Hi Sunscreen
in the past i was interested in tube sound but i here some audio note and other amps. but to be honest i do not want to change sometime tubes...
if the ACA is like a tube sound amp...i like it
i agree with all comments here. i like the ACA. i use it with 4R 84dB speakers and a 25m2 room with just 2,30 height. i like the sound..as aseptically if i mod it with premium parts. in future i try to find my best to use 2x ACA parallel because of my 4R speakers.
you will not be disappointed.
chris
in the past i was interested in tube sound but i here some audio note and other amps. but to be honest i do not want to change sometime tubes...
if the ACA is like a tube sound amp...i like it
i agree with all comments here. i like the ACA. i use it with 4R 84dB speakers and a 25m2 room with just 2,30 height. i like the sound..as aseptically if i mod it with premium parts. in future i try to find my best to use 2x ACA parallel because of my 4R speakers.
you will not be disappointed.
chris
Thanks Chris
I'm an old tube guy but I DO like a good sounding solid state amp,. Like my Marantz 250. I've only heard a few good ones over the decades. I find newer solid state amps to aggravate my tinnitus. With the ACA having more second order distortion I was hoping for a smoother more pleasing sound.
I'm an old tube guy but I DO like a good sounding solid state amp,. Like my Marantz 250. I've only heard a few good ones over the decades. I find newer solid state amps to aggravate my tinnitus. With the ACA having more second order distortion I was hoping for a smoother more pleasing sound.
Low or no feedback ACA?
I build SET tube amps for the most part, but have an ACA and really like it. I have a pair of the older style monoblocks, and they have been upgraded to the current spec by using 24 Volts and by doing the necessary circuit changes. I recently completed a new ACA build, and used the feedback resistor value used in the older ACA.
Has anyone built and listened to an ACA with even less feedback than the older model? How about no feedback? Is no feedback advisable?
I build SET tube amps for the most part, but have an ACA and really like it. I have a pair of the older style monoblocks, and they have been upgraded to the current spec by using 24 Volts and by doing the necessary circuit changes. I recently completed a new ACA build, and used the feedback resistor value used in the older ACA.
Has anyone built and listened to an ACA with even less feedback than the older model? How about no feedback? Is no feedback advisable?
Yes
The ACA sounds very good with a little less feedback and a little more bias current.
Tungsten Audio: I did a bit of searching and found your mod posts...
“I changed the input resistor R11 to 20k and the feedback resistor to 90.9k. The ratio was chosen to be the same as the Zen V4, a design which I've been studying for a while, and has a similar topology.”
Is this still your recommendation? How many DB of feedback does that work out to? My recent ACA build is a regular stereo amp in a single chassis, so
I won’t be bridging it.
I built it with the old input and feedback resistor values of 10K and 68.1K. I just finished it tonight and am listening to it right now. It sounds great! Here’s a photo.
Attachments
Hi tizman
nice amp...well done...
gain setteing - AFAIK :
for a stereo amp its better to use a 10k and a 68k as gain setting. its a bit high and you can use 37k instead for 68k. to get the gain down and i remember some measurements that then the THD is less. and final gain of 10,5 to 11,5 is better THD too. +10k input resistor injected less noise like a 20k input resistor.
for using L+R channel for parallel mono you get 10k//10k for your source! so its better to change the input resistor to 20k for each channel and set Rf 90k or less.
chris
nice amp...well done...
gain setteing - AFAIK :
for a stereo amp its better to use a 10k and a 68k as gain setting. its a bit high and you can use 37k instead for 68k. to get the gain down and i remember some measurements that then the THD is less. and final gain of 10,5 to 11,5 is better THD too. +10k input resistor injected less noise like a 20k input resistor.
for using L+R channel for parallel mono you get 10k//10k for your source! so its better to change the input resistor to 20k for each channel and set Rf 90k or less.
chris
Thanks chermann. It sounds great, like a SET amp, with great presence, but with much better bass. I am getting noise through the speakers though. It sounds like a random chattering sound like “tch tch tch”. My listening room is very quiet, so I came hear the noise coming through the speakers from the listening position. It raises the ambient noise in the room, and since it’s pretty much the only noise in the room, it’s noticeable. I am using Klipsch La Scala, which are very high sensitivity, and very sensitive to noise. I don’t recall my old style monoblock ACAs being noisy at all with these same speakers. I’ll have to try them in the same setup tomorrow. I am using the same two 24 Volt laptop supplies that I use with the older monoblock ACAs. Could it be that the noise is coming from the laptop supplies?
Hi Tizman
as zen mod wrote: noise from both channels?
SMPS can make some noise if the are in hickup mode = to much caps as load
or
SMPS which oare in diel mode are a bit mnoise = strange beep tone, and if they are under load then its quiet.
but noise over the speakers??
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Zen Mod: Yes. The amp has both channels in one chassis with two laptop supplies feeding it. I hear the same sound out of one channel when I unplug one of the supplies. It’s very quiet, but audible at the listening position.
chermann: Yes, noise through the speakers. The blocks get warm when in use for a while. They are identical 24 Volt, 2.5 amp supplies. Unplugging one leaves the same noise in the other channel. I have a different 24 Volt supply here, but it needs its plug changed to fit the inlet. I’ll do that and report back. Can I try using a 19 volt laptop brick to see if that makes the noise go away?
Zen Mod: Is it okay to try with a 19 Volt brick as a fast and dirty test? If not, I can change the plug on the 24 Volt one.