John Curl's Blowtorch preamplifier part II

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#51,841
It's very useful learning to use one's ears to make a judgement call - select a section of music which is difficult to listen to - it sounds very confused, messy; hard to work out what's going on. If making a change causes that piece to make more sense, it's easier to "understand" it - then you're on the right track ...
 
#51,844
I don't have access to an AP or a decent sound card right now, but we could test the proportion 'ferrites compromise the sound' by hooking up a simple divider with the ferrite in the series location and a 10k MF in the lower leg.

If it's a problem, I will immediately side with JC, CH and issue a public retraction.
 
#51,846
I will help, give me a sec.

Click on forums above. Pick a forum. Click on 'new thread'. Use the search function to see if the topic already exists. If not continue with the new thread.
 

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#51,847
Bonsai said:
I don't have access to an AP or a decent sound card right now, but we could test the proportion 'ferrites compromise the sound' by hooking up a simple divider with the ferrite in the series location and a 10k MF in the lower leg.

If it's a problem, I will immediately side with JC, CH and issue a public retraction.
Click to expand...

Thats not a suitable setup to eval anything but you already know that ....
 
#51,848
A ferrite on the input is not the preferred solution for keeping rf out. The high input impedance will render an inductance to stop rf of little use. 100 Ohm in series with the input shunted by 100 pF or thereabouts makes more sense. Otherwise, ferrites will do no harm imo.

Edit: on an mc headamp it might be worth the experiment, provided there was an rf problem to begin with.
 
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#51,850
vacuphile said:
A ferrite on the input is not the preferred solution for keeping rf out. The high input impedance will render an inductance to stop rf of little use. 100 Ohm in series with the input shunted by 100 pF or thereabouts makes more sense. Otherwise, ferrites will do no harm imo.

Edit: on an mc headamp it might be worth the experiment, provided there was an rf problem to begin with.
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Of course, I would place a cap after the ferrite to ground - perhaps I should have been clearer. But, for a distortion test, I would just use a 10 k for the lower L leg.

Resistors are ok and I use them on the input L filter on my power amps but this is more for shaping the HF response than for RFI - although it helps.

There could be an argument that ferrites may interact with the input capacitance of JFETs, but if that is the case, it's going to be well above the audio band.
 
#51,851
a.wayne said:
Dont have to agree Scott, still no justification to say the man is not grounded... 🙄
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Apparently ferrite filters on the mains side are also audible and degrade the sound.

And so it goes . . .

No proof, measurements or such are offered as evidence on any of the claims.

Now, the guy does produce nice products, no doubt about that - it's the other stuff that I don't think makes sense.

Anyway, I've stuck my neck out, and will accept being publicly corrected provided there are measurements to back it up.
 
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#51,852
The cores typically used in power line filtering are different metal make-up. They have more iron and other non-linear metals - like nickel - which makes it possible to saturate them if enough current is apploed. Then they will generate harmonics. Larger cores etc (not found in lower cost filters) are even more easily saturated, of course. This condition might be audible?

Still on Calif time in Bangkok.

-RNMarsh
 
#51,854
RNMarsh said:
The cores typically used in power line filtering are different metal make-up. They have more iron and other non-linear metals - like nickel - which makes it possible to saturate them if enough current is apploed. Then they will generate harmonics. Larger cores etc (not found in lower cost filters) are even more easily saturated, of course. This condition might be audible?

Still on Calif time in Bangkok.

-RNMarsh
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Richard - yes absolutely core saturation is a problem - but we are talking here about selecting the right size core. Ditto the challenge above about the ferrite on the input to quell RFI.
 
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#51,856
Tire Test

Kindhornman said:
Thanks Jan...Sort of like wondering how high a tire would bounce if you dropped it off a cliff, wouldn't have much relevance to how well it would roll down the road, though you could measure its rubber compounds for traction and resistance to rolling with other suitable testing...
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Sorry all,

I couldn't resist sharing this video germane to KHM's comment:
https://www.youtube.com/watch?v=f62Z8Ev9OXA

Enjoy,

Howie

Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
WXYC Chapel Hill, North Carolina - 89.3 FM
 
#51,858
Bonsai said:
John, fractions of an ohm (ferrite impedance at audio freqs) into a load of 10 k, often much higher is not audible or a big issue on an AP plot provided of course you select the right ferrite.
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Unfortunately, starting from the premise that no problem exists and a problem surfaces with ferrites may be the root of the conflict. Its not necessarily that the ferrites degrade the sound, just that its different when the impact of the ambient EMI is reduced, changes the sound. Its really hard to know unequivocally which is the case: ferrite degrades the sound or EMI reduction changes the sound. In some cases the extra texture from the EMI adds to the perceived transient qualities. Or the circuit is marginally stable (never happens!) and the ferrite helps with similar effects.

If I can get some ferrite beads I'll measure the distortion induced. They will cause some distortion, the questions are how much, under what conditions and is it audible.
 
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