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.
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.
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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
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
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
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
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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
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
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/images/performance/virgo_II/virgo_2_interior_isolation_lg.jpg
So should we all change to LDRs now ?
Patrick
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/images/performance/virgo_II/virgo_2_interior_isolation_lg.jpg
So should we all change to LDRs now ?
Patrick
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/images/performance/virgo_II/virgo_2_interior_isolation_lg.jpg
So should we all change to LDRs now ?
Patrick
hehe
LDRs are a very different issue and if one is ready for headaches than by all means... but this chip is interesting because it is a very serious effort by JRC to produce a very highend solutions for one of the most enduring problems in audio....ie: to get rid of the bottleneck problem of ...what volume control to use so as not to spoil a great preamp.
Each chip is a stereo set so for balanced...2 chips, and matching of channel can be done with a trimmer pot in each channel.
some ref material:
????????????: new_western_elec
Building a Pass XP-30 & XOno Preamplifier
Select & Volume | AKOUO Audio Solutions | DIY | Sabre | JRC | MUSES72320
The 1st and last are of particular interest because they address the balanced solution.
Anyway this is just to let you know that there is a "new kid" in town and now even John Curl is looking at it seriously...check longest thread in this forum
This is in no way to contest your option for the F5X preamp....but the discussion would never be avoided.
As far as I can tell from the datasheet, it is just a digitally switchable bipolar R2r network.
The choice of material for the resistor is restricted by the IC manufacturing processes.
And there are always active devices (switches) in the signal path.
Essentially all passive R2R multiplying DAC would do the same job.
There is no magic in IC manufacture.
Patrick
The choice of material for the resistor is restricted by the IC manufacturing processes.
And there are always active devices (switches) in the signal path.
Essentially all passive R2R multiplying DAC would do the same job.
There is no magic in IC manufacture.
Patrick
Of course not Patrick, no magic, but it was inevitable that the volume chip of the moment, and probably the first to be taken very seriously by high-end audio, would be a topic of discussion here.
I for one am first in line for your F5X Preamp
....after i finish something i have in hand 
Firstly a belated Happy New Year to everyone. And we thank you for your interest and your support to date.
2013 was a difficult year for us. More than one active member of our very small team lost loved ones, had prolonged period of overload at work, and/or other private issues to resolve that took them off hobbies for months. So we did not get much further than delivering GB2 for the F5X. We added more ideas and design to our list, but the list just got growing with no sign of finishing.
On top of that, people increasingly expect the impossible from us. We had multiple request to replace F5X heat sinks which have 1x1mm dents or slight scratches on the fins (extrusion defect, not machining or anodising). If we were to check for those and dress each of them by hand, or throw away altogether, we would have had to charge you 4x the price. I wonder which other supplier would be prepared to do that. And not to forget we just did this for hobby, not for business. (Just take our F5X top plate to a CNC shop and ask for prices for 25 pieces.)
2014 is not likely to get much better. It is more likely than not that we shall make little to no progress for the first half year, due to various private reasons. And we need to look seriously at how we want to operate in the future. There is a limited amount of time we have for DIY, and we want to spend them so that we still have some fun ourselves. That means more on realising design ideas ourselves than on baby-sitting large public projects.
How that might look like, we shall announce in due course. Most likely we can still support PCBs and matched devices. But we shall not spend the same amount of time and effort on this, or other projects, the same way we did for the power amp.
So while we are thankful for your continued interest and eagerness, we also hope that you understand our reality.
After all, it is a hobby. It should be fun, for us as well.
Patrick
2013 was a difficult year for us. More than one active member of our very small team lost loved ones, had prolonged period of overload at work, and/or other private issues to resolve that took them off hobbies for months. So we did not get much further than delivering GB2 for the F5X. We added more ideas and design to our list, but the list just got growing with no sign of finishing.
On top of that, people increasingly expect the impossible from us. We had multiple request to replace F5X heat sinks which have 1x1mm dents or slight scratches on the fins (extrusion defect, not machining or anodising). If we were to check for those and dress each of them by hand, or throw away altogether, we would have had to charge you 4x the price. I wonder which other supplier would be prepared to do that. And not to forget we just did this for hobby, not for business. (Just take our F5X top plate to a CNC shop and ask for prices for 25 pieces.)
2014 is not likely to get much better. It is more likely than not that we shall make little to no progress for the first half year, due to various private reasons. And we need to look seriously at how we want to operate in the future. There is a limited amount of time we have for DIY, and we want to spend them so that we still have some fun ourselves. That means more on realising design ideas ourselves than on baby-sitting large public projects.
How that might look like, we shall announce in due course. Most likely we can still support PCBs and matched devices. But we shall not spend the same amount of time and effort on this, or other projects, the same way we did for the power amp.
So while we are thankful for your continued interest and eagerness, we also hope that you understand our reality.
After all, it is a hobby. It should be fun, for us as well.
Patrick
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Happy New Year Patrick, and thanks for the update. Best wishes to you and the Xen team, and I hope 2014 proves to not be as difficult.
I for one really enjoyed being involved in part of the F5X amp project, and greatly appreciate everyone's efforts. It truly is a fantastic amplifier that I will enjoy for many years.
I completely understand how much work it is to lead these projects. I had a small role in the F5X related to the power resistor GB, but the number of hours was still great. I can only imagine how much work it was to not only come up with the amplifier design, but to also to create the chassis/boards kits for these amplifiers.
I for one was extremely excited about the matching F5X Preamp, and hopefully the project is still realized in some fashion. Perhaps the better route to go is to provide boards, critical matched parts and a build guide, and let people come up with their own chassis solution for the preamp. As great as it would be to have a matching preamp case, I'd imagine it would save you and the Xen team a great amount of time and effort.
Happy New Year, and best wishes for a great 2014.
-Greg
I for one really enjoyed being involved in part of the F5X amp project, and greatly appreciate everyone's efforts. It truly is a fantastic amplifier that I will enjoy for many years.
I completely understand how much work it is to lead these projects. I had a small role in the F5X related to the power resistor GB, but the number of hours was still great. I can only imagine how much work it was to not only come up with the amplifier design, but to also to create the chassis/boards kits for these amplifiers.
I for one was extremely excited about the matching F5X Preamp, and hopefully the project is still realized in some fashion. Perhaps the better route to go is to provide boards, critical matched parts and a build guide, and let people come up with their own chassis solution for the preamp. As great as it would be to have a matching preamp case, I'd imagine it would save you and the Xen team a great amount of time and effort.
Happy New Year, and best wishes for a great 2014.
-Greg