I am going to be relocating to a very hot area shortly and was wondering if it might be feasible just to have that resistor switched to make it easy to place it in/out of the circuit. I have the older boards without the new pads for it.
I plotted the distortion curves for different quiescent currents in post 713. An increased current seems to increase THD above 2KHz. It also increases the open loop gain slightly.
That should work just fine as long as the power supply can handle it.
That's Interesting. I diy not see that before, but it could explain the differences I hear, a more coherent sound with softer treble. Thanks for the hint
I have been sitting on a Kit of ACAs for a while now. Finally made some time to put it together. It is rather fun until it doesn't work. LOL.
I am needing some help.
One of the ACA fired up fine and I was able to set the bias and it sounds great.
The second one however, bias was set but when hooking up to the speakers, there was no sound. I started to probe with my DMM. There was distorted sound going through the speakers when I touched the 3rd leg of the Q1 mosfet. I thought maybe it was a cold solder joint so I redid it. Turning it back on, again no sound. I check the 2nd leg and it's now reading 18 volts from 10 volts before.
Turning it down, the lowest it goes is now 15 volts.
Is there a chance that a Mosfet is bad?
I am needing some help.
One of the ACA fired up fine and I was able to set the bias and it sounds great.
The second one however, bias was set but when hooking up to the speakers, there was no sound. I started to probe with my DMM. There was distorted sound going through the speakers when I touched the 3rd leg of the Q1 mosfet. I thought maybe it was a cold solder joint so I redid it. Turning it back on, again no sound. I check the 2nd leg and it's now reading 18 volts from 10 volts before.
Turning it down, the lowest it goes is now 15 volts.
Is there a chance that a Mosfet is bad?
Hi guys
About a month I decided to order the Nelson Pass ACA anp pcb boards from diyaudio. I wanted to try it with some Fostex FX120 speakers but was also curious how it would work with my HE-6 headphones which are notoriously hard to drive.
Yesterday I had it up and running and its worked really well driving the Fostex FX 120 which are diy Fonken enclosures.
I built a little adapter and have been running the HE-6 headphone off of the speaker taps with nice results. I'm going to try swapping out the 10uf electrolytic signal capacitors for some film ones next, but this inexpensive little amp I am sure with a little further tweaking is going to make a really sweet combo for my HE6 cans. Its also sounding good with the HD800 headphones but I have a little low level volume noise to chase down with it on them. I am pretty certain its from my unshielded adapter cabling picking up interference (I just used what I had in the parts box).
I put the two mono block amp sections in one home brew enclosure drawing on inspiration from other builds here and am using my Bottlehead Mainline (headphone amp) for preamp and volume control duty.
Its up and running but still requires a little tweaking I expect I will swap out the unshielded signal wires for shielded and try a few different film cap options but am pleased and very encouraged with the results I am hearing so far.
Cheers all its a lot of fun and 19V dc was a lot less nerve wracking than working on tube based gear.
I took some temperature measurements taken with a IR thermometer
After 2 hours the heat sinks are reading 49°C at the hottest spots radiating out to 37°C at the ends of the heat sink. This is with the amp configured to run at 6W. When running in 5W configuration and the heat sinks temperature was much lower below 37°C I would guess (no IR yesterday) but I could easily keep my hand on the heat sinks. Now at 49°C holding my hand on them for any more than a count of 10 is getting uncomfortable.
I was catching up on my paper work yesterday with speakers on and the amp definitely has that distracting quality to it that can draw you in and you end up stopping what your doing to listen!
About a month I decided to order the Nelson Pass ACA anp pcb boards from diyaudio. I wanted to try it with some Fostex FX120 speakers but was also curious how it would work with my HE-6 headphones which are notoriously hard to drive.
Yesterday I had it up and running and its worked really well driving the Fostex FX 120 which are diy Fonken enclosures.
I built a little adapter and have been running the HE-6 headphone off of the speaker taps with nice results. I'm going to try swapping out the 10uf electrolytic signal capacitors for some film ones next, but this inexpensive little amp I am sure with a little further tweaking is going to make a really sweet combo for my HE6 cans. Its also sounding good with the HD800 headphones but I have a little low level volume noise to chase down with it on them. I am pretty certain its from my unshielded adapter cabling picking up interference (I just used what I had in the parts box).
I put the two mono block amp sections in one home brew enclosure drawing on inspiration from other builds here and am using my Bottlehead Mainline (headphone amp) for preamp and volume control duty.
Its up and running but still requires a little tweaking I expect I will swap out the unshielded signal wires for shielded and try a few different film cap options but am pleased and very encouraged with the results I am hearing so far.
Cheers all its a lot of fun and 19V dc was a lot less nerve wracking than working on tube based gear.
I took some temperature measurements taken with a IR thermometer
After 2 hours the heat sinks are reading 49°C at the hottest spots radiating out to 37°C at the ends of the heat sink. This is with the amp configured to run at 6W. When running in 5W configuration and the heat sinks temperature was much lower below 37°C I would guess (no IR yesterday) but I could easily keep my hand on the heat sinks. Now at 49°C holding my hand on them for any more than a count of 10 is getting uncomfortable.
I was catching up on my paper work yesterday with speakers on and the amp definitely has that distracting quality to it that can draw you in and you end up stopping what your doing to listen!
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
no need , if you are satisfied with sound (brightness) and there is no oscillation
that's "just" gate stopper
for further fun , cascode input JFet with BC546 , base at , say, 12V
simple resistor divider with cap across lower one will do
say 12K down , 8K2 up , 12K bypassed with 10uF
that's "just" gate stopper
for further fun , cascode input JFet with BC546 , base at , say, 12V
simple resistor divider with cap across lower one will do
say 12K down , 8K2 up , 12K bypassed with 10uF
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Has anyone, or can you, make a headphone amp out of an ACA?
I wanted to see if I can make in one chassis, a B1 line stage with an additional headphone amp out of the ACA. I would like to make a balanced line stage that I believe would require two B1 boards. Making it balanced would require a more substantial power supply, I believe. Could this power supply also power the headphone amp portion as well?
Thanks and if was already covered my apologies, I just couldn't find it in the threads.
Thanks
I wanted to see if I can make in one chassis, a B1 line stage with an additional headphone amp out of the ACA. I would like to make a balanced line stage that I believe would require two B1 boards. Making it balanced would require a more substantial power supply, I believe. Could this power supply also power the headphone amp portion as well?
Thanks and if was already covered my apologies, I just couldn't find it in the threads.
Thanks
Yes you could build a scaled down in current - version of the ACA with IRF610 instead of '240s .
Keep in mind that is necessary to check polarity of the signals since ACA is inverting if using Headphones .
ACA is single ended , then non need for a balanced line stage IMHO , unless you would need it for inverting purposes , in that case BOSOZ would be a better choice compared to a double B1.
Hope that helps ,
S
Wood
Hi John
Thanks for your kind comments the type of wood is called Zebrano
Regards
Jamie
Hi John
Thanks for your kind comments the type of wood is called Zebrano
Regards
Jamie
An externally hosted image should be here but it was not working when we last tested it.
So far I have tried the ACA with Hifiman HE-6, Sennheiser HD800 & Beyerdynamic T1.
I am running straight from my Dac--->ACA (speaker tap adapter)--->Headphones. You will need a way to control the volume this way either a passive attenuator or via your media software if pc/server based. Its worked out so well I'm already thinking along the lines of building another this time with a passive attenuator and XLR head out built in to the enclosure.
Cheers
Jamie
Thanks for the information and the assurance. The idea was to have the ACA for headphones only and to a have balanced line stage for my other balanced sources and balanced output for my First Watt J2. I hope that makes sense? It's a shame to spend so much money a commercial companies version, if these well thought out diy options are available. I got the idea from reading another thread and also finding out that some headphones amps put out 4 watts, and in comparison the ACA puts out 5, which is close.
That sounds cool. I'm glad you responded, gives me confidence in doing it.
Thanks again
Its just seems like the ACA just fits as a headphone amp. Also, it could be another great way to get young people into hifi electronics because they are the reason for the exponential growth of the headphone business.
I still am not quite clear on the power supply. Is there the ability to power both the line stage and the ACA off the same power supply?