Hi Terry, yes I think you're right, maybe that bc556 is getting too hot (I used a small fuse holder as an improvised heatsink) and the heat is passing to the other pairs...
and yes I do think that my hiss is oscillation, what I don't understand is why does it oscillate with just with 2 boards connected ?
and yes I do think that my hiss is oscillation, what I don't understand is why does it oscillate with just with 2 boards connected ?
I have had at least 3 amps now that didn't misbehave until I put them in a case. Something about the grounding everything caused it. In some cases I ended up needing to ground the input ground to the case either with a 10R resistor or just straight to it. If you look back through the thread you will see where Carlos recommended changing one of the resistors to reduce the VAS current. I worked for me. The VAS is now just warm and the sound is excellent. If I have time later I will look for the post. Probably back a few pages now.
Found it. http://www.diyaudio.com/forums/solid-state/221741-dx-blame-st-together-dx-super-23.html#post3666358
Found it. http://www.diyaudio.com/forums/solid-state/221741-dx-blame-st-together-dx-super-23.html#post3666358
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I doubt anyone can hear that level of hum and hiss.
That is more than 100dB below maximum power.
If your DMM is reading close to a real value of the lower frequencies of the hiss, then these measurements shown that the Power Amplifier is not broken.
The hum returning when in the chassis points to a wiring fault.
The hiss returning when two are coupled up shows an instability fault. That could be down to MF and HF decoupling in the wrong place, or using the wrong components, or omitted.
Can you post close & clear view photos from the up and down side of your board?
I will try that later thimios (as I have to remove them from the heatsinks), however, back to basics, I think I have a PSU fault, I can clearly see that my negative rail is going down when I have the 2 boards connected, with only one board the voltages are spot on!
to the point where the "negative" side leds are going down...
to the point where the "negative" side leds are going down...
I realized this amplifier with the components mentioned and I have absolutely no hiss or noise audible (or must stick the ear to the speaker). No overheating on a component after hours of listening.
The only precaution I have taken is to isolate my input RCA chassis to avoid hum.
The only precaution I have taken is to isolate my input RCA chassis to avoid hum.
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I Agree there is no hum no hiss, this ampl. is deathly silence.
The only issue i have confronted is an overshot.
Have you scoped this amplifier?
Regards.
Thimios.
Strange. I am using my DX PSU with my SKA GB150. With it I am using a 40-0-40VAC transformer which produces about +-56VDC. I have the PSU turned down to +-50VDC and it is solid as a rock. I am using a Cap Multiplier with this DX Super A and both rails are stable. I'm thinking you have something wrong that is pulling the - rail down. Have you tried inserting a couple big resistors in place of your fuses so you can measure to see if one rail is pulling more power? That will tell you if it's the amp or PSU. If they measure the same then it is the PSU. If the one on the - rail has more voltage drop then it is the amp. Maybe a couple 10W 10R resistors.
So apparently AMP is OK ( it even produces great sound with the psu like this) and the hiss that I reported it's just when the psu can't cope... so maybe the transistors are bad (there aren't many parts to this psu) 
And I feel relieved, because working on the psu is rather simpler ain't it ?
And I feel relieved, because working on the psu is rather simpler ain't it ?
well i lost a driver when one of the fuses blew DANGIT!!!
So I whipped up and DIY'd a pair of speaker protects...Credit goes to "Metal" for the design and original layout as these were the ones included in a past Symasym group buy. I just re did the layout in PCB Express and etched a pair last night...
All good now!!! And I got the new drivers yesterday too...Dayton Audio 7"...so far I like them for the value.
So I whipped up and DIY'd a pair of speaker protects...Credit goes to "Metal" for the design and original layout as these were the ones included in a past Symasym group buy. I just re did the layout in PCB Express and etched a pair last night...
All good now!!! And I got the new drivers yesterday too...Dayton Audio 7"...so far I like them for the value.
NEW SUPPLY
new day, new supply !
problems reported: GONE
The amp is super silent POINT!
My 1st instinct was indeed right, something wrong with the supply, so I gathered some parts and used a brazilian board (I do prefer Juan's board, but this was the only one available) as when started to substitute parts, I lifted a lot of tracks on the blue supply pcb...
this one doesn't sag under load, I've used MJL4281/4302 for power, mje15031/15030 drivers, I notice though this one runs a lot hotter on the positive rail, I can't really understand why?!
Can someone check the temps near the psu trannies on both rails (I've got my amp emitters @~25mv each)
new day, new supply !
problems reported: GONE
The amp is super silent POINT!
My 1st instinct was indeed right, something wrong with the supply, so I gathered some parts and used a brazilian board (I do prefer Juan's board, but this was the only one available) as when started to substitute parts, I lifted a lot of tracks on the blue supply pcb...
this one doesn't sag under load, I've used MJL4281/4302 for power, mje15031/15030 drivers, I notice though this one runs a lot hotter on the positive rail, I can't really understand why?!
Can someone check the temps near the psu trannies on both rails (I've got my amp emitters @~25mv each)
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.
my guess... one or more of the TIP36 transistors, all the drivers (MJE15030/31) were ON semi samples, so no fakes there, I've measured and matched pretty much all of the components (including the large 4.700uF caps )
Your psu board layout is smarter, so if you have one left I would like to buy another from you Juan.
As for my last question, could you please see if you have one of your psu rails hotter than the other?
)Your psu board layout is smarter, so if you have one left I would like to buy another from you Juan.
As for my last question, could you please see if you have one of your psu rails hotter than the other?
Dear Carcass, i am in my own forum these days
Needing some help..then go there or use my personnal email...you are always welcome:
carlos.eugenio1951@yahoo.com
My forum....... under construction...... some upgrade being made...but you may be able to log in:
Amplificadores DX
I am still making amplifiers.... average is three new circuits each week...not sharing but researching... i have found a way, a method, to mimic tube amplifier sonics... picture is Tecton II, a prototype under research...not something to share... doing form my own group of local friends...Mitchel, Zimmer, Lira and Juan.... different circuits, different solutions...trying non standard methods.... Super A is a reference to me...i do comparison with a Super A amplifier..otherwise i will not be able if i am doing some progress or not.
No colours to avoid people to copy for selling purposes as happened a lot in early past.
Thanks by the pictures and reports about.
Abraços (hugs)
Carlos
Needing some help..then go there or use my personnal email...you are always welcome:
carlos.eugenio1951@yahoo.com
My forum....... under construction...... some upgrade being made...but you may be able to log in:
Amplificadores DX
I am still making amplifiers.... average is three new circuits each week...not sharing but researching... i have found a way, a method, to mimic tube amplifier sonics... picture is Tecton II, a prototype under research...not something to share... doing form my own group of local friends...Mitchel, Zimmer, Lira and Juan.... different circuits, different solutions...trying non standard methods.... Super A is a reference to me...i do comparison with a Super A amplifier..otherwise i will not be able if i am doing some progress or not.
No colours to avoid people to copy for selling purposes as happened a lot in early past.
Thanks by the pictures and reports about.
Abraços (hugs)
Carlos
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When I use the first Dx Power supply regulator prototype it didn't not get hot on the positive rail dear carcass I have the Dx Regulator "new blue board" but I do not have any adequate heat sink to check it out or better say test it out I apologize, did you check the zener diodes are they the same ? and yes I still got boards available
Smart decision from Carlos, to keep new designs away from scopes I mean, sniper scopes from piracy jejejejejejeje
Regards
Juan
Smart decision from Carlos,
to keep new designs away from scopes I mean, sniper scopes from piracy jejejejejejejeRegards
Juan
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Both sides of mine run about the same temperature and not very hot at that. I went to just some plates of aluminum for heatsinks.
I'm not sure I really understand Carlos's problem with others making his PCB's for sale. He has stated many times that he didn't want to make any money from this. It's not like they are making a lot of money from them. Most of them are cheaper than we can do in a group buy. I just had some boards made for another project and they are very nice but it took over a month to receive them. When I have bought some from eBay I usually got them in a week. If his goal is to bless DIY'ers with his designs, I would think he would welcome someone making them available to us at a reasonable price.
I don't blame him for wanting his own forum. It must be much easier typing in his native language.
Blessings, Terry
I'm not sure I really understand Carlos's problem with others making his PCB's for sale. He has stated many times that he didn't want to make any money from this. It's not like they are making a lot of money from them. Most of them are cheaper than we can do in a group buy. I just had some boards made for another project and they are very nice but it took over a month to receive them. When I have bought some from eBay I usually got them in a week. If his goal is to bless DIY'ers with his designs, I would think he would welcome someone making them available to us at a reasonable price.
I don't blame him for wanting his own forum. It must be much easier typing in his native language.
Blessings, Terry
Hi Terry I'm not sure but the problem maybe that Carlos has no control ver whoever is making the boards or where builders are sourcing their components me then he gets bad press from some of the members of this forum for poor designs when it may not be anything to do with the design at all.
If you go back a number of pages on this thread I'm sure you will get the picture. I may be wrong but this is the impression I get from the outside looking in, in his position I would be a bit upset as well. Ian
If you go back a number of pages on this thread I'm sure you will get the picture. I may be wrong but this is the impression I get from the outside looking in, in his position I would be a bit upset as well. Ian