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Audiolab DC Block


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24 minutes ago, MF 1000 said:

:rofl: x 7 

You're just tight :D

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5 hours ago, toprepairman said:

Made in China, so for political reasons should be shunned.

What are you posting on, an Amstrad?

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So if our mains carries no DC* then this device will make no difference, yes?  Or have I misunderstood it’s purpose?

* Is that achievable in practice, or does every mains supply have some?

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6 minutes ago, Nopiano said:

So if our mains carries no DC* then this device will make no difference, yes?  Or have I misunderstood it’s purpose?

* Is that achievable in practice, or does every mains supply have some?

Not every mains supply has any DC offset, no. Some may be caused by the odd domestic appliance. The old favourite was hairdryers with a half-speed setting using a diode, which dumps masses of DC back onto the line. Mostly it's if you have specific types of light industrial users on the same substation. However, as noted earlier by someone, this unit apparently does also offer some filtering, so may make a difference.

A little DC offset isn't totally uncommon, but it's only an issue for some transformers if there is enough DC. Other than that, it will not have any effect.

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8 hours ago, rabski said:

Not every mains supply has any DC offset, no. Some may be caused by the odd domestic appliance. The old favourite was hairdryers with a half-speed setting using a diode, which dumps masses of DC back onto the line. Mostly it's if you have specific types of light industrial users on the same substation. However, as noted earlier by someone, this unit apparently does also offer some filtering, so may make a difference.

A little DC offset isn't totally uncommon, but it's only an issue for some transformers if there is enough DC. Other than that, it will not have any effect.

And not every transformer that buzzes is doing it because of dc offset. A few years ago I had a transformer that would occasionally buzz. I leapt to thinking it was dc offset and bought a device to cure it. It made no difference at all. It turned out it was just high mains voltage (253) that was causing it.  At that time I bought a mains regenerator which totally cured the problem but also brought some SQ issues of its own. Now I would probably have sorted it with a much cheaper mains balanced transformer made to output the required lower voltage.

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Well I recently gave this DC block a try, just as an experiment as I was curious. I spent an entire day testing it in my system, I used it with the DAC and amp (but mostly the amp). I listened as carefully as I could with the DC block in and out of the system and came to 2 conclusions:

1. It does work - the DC block definitely allows electricity to run from the mains, through itself and out to the connected component.

2. It's totally transparent - I was unable to detect any difference whatsoever with the DC block connected to either the DAC or amp.

The DC block was promptly repacked ready for return.

It may work for some but certainly did nothing for me.

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55 minutes ago, AudioSurge said:

Well I recently gave this DC block a try, just as an experiment as I was curious. I spent an entire day testing it in my system, I used it with the DAC and amp (but mostly the amp). I listened as carefully as I could with the DC block in and out of the system and came to 2 conclusions:

1. It does work - the DC block definitely allows electricity to run from the mains, through itself and out to the connected component.

2. It's totally transparent - I was unable to detect any difference whatsoever with the DC block connected to either the DAC or amp.

The DC block was promptly repacked ready for return.

It may work for some but certainly did nothing for me.

You need to listen to the tranformers without music playing to see if any mechanical hum is reduced.

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14 minutes ago, Muckplaster said:

You need to listen to the tranformers without music playing to see if any mechanical hum is reduced.

I never thought the day would come but yes I 100% agree with you on this as being the correct test for whether the DC block is working.

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31 minutes ago, Muckplaster said:

You need to listen to the tranformers without music playing to see if any mechanical hum is reduced.

Yes, I do understand that, I should have said that I did listen for transformer hum with no music playing. There is no discernible hum from any of the transformers in my system to begin with so it's difficult to tell if the block was further reducing an already non existent hum. It felt like I was trying to solve a problem that did not exist.

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5 hours ago, Fourlegs said:

And not every transformer that buzzes is doing it because of dc offset. A few years ago I had a transformer that would occasionally buzz. I leapt to thinking it was dc offset and bought a device to cure it. It made no difference at all. It turned out it was just high mains voltage (253) that was causing it.  At that time I bought a mains regenerator which totally cured the problem but also brought some SQ issues of its own. Now I would probably have sorted it with a much cheaper mains balanced transformer made to output the required lower voltage.

253v isn’t high. It is within the tolerance quoted for delivered mains voltage in the U.K.

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4 minutes ago, toprepairman said:

Most foreign manufacturers seem to be unaware of that.

Indeed. It was a massive fudge to allow Europe-wide harmonisation without any country having to fix anything in their infrastructure. The official spec:

"In the UK, the declared voltage and tolerance for an electricity supply is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2 volts to 253.0 volts." In reality, because UK mains was always nominally 240V, the voltage you see will tend to be at the upper end of that range. Ours is sitting at 243 right now, but I have seen it as high as 253 but rarely less than 240.

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1 hour ago, Cable Monkey said:

253v isn’t high. It is within the tolerance quoted for delivered mains voltage in the U.K.

Well, we are indulging in pedantic quibbling here.

253V is the upper limit of the tolerance (230V +10%) and most people would regard it as being on the high side of what is expected as normal even if it is technically within the allowed limits.

I read somewhere that the older power stations and distribution are mostly on the old 240V nominal voltage but that as new ones come on line they are more likely to be based on the 230V nominal voltage.

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I went through a period where the transformer in my power amp was audibly humming which I'd wondered if was caused by DC but like @Fourlegs I believe the actual cause was high mains voltage. I forget the actual numbers but the voltage is now lower again and there is no issue.

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2 hours ago, Fourlegs said:

Well, we are indulging in pedantic quibbling here.

253V is the upper limit of the tolerance (230V +10%) and most people would regard it as being on the high side of what is expected as normal even if it is technically within the allowed limits.

I read somewhere that the older power stations and distribution are mostly on the old 240V nominal voltage but that as new ones come on line they are more likely to be based on the 230V nominal voltage.

Pedantic quibbling. Hmmm. 🤔
U.K. mains voltage has never changed. It was 240v +/- 6%. EU harmonisation resulted in our tolerance changing to 230v +10% -6%. That gave the same upper voltage tolerance but a lower one to accommodate the EU voltage. In short the upper limit has never changed and if you have a CE rated device that does not work correctly at 253v it is defective. That isn’t quibbling, it is actually the law. That is something you can’t insist isn’t so so I’d advise not suggesting otherwise.

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