The chassis is decent size, but I'm still a bit surprised you find it quite cool. Would you have an electric power monitoring device
(something like this: https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU ) that you can use to estimate
the power draw from the amp? At standard bias level, it should be drawing ~150W range.
Also, you can try measuring the gain of your preamp. First measure the AC output of a sine test signal from the DAC and then
measure the AC output through the preamp with the volume at max. The standard gain of your preamp is 20dB or 10x
so the preamp output should be 10x that of the DAC. If the gain has been reduced by 6dB then the preamp output will only be 5x
that of the DAC.
(something like this: https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU ) that you can use to estimate
the power draw from the amp? At standard bias level, it should be drawing ~150W range.
Also, you can try measuring the gain of your preamp. First measure the AC output of a sine test signal from the DAC and then
measure the AC output through the preamp with the volume at max. The standard gain of your preamp is 20dB or 10x
so the preamp output should be 10x that of the DAC. If the gain has been reduced by 6dB then the preamp output will only be 5x
that of the DAC.
I am back!!!
From the DAC I have about 1.44V on the output, I then measured the SP9 output on full volume at about 7V so it is what it is, the gain is about 5 times as by @Dennis Hui calculations, there is the 6db cut into the preamp gain.
I removed the bottom grille of the preamp and it seems the connection on the pads were interrupted, my guess is it takes a simple drop of soldiering but I rather have somebody good at it doing it for me and then I will have more current to feed to the F4 and the 6db should make it sound louder, am I correct?
From the DAC I have about 1.44V on the output, I then measured the SP9 output on full volume at about 7V so it is what it is, the gain is about 5 times as by @Dennis Hui calculations, there is the 6db cut into the preamp gain.
I removed the bottom grille of the preamp and it seems the connection on the pads were interrupted, my guess is it takes a simple drop of soldiering but I rather have somebody good at it doing it for me and then I will have more current to feed to the F4 and the 6db should make it sound louder, am I correct?
I handed it to my friend so that he can eventually also verify general health of the old SP9, he will hopefully build me the BA-3 in fall but I don't want to now listen the F4 through the little Adcom to have an extra gain so there the SP9 goes for a drop of solder and a general check
Grazie
Which pads need connecting? I see some butchery went on earlier. You got some iron marks on that main pad, looking like they severed the connection there between A and B (guessing that is the intent of the A and B markings). Also got some cut marks between the pads in question and the pad above it. Might be worth a call or email to Audio Research to verify correct "repair".
Relooking at the picture with my glasses on, guessing it is the A pads to the "T"? That's explain the cut marks. Butchery. Makes me a bit sad inside.
Relooking at the picture with my glasses on, guessing it is the A pads to the "T"? That's explain the cut marks. Butchery. Makes me a bit sad inside.
The AR SP9 is back with it'f full output and things got much better, I can tell the 25W of the F4 being on the edge for a 90dbW/m speakers, now it's about to be patient and wait for fall and to put together the BA-3, I can't recall it's output gain now but as somebody suggested I am dimensioning the power supplies to 32v as to get the max output/min distortion and, hey, if things still won't work, maybe a speaker upgrade (I should upgrade to a rich wife first...).
Too tired and strict on time to relax and enjoy it but now playing some Dire Straits, volume knob all the way to the max, sound pressure is ok, F4 quite cool, more to come but I just wanted to say, once more, GRAZIE to all of you for precious suggestions and patience
Too tired and strict on time to relax and enjoy it but now playing some Dire Straits, volume knob all the way to the max, sound pressure is ok, F4 quite cool, more to come but I just wanted to say, once more, GRAZIE to all of you for precious suggestions and patience
To get 25W at 8 Ohm, you need to feed your F4 with about 15Vrms.
Your SP9 has gain of 10X at its high level input or if your SP9 is a MkII or MkIII, it also has a CD input with a gain of 2.8X (9dB). The SP9 is capable of outputting 50Vrms (5Vrms input). So if you use the high level input, your source needs to output 1.5Vrms to your SP9 in order for your F4 drive 8 Ohm speakers to 25W. So the SP9 is capable of driving your F4 to maximum output as long as you have enough input voltage to feed it.
ARC SP9 Information
Your SP9 has gain of 10X at its high level input or if your SP9 is a MkII or MkIII, it also has a CD input with a gain of 2.8X (9dB). The SP9 is capable of outputting 50Vrms (5Vrms input). So if you use the high level input, your source needs to output 1.5Vrms to your SP9 in order for your F4 drive 8 Ohm speakers to 25W. So the SP9 is capable of driving your F4 to maximum output as long as you have enough input voltage to feed it.
ARC SP9 Information
Giovanni,
Earlier you mentioned a 1.4V rms measured output from your DAC. If your SP9 now gives a gain of 20dB (10x) then at max signal you should get near the max output of the F4. (You can measure the output from your preamp again to verify the gain.)
It's possible with your speakers, room size and listening preference, that you need a more powerful amp.
Would you be able to try this test using your original amp? (I'm assuming your original amp is loud enough.)
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
It'll show how much voltage swing you need and whether it's higher than what the F4 can provide.
Cheers,
Dennis
Earlier you mentioned a 1.4V rms measured output from your DAC. If your SP9 now gives a gain of 20dB (10x) then at max signal you should get near the max output of the F4. (You can measure the output from your preamp again to verify the gain.)
It's possible with your speakers, room size and listening preference, that you need a more powerful amp.
Would you be able to try this test using your original amp? (I'm assuming your original amp is loud enough.)
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
It'll show how much voltage swing you need and whether it's higher than what the F4 can provide.
Cheers,
Dennis
Hi,
I have been enjoying this preamp for the last 2 weeks.
It is an outstanding preamp - for me the best sounding one I have built/owned with an excellent soundstage and very musical. Thanks to Mr. Nelson and the diy community.
I can highly recommend shunt regulators to pair them with BA-3.
Cheers.
I have been enjoying this preamp for the last 2 weeks.
It is an outstanding preamp - for me the best sounding one I have built/owned with an excellent soundstage and very musical. Thanks to Mr. Nelson and the diy community.
I can highly recommend shunt regulators to pair them with BA-3.
Cheers.
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I am finishing up work on a BA-3 as a preamp - using a Super Regulator power supply from DIYAudioStore.
The Super Regulator has independent positive and negative supplies with independent ground/returns. The BA-3 has +, - supply and ground per channel.
Possibly dumb question - can the independent returns to the Super Regulator + and - sides be linked? And can the BA-3 left and right grounds be linked to that?
Thanks in advance for any insights.
bmdduck
The Super Regulator has independent positive and negative supplies with independent ground/returns. The BA-3 has +, - supply and ground per channel.
Possibly dumb question - can the independent returns to the Super Regulator + and - sides be linked? And can the BA-3 left and right grounds be linked to that?
Thanks in advance for any insights.
bmdduck
I went full dual mono for the very highest performance possible and least interchannel crosstalk in my preamp. It's controversial but that's the path I chose.
https://www.diyaudio.com/community/threads/super-regulator.247281/page-132#post-6953315 (and my following responses to questions)
All "combining" of the wires needs to take place at the load, not at the Superreg itself. The old Super Regulator articles are extremely helpful in understanding how to properly implement them in your system.
https://www.diyaudio.com/community/threads/super-regulator.247281/page-132#post-6953315 (and my following responses to questions)
All "combining" of the wires needs to take place at the load, not at the Superreg itself. The old Super Regulator articles are extremely helpful in understanding how to properly implement them in your system.
