Senior Member
Location: Alicante. Spain.
Posts: 1,885
I'm Adrian.
Help - techie question - DC on amp
Ok so I've been listening to my Hiraga (bought from Jake) amp and enjoying it but today I decided to measure for DC at the outputs - I wish I hadn't.
I set the multimeter as in the pic, disconnected speakers and switched the amp on. Measuring both channels fluctuates around 190mv and higher - can this be right? Am I doing something wrong? Am I frying my Tannoys?
Technics SP10 mk2
Jan Allaerts MC 1 Boron mk1 cart
Miyajima Shilabe cart
Hashimoto HM-X SUT
Siggwan (gimballed not unipivot) Cocobola 12"
Aurorasound Vida LCR Phonostage
The Truth linestage
Dave Slagle Autoformer Volume Controller
Cary 805c SET amps
Audio Note ANe-SPX speakers
Townshend Isolda speaker cables
Cardas Golden Presence interconnects
Super Moderator
Location: W Lothian
Posts: 99,005
I'm Grant.
Should be ok at that. Much depends on the speaker etc. will probably equate to less than a tenth of a watt. think 100mv is classed as low.
Regards,
Grant.... ؠ ......Don't be such a big girl's blouse
I've said it before and I'll say it again: democracy simply-doesn't-work.... ..... ...... ...... ................... ..... ..... ..... ..... .....
FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -
Oh my god! There's nothing wrong with the bidet is there?
“Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".
“You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”
"You don't have free will. You have the appearance of free will.”
“There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”
***SMILE, BE HAPPY***
Super Moderator
Location: W Lothian
Posts: 99,005
I'm Grant.
Think the calc is volts squared, divided by impedance = power (ie ohms law)
Last edited by struth; 25-10-2017 at 15:21.
Regards,
Grant
I've said it before and I'll say it again: democracy simply-doesn't-work.... ..... ...... ...... ................... ..... ..... ..... ..... .....
FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -
Oh my god! There's nothing wrong with the bidet is there?
“Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".
“You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”
"You don't have free will. You have the appearance of free will.”
“There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”
***SMILE, BE HAPPY***
Senior Member
Location: Alicante. Spain.
Posts: 1,885
I'm Adrian.
I read that any DC on the outputs was bad though 0-15mv was acceptable. Hence my worry.
Technics SP10 mk2
Jan Allaerts MC 1 Boron mk1 cart
Miyajima Shilabe cart
Hashimoto HM-X SUT
Siggwan (gimballed not unipivot) Cocobola 12"
Aurorasound Vida LCR Phonostage
The Truth linestage
Dave Slagle Autoformer Volume Controller
Cary 805c SET amps
Audio Note ANe-SPX speakers
Townshend Isolda speaker cables
Cardas Golden Presence interconnects
Super Moderator
Location: W Lothian
Posts: 99,005
I'm Grant.
The maximum dc offset tolerated by a speaker is a percentage of the linear excursion of the driver that is acceptable, usually 10 to 15%, or so i,m told. The formula used is:
Vdc(max) = % excursion x excursion x driver impedance/[Force Factor x Suspension Compliance]
All these parameters are found in the manufacturer's spec sheets.
You could easily get fitted, dc protection circuit for the speakers
Regards,
Grant
I've said it before and I'll say it again: democracy simply-doesn't-work.... ..... ...... ...... ................... ..... ..... ..... ..... .....
FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -
Oh my god! There's nothing wrong with the bidet is there?
“Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".
“You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”
"You don't have free will. You have the appearance of free will.”
“There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”
***SMILE, BE HAPPY***
Senior Member
Location: England
Posts: 290
I'm James.
I wouldn't worry too much about that.
What does it measure with Speakers connected? That'd be a more accurate test for me.
Jim.
Senior Member
Location: The Black Country
Posts: 6,089
I'm Alan.
Was just about to suggest repeating the measurement with speakers connected, good one James. Will be a more useful reading.
Senior Member
Location: Alicante. Spain.
Posts: 1,885
I'm Adrian.
Am at work now but will try wth speakers connected in morning and retest. I don't like the thought of why DC going into my speakers.
Technics SP10 mk2
Jan Allaerts MC 1 Boron mk1 cart
Miyajima Shilabe cart
Hashimoto HM-X SUT
Siggwan (gimballed not unipivot) Cocobola 12"
Aurorasound Vida LCR Phonostage
The Truth linestage
Dave Slagle Autoformer Volume Controller
Cary 805c SET amps
Audio Note ANe-SPX speakers
Townshend Isolda speaker cables
Cardas Golden Presence interconnects
Trade: Radford Revival
Location: South West of England
Posts: 263
I'm Will.
The amount of power this will deliver into the voice coil, assuming a 5 ohm DC resistance (and it is probably more), can be calculated by 0.22 / 5, ie V2 / R, which is a whopping 8mW (0.008W)
AKA not much to worry about assuming there is no other problem!
Radford Revival
www.radfordrevival.co.uk
Senior Member
Location: London
Posts: 685
I'm James.
Surely it is not difficult to adjust the DC offset anyway, aren't there a couple of screwpots under the lid that achieve this function? Should be able to get it down to low millivolt levels though beware as it may drift as the amp warms up. This was a DIY amp wasn't it?
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