ACA V1.5 Illustrated Build Guide

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#102
Here's my suggestion for troubleshooting -

1) Remove both the switch and the XLR.

2) Wire the speaker posts as shown in the guide.

3) See (listen) and find out of it works properly with speakers, if yes;

4) Make some fly wires off the back of the XLR jack and connect to the speaker posts and test the headphones
 
#104
Oh shoot, you know what, I didn't adjust the bias. Can you enlighten me on how to properly check the bias? I know you adjust it by rotating the meter on the blue component (the name of that thing slipped my mind, whoops) Also, how do you check the rail voltage?
 
#105
It is best to check 6L6's fine guide.....he uses a multimeter (set to DC voltage) and he measure from ground to one of the pins (middle pin I think) on the MOSFET output transistor (Q1). But check the fine pictures in the guide in this thread......
 
#106
Thanks, I looked just now, I had the guide opened since a week ago on my phone and I think my phone just had the website cache'd so when he updated the thread with the Measurements portion my phone hadn't refreshed the page and I was unaware that part was updated

Anyway, I'm going to do that now!
 
#109
An update, I bring good news!

6L6/Meper, thankyou for your time and suggestions!

I was successfully able to adjust the voltage to 10v via the potentiometer! That gave me a good indication that I set everything up correctly.

Before I ended up taking some advice that 6L6 gave me in a private message and tried setting up the unit stock by disconnecting the toggle switch/xlr-4 jack I decided to do a simple test and see if it truly was an issue with pairing between the ACA/nfb11. This time I got a 3.5mm to RCA adapter and ran it through my phone, a Motorola Z force via dongle adapter (why that's even becoming a thing is confusing to me. I'm actually considering getting an LG V30 so I have access to a proper headphone jack).

Guess what, it worked! For both the speaker outs/xlr-4 jack!

Now that I know the ACA/nfb11 pair is iffy at best, I'm going to try my spare Micca OriGen+ DAC/headphone amp that I have lying around and try using that as my dac/preamp. Hopefully it works! I'll post later after experimenting.

This project isn't over just yet but I hope I'm nearing the finish line 🙂
 
#110
It works! the Micca OriGen+/ACA combo works like a charm! I know that I'm using a subpar DAC but damn, this amp really packs a punch! No joke, I'm hearing details I hadn't heard before and everything sounds so smooth. I'm using a set of Sennheiser 6xx's to listen and prior to this amp the mids/vocals sounded recessed, like they were coming a little farther back than the rest of the instruments; however, this little ACA fixed that problem altogether and it sounds like it's up front and center like the rest of the instrumentation! Incredible!

Thoroughly impressed and I can't wait to listen to this amp through my ZMF Cocobolo Atticus. Now all I need to do is make a balanced cable for them!

Thanks for your help guys, I appreciate it!
 
#111
I finished the amp yesterday after a careful, methodical build (rather than the frenzied, impatient excitement which I have to curtail). Powered up and it works perfectly, even through the cheap inefficient speakers I used for the test. I must really pass on my gratitude to everyone involved in this project, it sounds great and looks stunning.

The build guide deserves special mention though, it really is perfect for newcomers like me. The photography is excellent and there's no ambiguity with regard to what to do.

I have one small question though....

On power up the amp emits what can best be described as a short fart! Is this normal for this amp or should I take it to the clinic?

Cheers
Neal
 
#112
Good it works and nothing is smoked!


I have a general question regarding the 5k bias pot. Does it come "centered" or turned all the way "anti clockwise" I guess to give minimal bias current?
Any recommendation to turn it all the way in the position so it gives minimal bias current or is the amp safe with any position...e..g max setting for the bias?
It seems people just turn on the power after it is assembled so maybe best that the pot is set to minimum bias?
 
#114
MEPER said:
Good it works and nothing is smoked!


I have a general question regarding the 5k bias pot. Does it come "centered" or turned all the way "anti clockwise" I guess to give minimal bias current?
Any recommendation to turn it all the way in the position so it gives minimal bias current or is the amp safe with any position...e..g max setting for the bias?
It seems people just turn on the power after it is assembled so maybe best that the pot is set to minimum bias?
Click to expand...

I just finished mine, no problems.
The pot came with centered setting and gave a bias of 8-9 volts. I think the setting is now at around 7:00.
The amp produces thump on turn off but fixed it by adding a 33k uf cap.
I will be putting the power supply inside and change the connector to Neutrik Powercon.
 
#116
clowkoy said:
I just finished mine, no problems.
The pot came with centered setting and gave a bias of 8-9 volts. I think the setting is now at around 7:00.
The amp produces thump on turn off but fixed it by adding a 33k uf cap.
I will be putting the power supply inside and change the connector to Neutrik Powercon.
Click to expand...



About the use of PowerCon for the power I asked Neutrik what they would recommend for DC power. They recommended the SpeakOn connectors. But probably not "a big deal" considering the relative low current.


Here was the answer:
I would not recommend to use the PowerCON for anything else than 230V applications as it is “sold as such” and you will run into the risk that someone “hooks it up to 230V” and you will have to “re-order”…..


Yes, all of our products are AC rated as we originally are a company that designs and produces for Audio applications. And audio is AC…..


However, that does not mean that our products cannot be used for DC but as our ‘Target Market” has hardly any interest in that we do not specify those (DC) properties.


I could recommend our Speakon line of products, made for higher currents and lower voltages (less risk when mixed up with other applications). They basically have the same form factor so that should fit you as well.


http://www.neutrik.com/en/speakon/
 
#117
Trimmer potentiometers come centered (or close to it) from the factory, and in this amp that's a completely fine starting point.

The startup noise is the output coupling cap charging up, it's normal.

I've used SpeakOn connectors for DC umbilical, they work beautifully.
 
#120
MEPER said:
About the use of PowerCon for the power I asked Neutrik what they would recommend for DC power. They recommended the SpeakOn connectors. But probably not "a big deal" considering the relative low current.


Here was the answer:
I would not recommend to use the PowerCON for anything else than 230V applications as it is “sold as such” and you will run into the risk that someone “hooks it up to 230V” and you will have to “re-order”…..


Yes, all of our products are AC rated as we originally are a company that designs and produces for Audio applications. And audio is AC…..


However, that does not mean that our products cannot be used for DC but as our ‘Target Market” has hardly any interest in that we do not specify those (DC) properties.


I could recommend our Speakon line of products, made for higher currents and lower voltages (less risk when mixed up with other applications). They basically have the same form factor so that should fit you as well.


http://www.neutrik.com/en/speakon/
Click to expand...

It will be for the AC voltage.
 
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