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PostPosted: Tue Mar 14, 2017 11:36 am 
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An idea I wanted to float for fixing the Phaser clipping with high output guitar pickups. What about using the unused portion of the IC2 (B) and using it for something like a MXR microamp output? Shouldn't be too involved, no?


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PostPosted: Tue Mar 14, 2017 11:38 am 
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Put a pot in the feedback loop to determine the appropriate resistance for the desired output level and tack in a fixed resistor?


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PostPosted: Tue Mar 14, 2017 11:50 am 
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http://www.freeinfosociety.com/electron ... phaser.gif Take a look at the korg phaser. Essentially the phase royal/phase90 with an op amp output buffer.

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PostPosted: Sat Jun 10, 2017 8:23 pm 
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The output circuit of the Phase Royal is based on that of the MXR Phase 90. However the original Phase 90 circuit has this stage DC coupled, while the Phase Royal de-couples the base of that transistor through a capacitor. Also I believe that the original Phase 90 used a 3V Zener for the circuit reference voltage. The BYOC circuit uses a 5.1V. All of which means that Q7 may not be optimally biased and tends to clip the signal, hence the distortion.

First check that you really do have 5.1V or thereabouts from the zener and ideally use a low power zener with a smaller feed resistor. A 4K7 may do the trick. Zener diodes won't produce a stable voltage unless they are passing enough current and the higher power rated zeners require more current. Once you have done that, place a 68K resistor between the base and the emitter of Q7 which should re-bias the transistor for maximum signal swing.

Also bear in mind that the original phasers like the Phase 90 where designed for signal cancellation, or notch filtering, where the reduction of signal won't cause clipping. Once a resonant feedback path is introduced you create boosted peaks between the notches where, at resonance, the signal is significantly amplified and may well clip against the 9V supply.


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PostPosted: Sun Jun 11, 2017 9:43 am 
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Tark,
Saw you post and decided to take a look at the schematic. Agree that asymmetrical clipping could occur, etc., pretty much as you say. Issues such as this make me think there may not be an actual engineer who double checks the designs before they go into production. Of course, besides good electrical design and evaluation for potential interface issues with external devices, for products of this nature listening tests are also essential. Seems like they are pretty good at the latter, but maybe could find some benefit from occasional assistance with the former. The present model seems to rely on customer feedback after the fact, which on the face of it seems less than optimal. Especially so as the business continues to mature and, hopefully, grow.

Cheers,
Mark


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PostPosted: Wed Jul 26, 2017 12:42 pm 
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Can someone please help me identify which legs of the Q7 are the Base and Emitter?


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PostPosted: Wed Jul 26, 2017 2:34 pm 
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Search for the data sheet. That will give you what you need.


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PostPosted: Wed Jul 26, 2017 2:56 pm 
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I'm afraid I need a little more context...


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PostPosted: Wed Jul 26, 2017 3:18 pm 
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jimilee wrote:
Search for the data sheet. That will give you what you need.

All shall be revealed: http://www.onsemi.ru.com/pub/Collateral/2N5087-D.PDF

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PostPosted: Wed Jul 26, 2017 3:21 pm 
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perfect thanks!


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