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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 11th February 2013, 07:43 PM   #34821
qusp is offline qusp  Australia
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other options are possible yes and I gather common mode solutions are not as often tried in an experimental sense, due to it being more important to know the source and load impedance as well as frequency spectra you want to filter and these arent always easily available until youve actually built the thing, if at all. a mix of the 2 seems best and common mode only next, it seems a better way to isolate the noise without effecting the signal. depends what the noise source is of course, but we were talking about RF, which will be common mode, a differential filter surely wouldnt be terribly effective..

its the compound filters in their catalog that interest me though and they allow 4 and 5th order filters in a single small part, SMD feedthrough caps etc. seems a very comprehensive range. of course there are alternatives, but ive found the materials to be of great help and are well written in a way that helps demystify the process.

Last edited by qusp; 11th February 2013 at 07:48 PM.
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Old 11th February 2013, 07:49 PM   #34822
Esperado is offline Esperado  France
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Originally Posted by qusp View Post
common mode solutions are not as often tried in an experimental sense
+1. But it is reserved to old fashion guys, kids refer to simulations and believe their computers.

OOT: The France is saved, Bruce Willis had been honored by our medal of 'commander' of arts and literature.

Last edited by Esperado; 11th February 2013 at 07:53 PM.
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Old 11th February 2013, 07:56 PM   #34823
RNMarsh is offline RNMarsh  United States
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John Curl's Blowtorch preamplifier part II
Default Ferrites and PLC.

Quote:
Originally Posted by qusp View Post
other options are possible yes and I gather common mode solutions are not as often tried in an experimental sense, due to it being more important to know the source and load impedance as well as frequency spectra you want to filter and these arent always easily available until youve actually built the thing, if at all. a mix of the 2 seems best and common mode only next, it seems a better way to isolate the noise without effecting the signal. depends what the noise source is of course, but we were talking about RF, which will be common mode, a differential filter surely wouldnt be terribly effective..
This does work well. Some HF/Rf signals are on the ac line that are wanted --- Power Line Communications (PLC) is popular for streaming video from room to room without rewiring the building. However, you dont want it in your computer, video and digital and video etc. I use the ferrites to do two things on my PLC shared ac power wires: Place a ferrite of the proper type for the PLC freq's on everything else. This also keeps the PLC signal strength at it highest for distance and quality/speed. parallel equipment on the ac line attenuates the PLC signal. And, conversly you dont want all the junk put on the ac pwr lines by your electronics to interfer with the PLC signal. I use them for selective isolation between wanted and unwanted.

See attachment;

I use a ferrite readily avail at a local electronics, A-V chain store called FRY's Electronics in Calif. Look for them under the System Cabling Accessories as noise filters.

BTW -- the speed and operation with the ferrites on everything was measurably increased after their application. In my case almost doubled the PLC data speed. I use the PLC for streaming HD video in real time while watching the movie (Netflix). And, i use PLC to access and select music files on remote server in another room for music playback.

Note too -- power line filters will remove the PLC signal. Only certain Monster ac line filtering has unique circuitry to prevent this on dedicated outlets for PLC use while filtering all other freqs. [not a commercial - just a fact]

Thx-RNMarsh
Attached Images
File Type: jpg ferrite use & PLC.jpg (320.6 KB, 160 views)

Last edited by RNMarsh; 11th February 2013 at 08:04 PM.
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Old 11th February 2013, 08:00 PM   #34824
Max Headroom is offline Max Headroom  Australia
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Default Listen For The Difference...

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Originally Posted by marce View Post
True, you have to match the ferrite to the problem (the noise that is of concern) though the clip on ones are quite often broadband (25MHz - 100/300MHz) and I would suspect that these are the most frequently used as they are the 'standard' or basic clip on most of us are likely to buy. Operating at frequencies though of a magnitude of 1250X the hihest audio frequencies are they (rf aside) going to affect the audio waveform, and if so by how much?
The tonal effect I describe is subtle, but present on every system I have tried them on....also headphones.

Dan.

Click the image to open in full size.
Specifications:
Impedance (25MHz): 180Ω
Impedance (100MHz): 275Ω
Dimensions: 15mmOD x 29.4mmL x 6.5mmID

Last edited by Max Headroom; 11th February 2013 at 08:11 PM.
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Old 11th February 2013, 08:00 PM   #34825
qusp is offline qusp  Australia
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Quote:
Originally Posted by Esperado
+1. But it is reserved to old fashion guys, kids refer to simulations and believe their computers.
ha yep, not all that helpful if you dont have a model for the IC that includes the source impedance and none of the models include the noise spectra in your particular application/location, so you just gotta build it and see, build up a prototype with a few options, which is where i'm at at the moment.

these sort of things are not all that fashionable either, since it ruins all that uber wide bandwidth and below zero impedance

Richard: thanks very much for the info/confirmation, leaving this open for the morning so I can read and absorb, not gonna happen at the moment, the brain is in shutdown. do you filter out your power line signalling so it doesnt pollute the lines? (other peoples)

Last edited by qusp; 11th February 2013 at 08:10 PM.
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Old 11th February 2013, 08:19 PM   #34826
Esperado is offline Esperado  France
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Originally Posted by Max Headroom View Post
The tonal effect I describe is subtle, but present on every system I have tried them on....also headphones.
Near 'every': I suppose it will make no change between a 0 feedback amp and an electro-acoustic speaker.
No change too between a Blowtosch and a power amp with accurate low pass filter at the input for the same reason.
It is really in the feedback loop of the output stage that the change is most effective and reduce distortion. Specially if, following the actual fashion, there is no inductance to protect the outputs.

Last edited by Esperado; 11th February 2013 at 08:24 PM.
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Old 11th February 2013, 09:17 PM   #34827
RNMarsh is offline RNMarsh  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by qusp View Post
Richard: thanks very much for the info/confirmation, leaving this open for the morning so I can read and absorb, not gonna happen at the moment, the brain is in shutdown. do you filter out your power line signalling so it doesnt pollute the lines? (other peoples)

HF/RF from PLC does not travel long distances on ac power wires as their series inductance is just too high.. too lossy. It doesnt get to your nearby neighbors -- maybe in an apartment, yes. However, for PLC to get approval... it cant go far enough to interfer with neighbors.... via conducted mode nor as radiated (anetnna) from the ac wires.... [ditto WiFi in homes etc.] So that has been addressed at the design level.

However. having said that, you can do what i do -- locate your Service Entrance panel (circuit breaker box). On the oppose wall, inside... often a garage ... there will be a utility outlet which is closest to the Panel. Plug in a surge protector right there.... it will catch any transients on the line at the earliest point of entry into the home. An MOV is fine as it also has enough capacitance to do some RF filtering across the line all the time... paralleled MOV would do better in regard to RFI in/out thru the Service Entrance panel. [you could this on other branches as well]

Enjoy!

-RNMarsh

Last edited by RNMarsh; 11th February 2013 at 09:32 PM.
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Old 11th February 2013, 09:28 PM   #34828
RNMarsh is offline RNMarsh  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by RNMarsh View Post
However. having said that, you can do what i do -- locate your Service Entrance panel (circuit breaker box). On the oppose wall, inside... often a garage ... there will be a utility outlet which is closest to the Panel. Plug in a surge protector right there.... it will catch any transients on the line at the earliest point of entry into the home. An MOV is fine as it also has enough capacitance to do some RF filtering across the line all the time... paralleled MOV would do better in regard to RFI in/out thru the Service Entrance panel. [you could do this on other branches as well]

Enjoy!

-RNMarsh
Something like this might help in several ways --
Attached Images
File Type: jpg DSC00600.jpg (567.5 KB, 135 views)

Last edited by RNMarsh; 11th February 2013 at 09:33 PM.
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Old 11th February 2013, 09:59 PM   #34829
jcx is offline jcx  United States
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Old 11th February 2013, 10:06 PM   #34830
DF96 is offline DF96  England
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Quote:
Originally Posted by qusp
depends what the noise source is of course, but we were talking about RF, which will be common mode, a differential filter surely wouldnt be terribly effective..
It may depend on RF frequency and the type of cable. I would expect higher frequencies to be mainly common mode (cable acts as a short antenna), but lower freq to be differential mode (cable acts as a long but narrow magnetic loop). Of course, using coax or twisted pair will largely defeat differential mode.
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