Amp Camp Amp - ACA

I like the combo driving a pair of 2 Pi Towers that are about 95 db sensitive and are easy to drive.

Listen to jazz most of the time and other stuff mixed in from time to time. It generally isn't really loud but that's just my preference for listening. It'll go past the level of having a reasonable conversation if you want it to.

There are several other preamp options out there with gain that look interesting simply because others in this thread have stated a preference a preamp with gain for the ACA. Wayne's 2018 preamp looks interesting as does his Whammy headphone amp. If anyone has anything to share on those units please chime in. :D

Thanks Barryso and others,

Currently I use a Magni 3 with ACA, the volume is OK in my small office room even though my Buchardt S300MK2 are not very efficient (4ohm, 88db).

I never need to turn the volume past 12PM position in most cases.

The Magni is a just a headphone amp of 17db gain with line output, and I do need to manage multiple inputs, from a DAC and a phono, that's why I am thinking to build a preamp in the near future.
 
I like the combo driving a pair of 2 Pi Towers that are about 95 db sensitive and are easy to drive.

Listen to jazz most of the time and other stuff mixed in from time to time. It generally isn't really loud but that's just my preference for listening. It'll go past the level of having a reasonable conversation if you want it to.

There are several other preamp options out there with gain that look interesting simply because others in this thread have stated a preference a preamp with gain for the ACA. Wayne's 2018 preamp looks interesting as does his Whammy headphone amp. If anyone has anything to share on those units please chime in. :D
If you see yourself listeningto headphones as well, build the Whammy! It has great sound and the gain is (for me at least) the perfect match for the ACA and you win a nice headphone amp.

I'm very happy with my setup.
Rafa.
 
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Joined 2013
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I'm building the Balanced Zen line stage, I want to use the balanced outputs for my mono block ACA's. I'm currently using the ACA's in Bridged mode using a Hafler 915 preamp. N.Pass was kind enough to send me the Gerber files to have PC boards made, he even suggested a company in China to make them. I ordered 10 line stage and power supply boards from PCBway, they sent me 11 of each, they were delivered in 1 week!
I'm just finishing the remote power supply which also has two switched AC outlets to control the ACA power supplies and DAC, CD, tuner etc. I have the line stage board completed, just waiting for the enclosure and the 24 step ganged 5K pot. By having balanced inputs I can use my Threshold FET 10Pe phono stage which has balanced outputs along with my Music Hall 25.2 DAC which has quad chips in balanced output and tube stage output for the RCA output.

Go to PassDIY and read the article for the Balanced Zen line stage, the parts are very reasonable as I used Nelson's BOM and bought them from DigiKey since he listed there part numbers.
 
I'm building the Balanced Zen line stage, I want to use the balanced outputs for my mono block ACA's. I'm currently using the ACA's in Bridged mode using a Hafler 915 preamp. N.Pass was kind enough to send me the Gerber files to have PC boards made, he even suggested a company in China to make them. I ordered 10 line stage and power supply boards from PCBway, they sent me 11 of each, they were delivered in 1 week!

I bought one of each PCB from elwood625 and he delivered promptly. The PCBs appear just fine. The BOM is old, but many items at Digi-Key had the same part numbers. Some were obsolete and required substitution but weren't difficult to identify. I'm interested in the balanced design for the same reason as elwood625.

I've put off starting the build because I was wondering if a newer design might not prove better. I'll keep watching this thread for ideas. Any comments on my plans are welcome.

Cheers,
Jim
 
It bothered me the way Bridge mode was accomplished in the ACA kits. No one could answer my questions so I made my own measurements. Below are the 1KHz THD plots for bridge mode output with single ended and balanced drive. Also attached are the analyzer outputs taken at 1% THD in each mode.
 

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According to your graph which is attached, the amount of noise in Balanced mode 10 Watts is the same noise level of the Bridged mode at 2 Watts.
Using my Hafler 915 preamp with RCA's had less noise than the EL34 Push-Pull 35 watts or Single Ended at 15 watts the ACA's replaced. Yet, with no input signal, the ACA's were not exactly pitch black.
I knew there was some reason the diyAUDIO kits had the XLR connector dead center of the back panel.
 
According to your graph which is attached, the amount of noise in Balanced mode 10 Watts is the same noise level of the Bridged mode at 2 Watts.

Yes, THD is higher in the SE drive mode, but many people like the 2nd harmonic. Below are analyzer output of each side. Try it each way and tell us which way you like.
 

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The analyzer is an Audio Precision System 1. That's what made the graph in post 7038. In post 7040 the left screen of each attachment is a Tektronix 2465B monitoring the analog outputs of the AP S1. The right screen is a Tektronix 7L5 plugin (monitoring the top waveform seen on the 2465B) in a Tektronix 7104 mainframe. The on screen readout on the 7104 is generated within the 7104 by a completely bizarre chip set that was designed at Tektronix around 1970. If you can find an old 7000 series mainframe (except 7854) with readout, it will have that chipset.
 
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ACA build.

Hello DIYAudio community,

I have just completed my ACA build and would like to thank 6L6 for creating a superb guide, each time I was a little unsure of how to proceed; I reread the guide and all the info required was there, so I would like to add my name to the list of first time successes and say that I found the whole process very enjoyable, apart from switch on which was nerve wracking, does this go away with experience or is it the same with every build?
I am a novice with little understanding of exactly how it all works so please be gentle if this is a stupid question. I am using RCA interconnects so do not need the XLR but I am curious as to how it works, my understanding is that the signal is flipped over by some internal circuitry as it passes from one device to the next, so having built my ACA I was wondering which part or parts is doing the signal switch over?
 

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