I have been asked by management to comment on a couple of subjects
relating to the updates on the original ACA.
Power supply:
It's not that the original 19V supply had any real problems, but it ran
warmer than I liked, had some RF noise (they all have some), and
being surplus had availability issues.
We have tested several 24V desktop switchers for use in these
amplifiers, and selected one, the Meanwell GST120A24-P1M.
A good price has been negotiated from distribution , it is reliable with
warranty, runs cool, and was quieter than the others tested. It will be
available in the store.
Performance of the newer ACA:
The name has gotten confused, originally being ACA 1.1 on the artwork,
then ACA 1.5. Doesn't matter, it's now the 1.5 for sure.
I have run some distortion and power curves on these various versions
to give some idea of the differences in performance. You will see these
below, and to put it simply, the ACA 1.5 has lower distortion, and with the
24V transformer, more power. Probably the cheapest and most effective
tweak you would ever want.
You can use also this supply on the original ACA, but you will want to
adjust the DC value on the output up to 12V. You can also adjust the
feedback resistor and bias resistors down to the values of the ACA 1.5.
The ACA 1.5 being stereo, there is the possibility of driving it with
balanced lines so as to have more power. You can install the XLR
input on the back, and if you have a balanced source, you're all done,
you just connect your speaker across the black output terminals,
with the left ch being "+" phase, and the right ch being "-" phase
(the channels each being inverting, the red terminals are ground,
and not used).
Any questions, you can post them here.
relating to the updates on the original ACA.
Power supply:
It's not that the original 19V supply had any real problems, but it ran
warmer than I liked, had some RF noise (they all have some), and
being surplus had availability issues.
We have tested several 24V desktop switchers for use in these
amplifiers, and selected one, the Meanwell GST120A24-P1M.
A good price has been negotiated from distribution , it is reliable with
warranty, runs cool, and was quieter than the others tested. It will be
available in the store.
Performance of the newer ACA:
The name has gotten confused, originally being ACA 1.1 on the artwork,
then ACA 1.5. Doesn't matter, it's now the 1.5 for sure.
I have run some distortion and power curves on these various versions
to give some idea of the differences in performance. You will see these
below, and to put it simply, the ACA 1.5 has lower distortion, and with the
24V transformer, more power. Probably the cheapest and most effective
tweak you would ever want.
You can use also this supply on the original ACA, but you will want to
adjust the DC value on the output up to 12V. You can also adjust the
feedback resistor and bias resistors down to the values of the ACA 1.5.
The ACA 1.5 being stereo, there is the possibility of driving it with
balanced lines so as to have more power. You can install the XLR
input on the back, and if you have a balanced source, you're all done,
you just connect your speaker across the black output terminals,
with the left ch being "+" phase, and the right ch being "-" phase
(the channels each being inverting, the red terminals are ground,
and not used).
Any questions, you can post them here.
Attachments
and yes , question regarding 1.1 vs. 1.5 version , is certainly most intriguing and important one in last decade .....
It seems there is not much gain in power to drive the ACA in balanced mode. 7W vs. 10W at 1% distortion in 8 ohm?
Threre is a relative big improvement in performance going from 19V to 24V. Is 24V the optimal voltage or could we still se a improvement going to e.g. 28V?
Hoes does the ACA perfrom driving a 4 ohm speaker?
Is the output cap large enough to drive a 4 ohm speaker at low frequencies?
Threre is a relative big improvement in performance going from 19V to 24V. Is 24V the optimal voltage or could we still se a improvement going to e.g. 28V?
Hoes does the ACA perfrom driving a 4 ohm speaker?
Is the output cap large enough to drive a 4 ohm speaker at low frequencies?
IT'S ALIVE!
I plugged in speakers, input, and power supply and not realizing that the phone was still playing Spotify, flipped the power switch.
I looked for sparks or the magic smoke; one second, two seconds, three seconds and suddenly glorious music! An unknown song from Spotify, nondescript $15 dollar Tang Band drivers in my shop speakers, and clearly better sound!
So success first time. The bias before setting was 9V on one channel, 11V on the other so fairly close.
It's all buttoned up now and playing with my Alpair 7.3 Metronome Tributes in the living room. Better supported bass and balance to the sound. You can hear deeper into the music.
A huge thanks to Nelson Pass, Variac, 6L6 and the whole DiyAudio community.
-Tom-
PS: The bad news is that the sound of the air-conditioning on the "Mining for Gold" from Cowboy Junkies Trinity Sessions is now really obtrusive!
I plugged in speakers, input, and power supply and not realizing that the phone was still playing Spotify, flipped the power switch.
I looked for sparks or the magic smoke; one second, two seconds, three seconds and suddenly glorious music! An unknown song from Spotify, nondescript $15 dollar Tang Band drivers in my shop speakers, and clearly better sound!
So success first time. The bias before setting was 9V on one channel, 11V on the other so fairly close.
It's all buttoned up now and playing with my Alpair 7.3 Metronome Tributes in the living room. Better supported bass and balance to the sound. You can hear deeper into the music.
A huge thanks to Nelson Pass, Variac, 6L6 and the whole DiyAudio community.
-Tom-
PS: The bad news is that the sound of the air-conditioning on the "Mining for Gold" from Cowboy Junkies Trinity Sessions is now really obtrusive!
Attachments
Would you mind sharing with the class the connection for the XLR connector? Assume you just move the left and right inputs to pin 2 and 3 of the XLR? Just want to verify.
With really efficient speakers - one watt out of this amp is lots of sound! Expect the more power may come in handy for less efficient speakers or auditoriums!
Great work!
With really efficient speakers - one watt out of this amp is lots of sound! Expect the more power may come in handy for less efficient speakers or auditoriums!
Great work!
Thanks for that ZM. I have some nice foil resistors for those values, right on the edge. Hope about C2 needed quality! I have some ruby MBZ 1500uf 16v for there, ok? What is it doing in the circuit? Trying to build this with recycled parts mostly, with a Frankin(stien) heat sink enclosure. Will post a photo when operating