Quote: Simple question – to run the ACA mini in parallel mono, do I parallel both the positive and negative outputs and run a Y cable into the inputs?
YES
Now, to make it even simplier, if my memory serves me well - seems I did it ages ago - the inputs grounds are already in parallel (though you might not bother if using Y cables) and the output/LS grounds are already in parallel so that saves you 50% of the work on that side. Note that paralleling them didn't change anything and didn't at mine introduce any ground loops, but well, it is not needed as already there at grounds so we did without.
I hope this helps
Claude
YES
Now, to make it even simplier, if my memory serves me well - seems I did it ages ago - the inputs grounds are already in parallel (though you might not bother if using Y cables) and the output/LS grounds are already in parallel so that saves you 50% of the work on that side. Note that paralleling them didn't change anything and didn't at mine introduce any ground loops, but well, it is not needed as already there at grounds so we did without.
I hope this helps
Claude
Ah, a useful picture has been posted exactly same time I posted my long text,- I probably should have waited for a few minutes LOL!
That's what I did, but if I remember well the ground connection at the RCA inputs is not needed as already there on the Mini - just check please to make sure. On 6L6's excellent picture that would be the blue bottom "smiley" cable LOL
All other cables in the pix are mandatory needed
That's what I did, but if I remember well the ground connection at the RCA inputs is not needed as already there on the Mini - just check please to make sure. On 6L6's excellent picture that would be the blue bottom "smiley" cable LOL
All other cables in the pix are mandatory needed
Thank you, Stanislav and ClaudeG.
I knew it was in there, but the search function didn’t turn it up. And 3000+ posts is a lot to scroll through!
Also, the reply from 6sX7 above, directing me to the ACA mini directions, was different/ that one connected the black (negative) outputs, whereas the 6L6 photo connects the red (positive) outputs. As ClaudeG says, if the negatives are already connected, it won’t matter.
Thank you again- I’ll keep looking for the post from 6L6 thst came with the photo!
I knew it was in there, but the search function didn’t turn it up. And 3000+ posts is a lot to scroll through!
Also, the reply from 6sX7 above, directing me to the ACA mini directions, was different/ that one connected the black (negative) outputs, whereas the 6L6 photo connects the red (positive) outputs. As ClaudeG says, if the negatives are already connected, it won’t matter.
Thank you again- I’ll keep looking for the post from 6L6 thst came with the photo!
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^ As you sort this all out... it's critical to note that the "signal" or "out" for the original ACA is connected to the 'black' binding posts sometimes noted as '-' for a typical build. The red binding posts sometimes noted as '+' are connected to audio GND.
The ACA Mini has the "signal" or "out" connected to the 'red' or '+' in a typical build.
DO NOT follow the instructions for the original ACA per 6sX7. That is not directly applicable to the Mini.
DO follow the pic posted above from Stanislav. Note that ClaudeG has advised correctly that it's not necessary to have the GND tabs on the RCA inputs shorted with a jumper wire b/c they are connected via traces on the PCB. (See the article and/or beep it out / look at the traces on your board). However, if you intend to use a simple commercial "Y-cable" with the GND internally connected, it won't hurt a thing.
The ACA Mini has the "signal" or "out" connected to the 'red' or '+' in a typical build.
DO NOT follow the instructions for the original ACA per 6sX7. That is not directly applicable to the Mini.
DO follow the pic posted above from Stanislav. Note that ClaudeG has advised correctly that it's not necessary to have the GND tabs on the RCA inputs shorted with a jumper wire b/c they are connected via traces on the PCB. (See the article and/or beep it out / look at the traces on your board). However, if you intend to use a simple commercial "Y-cable" with the GND internally connected, it won't hurt a thing.
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Thank you for the explicit confirmation, ItsAlInMyHead. And for the +/- reminder about the outputs.
I’m ready to do it now!
I’m ready to do it now!
^ Any time.
Also - For reference. Links below should take you to Posts 1833 and 1840
Also - For reference. Links below should take you to Posts 1833 and 1840
I want to house my aca mini in a spare aca case, obviously it means having the mosfets on extension cables to the heatsinks, are there any issues with this? Also any thermal issues pairing mosfets on the same heatsink for this design??
I've done exactly that, fitted the ACA Mini in a proper case with the FETs on a common sink and gate resistors just in case.
Check post #2527 for all the details.
Check post #2527 for all the details.
That's great, just what I wanted to hear. Forgive my ignorance but what are the gate resistors for?
As a precaution. In case of HF oscillations.
May not be needed but I wanted to be safe, like wearing belt and suspenders.
Try without and check with a CRO for oscillations.
P.S. I said CRO as I still use an old HP one. Most oscilloscopes are now of the digital variety.
May not be needed but I wanted to be safe, like wearing belt and suspenders.
Try without and check with a CRO for oscillations.
P.S. I said CRO as I still use an old HP one. Most oscilloscopes are now of the digital variety.
An old pair of ears are my scope, the real thing is way above my pay grade, so of course I'm going to crack on and case the amp without the gate resistors. Would these oscillations be audible?
Audible is hard to say, we don't hear that high.
But HF oscillations are dangerous for the health of the amp, they usually destroy the output devices by generating extra heat quite quickly. By the time you know your amp is oscillating it will be too late to prevent it.
I think that's what happened to the original FETs in my Mini.
On the original PCB the output FETs don't need gate resistors as the signal path is very short.
When you put your output FETs further away and connected with some wires to the PCB you create some parasitic resistances and probably some inductance too.
This could be one reason why parasitic oscillations occur in amp circuits.
I'm sure more learned guys than me will jump in and better explain why oscillations happen and what to do about them.
I also know that some people hate gate and source resistors with some passion.
I'm not from that clan, I like to play it safe and simple.
Let us know how you go, always interesting to hear other peoples experience.
Have fun and good luck.
But HF oscillations are dangerous for the health of the amp, they usually destroy the output devices by generating extra heat quite quickly. By the time you know your amp is oscillating it will be too late to prevent it.
I think that's what happened to the original FETs in my Mini.
On the original PCB the output FETs don't need gate resistors as the signal path is very short.
When you put your output FETs further away and connected with some wires to the PCB you create some parasitic resistances and probably some inductance too.
This could be one reason why parasitic oscillations occur in amp circuits.
I'm sure more learned guys than me will jump in and better explain why oscillations happen and what to do about them.
I also know that some people hate gate and source resistors with some passion.
I'm not from that clan, I like to play it safe and simple.
Let us know how you go, always interesting to hear other peoples experience.
Have fun and good luck.
That's a great explanation Stanislav thanks a lot, think you have talked me into using gate resistors!! Next obvious question is what value and where exactly do they go?
Parasitic oscillation whether audible or not will worsen the technical performance of any amp significantly . Depending on the frequency it could also endanger tweeters with large amounts of energy that you can not hear.
Fit the resistors. Something like 120 ohm @ 1/8 or 1/4 watt is fine. Fit them as close to the FET as practicable. Job done.
Fit the resistors. Something like 120 ohm @ 1/8 or 1/4 watt is fine. Fit them as close to the FET as practicable. Job done.