Amp Camp Amp - ACA

[TonyTecson]

that should survive and you can power two channels with that, like i do in mine...

in some of my builds, the smps boards share the same chassis and it was very quiet..

this is a bridged ACA i built with a tube line amp integrated into the chassis...

 

[kmj]

Nice work!
I haven't thought much about SMPS since, in my experience, they are frowned upon compared to traditional PSUs.

 

[TonyTecson]

today's smps are matured enough to go mainstream and i think the way forward....

 

[kmj]

I think so to.
I have some small projects that I would love to try some out on but usually I need some "buck-converters" as well to get the correct voltages.

200V and 6 or 12V (tube preamp)

I'll think that I will check what is available on ebay.

 

[Eric]

A couple of the keratherm pads I used had been penetrated by the screw holes of my chassis...

I've done this more than once on my builds - welcome to the club! Glad to hear that you solved your problem!

I've made a few changes to my build protocol because of problems like this. First is to be extra careful inspecting the mosfet mounting site before I mount anything to make sure that it is completely smooth and that no burrs or lips are sticking up. Second, I no longer use soft pads for transistor mounting. I prefer using Aluminum Oxide Ceramic like Aavid 4180G from Mouser. They transfer heat better than any soft pad I've found. Third, after mounting each transistor, take your meter and check for continuity between the middle pin and the sink. You should get an open loop reading.

Congrats on a successful build.

 

[triode_al]

ACA - Simulation version of a headphone implementation

as to the request of Nadeau:
It has two versions that I use to compare. Play with it!

 

[thomasnadeau]

as to the request of Nadeau:
It has two versions that I use to compare. Play with it!

Thank you!

--Tom

 

[chermann]

Hello


i have a question about double the MOSFET for sharing the current /heat for a Turbo version. Which current must have the JFET? normally its for one MOSFET (IRFP240) about 7mA.


thx
chris

 

[Mooly]

I'm not sure I understand your question

The input JFET can support 'any number' of parallel output devices at DC because the MOSFET's draw essentially zero gate current. So the JFET operating conditions remain unchanged.

Parallel MOSFET's do however need other arrangements to equally share the current... so that means a redesign of the output stage. Just paralleling devices will not work satisfactorily. They will not share equally and the sharing will be variable and prone to drifing.

Parallel MOSFET's present a higher capacitive load to the FET driving them and that has the possibility to alter the bandwidth of the overall amp although just a parallel pair should be OK in that regard.

 

[chermann]

Hi Mooly
Thanks for your prompt answer. i just remember wrong that this is needed.

 

[TonyTecson]

not only that, if you parallel several irfp240, then you have to match them for Vgs or else current hogging will occur...

 

[umut1001]

Hi.I checked but could not find any.I have 4ohm fullranges and i love them.Can i get 8w class a sound from ACA or should i make revisions?Thanks

 

[Dneu2011]

Build another one and wire them in parallel monoblocks for 16 watts per channel.

 

[TonyTecson]

Hi.I checked but could not find any.I have 4ohm fullranges and i love them.Can i get 8w class a sound from ACA or should i make revisions?Thanks

the wattage ratings of the ACA nor any amp for that matter does not mean anything once you are playing music, you will be surprised to find that the actual real power to your speakers with music hardly go over a watt....so just enjoy what you have...

i have stopped counting the watts, which was derived using sine waves a long time ago....

 

[umut1001]

Yes i agree.I was surprised when i measured just about 1v RMS sine wave on speakers made too much sound in the room.We should stop counting watts or dollars ,we will be counting the stars

 

[TonyTecson]

as long as the amp can drive the amp to your liking, then all is fine...

 

[umut1001]

I have this pcb.I will use 2x2sk209gr instead of 2sk170bl.Should i make any revisions for working with 24v? And i have 0r4 3w mox resistors and 0r68 vitreous 4w vishay g202 resistors.Can i use them in this circuit or should make revisions?Thanks

 

[umut1001]

And can i use large film caps on output lets say 2x160uF paralelled instead of 3300uF electrolytic capacitors for biamping?(i do not need such low frequency response on my fullranges,100Hz F3 ok for me) Thanks

 

[planet10]

That’s a good idea. I do have removable inut caps on mine so as to insert a smaller cap to create a “PLLXO”. Much higher quality part as well.

dave

 

[triode_al]

I have this pcb.I will use 2x2sk209gr instead of 2sk170bl.Should i make any revisions for working with 24v? And i have 0r4 3w mox resistors and 0r68 vitreous 4w vishay g202 resistors.Can i use them in this circuit or should make revisions?Thanks

Nice sub circuit. Where did you find it?

• Could small MOSFETS be used? Why not?

This way, the 2SK1078 I have, could be used - it is a SMD version of the larger 2SK135, I mean, made with the same negative tempco, and these mosfets have a very high admittance, typically 0,75 at quite a 400 mA current but still at 10 mA it is considerable and the output resistance is low. The Vg is about +1,3 volt typically. so that suffices to replace the input 2SK170. There are more types around, such as BSS89.
Now I solder wires on the pins to attach to a circuit board But the body-pins might break off that way.