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Black Lace - 6V6 power amp, direct mains, old school
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Author:  mwhouston [ 14 Aug 2016, 19:08 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

Firstly the LEDs are 240V types with a switch mode built into the lamp.
Secondly the test gear was running on USB power and the laptop was on batteries.
Thirdly the amp, Black Lace, has a RFI\EMI power filter prior to the power tranni and a ferrite choke on the power cord.
Fourthly a good chance of contamination through the wall outlet as the two wall outlets are only meters apart.
Fifth the LED lights are directly amp my test place and there is four of them.

Regardless I realised there was something wrong when there was as much noise with the amp on as when it was off. That is what lead me to try with lights off.

Author:  M. Gregg [ 15 Aug 2016, 00:46 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

mwhouston wrote:
Regardless I realised there was something wrong when there was as much noise with the amp on as when it was off. That is what lead me to try with lights off.


:eek: Were the PSU caps keeping the amp up after power off????

:D LOL

On a more serious note I noticed a PSU I built was noisier with the mains earth connected than left floating, just goes to show the amount of dirt on the supply grid. I guess its a wonder we manage to get anything working, just think about the sensitivity of medical equipment and the impact of aging electrolytic caps.

In my experience mains filters leave a lot to be desired we fit them without considering if they actually work!
Just think about "Y" cap suppression.. dumping all that hash onto the chassis ground.

http://powerblog.vicorpower.com/2013/06 ... apacitors/

Regards
M. Gregg

Author:  mwhouston [ 15 Aug 2016, 04:30 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

No I waited long enough for the caps to drain.

Author:  famousmockingbird [ 15 Aug 2016, 11:15 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

What frequency is the noise at?

Are you saying that the noise is being induced into the amp? Does the amplitude of the noise increase if you move the DUT in closer proximity to the LED lamp?

Have you tried lifting the ground on the LED lamp with a cheater plug?

Author:  mwhouston [ 15 Aug 2016, 19:13 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

I'm really not too concerned about the content of the noise just that it now has gone. I'm assuming 50hz. I didn't try moving to see if the noise from the LEDSs dropped. The amp is played in another room so no concern. What I was trying to highlight that when testing gear, particular looking for very low voltages, lights etc. can influence results.

A friend, who builds speakers, can hold a tweeter in his hand and stand under his LED light and the tweeter buzzes. I heard it myself.

These are in-ceiling lights. I don't think there is a ground.

Author:  M. Gregg [ 16 Aug 2016, 02:40 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

Slightly off topic,

I have seen lights have an effect on a circuit where some paint had broken off a glass diode and the fault only showed with the equipment open, the light was having an effect a bit like a photo diode.

Really interesting about the tweeter, I didn't realise LED lamps emitted such an amount of RFI/EMI.
Did it happen with standard power saver lamps or just LED?

Regards
M. Gregg

Author:  mwhouston [ 16 Aug 2016, 04:33 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

M. Gregg wrote:
Slightly off topic,

I have seen lights have an effect on a circuit where some paint had broken off a glass diode and the fault only showed with the equipment open, the light was having an effect a bit like a photo diode.

Really interesting about the tweeter, I didn't realise LED lamps emitted such an amount of RFI/EMI.
Did it happen with standard power saver lamps or just LED?

Regards
M. Gregg


Can't answer that. Will ask next time I see the guy.

Author:  M. Gregg [ 16 Aug 2016, 04:43 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

mwhouston wrote:
Can't answer that. Will ask next time I see the guy.


:up:

Regards
M. Gregg

Author:  mwhouston [ 11 Oct 2016, 19:18 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

I have been listening a lot to my DIY 250W IRS Class D amp on my DIY 99db efficient 15"Bayma concentrics. But the other day - mid track - I changed over to my DIY pre-warmed 6V6 SE UL amp - Black Lace. I had been listening at a high volume levels and expected to have to bring the vol up with Black Lace in place. But not so the little amp played just as loud with no strain, distortion or clipping. Also I was amazed how similar the two sounded. Not sure if this means the bid "D" is tube like or the 6V6 is "D" like. Either way between the two, on a few levels, they were close.

Where the big "D" won was on bass extension. The "D" does 40Hz easy where the 6V6 just makes 50Hz. For classical all that really doesn't matter and I don't feel I'm missing anything with Black Lace making loud. While listening I just found myself checking that it really was the 6V6 in system and not the other amp. Very impressed. And the beauty of good high efficiency speakers, you can play anything.

Author:  Peter W. [ 13 Oct 2016, 14:22 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

gofar99 wrote:
Ugh. I have ranted on this before several times. There is no way I would allow such a thing in the house. A single fault in either the house wiring (I found a reversed hot and neutral just last year and we have been here 30+ years) or in the unit itself can place the full line voltage on the chassis and anything connected to it. I figure that as long as transformers are cheaper than headstones, I believe I'll stick to transformers.

Good listening
Bruce


Yeah - at a plate voltage that could be at/around 425V that could hurt. How many milliamps do you think it would take to put more than 1/4 watt of current through a 10,000 resistor at 425V?

I = 425/10000 = 0.025

Or, not many.

Why that equation? A healthy adult human may be substituted for a 10,000 ohm, 1/4 watt resistor. Anything that puts more than that amount of current through 10,000 ohms will cause damage to either unit.

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