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Heifetz

stepped attenuator differences

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@georgehifi

Hello George,

I am enjoying the LightSpeed very much. It has a transparency that receives the mids. 

I had a question about the resistors. Would different resistors in the LS change the sound? 

I ask this because in a previous preamp I changed the resistors on the stepped attenuator to the Charcroft 100k 0.4w Z Foil Resistor. I loved the improvement in the character of the sound from that change to the Charcrofts. 

Is it possible to change the resistors in the LS to Charcroft 100K and what do you think the kind of change I might experience?

Thank you, Bob

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32 minutes ago, Heifetz said:

@georgehifi

Hello George,

I am enjoying the LightSpeed very much. It has a transparency that receives the mids. 

I had a question about the resistors. Would different resistors in the LS change the sound? 

I ask this because in a previous preamp I changed the resistors on the stepped attenuator to the Charcroft 100k 0.4w Z Foil Resistor. I loved the improvement in the character of the sound from that change to the Charcrofts. 

Is it possible to change the resistors in the LS to Charcroft 100K and what do you think the kind of change I might experience?

Thank you, Bob

I don't think there are resistors in the signal path.

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1 hour ago, Heifetz said:

I had a question about the resistors. Would different resistors in the LS change the sound? 

 

41 minutes ago, misternavi said:

I don't think there are resistors in the signal path.

Correct, there are no resistors in the signal path, just one LDR.

 

Cheers George

Lightspeed Attenuator MkII Circuit Diagram.jpg

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17 minutes ago, georgehifi said:

Correct, there are no resistors in the signal path, just one  LDR

LDR = Light Dependent RESISTOR  :) 

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Thank you,

Bob

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@georgehifi

I have read that a battery can be used instead of the mains.

 

Is this something that you advocate and what differences would be noticeable?

Which brand/type would you recommend?

Thx so much, Bob

 

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15 minutes ago, Heifetz said:

I have read that a battery can be used instead of the mains.

 

Is this something that you advocate and what differences would be noticeable?

Which brand/type would you recommend?

Thx so much, Bob

Yes, many use a 12vdc battery, just make sure it's has a 2.1mm X 5.5mm plug, and very important centre is positive.

 

I recommend these rechargeable lithium-ion (li-ion) ones, which would give up to a couple of  weeks of listening, before a recharge is needed.

 

 https://www.ebay.com.au/itm/Portable-3500mAh-DC12V-Lithium-Battery-Pack-Rechargeable-Li-ion-LED-Board-CCTV/182278402926?hash=item2a70a3b36e:g:UTAAAOSwAfVb3UP6

Make sure with the seller it has a 2.1mm x 5.5mm plug and center is positive.

 

Cheers George

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Thank you George,

 

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1 hour ago, georgehifi said:

I recommend these rechargeable lithium-ion (li-ion) ones

Hello George,

Is the benefit of the battery due to it supplying 'cleaner' power?

Thx, Bob

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15 minutes ago, Heifetz said:

Hello George,

Is the benefit of the battery due to it supplying 'cleaner' power?

Thx, Bob

Yes even though the power supply that comes with the Lightspeed is a toroidal supply and very low in noise, the battery has just a touch less measured noise, and many say they can hear a difference but couldn't A/B it, it's small but there, for an even blacker background.

 

BTW stay away from SMP (Switch Mode) wall warts they are noisy

Cheers George 

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Is it the power coming through from the mains that is 'dirty' or is it the wall wart that makes the power 'dirty' or is it both?

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Both, SMP's make even more hf noise.

 

Cheers George

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Here's a novel little experiment to show how bad SMP's can be, get an AM portable radio set it low on the dial off station, turn up the volume control and go near to an SMP with it, and hear it squeal like a stuffed piglet.

 

Cheers George

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Posted (edited)
1 hour ago, georgehifi said:

Here's a novel little experiment to show how bad SMP's can be, get an AM portable radio set it low on the dial off station, turn up the volume control and go near to an SMP with it, and hear it squeal like a stuffed piglet.

 

Cheers George

 

I'm sure what you described has that effect.  However what that experiment does, surely, is show how much EMI is coming off the SMPS ... which is impacting the AM portable radio's aerial?

 

Whereas an equally bad result from a crappy SMPS (particularly a 'wallwart') is that they inject crap back into the mains - to 'infect' other components.

 

 

(I always use a hash filter between a SMPS and the wall socket, to stop this hash transfer.)

 

Andy

 

Edited by andyr

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Posted (edited)
40 minutes ago, andyr said:

However what that experiment does, surely, is show how much EMI is coming off the SMPS ... which is impacting the AM portable radio's aerial?

Yes and also penetrating any unshielded audio cable/equipment in vicinity, and radiating back into the mains.

 

Cheers George

Edited by georgehifi

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1 hour ago, georgehifi said:

Yes and also penetrating any unshielded audio cable/equipment in vicinity, and radiating back into the mains.

 

Cheers George

 

Absolutely, George!  :thumb:  Then again, IMO anyone who uses unshielded interconnects deserves what they get.  :lol:

 

And surely equipment cases - well, those that have 3-wire power cords, anyway - are earthed?

 

Andy

 

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