen USB device, iFi iDSD micro, Kondo M77 clone, PassDIY F5 mono blocks into Infinity RS3a speakers. The latter are not particularly easy to drive but the F5s manage very well.
The SECA amps (I tend to build mono blocks) sound as good as the F5s in all areas and better them in the bass where the SECA seems to go lower and is tighter, better defined. Low level detail abounds throughout the spectrum and to say that it is easy to listen to is a bit of an understatement.
Anybody hearing my system may think it is a little 'slippers and pipe' but it suits me.
Once I have made the cases and installed the amps I will take some photos - just want to make sure the mains police don't visit me! At that point people would be welcome to come to Farham and have a listen.
Just to reiterate my first point I cannot pretend to be un-biased about the kit.
'Slippers and pipe'????
Must be the rest of the system. Although I haven't yet heard the kits, the Iridium and the Green Goddess are anything but!
That's why I love Colin's SECAs so much, and really don't like (m)any of the other Class A amps I've heard.
Hi Dave I bring one down for you to review sorry it will not be Green but I could do a real blind test with a hankie over your eyes, a clean one honest.
Found this box section aluminium on ebay which may be of interest for building these. I just bought a couple of 150x150x3mm 300mm length sections, and a couple of 150x150 sheets for end plates. £33 inc delivery for 2 cases basically.
I was thinking like naim amps where you have an outer sleeve. So basically the whole monoblock slides in, with the heatsink connected to the front plate and all the other connections at the back.
Oh yes the improved mods use the same PCB but with a few bit cost lots more I am sorry to say but well worth it. I have one now with the upgraded bits, Sam is standard and Paul I suspect will do what I have done. The FET has gone to a monster and the Darlington has been replaced with a FET, the same one as the drive, it 1.5mR RdsON and only 350A but the SOA is much nicer tons of room for higher current IQ. The FET driver stage IQ has also gone up but now the BD139/140 have to be fitted with heats sinks. It sung beautifully before but now it is shear angel music, with the harp top and the bass of a cannon.
The BOM will reflect the upgrade but you may need a mortgage. Sorry lads.
Yep........my mono build should have the posh bits in it !
Got one running at the weekend (minus the PS board) and had a play around with an 80mm fan I nicked from an old PC
Running at 5v directly at the pair of heatsinks, it was reasonably quiet (will use some better 120mm ones in the final build) and can now crank the bias up to 2.5 amps with the sink @ 45 degrees.
Comments
Thanks Col.
Just finished it. Will test and have a listen tomorrow
These Wonfor Class A amps ooze scale and size of sound window, one year on and my amp still takes me by surprise and impresses me.
In stark contrast to Paul's work of art above, I suspect my effort would resemble...
X_X
Would have carried on but someone wants to watch TV.......doh.
Although I only have the one channel of the TOCA built, i would say that at low to medium levels, this gets 90% there.
One of the great things about these SECA amps is the ability to sounds rich and full, even at low levels and this one doesn't disappoint.
Considering the TOCA cost several K over 20 years ago and is much more complex, thats some performance for an amp thats very simple and costs under £400 to build.
A big thanks to Colin for making these boards available.
After this I plan to tackle the DIY one you have just built but using the two power supply boards.... Then I plan to just listen to music for a while ;-)
I've got the amp and PSU boards sitting here. I need to pull my finger out and place an order with Farnell.
I totally agree with your comments about TOCA vs the new boards, I expect the dynamic PSU will turn the tables completely.
Where did you source the case and heatsinks? It all looks so good together.
Alan.case is an ebay jobbie from china. Sinks from cpc.
Still sounding lovely. A touch sweeter at the top I think.Temp now spot on.
Anyone who thinks low powered Class amps don't do bass properly, should try some Marcus Miller or Jon Hopkins through this thing........
Its a lovely machine. The sound of that flat six at full tilt, is something else.....like a big Class A amp hehe.
Its about 30mm or so lower then stock........just about right imo.
I hardly ever use it though. Parking is a nightmare here, so it spends alot of time at my parents, only 20 mins or so walk, but still a PITA
So I have built both the Amp and Tracking Power Supply boards and they have been mounted on their heatsinks but are not yet in their cases which I have to make.
I disabled the Thump Buster circuit removing diode D7 - I have not experienced any switch on problems.
The amps are set to have a bias of 1.5 amps by adjusting the voltage across R11 or R12(the .1R resistor) to be 150 mV. The temperature is settling at about 50 degrees C, the ambient room temp is about 26-27 C.
So how does it sound - in a nutshell, bloody marvellous! OK so some context is required. My system has changed recently and now is Windows 7 / XXHE, Uptone Regen USB device, iFi iDSD micro, Kondo M77 clone, PassDIY F5 mono blocks into Infinity RS3a speakers. The latter are not particularly easy to drive but the F5s manage very well.
The SECA amps (I tend to build mono blocks) sound as good as the F5s in all areas and better them in the bass where the SECA seems to go lower and is tighter, better defined. Low level detail abounds throughout the spectrum and to say that it is easy to listen to is a bit of an understatement.
Anybody hearing my system may think it is a little 'slippers and pipe' but it suits me.
Once I have made the cases and installed the amps I will take some photos - just want to make sure the mains police don't visit me! At that point people would be welcome to come to Farham and have a listen.
Just to reiterate my first point I cannot pretend to be un-biased about the kit.
I have made this batch with a higher density Cu so we can run the driver if required at a high bias this will increase the Bandwidth to over 1MHz.
The circuit has been designed to run current in A Class in the driver stage with a standing current of 10mA but now it can be pushed to 30mA see table.
R set...........I Drive Current....P dis W..............HS Type
68..................9.68.............. 0.174
56.................10.77..............0.193
51.................11.76..............0.212....... .....Heatsinked.....PCB
47.................12.77..............0.230....... .....Heatsinked.....PCB
39.................15.38..............0.277....... .....Heatsinked.....PCB
33.................18.18..............0.327....... .....Heatsinked......Al
27.................22.22..............0.400....... .....Heatsinked......Al
22.................27.27..............0.491....... .....Heatsinked......Al
18.................33.33..............0.600....... .....Heatsinked......Al
The FET has gone to a monster and the Darlington has been replaced with a FET, the same one as the drive, it 1.5mR RdsON and only 350A but the SOA is much nicer tons of room for higher current IQ.
The FET driver stage IQ has also gone up but now the BD139/140 have to be fitted with heats sinks.
It sung beautifully before but now it is shear angel music, with the harp top and the bass of a cannon.
The BOM will reflect the upgrade but you may need a mortgage. Sorry lads.
Got one running at the weekend (minus the PS board) and had a play around with an 80mm fan I nicked from an old PC
Running at 5v directly at the pair of heatsinks, it was reasonably quiet (will use some better 120mm ones in the final build) and can now crank the bias up to 2.5 amps with the sink @ 45 degrees.