Toroid mounting -
The original mounting arrangement was good, no shorted turn there.
New "upgrade" with the bar = BAD, we don't want a conductive loop around the transformers like that. You need to break that path somehow. Remove the bar, cut a section out of the bar, something....
Safety ground -
We need a close up picture of the IEC inlet. For safety, you need to have a secure connection between the IEC ground/earth terminal and your conductive chassis. Make the connection close to the IEC. Use heavy wire, scrape chassis paint if needed, use star washers, etc. Guys here will usually use a CL-60 thermistor (our "ground lift") between the power supply circuit ground and this chassis ground that we've created. There's a picture of that early in the F4 build guide somewhere. I can't tell from your pictures where, or how the ground connections have been made.
The original mounting arrangement was good, no shorted turn there.
New "upgrade" with the bar = BAD, we don't want a conductive loop around the transformers like that. You need to break that path somehow. Remove the bar, cut a section out of the bar, something....
Safety ground -
We need a close up picture of the IEC inlet. For safety, you need to have a secure connection between the IEC ground/earth terminal and your conductive chassis. Make the connection close to the IEC. Use heavy wire, scrape chassis paint if needed, use star washers, etc. Guys here will usually use a CL-60 thermistor (our "ground lift") between the power supply circuit ground and this chassis ground that we've created. There's a picture of that early in the F4 build guide somewhere. I can't tell from your pictures where, or how the ground connections have been made.
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I wouldn't want to make some mistake with grounding and blow the whole thing out, I would rather ask my friend when he comes to visit about ground, I can take a video and post it somewhere for you guys to check.
How can I instrumentally check about ground?
By the way I wanna fix the bias and DC offset then eventually work on the ground bit
How can I instrumentally check about ground?
By the way I wanna fix the bias and DC offset then eventually work on the ground bit
OK, many others have given you very good input, but I'll give you some more since I'm sort on the same boat as you: I only have ONE F4 amp. You have a preamp with 10V max output, so that will not run the F4 to its limits.
Unlike you, my Conrad Johnson PV9 will swing 20V, which means it has enough voltage to drive the F4 to its rated output... going into my new 90db/watt efficient speakers it plays quite loud, thank you. (*)
And running an F4 as a monoblock won't help you with the power, it will help you with the current, so you ought to be able to drive very low impedance loads like 2 ohms and the like... but remember you need the preamp to provide the voltage gain. (**)
So, one path for you, might be to get a preamp with more voltage swing. At one point I spoke with ARC about the LS17SE and it swings about 15V max... they have had good results driving a single F4 but they didn't specify the speakers. They have not tried driving a parallel pair of F4s. I thought I could use its balanced output for the second path, but no.... so
The other path is to build a BA3 with a balanced output (or get a balanced preamp that drives 35V across its balanced outputs) and get a second F4.. .driving them as the manual states.
In such a configuration, you'll get 100/150/200 wpc into 8/6/4 ohms.
That's my path forward... and just to make things fun, I want my BA3B build to be near full function: several inputs, tape monitor, balance and three variable outputs... two balanced, one single ended. We might put a headphone amp in there too... That preamp will drive two F4s. So we'll see. that set up will offer 200 wpc into the Maggies, which will allow me to compare it with the A2s ( I'll run those in balanced mode too).
Good luck, but I think that is The Way Forward...
Short term, you got a system misconfiguration for the F4: the wrong preamp and/or your speakers are simply not efficient enough for the 10wpc you are getting.
( You might have a problem with the F4 too.... since it should sound good at low levels too... unless you are trying to drive Maggies with 10 wpc...).
Have fun, because you are in the right path. That F4 is beyond outstanding, the only thing better will be running dual F4s in parallel configuration.
(*) Actually, I should be more accurate about the sound.. the PV9->F4->AN speakers sounds.... perfect in 99.99% of everything I throw at it... When I added the Entec MX5 woofers, well.... I have achieved a point of nirvana. At this point, most sensible people would throw in the towel and play music... but, I am not that sensible. Cheap? yes! Sensible? Never! I want to achieve NIRVANA, no matter how Quixotic this might be... and I want to do it on an hand crafted IPA beer budget, not splurge with beluga and Veuve Cliquot.
(**) I tried to start a discussion a while back about driving some amps I have laying around in parallel mode so I could drive some low impedance loads but instead some people -who I have blocked- started with Ohm's Law and did not bother to read what I was writing. Not taking into account the point I was making about low impedance loads requiring more current... anyhow, there are other issues in amplifier matching that makes running them in parallel a tricky proposition... so it will be fun running the F4 amps in parallel mode as they seem to be made for 'sort of' such operation.
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Recommend fixing the grounding and x-former mount issues first as they are related to safety.
Giovanni,
Can you please take an in focus photo of the IEC connector? (See attached). It looks like the earth pin is not connected. This is a safety feature and is what William is concerned about.
More photos of the interior, with special attention to the power supply will be useful.
Can you please take an in focus photo of the IEC connector? (See attached). It looks like the earth pin is not connected. This is a safety feature and is what William is concerned about.
More photos of the interior, with special attention to the power supply will be useful.
Attachments
@Dennis Hui here you go, you are right, the ground pin is not connected, tomorrow I will ask my friend why as I have no clue
edit: the bar connecting the transformers is non-magnetic so no ground loops and the fact the ground is not connected is on purpose, he'll explain me once we meet in person
edit: the bar connecting the transformers is non-magnetic so no ground loops and the fact the ground is not connected is on purpose, he'll explain me once we meet in person
Attachments
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The decision to go for an F4 came because of the relatively high gain of my AR SP9 and here on the forum I got several good feedbacks about both the sound quality of the amp as well as being able, with my preamp, to drive the big and old 90dbW/m JBL L220.
On the long term goal I have been also thinking of upgrading the preamplifier and the idea got more concrete once the F4 got home, first and foremost total disappointment, later on, still with help of skilled and experienced forum members I found out that ex owner of my SP9 decided to cut the gain and broke a connection on the board which is well explained in the user manual, my skilled tech friend did the repair for me and even with the full voltage swing of the SP9 the F4 felt weak, I don't know how to explain, it's not just a matter of volume pot, with my 50W KT88 amp I can't turn the know over hour 11, it gets too loud and the sound is "full", with the F4 even fully turned the music is loud but weak and by the end of the day, thanks to the forum members who are kindly helping me, I bit the bullet and with the multi meter found out that my amp has not been tuned/biased correctly.
Besides this I have already got BA-3 boards and dimensioned the preamp with almost 30V swing which should give quite ad advantage over the SP9, got an extra board just in case and the idea to make it balanced and to add another F4 has been keeping me busy for quite a while but it will become complicated, not just for me as I am not the one in charge of putting it together but even for my friend, the preamp will be anyways dual mono so all it takes to make balanced is to add the other board etc but then it would also mean to make of my F4 a bridged one and then to build another one.
Long story short, let's first see what happens once the amp gets correctly biased and the DC offset tuned, if it still doesn't do it then next comes the BA-3 based preamp and if even that doesn't work I have my old Sansui on a shelf, recently restored, throw everything away and just enjoy music... :-D
According to the Pass F4 description, you don't need to do anything to your F4, all you need is the balanced to dual single ended cable and wire the speakers accordingly. And, yes, we got the BA3 boards - many, MANY thanks!!! - so I figure that anyone building a BA3 preamp should just make it with balanced outputs. I considered asking for a balanced input ( for my RME AD/DAC ) but decided against it -for the time being.... I might regret this one decision but I must establish a limit to the madness.
Your SP-9 is contemporary with my CJ PV9... bravo! As an aside, I put teflon caps in my PV9, see if you can do that in your SP9. That was a great ARC preamp... I have been looking after the SP-14 but the sellers are nuts.
To drive the F4 to its rated output of 25wpc/8ohms you need ~14V input. My PV9 does that, but I don't know if your SP-9 will do so. I believe someone wrote that it only puts out 10V, so that means 12.5wpc/8ohms.
Now, volume settings... when I play my PV9 into a "normal" amplifier... the volume knob seldom goes higher than 10 o'clock... with the F4 it goes up to 2 or 3 o'clock. Higher than that I can hear some 'fuzzy" distortion... mostly on the voices, but not your typical..
-SIDE NOTE: Gloria, Gloria all'Egitto (*).. the massed voices, the trumpets, the royal cadence, dancing girls... all my life I've heard those. Truly awesome.... hard to concentrate... Anyhow, back to our scheduled program...
... clipping behavior... so I know the preamp is fully driving the amp. In your case it sounds like your preamp is doesn't have enough juice. Given how it works with other amps, I assume your sources swing enough voltage.
My little AN speakers are 90db/w but they have a 6 ohm rating, so that means in my case the PV9/F4 combo is putting out about 33 wpc. And it does this well, so a well running F4 should have no issue with a voltage input of 10V. But even so, assuming your speakers are working fine, the sound should be quite good. Prior to the AN speakers I was using some Elacs with only 85 db/watt and the sound was spectacular... a lower over all volume but all the of the music and soundstaging was there. So, the magic should be there so long as the speakers are not... ahem! current hogs.
With a properly functioning SP9/F4/JBL configuration you will get the magic, just not LOUD magic... so there you either need Lowthers/Horns or you will have to up the preamp.
Hmm... would it be possible to get a transformer between the SP9 and F4? It would have to be of extremely high quality, but all you would need it to up the voltage a little and the F4 should not be drawing much current anyhow.
Anyways, seems like we both are on the same quest. I'm not building these... just an American Acquaintance with a taste for Hoff's music and an awesome ability to crank out great stuff - I doubt he listens to Villa Lobos even. (**). But the end result, shall be glorious, I think.
To drive Maggies with the F4s. Perhaps Harbeth M30.1?
We should call our set up... the F4 Turbo.
Someday, I shall be able to play Aida and the elephants in The Triumphal March will sound lifelike. Who knows? I might have to build myself a Throne to listen to it.
Oh, what Sansui? I just had a G-7500 fully rebuilt. Getting a hold of replacement power transistors was long and arduous but we kept the unit sounding original. I mean, it sounds very good, but it is still vintage. Don't give up the ghost.
Oh, btw, you could always try a B1K with a pair of A2s.... THAT will rock the Titanic.... I know... Different sound, yes, but still awesome. Heck with efficient speakers, a B1K/A5 combo might just be your nirvana. It was mine for a bit, then I discovered the Moon has a Far Side.
(*) BTW, I'm listening to Aida in my office stereo: molto buono, trionfante in piccola scala!
(**) Of course, I might be wrong, for all I know he's into Shostakovich too, I should ask.
Your SP-9 is contemporary with my CJ PV9... bravo! As an aside, I put teflon caps in my PV9, see if you can do that in your SP9. That was a great ARC preamp... I have been looking after the SP-14 but the sellers are nuts.
To drive the F4 to its rated output of 25wpc/8ohms you need ~14V input. My PV9 does that, but I don't know if your SP-9 will do so. I believe someone wrote that it only puts out 10V, so that means 12.5wpc/8ohms.
Now, volume settings... when I play my PV9 into a "normal" amplifier... the volume knob seldom goes higher than 10 o'clock... with the F4 it goes up to 2 or 3 o'clock. Higher than that I can hear some 'fuzzy" distortion... mostly on the voices, but not your typical..
-SIDE NOTE: Gloria, Gloria all'Egitto (*).. the massed voices, the trumpets, the royal cadence, dancing girls... all my life I've heard those. Truly awesome.... hard to concentrate... Anyhow, back to our scheduled program...
... clipping behavior... so I know the preamp is fully driving the amp. In your case it sounds like your preamp is doesn't have enough juice. Given how it works with other amps, I assume your sources swing enough voltage.
My little AN speakers are 90db/w but they have a 6 ohm rating, so that means in my case the PV9/F4 combo is putting out about 33 wpc. And it does this well, so a well running F4 should have no issue with a voltage input of 10V. But even so, assuming your speakers are working fine, the sound should be quite good. Prior to the AN speakers I was using some Elacs with only 85 db/watt and the sound was spectacular... a lower over all volume but all the of the music and soundstaging was there. So, the magic should be there so long as the speakers are not... ahem! current hogs.
With a properly functioning SP9/F4/JBL configuration you will get the magic, just not LOUD magic... so there you either need Lowthers/Horns or you will have to up the preamp.
Hmm... would it be possible to get a transformer between the SP9 and F4? It would have to be of extremely high quality, but all you would need it to up the voltage a little and the F4 should not be drawing much current anyhow.
Anyways, seems like we both are on the same quest. I'm not building these... just an American Acquaintance with a taste for Hoff's music and an awesome ability to crank out great stuff - I doubt he listens to Villa Lobos even. (**). But the end result, shall be glorious, I think.
To drive Maggies with the F4s. Perhaps Harbeth M30.1?
We should call our set up... the F4 Turbo.
Someday, I shall be able to play Aida and the elephants in The Triumphal March will sound lifelike. Who knows? I might have to build myself a Throne to listen to it.
Oh, what Sansui? I just had a G-7500 fully rebuilt. Getting a hold of replacement power transistors was long and arduous but we kept the unit sounding original. I mean, it sounds very good, but it is still vintage. Don't give up the ghost.
Oh, btw, you could always try a B1K with a pair of A2s.... THAT will rock the Titanic.... I know... Different sound, yes, but still awesome. Heck with efficient speakers, a B1K/A5 combo might just be your nirvana. It was mine for a bit, then I discovered the Moon has a Far Side.
(*) BTW, I'm listening to Aida in my office stereo: molto buono, trionfante in piccola scala!
(**) Of course, I might be wrong, for all I know he's into Shostakovich too, I should ask.
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that bar is electrically conductive, so remove it!!!!!!
and, your Buddy is, mildly said - Bloody Idiot; every metal enclosure must have Safety Ground connected.
Safety ground not connected to chassis is a safety issue. You risk shock or electrocution if there is an accidental short to chassis.
The bar connecting the transformers may form a shorted turn at each transformer - not a good thing. You can check by measuring the resistance between the bar and the chassis. If there is continuity between the bar and chassis, you have a shorted turn.
I see ZM beat me to it.
Yet, yet... I got a bunch of vintage Japanese components and they all have a two prong plug.
Some have wooden cases, some don't.
So what has changed in the intervening 40 years? Did Godzilla get electrocuted? I thought Mothra took care of that, until we found out, by some American revisionist movie, that Godzilla is a girl and eats fish, not Toyopets.
Maybe they were heavy smokers. I recall seeing one Trio integrated that had just been brought in from the Land Of Yamato. It was covered with soot inside AND outside. Natural insulation.
But, think! 100./120VAC are survivable... 240V.. hmm... as a kid I recall being told to be VERY careful about touching "la fuerza" plugs.... then the whole country went to 240, Cruyff showed up and we went West. And I mean, real West, West... like the Eagles sang... we went looking for our Paradise.
They call it paradise
I don't know why
You call someplace paradise
Kiss it goodbye
Maybe a bit of a shock in the land of 100/120VAC is not a bad thing... it will wake you up... but the poor french... perhaps going to 240VAC was a cruel joke by the Telefunken Company?
I think it's all lawyers. Too many lawyers. Liability insurance. I want my stereo to have some crack, snapple, fizz... to be exciting, you know? Sparks!
But, think! 100./120VAC are survivable... 240V.. hmm... as a kid I recall being told to be VERY careful about touching "la fuerza" plugs.... then the whole country went to 240, Cruyff showed up and we went West. And I mean, real West, West... like the Eagles sang... we went looking for our Paradise.
They call it paradise
I don't know why
You call someplace paradise
Kiss it goodbye
Maybe a bit of a shock in the land of 100/120VAC is not a bad thing... it will wake you up... but the poor french... perhaps going to 240VAC was a cruel joke by the Telefunken Company?
I think it's all lawyers. Too many lawyers. Liability insurance. I want my stereo to have some crack, snapple, fizz... to be exciting, you know? Sparks!
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well, frankly - I'm the first using (some) not grounded equipment - my CRO is floated 95% of time
but, considering how many Greenhorns are constantly amassing DiyAudio ( which is good) it is clever if we endorse some (oven better - all) of safety precautions
and cautions
Hafler made 2-prong toys (had and have them)
HK too, toys; even expensive ones, made by EC brains, produced by Shin Shirasuna
Quad UK made toys
ReVox made toys too, Telefunken playground
clever ones amongst them did embrace 3-prong, why not, it's clever
and- even if life is cheap, they did learn that legal actions are costly
but, considering how many Greenhorns are constantly amassing DiyAudio ( which is good) it is clever if we endorse some (oven better - all) of safety precautions
and cautions
Hafler made 2-prong toys (had and have them)
HK too, toys; even expensive ones, made by EC brains, produced by Shin Shirasuna
Quad UK made toys
ReVox made toys too, Telefunken playground
clever ones amongst them did embrace 3-prong, why not, it's clever
and- even if life is cheap, they did learn that legal actions are costly
As one of those solder slingers I would say:
Surviving or avoiding electrocution is a good starting point for building further amps - if fearless amplifier builder or frightened -
or completely sissied.
Good night!
Dirk is going to have a nap 😴
Surviving or avoiding electrocution is a good starting point for building further amps - if fearless amplifier builder or frightened -
or completely sissied.
Good night!
Dirk is going to have a nap 😴
Eons ago ( Nelson and I are approximate the same age ) I needed a quick power supply to use in the lab.
I wired it up.
Naturally, I didn't need no sissy grounds, heck... my power supply didn't even need an ON/OFF switch.
I grabbed the largest caps I could find in the drawer, put it together and plugged it in while I reached over for the analog multi meter.
You got it.
I had a lot of clean up afterwards. At least I was three feet away when it happened.
Then there was the night when I blew up $250K of electronics at the lab... I didn't get in trouble, but I had to fill lots of paperwork.
After that, I decided that writing firmware is a lot cleaner.