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Chip Amps Amplifiers based on integrated circuits

My_Ref Fremen Edition - Build thread and tutorial
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Old 17th June 2018, 01:22 PM   #3911
lehmanhill is offline lehmanhill  United States
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Quote:
Originally Posted by Mituisho View Post
Hi Dario

I am finishing my build and wonder if it is ok for me to reduce the value of R23 in order to get a higher voltage (say 4v DC) for the external LED for cosmetic reasons?

The voltage I measured across R23 and LED are 15.7v and 1.7v respectively.

Thanks!
Hi Mituisho,

I know you asked Dario, but I can answer as he is probably very busy with Group Buy 12.

It should be no problem to change R23 for a different color/voltage LED. The original value of R23 (6.8k) assumes a red LED at 1.7 V. That is about 2 mA which is safe for long life on a red LED. You will want to keep the current about the same so that you don't steal current from the speaker protection circuit, but it shouldn't be too sensitive.

Using your numbers and keeping 15.7V across the 4V LED and resistor, you will have 11.7V across the resistor. At 2 mA, the resistor should be about 5.8k. A 5.6k is close enough.

By the way, you may want to check the voltage drop across the 4V LED at about 2 mA because it may be rated 4V at a different current.

Jac
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Old 17th June 2018, 01:57 PM   #3912
Mituisho is offline Mituisho  Hong Kong
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Hi Jac

Thanks for the detailed reply. I will try that out.

Tim
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Old 22nd June 2018, 03:49 AM   #3913
olivosunlight is offline olivosunlight  Viet Nam
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Originally Posted by lehmanhill View Post
If you are asking if RCA and speaker output (binding posts) are electrically connected to the chassis, then the answer is no.

I hope that helps.

Thank you for your advice, Jac.


I checked i found there are insulations both RCA n Binding posts.


Best regards
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Old 24th June 2018, 09:18 AM   #3914
danny_66 is offline danny_66  Belgium
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Originally Posted by Luca72c View Post
As already suggested, don't forget to try speakers crossovers resistors, like Mundorf Supremes, Duelund Graphite or Jantzen Superres. They are rated > 10W, non-inductive and are meant (on paper, at least) for keeping the signal clear, natural and uncolored.
They are expensive, but only 2 of them are needed...
All those are beaten on paper and in measurements by the Isabellenhuette PBH
They were also tested in the doc: "Resistor Current Noise Measurements"
You have to zoom in on the graphs to better see the thickness of the different traces.

I use them in the crossover of my speakers and in my amplifiers (source, emitter, feedback resistors).
They are also available in different SMD packages, the SMR and SMV packages are easy to solder directly a wire to it.

I buy mine at buerklin, they have different series.

Definitely a resistor to put on the list !

Regards,
Danny
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Old 24th June 2018, 12:12 PM   #3915
lehmanhill is offline lehmanhill  United States
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Originally Posted by danny_66 View Post
Isabellenhuette PBH
They were also tested in the doc: "Resistor Current Noise Measurements"

I use them in the crossover of my speakers and in my amplifiers (source, emitter, feedback resistors).
I buy mine at buerklin, they have different series.

Definitely a resistor to put on the list !

Regards,
Danny
They clearly measure better than the Caddocks. Unfortunately, they are not very available in the US, but an interesting choice.

Jac
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Old 24th June 2018, 12:29 PM   #3916
Luca72c is offline Luca72c
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Quote:
Originally Posted by danny_66 View Post
All those are beaten on paper and in measurements by the Isabellenhuette PBH
They were also tested in the doc: "Resistor Current Noise Measurements"
You have to zoom in on the graphs to better see the thickness of the different traces.

I use them in the crossover of my speakers and in my amplifiers (source, emitter, feedback resistors).
They are also available in different SMD packages, the SMR and SMV packages are easy to solder directly a wire to it.

I buy mine at buerklin, they have different series.

Definitely a resistor to put on the list !

Regards,
Danny

Very interesting! I considered Isabellenhutte before, but i couldn't find the right wattage - rated resistance combo.
Surely i missed those PBHs. Did you try them on My_ref FE output?
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Old 24th June 2018, 08:08 PM   #3917
danny_66 is offline danny_66  Belgium
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Originally Posted by Luca72c View Post
Did you try them on My_ref FE output?
No, because I don't have a My_ref FE, but I've used them in other amps and in my speakers.
If the circuit calls for a high quality, high power resistor, the Isabellenhuette's are my de facto standard.
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