I know about this discussion, and someone answered with brilliant quote "“If it measures good and sounds bad, — it is bad. If it sounds good and measures bad, — you've measured the wrong thing.”
Yes it could play with any speaker but how would it play is another story...
Good morning
Yes the ACA is really sounding very fine and bigger that you imagine
. after a long break i had a very nice music session with my brother yesterday and he knows his F5 clone very well. my version of ACA is still near by sound with the F5. its still fantastic if you do it right = setting as recommended what 5-6W what can do to 4R speakers .
This motivate me to go ahead with my premium ACA
thank you Nelson Pass!!
chris
Yes the ACA is really sounding very fine and bigger that you imagine
. after a long break i had a very nice music session with my brother yesterday and he knows his F5 clone very well. my version of ACA is still near by sound with the F5. its still fantastic if you do it right = setting as recommended what 5-6W what can do to 4R speakers .This motivate me to go ahead with my premium ACA
thank you Nelson Pass!!
chris
Help!! So I thought everything was going well until I tried to play some music, then nothing!!. Well not quite nothing as I could hear VERY faint music with my ear right up to each speaker but much more than a meter away nothing.
I have built 2 amps simultaneously and the problem is the same with both when set up as individual stereo amps. The very faint music I can hear is the same with the rear switch in all 3 positions.
When I switch on the LEDs light up with no flickering.
All 4 channels biased ok at around 12v (24v supply).
Preliminary checks;
No continuity between mosfet drain and ground.
No continuity between each individual input and output sockets plus and minus.
Around 0.98k resistance across red and black speaker sockets (starts around 0.75 and rises to 0.98k after about 20 seconds!)
Not sure what to do next, if anyone could help please.
I have built 2 amps simultaneously and the problem is the same with both when set up as individual stereo amps. The very faint music I can hear is the same with the rear switch in all 3 positions.
When I switch on the LEDs light up with no flickering.
All 4 channels biased ok at around 12v (24v supply).
Preliminary checks;
No continuity between mosfet drain and ground.
No continuity between each individual input and output sockets plus and minus.
Around 0.98k resistance across red and black speaker sockets (starts around 0.75 and rises to 0.98k after about 20 seconds!)
Not sure what to do next, if anyone could help please.
Attachments
Nothing obvious, caps are in the right way round and the transistors. Impossible to make out the resistors from your pictures though.
Really dumb question, I'm not familiar with that 24 volt input connector, so is the wire between the two red speaker terminals soldered to the outer ring / tab? I think I can see a 'free' tab in the picture.
Then measure the resistance from the centre of each RCA to the outer, it should be about 50kΩ.
Really dumb question, I'm not familiar with that 24 volt input connector, so is the wire between the two red speaker terminals soldered to the outer ring / tab? I think I can see a 'free' tab in the picture.
Then measure the resistance from the centre of each RCA to the outer, it should be about 50kΩ.
Fine with the 24 volt part then.
Then I should have said do the resistance test with the switch in the central position. Other wise you get resistors in parallel.
Still odd results though. Please check again and look at the schematic. The centre of the RCA connects to R11 (10kΩ) then to R12 (39kΩ) then to R14 (1kΩ), so the path to the outer ring or ground has to be 10 + 39 + 1 = 50kΩ.
Check for the correct resistor values in the correct locations, then for shorts etc.
Alan
Then I should have said do the resistance test with the switch in the central position. Other wise you get resistors in parallel.
Still odd results though. Please check again and look at the schematic. The centre of the RCA connects to R11 (10kΩ) then to R12 (39kΩ) then to R14 (1kΩ), so the path to the outer ring or ground has to be 10 + 39 + 1 = 50kΩ.
Check for the correct resistor values in the correct locations, then for shorts etc.
Alan
so with the switch in the centre one amp gives about 10.9k for each RCA and the other has 10.9k in one channel and still zero for the other.
If any of the signal wires on the board reached the heatsink I would get continuity at the sockets right? If so then all is ok on these.
Yes the binding post were meant to have solder tags but didn't so I went straight onto the threads, its ugly but seems ok.
I would be amazed if it was a wrong resistor value as I was very methodical in measuring and separating but of course I can't rule it out. Likewise for any shorts as I did inspect the boards before mounting, but of course I will check all these again.
Whatever I have done seems to have repeated on all 4 boards. I'm curious if some sort of short on one board would also affect the other channel?
If any of the signal wires on the board reached the heatsink I would get continuity at the sockets right? If so then all is ok on these.
Yes the binding post were meant to have solder tags but didn't so I went straight onto the threads, its ugly but seems ok.
I would be amazed if it was a wrong resistor value as I was very methodical in measuring and separating but of course I can't rule it out. Likewise for any shorts as I did inspect the boards before mounting, but of course I will check all these again.
Whatever I have done seems to have repeated on all 4 boards. I'm curious if some sort of short on one board would also affect the other channel?
Umm,
The 1K should be good, you measure 1k across the speaker terminal. I think the 10k is correct too, you get 11k total. So R12 the 39.2k is wrong.
If you look it should be Orange, White, Red, Red, Brown. But if you look at the picture the 2nd Red band on yours is a different colour. Measure that next.
On the channel with the 0kΩ reading, unsolder the +IN wire from the board. Now measure the resistance again at that RCA connector. If it reads 0 ohms still the socket or wiring is short. If it reads open circuit (it should) then the short is at the board.
The 1K should be good, you measure 1k across the speaker terminal. I think the 10k is correct too, you get 11k total. So R12 the 39.2k is wrong.
If you look it should be Orange, White, Red, Red, Brown. But if you look at the picture the 2nd Red band on yours is a different colour. Measure that next.
On the channel with the 0kΩ reading, unsolder the +IN wire from the board. Now measure the resistance again at that RCA connector. If it reads 0 ohms still the socket or wiring is short. If it reads open circuit (it should) then the short is at the board.
Attachments
Last edited:
That's great Alan yes the R12's are all 39.2 not 39.2K!!! Just checked my Mouser order and I ordered the wrong size, what a fool. I would never have spotted that myself as I was so convinced that all the parts were ok so thanks a lot.
I still have the problem of zero resistance across 1 RCA, is that most likely a short?
I still have the problem of zero resistance across 1 RCA, is that most likely a short?
We've all done that, no shame. It does not need to be 39.2kΩ, a normal 39kΩ (or even 47KΩ) will do. If you have 'spares'.
If you have the wire off the board and the RCA still reads 0Ω then you are very close to the problem. A whisker or solder blob perhaps.
A close up of the rear of the socket might help us see too.
Alan
PS: Have a look at the switch too, a whisker or blob there to the switch body will give you a short to 0 volts through the chassis...
If you have the wire off the board and the RCA still reads 0Ω then you are very close to the problem. A whisker or solder blob perhaps.
A close up of the rear of the socket might help us see too.
Alan
PS: Have a look at the switch too, a whisker or blob there to the switch body will give you a short to 0 volts through the chassis...
Last edited:
one sure way to check, your output note should be adjustable to 1/2 b+, if you are not able to do this, then there is something definitely wrong...look for parts of wrong value and to92's inserted the wrong way....
this amp will work the first time after setting the output node to 1/2 b+...
this amp will work the first time after setting the output node to 1/2 b+...
You have filled me with envy with those Harbeths! I hold this secret desire to one day one a pair of the slightly bigger 30s, but the P3ESR are always so well regarded. I believe that you will find that most people that invest in high-cost speakers, don't usually pair them with $600 DIY equipment usually. But I'm mostly on your boat: I can trust myself to build reasonable AMPs, but probably not anyway to produce good speakers, so I'd rather have the best speakers I can buy, and then play with the other parts done by me.
As for two ACAs driving them, I think you really should give it a try. I have similar sized 8 ohm 88db Totem Kin Mini speakers that suggest 20 ~ 100W. I use a single ACA is V1.1 (I think? could be 1.0), with 18V PSU. I have all the power I need for almost all listening needs.
If you will use 2 with the 24V, I think you will enjoy them!
Good luck on your journey! Best regards,
Rafa.
Last edited:
Just saw this pop up. I recently bought a pair of Harbeth 30.2 XD in Walnut and had just build a pair of Rudi Rozek’s torroidal Amp Camps for another set of speakers. I can try the combination out and give my impressions.
Using an F6, M2x and of course F5 turbo gave me good enough sound with a nice Rel sub.
Using an F6, M2x and of course F5 turbo gave me good enough sound with a nice Rel sub.
Attachments
I would love to hear what your opinion is with the 30.2!!! Those are my dream speakers. One can always dream.
Just be sure to turn both AMPs on, as in your pic you have one on and the other off... that is certainly the recipe to very weird stereo imaging problems!
Joking aside, love your front panel finish on the ACAs!
Just be sure to turn both AMPs on, as in your pic you have one on and the other off... that is certainly the recipe to very weird stereo imaging problems!
Joking aside, love your front panel finish on the ACAs!
I'm with you on that. Unfortunately some posters assume everyone here are EE's.
It's the b+ that threw me.
.
Last edited: