This amplifier PSRR is excellent. The most important thing is that you don't hear any thing when the amplifier is powered and inputs/outputs are connected. This means the amplifier is dead silent. If you hear hum, then this is the real trouble.
You did not tell us your impressions about this amplifier? What songs did you play? Tell us please. We spent two months working on this, least thing we expect is that people who build it tell us their impressions about it.
You did not tell us your impressions about this amplifier? What songs did you play? Tell us please. We spent two months working on this, least thing we expect is that people who build it tell us their impressions about it.
4mVac at the output does not say "I am perfect".
To me, it quietly says "something is not quite right".
I would begin investigating the cause.
Start by listening to the noise.
I think it could be made a lot better, at least 20dB better and maybe as much as 38dB better if it can be got down to <~0.05mVac. That is a reading of 0.0mVac on a DMM with an AC scale of 200.0mVac.
There is something not quite right. The DX ST amplifier deserves better than accepting sub standard performance.
To me, it quietly says "something is not quite right".
I would begin investigating the cause.
Start by listening to the noise.
I think it could be made a lot better, at least 20dB better and maybe as much as 38dB better if it can be got down to <~0.05mVac. That is a reading of 0.0mVac on a DMM with an AC scale of 200.0mVac.
There is something not quite right. The DX ST amplifier deserves better than accepting sub standard performance.
First impression very hard to tell,mids and hights very clear seems to have a lot of detail.The bass was a bit shy but as I sad earlier the test room isn't the ideal place to run some soundtests and the speakers I used weren't that big or bass monsters.Must build the second channel to test it more in detail.I hope I like it because I'm realy a fan of Classe A amps(Nelson Pass).
I know myself it has to be 0.0mVac for me too.But what could I do about it and how?
Hi Meanman,
If you do, as suggested, and listen....what does it sound like? Is it hash like a radio off-station? Is it mains hum at 100Hz?
Leave meter connected to output as before and carefully move the power wiring away from signal areas with an insulated ruler or such. Watch reading. Does it change? Think about hum from transformer field too. At no power output there should be little hum generated so you need to consider what could be happening. The sources of hum are obvious-everything from the rectifier diodes to the power rails and caps onboard. Even the leads to CCS, VAS. are entry points.
There are further techniques to try but lets find out what you really have first
If you do, as suggested, and listen....what does it sound like? Is it hash like a radio off-station? Is it mains hum at 100Hz?
Leave meter connected to output as before and carefully move the power wiring away from signal areas with an insulated ruler or such. Watch reading. Does it change? Think about hum from transformer field too. At no power output there should be little hum generated so you need to consider what could be happening. The sources of hum are obvious-everything from the rectifier diodes to the power rails and caps onboard. Even the leads to CCS, VAS. are entry points.
There are further techniques to try but lets find out what you really have first
Dear Meanman, if you need something, i am here to answer your questions
for sure i know much more about this amplifier than these gentlemen that are around.
I would like to explain to you dear Meanman, that Mr. Pavel and Mr. AndrewT are not Dx Corporation designers, not builders, not consultants nor representative.
Omar (Metal), Todd Johnson, Rudi Ratlos, Alexmm.... these are the ones can answer by me when i am impeached to talk or absent.
So, what they say are their own opinions and not the official information about the amplifier, something the designer can give you .
4 milivolts as off set is considered normal, factories accept till 25 mV, and these factories have professional designers, they are reducing to zero to use this to reduce the amplifier importance, they are moved by bad feelings and not better intentions.... these gentlemen knows theories, they are written in the books and they just repeat what they have in the memory, i am afraid they do not even knows hot to assemble amplifiers..seems to me they have not practice, because if they had would not say these things about off set, because for sure they would have face much more than that in hundreds amplifiers, even in the best brands.
I do not want their help, neither their presence, as they use to be annoying, they are forcing their presence because forum is free..they are using the forum freedom as a weapon to achieve their evil targets.
It is an absurd, only having bad intentions, to say 4 milivolts is a big off set.
This shows lack of respect, as saying these things they are also telling to everyone of us that we have not knowledge, so, they intend to fool us or to make us fools..they can say several things...but be sure..all they want is to bother, moved by envy, as usual....because people does not listen them, also do not assemble their units....so....what they want visiting and staying in a thread the opener does not appreciate them, and have said that clear and several times...to impose their presence, searching for small details to bother....now that ridiculous post saying 4 milivolts is high off set....playing with you Meanman, thinking you gonna buy this.
The problem is clear..and a sentence can explain...."as i cannot be so good as he is, then i will destroy what bothers me...will be there bothering, imposing my presence till he looses patience and the thread will be closed by moderators".... using moderator's behavior against themselves...very evil behavior..... moderators will carry the blame...they are playing with moderators too.
As you have perceived, dear Meanman, the amplifier is really shy in the bass, this was posted since the thread first posts.... also this is a result your heavy driver that needs a lot of power to move.... but you got and very fast..the amplifier is really shy in the bass...not that way, because your driver, but it really is and i have never dennied that, i have posted that several times.
Some guys that have built said the bass is strong....i felt good knowing some of them perceive it good enougth in the deep bass area... i would like to agree with them...sadly i cannot.... i have other amplifier here and i feel it a little bit shy.
Based on your informations, your amplifier is fine..there's anything to worry about, go to listen and enjoy, i suggest you to avoid post details to them, they will twist things to start panic as they have tried about off set...everybody know, all countries, north south, east and west, that 25 milivolts is the value all factories accept as normal.... this means nothing..does not bother performance or sonics... reduce it to zero is not needed, is futile, waste of time only.
regards,
Carlos
for sure i know much more about this amplifier than these gentlemen that are around.
I would like to explain to you dear Meanman, that Mr. Pavel and Mr. AndrewT are not Dx Corporation designers, not builders, not consultants nor representative.
Omar (Metal), Todd Johnson, Rudi Ratlos, Alexmm.... these are the ones can answer by me when i am impeached to talk or absent.
So, what they say are their own opinions and not the official information about the amplifier, something the designer can give you .
4 milivolts as off set is considered normal, factories accept till 25 mV, and these factories have professional designers, they are reducing to zero to use this to reduce the amplifier importance, they are moved by bad feelings and not better intentions.... these gentlemen knows theories, they are written in the books and they just repeat what they have in the memory, i am afraid they do not even knows hot to assemble amplifiers..seems to me they have not practice, because if they had would not say these things about off set, because for sure they would have face much more than that in hundreds amplifiers, even in the best brands.
I do not want their help, neither their presence, as they use to be annoying, they are forcing their presence because forum is free..they are using the forum freedom as a weapon to achieve their evil targets.
It is an absurd, only having bad intentions, to say 4 milivolts is a big off set.
This shows lack of respect, as saying these things they are also telling to everyone of us that we have not knowledge, so, they intend to fool us or to make us fools..they can say several things...but be sure..all they want is to bother, moved by envy, as usual....because people does not listen them, also do not assemble their units....so....what they want visiting and staying in a thread the opener does not appreciate them, and have said that clear and several times...to impose their presence, searching for small details to bother....now that ridiculous post saying 4 milivolts is high off set....playing with you Meanman, thinking you gonna buy this.
The problem is clear..and a sentence can explain...."as i cannot be so good as he is, then i will destroy what bothers me...will be there bothering, imposing my presence till he looses patience and the thread will be closed by moderators".... using moderator's behavior against themselves...very evil behavior..... moderators will carry the blame...they are playing with moderators too.
As you have perceived, dear Meanman, the amplifier is really shy in the bass, this was posted since the thread first posts.... also this is a result your heavy driver that needs a lot of power to move.... but you got and very fast..the amplifier is really shy in the bass...not that way, because your driver, but it really is and i have never dennied that, i have posted that several times.
Some guys that have built said the bass is strong....i felt good knowing some of them perceive it good enougth in the deep bass area... i would like to agree with them...sadly i cannot.... i have other amplifier here and i feel it a little bit shy.
Based on your informations, your amplifier is fine..there's anything to worry about, go to listen and enjoy, i suggest you to avoid post details to them, they will twist things to start panic as they have tried about off set...everybody know, all countries, north south, east and west, that 25 milivolts is the value all factories accept as normal.... this means nothing..does not bother performance or sonics... reduce it to zero is not needed, is futile, waste of time only.
regards,
Carlos
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DX, did I post a last warning not to paint each other only a few hours ago for nothing? What is this personality painting and evil empire stuff? 7 days in the sinbin for you to freshen up. 
I just measured an old pioneer home theatre amp I have. It had 3.3mV DC offset right channel measured at speaker terminal out at back and 1.2mV DC offset left channel. These were measured with no speakers connected and no inputs connected at maximum volume.
When measuring AC offset out of the amp I got zero mV on both channels. If I had a bad multimeter lead connection then I could see fluctuating .5mV. Once good leads connection established, then 0mV AC.
I just wish my Blame st was built so I can test it, but I am still waiting on power supply parts. I have been working on the chassis and a soft start circuit though, but can only post pics when I get new batteries for my camera.
When measuring AC offset out of the amp I got zero mV on both channels. If I had a bad multimeter lead connection then I could see fluctuating .5mV. Once good leads connection established, then 0mV AC.
I just wish my Blame st was built so I can test it, but I am still waiting on power supply parts. I have been working on the chassis and a soft start circuit though, but can only post pics when I get new batteries for my camera.
These are discrete regulators positive and negative special made for amplifiers.Here's what I'm gonna do.Build the other channel build the PSU like I intend to do with all the proper wiring and get back then for the result.
Here's the soft start from elliot sound website Soft-Start Circuit For Power Amps
Control circuit has tested a ok.
Control circuit has tested a ok.
Attachments
Carlos,
I can only give my opinion about the sound after I build the whole amplifier with the speakers I'm planning to use. I'm also a speakerbuilder and I know you can't evaluate the sound with one channel and it has to be done in the right place and my hobby room isn't.
It has been said enough times now; a residual AC output or hum and noise, not DC offset, is the concern. As a speaker builder, Meanman, you will realise all that is required to hear 100 Hz and hash in 1-5 kHz nominal ranges. A cheap bare driver and two wires are sufficient. We are not asking you to audition the amplifier's sonics - just to listen and describe the noise that your measured 4 mV AC reading relates to.
Please advise.
BTW, assuming you have a budget DMM, what does it read on AC with shorted probes?
We assume instruments are correct when bought - but I have one here that is about 10 years old and now unused. With a good battery, it reads 0.011 VAC with shorted probes alone! That, folks, is why it's unused.
Please advise.
BTW, assuming you have a budget DMM, what does it read on AC with shorted probes?
We assume instruments are correct when bought - but I have one here that is about 10 years old and now unused. With a good battery, it reads 0.011 VAC with shorted probes alone! That, folks, is why it's unused.
Here it goes,speaker connected input not shorted a slight hum noise you can hear it only when you put your ear against the speaker otherwise you don't hear it.With input shorted the AC reading drops from 4mV to 2.1V and noise is gone.My Fluke is reading with shorted probes 0.001VAC and my other one 0.003-4VAC.Is this what you mean?
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