well, let's not forget that someone actually was defending reasons for using big honking 35V cap, in place where 16V one (4 times smaller, too) will do the job
so, who we are to prevent them to spend some greenies, buying motorrun conveniently suited in bronze tube ........
and, when you dial it, solder it in sockets
unreliable bstrdz........ good only for tiny IC pins
@adason
sleeping better is good
hearing positive difference when you put nice bypass is good, too
frankly, I stopped looking (listening ) is there a difference years ago, now doing it as habit, counting that last time when I cared I wasn't complete Loonie
i put small mp's from the bottom, i doubt i will hear the difference, but it already sounds amazing
now to build the box for it, that may take some time
It can absolutely be smaller... there’s a story around that.
Remember at Burning Amp ‘19 the ACP+ build event had us using up an inventory of specific wall wart power adaptors that happened to have the plug wired center negative. This is why most photos of the original ACP+ will have the power brick soldered directly to the PCB with no barrel connector.
Those specific bricks were 500mA 24v and although they played beautifully with the amp once in steady state, they struggled on startup to charge all the filter capacitors and bias the output stage at the same time. This is why there is the quip about seeing the LED flash in brightness once or twice in the manual.
The 3300uF across the 4N35 value was chosen specifically to slow down the charging of the output stage bias a handful of milliseconds in order to give those little wall warts a chance to breathe. That’s it. The cap was originally intended to be 1000uF (like all the other electrolytic caps on the board except the input coupling cap) and operates at a voltage around half the rail.
Will changing the value of the capacitor to 1000uF instead of 3300uF sound better? Nope. Could you change it to 1000uF if using a slightly bigger PSU? Yes. Does the cap need to be rated for 25V? No, the 3300uF on the original are 16V parts which helps keep the physical size down.
“Hey Jim, if you wanted to ‘upgrade’ the parts on the ACP+, on what parts would you spend the money?” Honestly, build it as it was shown at BAF. Nichicon and Elna caps, Vishay or Dale resistors, LSJ74 Jfets, etc... It’s not a budget design at all. This is a wickedly good amp as Nelson engineered it, and gilding the lily will assuredly succeed in making your wallet lighter, but past that there are no promises. But for those dying to throw some money at this, (or anyting powered by a wall wart) I have had great success with the LCLC inline filter for SMPS wall warts named “PO89ZB” by Mark Johnson PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
But much more importantly, this amp is a great opportunity to take that money and upgrade your headphones.
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You could also use a 200R trimpot in place of R4 temporarily. I did this, and put them in sockets so I could remove them easily to measure the resistance as I got closer to the optimal value. To any newbs reading this, you’ll want to remove the trimpot and sockets and replace them with a fixed resistor once you figure out the right value of R4 to give 10ma through R4.
FWIW, I ended up at 40R on one channel and 45R on the other. I started at 125R and was only getting something like 4ma. But your experience may vary of course.
Yes.
I assume the follow-up is, what do I think. My standard WHAMMY with the Burson V6 Classic (LED reference w/o the Burson cap mod) is closer to the sound of my ACP+ overall. I've done no modifications to the ACP+. It is straight from the build kit from BA 2019. I may look at Mark's design that 6L6 linked though, just for fun.
To my ears with my higher impedance headphones, (Sennheiser HD800S and HD820) I'd toss a coin.
Where would I consciously pick one to use over the other? Two situations:
1) Perhaps, and ooooooonly perhaps, the ACP+ is a bit better with my lower impedance planars (Mezze Classic). I don't know why.
2) My ACP+ is better with low impedance + high sensitivity IEMs. I get a bit less hiss from the ACP+. I honestly thought with using a SMPS wall-wart in the ACP+, it would be the opposite. Live and learn. Is the hiss from my WHAMMY enough to worry about at normal listening levels, no. It does not vary with attenuation and/or no input so it just hides in the background. I use it all the time with IEMs. That slight difference could be deficiency in my personal WHAMMY build vs. a normal outcome due to design. Mine likely may not represent "an average" build by an experienced DIYer / noise chaser. It was one of the first things I built. When it worked, I left it alone for over a year until I had the opportunity to try out the Burson OpAmps.
Conclusion: I love both. It would be a Sophie's choice to choose between them.
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I'm pretty sure the Meze 99 Classics use standard dynamic drivers. The Meze Empyreans are planars.
to Adason #728
Hello Adason,
I've built the Whammy, ACP+ and Waynes Line Stage
for use as preamps and
for use as headphoneamps.
Your question: How do they compare?
I have the similar problem like others to decide which is the best?
Whammy:
I prefer the Whammy as a headphoneamp (although I have built it with RCA-output for use as a preamp). I also used the Whammy to drive my poweramps.
And it sounds really good.
The most important point for me about the Whammy is: OPAmp-rolling and
learning about different 'sound-characters' of OPAmps.
And Whammy is the easiest to build (my opinion).
ACP+:
I prefer it as an preamp to drive a poweramp. But it is an excellent headphonamp also! A tough contender to the Whammy.I think it has a 'smoother' sound-character than the Whammy. You have to adjust your outputresistors to your headphone - resistance.
Waynes Line Stage:
If you search for a very detailed sound (without harshness in the highs) and solid bass - this is the machine. I like it as a preamp as well as a headphoneamp (big BJTs in the output necessary). But you shouldn't be afraid of SMD-soldering.
Which is the best? - none!!!
They are only different in their 'sound-character'. If I had to chosse -
I couldn't! So this was my dilemma - I had to build them all three. And I don't
wanna miss one of them!
So, Adason: my words will not help you - I know
I use a Beyerdynamic DT880Pro (250 Ohm version) with these headphone-/preamps.
Greets
Dirk
Hello Adason,
I've built the Whammy, ACP+ and Waynes Line Stage
for use as preamps and
for use as headphoneamps.
Your question: How do they compare?
I have the similar problem like others to decide which is the best?
Whammy:
I prefer the Whammy as a headphoneamp (although I have built it with RCA-output for use as a preamp). I also used the Whammy to drive my poweramps.
And it sounds really good.
The most important point for me about the Whammy is: OPAmp-rolling and
learning about different 'sound-characters' of OPAmps.
And Whammy is the easiest to build (my opinion).
ACP+:
I prefer it as an preamp to drive a poweramp. But it is an excellent headphonamp also! A tough contender to the Whammy.I think it has a 'smoother' sound-character than the Whammy. You have to adjust your outputresistors to your headphone - resistance.
Waynes Line Stage:
If you search for a very detailed sound (without harshness in the highs) and solid bass - this is the machine. I like it as a preamp as well as a headphoneamp (big BJTs in the output necessary). But you shouldn't be afraid of SMD-soldering.
Which is the best? - none!!!
They are only different in their 'sound-character'. If I had to chosse -
I couldn't! So this was my dilemma - I had to build them all three. And I don't
wanna miss one of them!
So, Adason: my words will not help you - I know
I use a Beyerdynamic DT880Pro (250 Ohm version) with these headphone-/preamps.
Greets
Dirk
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