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Old 9th February 2012, 07:57 AM   #51
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Nikon1975 View Post
as far as I know the for DCB1 25k is the maximum value for pot recommended.
Given the B1 buffer is basically just a J-Fet, it has very high input impedance. I cannot see why anyone would limit the value pot ahead of it to something as low as 25K.

100K should be just fine. I would ask for the rational behind the 25K limit.

Ciao T
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Old 9th February 2012, 08:16 AM   #52
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Quote:
Originally Posted by Nikon1975 View Post
Thorsten,

Dimkasta, the evil is in the details. Without the buffer you will have troubles in driving the transformers, depending on your source.
The problem is the attenuator?
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Old 20th December 2012, 06:00 PM   #53
Jos v E is offline Jos v E  Netherlands
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Smile new RelaiXedSMD DIY preamp available

Hi readers for a balanced pre-amp:
I would just like to show the availability of my latest RelaiXed design: a renewed implementation on a more compact PCB due employing more SMD components:
- 4 single-ended and 4 balanced inputs, balanced outputs
- The metal-can LME49720 opamps provide really good sound.
- No 'plastic' capacitors in the signal path (only a Mica for high-frequency decoupling)
- very low-noise/clean powersupply for these opamps
- volume and balance control through relays and remote control
- PIC microcontroller software is open-sourced, controls amplifier board through I2C
see: RelaiXedSMD -- Documentation
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Old 20th December 2012, 07:38 PM   #54
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Great work!
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"You have a hierarchy: a mathematician, a physicist (which is a failed mathematician), and an engineer (which is a failed physicist)." - Andrew Jones
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Old 20th December 2012, 08:48 PM   #55
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Hi,

Please consider this simple SE to Balanced circuit, that only use one active NPN transistor. Only local feedback is in play here, so you shall expect it to sound very open and dynamic !

THD is very good. 2Vrms@10kHz into 22k = 0.004% THD. (analyzed on one output)

Higher rail voltage will help on lowering THD. Resistors need to be scaled if lower rail voltage is used . The NPN can be almost any standard transistor: BC546

Cheers
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Old 27th December 2012, 11:33 PM   #56
Jos v E is offline Jos v E  Netherlands
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Quote:
Originally Posted by BachAudioDK View Post
Hi,
Please consider this simple SE to Balanced circuit...
THD is very good. 2Vrms@10kHz into 22k = 0.004% THD. (analyzed on one output)
...The NPN can be almost any standard transistor: BC546
Well-done! Indeed, good results are obtainable with few transistors, and higher power-supply voltages do help. The tiny (1%) imbalance on your outputs would be negligible in practice, results from the transistor Hfe, and would vanish when applying a Fet. It would be nice to see as comparison your distortion-figures when a Fet is inserted. Which circuit analysis program is this?
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Old 28th December 2012, 10:56 PM   #57
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Hi,


Ill try with a FET some day soon. It is National Instruments MultiSim 12.0 (eval version)

Would you recommend any Particular FET ?

Cheers
Flemming
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