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Awesome news to hear! I know how disappointing it is to finish a project and not have it live up to your expectations... Glad to hear this isn't the case any longer!
Thanks Eric, "I'll be back" as a governor of California famously said.
In the meantime thanks for all your inputs. I am now off to the Objective2 headphone amp forum to get some build tips, but I'll return with some observations and of course photos of the ACA as you've never seen before I'm guessing (think lots of wood in the construction).
ACA with scrap aluminum chassis
Just finished an ACA and listening to Bill Charlap - Stardust CD. I built this up from scraps I had lying around and the shape is a change from the store chassis. The heatsinks are about 6 x6.5h and 2” deep with a 3/8” base. They are more suited to forced convection with the narrow fin spacing, but do get the job done for the ACA. Overall the chassis is about 8.5” wide. The bottom and front are about 1/2” thick so it is pretty solid. With all that mass to heat up it takes it quite a while to reach full temp. It gets pretty warm but you can keep your hand on the heatsinks indefinitely. Maybe a little room to turn up the current!!
Sounds pretty nice so far. Tested at about .6% thd at 1w 8 ohms. The bandwidth reached -3db out past 250khz when driven from my 50 ohm signal generator. Is that normal? Seems a bit higher than the example in the documentation.
Quiet! I had to put my ear in the HF horn of my 95db/w Pi 3 speakers and listen really closely in a dead quiet room to hear anything. I am using a Lambda 24v 6.5 amp switching supply to power it. This supply was given to me for parts as it was “unserviceable” but it turns out it needs a remote dc voltage input to make it start up. I think I will use a 9v battery and have the battery provide the startup voltage. I don’t have the PS chassis done yet. This supply has only 4mv of ripple when supplying 3 amps. I have an LC filter in the ACA that lowers that to less than 1mv. I did not connect the ACA chassis back to the ps ac safety ground. I have a wire in the ps cable in case I need to do that.
Now I have 3 levels of SS power- ACA ,Aleph J and F5V3
Thanks to Papa Pass, DIY audio, 6L6 and all the dedicated helpful DIYers on this forum who make these great projects possible for everyone no matter what their skill level.
Just finished an ACA and listening to Bill Charlap - Stardust CD. I built this up from scraps I had lying around and the shape is a change from the store chassis. The heatsinks are about 6 x6.5h and 2” deep with a 3/8” base. They are more suited to forced convection with the narrow fin spacing, but do get the job done for the ACA. Overall the chassis is about 8.5” wide. The bottom and front are about 1/2” thick so it is pretty solid. With all that mass to heat up it takes it quite a while to reach full temp. It gets pretty warm but you can keep your hand on the heatsinks indefinitely. Maybe a little room to turn up the current!!
Sounds pretty nice so far. Tested at about .6% thd at 1w 8 ohms. The bandwidth reached -3db out past 250khz when driven from my 50 ohm signal generator. Is that normal? Seems a bit higher than the example in the documentation.
Quiet! I had to put my ear in the HF horn of my 95db/w Pi 3 speakers and listen really closely in a dead quiet room to hear anything. I am using a Lambda 24v 6.5 amp switching supply to power it. This supply was given to me for parts as it was “unserviceable” but it turns out it needs a remote dc voltage input to make it start up. I think I will use a 9v battery and have the battery provide the startup voltage. I don’t have the PS chassis done yet. This supply has only 4mv of ripple when supplying 3 amps. I have an LC filter in the ACA that lowers that to less than 1mv. I did not connect the ACA chassis back to the ps ac safety ground. I have a wire in the ps cable in case I need to do that.
Now I have 3 levels of SS power- ACA ,Aleph J and F5V3
Thanks to Papa Pass, DIY audio, 6L6 and all the dedicated helpful DIYers on this forum who make these great projects possible for everyone no matter what their skill level.
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From scrap aluminum, eh?
My compliments, sir. Looking very good, indeed.
I too can leave my hand on the heat sinks of my ACA's indefinitely.
They are in the kit chassis. All 4 bias readings are 12 +/-.05VDC.
I am mightily tempted to embark further down the Pass road, starting with a 4U or 5U chassis and power supply to try multiple Pass designs as desired.
My compliments, sir. Looking very good, indeed.
I too can leave my hand on the heat sinks of my ACA's indefinitely.
They are in the kit chassis. All 4 bias readings are 12 +/-.05VDC.
I am mightily tempted to embark further down the Pass road, starting with a 4U or 5U chassis and power supply to try multiple Pass designs as desired.
I have a SYS in front of my ACA's now and they sound wonderful until the music gets up in the high mid area and above, when things start sounding a bit distorted.
Breaking in new speakers, could be problematic up there as well.
Running pair of ACA's in bridged mono block. Plan to try them in parallel mono shortly, just to see if it's better, ya know?
Cuz I can. These little amps are a hoot to play with as well as the best sounding amplification I've had the pleasure of listening to. Until we get past the upper mid range, that is.
Schiit Saga arrives tomorrow. Hoping for benefit from improved impedance matching and insert some tube-ness in the string.
Preamps are new to me, grasshopper has much to learn.
Been reading and reading, but still don't feel like I'm quite getting exactly how to figure the output impedance of a passive pre.
Thank You for the compliments. Building a chassis from pieces is often much more time consuming than doing the wiring and circuitry. I spent quite a few hours slaving over a hot drill press and tapping holes but it did turn out Ok after a coat of paint. So much easier to use a pre built chassis. I built my F5V3 monoblock with separate ps boxes. I bought the amp chassis but built the ps boxes. 4 chassis total and many hours of metal work. The chassis sold in the store with the pre drilled UMS heat sinks will save you many hours of work. I would go for the 5u version. No such thing as too much heatsink!
I really don’t have a good handle yet on how an Aleph J sounds different than a F5. The F5V3 has more bass authority and can drive low impedances without flinching. Mine is set up for about 70w classA into 8 ohms and about 100W class AB. Aleph J is superb on vocals.
I’m still Listening to the ACA as I type. Frank Sinatra Live at the Sands is playing now. 5W is enough with the Pi3 to play at reasonably loud levels.
I second those comments, very impressive indeed.
I too know the toils of drilling and tapping, although I bought the 2U chassis direct from Italy, it wasn't tapped for the ACA, but a bit of drilling and tapping later, and voila, an ACA emerges.
Mine too will look different, I'll post pics, but think burr walnut...
I love knowing what people listen to when they first finish a build, as it must be music they think is special. I always try to listen to the these recordings if I haven't heard of the artist. His voice on the second track and the sax on the third track sound amazing through the ACAs. Haven't gotten any further through the recording.
After you've spent a while with your new amp, I'll be curious to know which one is your favorite and why. I've an F6 and the ACA bridged monos. I think they both sound great but for different reasons.
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Bill Charlap is a recent find for me as well. I believe the voice you are hearing on the second track is Tony Bennett. Stardust is one of many Bill Charlap recordings out there. I’m a bit of a Jazz fan so I listen to a lot of Jazz piano recordings and Bill Charlap is certainly up there on my list. Something else I was listening too on the ACA tonight was Christian McBride- Conversations with Christian- if you like the double bass or bull fiddle as it’s sometimes called. He does songs with various artists on this cd. It’s Your Thing and Consider Me Gone which he does with Sting are 2 songs I like a lot. The Holly Cole CD -Temptation is one I was also playing tonight and has been a CD I come back to again and again over the years.
The ACA sounded a bit rough around the edges when I first started listening but it seemed to mellow and improve as it got up to temp. It was fresh off the test bench, so only maybe 2 hours on it. I forgot all about it only being 5 watts and just enjoyed the music- a good sign!
I know you're right about going for the 5U.
Doesn't cost that much more.
Add my voice to the chorus, the less chassis work I have to do the better.
Learned that during my initial forays into DYI a few years back, a DAC and a 3 band analog crossover.
F5V3 sounds like a beast, 70W Class A is nothing to sneeze at.
Yes, it’s out there. A 4 chassis monoblock/power supply build. There is info and pics in the F5turbo build thread. Pics at post 4763 F5 Turbo Builders Thread
Cheers
Sorry Puggie, I missed this post, thanks for the offer, if I need any I'll PM you.
By the way, is it any different to the screened cable for alarm installations?
For me it was what I happened to have at hand, but with the caveat that I'd only happen to have music that I love to hand.
I put on two tracks : Watchtower by Hendrix, and Abre la Puerta by Triana (a prog rock band from Spain in mid seventies)
The last alarm cable i used was 8 core, bit like a screened network cable without the twisted pairs. I tend to use this stuff where space in tight (it has a fail screen with the uninsulated drain wire):
http://www.vdctrading.com/uploaded/products/large/1493290350-1357659212-268-001-000.jpg
and I have some of the fat BBC spec brown twisted pair double helically screened stuff when I can afford the space (think that was a canford purchase).
It was just an offer as if you need 12" of cable and can only buy by the metre+exorbitant postage costs it can be a bit annoyiong
I've got a Freya in front of mine. Works great. I reckon you're in for some good times.
That said, I've got a BA-3 Pre on my build list ... all in good time ...
Thanks for the link oc11, they look quite good, it's always an option when building a power amp to have one of these passive controls to see how it performs before building a preamp with gain in it, that way I can decide which way to go.
Definitely a tool worthy of the electronics box.
