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Old 24th May 2013, 09:50 AM   #81
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Hi Patrick,

looks very nice and eh..... symmetrical!

Wiliam
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Old 24th May 2013, 09:52 AM   #82
EUVL is offline EUVL  Europe
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William,

I'll get in touch for Beta test when the proto is fully assembled and working.
Stay tuned.




Patrick
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Old 24th May 2013, 10:59 AM   #83
AndrewT is offline AndrewT  Scotland
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looks very F5x like
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Old 14th August 2013, 08:28 PM   #84
Horio is offline Horio  United States
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Any interesting progress on the F5X preamp?

EUVL, one thought I had when looking at your populated preamp board was the orientation of the potentiometers. In your beta board you used the same type of pots as those on the F5X amplifier (adjusted at the ends of the pot). For the F5X preamp, does it make more sense to use potentiometers that are adjusted from the top? This would allow you to make adjustments while the board is inside of the case by simply removing the lid.

Just a thought I had.

Last edited by Horio; 14th August 2013 at 08:38 PM.
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Old 15th August 2013, 01:40 PM   #85
EUVL is offline EUVL  Europe
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In the final layout, all the components will face downwards.
This is such that the MOSFETs can be connected to the bottom plate of the enclosure for heat dissipation.

I do not expect 50degC steady state temperature.
So perhaps the trimmers are less critical. But we'll see.

Too busy with work and other private things right now.
And the factory is fully booked for business work.
So I am not getting mechanical parts done for hobby.

Sorry for the delay.
But then only a handful of people have finished the power amp.
So no point starting a preamp project before the first one is finished.


Patrick
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Old 17th September 2013, 09:48 PM   #86
mlloyd1 is offline mlloyd1  United States
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EUVL:

nice project

assuming i understand what your team proposed for the attenuation scheme, are there concerns about changes in common mode gain as the volume changes?
also wondered if you considered using one of the newer digital pots (with no internal op amps) as attenuators?

mlloyd1

Last edited by mlloyd1; 17th September 2013 at 09:51 PM.
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Old 18th September 2013, 04:22 AM   #87
EUVL is offline EUVL  Europe
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I have been using this attenutaor for years.
The only thing is that it is not constant impedance.
If you have decent sources with low output impedance (say 100R), it is not an issue as far as I am concerned.

Of course you can use anything else you like, including IC's.
But like the relayed-controlled constant-impedance attenuator, you need to use two well matched ones for balanced.
We like to use a simple circuit and have the freedom to choose our resistors.
So we, for ourselves, WILL stick to this.


Thanks for your interest,
Patrick
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Old 5th January 2014, 10:09 AM   #88
dodo is offline dodo  Poland
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a specially for this project I kept in my parts beam perfectlly mached pairs of dual jfets
2sk389V - 2sj109V
Any chane I will use tchem soon ??
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Old 5th January 2014, 10:31 AM   #89
CeeVee is offline CeeVee  Portugal
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Quote:
Originally Posted by EUVL View Post
I have been using this attenutaor for years.
The only thing is that it is not constant impedance.
If you have decent sources with low output impedance (say 100R), it is not an issue as far as I am concerned.

Of course you can use anything else you like, including IC's.
But like the relayed-controlled constant-impedance attenuator, you need to use two well matched ones for balanced.
We like to use a simple circuit and have the freedom to choose our resistors.
So we, for ourselves, WILL stick to this.


Thanks for your interest,
Patrick
Patrick,

I expected this would be a discussion issue here since some of us here discovered the MUSE volume control chip NP uses in the XP30...( discussion in other thread ) ...with this chip is quite easy to match channels.

It is difficult to get in small quantities ie: less than 100 and not cheap.

Anyway as you say it is going to be fun comparing your choice of volume control with the MUSE....in due time

Carlos
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Old 5th January 2014, 11:05 AM   #90
EUVL is offline EUVL  Europe
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It is a single ended chip, and the input resistance is specified at 14k min., 20k typical.
That sounds like not matched in one chip.

How would you like to use it for a balanced amp ?
Just treat each phase as single ended ?

Constellation Audio uses LDRs in their Reference Class Preamp.
http://www.constellationaudio.com/ca...olation_lg.jpg

So should we all change to LDRs now ?




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