100W Ultimate Fidelity Amplifier

[xrk971]

Pioneer A30

One can buy a brand new A30 with case, PSU, prea-amp, motorized remote control(?) etc... for about $400, and used for $100 on eBay. Seems like a deal if one was good with the topology. You can't DIY a finished boxed amp and PSU for less.

 

[egra]

That looks real nice, would anyone happen to have a SPRINT or Gerber files for it (50mm x 50mm would be sweet).

It is simple enough for p-2-p on a perf board but would be so much cleaner on a custom PCB.

Thanks.

As I know pcb still isn't released. Headphone amp:

 

[xrk971]

I should just make the headphone amp and use as either a preamp or headamp.

How much power into 60ohms is possible?

 

[apexaudio]

One can buy a brand new A30 with case, PSU, prea-amp, motorized remote control(?) etc... for about $400, and used for $100 on eBay. Seems like a deal if one was good with the topology. You can't DIY a finished boxed amp and PSU for less.

You can buy used amp for $100 but with 100VA transformer, plastic speaker terminals, 100g heatsinks, about 6800uF caps... or you can diy $1000 amp

 

[btesize]

The end [emoji38]

 

[thimios]

The end [emoji38]

 

[xrk971]

I don't disagree, touche.

What amp is that btw?

 

[apexaudio]

I don't disagree, touche.

What amp is that btw?

Can be FX8 if you want

 

[xrk971]

Can be FX8 if you want

Maybe 6 channels of FX8 which is exactly what I am building so am looking for a case.

Btw, the Apex headphone described earlier with the BD139/150 output stage, what kind of power can that drive?

 

[apexaudio]

Maybe 6 channels of FX8 which is exactly what I am building so am looking for a case.

Btw, the Apex headphone described earlier with the BD139/150 output stage, what kind of power can that drive?

You can DIY case for your amp... amp with BD139/140 can drive any headphone.

 

[xrk971]

I guess those BD139/140's are 1.5 amp capable and with 24 volt rails, that is a lot of watts actually. Could probably drive a small set of speakers nicely.

 

[apexaudio]

I guess those BD139/140's are 1.5 amp capable and with 24 volt rails, that is a lot of watts actually. Could probably drive a small set of speakers nicely.

Yes, but only 32 ohms speakers

 

[xrk971]

Hmm... what is it that limits the impedance of the load on the output? I recently made a JLH class A head phone amp with a pair of TIP41's on the outputs and it seems to drive 8ohm speakers pretty nicely, but only up to 1.6w.

 

[erik777]

I have an signal line input transformer, I would like to try out.

So far I have on the delete list: 10uF, 2k2,22k,100pf.

 

[xrk971]

So the trafo allows removal of all those components via balanced inputs with no DC? Let us know how it sounds. Is this the FX8?

 

[erik777]

So the trafo allows removal of all those components via balanced inputs with no DC? Let us know how it sounds. Is this the FX8?

Thats the beauty of a trafo, It blocks the DC.
More over, removing the R & C from the signal chain, improves the SQ immediately, high input capacitance is no good. Which is why the K1058's are a good choice, they also have lower input capacitance when compared to some other MOSFETS.

 

[xrk971]

Can you hear the improvement in SQ already?

 

[xrk971]

5cm Square FX8 First Sound

The Hitachi lateral FETs came in today. I installed a pair of 10ohm safety resistors in series with the power rails so that I can measure the quiescent bias current. I set the pot at about midpoint. Flipped the switch and observed about 550mA bias so quickly adjusted the pot down to 100mA current. The offset voltage was -15mV and there is no adjustment for that other than matching the LTP stage (which I forgot to do). -15mV is very livable though. I am using a Dx PSU with 250VA 25V toroid for 35.6v rails.

Removed the safety resistors, hooked up the speaker and gave it input from my CD player (laoded with a Suzanne Vega track) headphone out (like a pre-amp to control volume). Flipped the switch and sweet music plays! Sounds real nice, very clear, no sign of distortion.

The heatsinks feel average warmth for a class AB at 100mA bias (probably circa 45C at moderate volume). Seems like a good place to be. The BD139/140's do feel a bit hot - probably needs a small heatsink as was shown on the silkscreen.

Anyhow, this is a nice compact amp, I really like it and will build up 5 more units for a 6 channel active amp.

 

[still4given]

 

[apexaudio]

The Hitachi lateral FETs came in today. I installed a pair of 10ohm safety resistors in series with the power rails so that I can measure the quiescent bias current. I set the pot at about midpoint. Flipped the switch and observed about 550mA bias so quickly adjusted the pot down to 100mA current. The offset voltage was -15mV and there is no adjustment for that other than matching the LTP stage (which I forgot to do). -15mV is very livable though. I am using a Dx PSU with 250VA 25V toroid for 35.6v rails.

Removed the safety resistors, hooked up the speaker and gave it input from my CD player (laoded with a Suzanne Vega track) headphone out (like a pre-amp to control volume). Flipped the switch and sweet music plays! Sounds real nice, very clear, no sign of distortion.

The heatsinks feel average warmth for a class AB at 100mA bias (probably circa 45C at moderate volume). Seems like a good place to be. The BD139/140's do feel a bit hot - probably needs a small heatsink as was shown on the silkscreen.

Anyhow, this is a nice compact amp, I really like it and will build up 5 more units for a 6 channel active amp.

Nice work.
Regards