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Oneminde 23rd June 2019 04:52 PM

UGS MUSES Scion Preamplifier.


Scion derives from the Middle English sioun and Old French cion and is related to the Old English cīth and the Old High German kīdi (meaning "sprout" or "shoot"). When it first sprouted in English in the 14th century, scion meant "a shoot or twig." That sense withered in horticultural contexts, but the word branched out, adding the grafting-related meaning we know today.
Welcome to the official construction and build thread of the UGS MUSES Scion Preamplifier. The reason I am starting this build thread is to share, have fun and receive feedback and input. Since its heavily based on the original UGS (Universal Gain Stage) MUSE edition preamplifier developed by Alex_TWN and Eric.D over at all credits goes to them for making my version possible. I ended up at the original UGS-Muse Edition Pre.amp as a result of stumbling over the Pass Laboratories XP-30 line preamplifier which use the NRJ MUSE volume IC (MUSES72320) (New Japan Radio and a few clicks later, the UGS-Muse Edition Preamplifier was a fact. This preamplifier will make it possible to develop and build a state of the art preamplifier, but with custom solutions.

This custom preamplifier is heavily influenced by TacT/Lyngdorf Millennium Amplifier which is no longer manufactured. It was a digital amplifier similar to NAD M2 Direct Digital Amplifier which is also no longer manufactured. What really made Millennium Amplifier different was the volume attenuator wheel. It had a very lush and firm feeling. Nothing obscured the rotation and it felt like it could spin for ever, there where no mechanical input and no play - it was rock solid. I first encountered this amp back in 1999 and I still remember to this day the feeling, in other words, I got obsessed with it.

The third inspiration is 1970's style LED displays - very old school, but I am in love with does types of displays. Therefore the display information will use the LED Matrix style found via Liteon LTP-305HR - the same led display can be found in Soulution from Switzerland.

So the fact that the original use of OLED's in the UGS MUSES Edition is being thrown out in favor for this display and optical gain stage requere me to redesign the front end (controller board) and with that, generate a new firmware. This section of the preamplifier will therefore be my own, but it will use certain sections of the original UGS Controller Card.

To top things of, I have to learn a PCB CAD software so that I can design this new controller card in conjunction with all the other cards simply because I want all of my cards to be flat black ENIG gold and black screen print for a stealthy look. Lastly I need to learn Arduino programing.. as well as designing the chassi and all the parts that go along with it. There are a lot of things that need to be done in order for this project to see the light of day, therefore, be aware that it will take a while to finalize it.

In conjunction with this preamplifier, I will also work on the DIY Honeybadger which is the power amplifier of choice. The UGS MUSES Scion and Honeybadger will use separate chassis simply due to the fact that I will also build a Class D amplifier at some point, so to avoid needing two integrated amplifiers, separates are the best choice.

As a bonus I will design a remote controller featuring the exact same volume wheel and display together with the physical buttons. Buttons will be capacitative touch variants which I have ordered. Whether or not I will use them as is (individual) or design a new card for multiple input remains to see, if I redesign, then I will simply move the components, so no matter, I will have the components for it.

So exactly where am I in this process ? The dominant part is actually the display, this will determine the the size and from there, I will be able to design the housing or mounting structure for it, after that, the volume wheel should be fairly easy.

In the beginning while learning PCB CAD, it will take a while before I start producing results. But Once I do, it should move forth in a steady pace. The wonderful thing about designing things these days is the use of software's, the integration and visualization is outstanding and almost any issue can be discovered in the planing stages.

So until my next entry, take care and enjoy the remaining summer of 2019. Don't hesitate to ask or drop a comment or two :)

- Update 1 - 2019.06.30 -

It has come to my attention that the gain stage of the UGS preamplifier is built around Nelson Pass Super Symmetry (SuSy) circuitry which is patented. But Nelson made it available for the DIY community. Due to this fact, my UGS Muse Scion edition can never become a commercial product, which by the way was never my plans in the first place, but it opens up the possibility for it to possibly be available as a DIY project for others who are interested. I will make you aware that as of writing this I have not made a firm decision that this will be the case and no matter, my version must first be fully realized and tested before such a thing can happen.

- End of update -

- Update 2 - 2019.07.01 -

Thanks to Zen Mod who gave some valuable information:

2sk389BL is practically pair of 2SK170BL on same die and in one 7-pin case ; 2SK170BL you can replace with LSK170B
2SJ109BL is practically pair of 2SJ74BL on same die and in one 7-pin case; 2SJ74BL you can replace with LSJ74B

Both 2sk389BL and 2SJ109BL are used in the original UGS Buffer, called M1 in the UGS Muse Edition. In the JFet Output Buffer by Flatlabs, called M2, only 2sk389BL is used - These are more or less obsolete and will be replaced with LSK170B and LSJ74B. Regarding the BJT ZTX450/550, these are available.

- End of update -

- Update 3 - 2019.07.01 -

To does who asked if this amplifier will become available as a diy kit, I can now firmly answer this question. Yes it will.

I did an attempt at contacting Alex_twn out of courtesy, asking for permission to use the specific MUSE section of this amplifier, but he has so far not responded. When it comes to the actual heart of this preamplifier, that construction belong to Nelson Pass as mentioned earlier. It has come to my attention that the UGS was made available to the diy community back in 2006.04.10 with the following agreement:

“This scheme uses a Nelson Pass patent. So I asked his permission before publishing the diagram, permission he kindly granted me. Under the express condition of non-commercial use. You are therefore free to have fun with it, as long as you do not seek to make any profit other than that of your auditory pleasure. You can also use preamp PCBs, reproduce them, modify them, I have no problem if it's for you. For those of the power supply, same thing, no problem. In the hypothetical case of a batch order of preamp PCBs, a reference to Nelson Pass will have to be written on the PCB in order to remove any ambiguity. Any other use than DIY that would come to our ears would be reported to Mr Pass, and you would manage with his lawyers.” - Sincerely, François aka Flatlabs

When it comes to DIY kits and cards, understand that:

1.) This preamplifier will be re-designed according to how I want things, such as type of capacitor, resistor etc. The overall functionality as per UGS and UGS Muse edition will remain intact.
2.) The UI or front end will deviate from prior UGS Preamp's as per description earlier in this post.
3.) The final case incl. the functionality, construction, drawings etc. will also be made available so that anyone who wants to build the UGS Muse Scion Preamplifier will be able to do so.
4.) Distribution of PCB kits will be finalized when the amplifier is fully realized.

- End of update -

- Update 4 - 2019.07.10 -

The JFET Companion is complete.

- The JFET companion was written to be a support for learning and understanding JFETs and assorted quality factors. It contains both definitions and key descriptions found in different lectures and articles. The reference material can be found at the end of this paper if you wish to read the sourced material in its entirety. Due to different “styles” used in describing what JFETs are, their function and how to operate them, I have taken the liberty to reorganize the literature in such a way that it is more coherent and linear, from simple to advanced.

- This document was created in part to teach myself what JFETs are in order to quantitatively and objectively perform calculations, simulations and measurements, and as support for a preamplifier project I am working on. It’s the authors first time being involved in an electronics project on this scale, so it was important to collect information and data such that the project could proceed with a focus on quality and great understanding of what’s involved when selecting JFETs and controlling their range of operation with a minimum set of damaging and destructive parameters for music reproduction.

- Although this document will focus on JFETs, I have included a bonus section which will cover a few amplification stages and topologies as well as describing the underlying structure of the preamplifier that I am personally working on. The preamplifier use something called a Voltage and Current Buffer and what that is among other things will be covered in the bonus section, but is not essential for the JFET section.

You can read online or download: The JFET Companion.pdf - Google Drive

- End of Update -

- Update 5 - 2019.08.05 -

The original UGS for Dummies has been translated from French to English and will serve as a platform for the math involved in the refreshed version.

UGS for Dummies.pdf - Google Drive

- Update 6 - 2019.30.08 -

Big News.

As of today, unless something unforeseen should happen, the UGS MUSES Scion preamplifier will diverge in a very significant way compared to its predecessors. For two generations, the 2006 UGS preamplifier and the 2015 UGS MUSES preamplifier used the special edition UGS gain stage designed by Flatlabs. It is known as UGS3a or UGS V3. This gain stage was officially approved by Nelson Pass to be used in the DIY community and so far that was the intended gain stage for the UGS MUSES Scion. I also left the door open to include the CUGS version which use paralleled BJT's, alongside the additional or secondary gain stage designed by Flatlabs in 2015 for the UGS MUSES preamplifier. Besides the MUSES volume IC and the secondary gain stage, not much had changed.

As of 2019.08.30 this will change.

Through a private email conversation with Nelson Pass, I was given the permission to move away from the unofficial UGS gain stage and towards using an official UGS gain stage. That's correct, an official Pass Labs UGS gain stage. It is not the latest generation since that would be in direct conflict with Pass Labs current product line, this one is a few generations behind but maintain the core architecture. It simply mean that we are still using Super Symmetry (SuSy) but instead of a bipolar (BJT) output gain stage, this UGS uses MOSFETs in the output, very much like Pass Labs current line up. There are other changes to this UGS gain stage that further reduces the overall noise present. This gain stage superseded the one Flatlabs based his on. Meaning we are up two levels in terms of performance. Also, the rail or supply voltage will increase, from +/-24VDC to +/-32VDC which is what PASS use on these, meaning a higher gain.

This effectively renders the CUGS paralleled version and the secondary or complimentary gain stage obsolete. As you might remember, there were talks about this secondary stage a while back and the overall consensus is that it does very little for the overall performance. I have seen measurements with and without this stage in place. Since this is the case, spending time on incorporating it makes little to no sense.

The UGS MUSES motherboard will therefore be redesigned to accept just one gain stage. This reduces the overall amount of components and should be more coherent.

All credit goes to Nelson Pass, Wayne Colburn and Pass Labs.

- Update 7 - 2019.09.29 -

Post #169 on page 17 presented the UGS4 gain stage which will be used in this preamplifier.


Oneminde 23rd June 2019 08:46 PM

Ding ding ding. Found it. The LED driver comes from ISSI, model: IS31FL3733. It can drive up to 192 led's. Meaning I will be able to have 5x(5x7+DP) = 180 LED's/row and have some left over to drive my MUTE and LOCK led's. In the end, I will use 2 rows of 5 display's, so 2 drivers all in all. :)


randytsuch 27th June 2019 04:55 PM

Looking forward to your progress, very cool project.

Oneminde 27th June 2019 05:03 PM

Thanks, I am really looking forward to this one. Lots of work but what the heck, what is life without some challenges :)


Oneminde 27th June 2019 06:36 PM

Made another thread which I will link to if you are interested.

The way forward (Soldering).

AuroraB 27th June 2019 06:52 PM

Very intersting....Will you be selling boards for this project..?

Oneminde 27th June 2019 07:03 PM


Originally Posted by AuroraB (
Very intersting....Will you be selling boards for this project..?

Oh wow... hmm. Allow me to answer with; I don't know, followed by an explanation.

As you know, the original UGS-Muse Edition is not my work, I will use it as a base for my version which is a bit different compared to the original one. One of the differences will be no WiFi or streaming, that part will be take care of by the DAC. And due to a different front end as mentioned, the controller board will be redesigned.
As I write this, I don't know how the original designers feel if someone ells is making their cards available. This is something I have not investigated yet, and it might mean Alex_TWN and Eric.D want royalties. If this is not the case and cards can freely be distributed, then selling cards (kit) is not out of the question.

Do note that it will take a while for this project to be finalized, but if you are in no rush, by all means, stick around and follow the development and in time we will have a proper answer to your question :)


Oneminde 27th June 2019 08:10 PM


Originally Posted by AuroraB (
Very intersting....Will you be selling boards for this project..?

Are you by any chance Aurora over at ? :)

randytsuch 27th June 2019 08:41 PM

I'd also be interested in boards, if they become available.

Did some quick research, found this
UGS-muse preamp GB
Which appears to say at least some of the circuit comes from pass labs.


Oneminde 27th June 2019 09:10 PM


Originally Posted by randytsuch (
I'd also be interested in boards, if they become available.

Did some quick research, found this
UGS-muse preamp GB
Which appears to say at least some of the circuit comes from pass labs.


Its an upgraded UGS Preamplifier which I guess is inspired by Nelson Pass or Pass Labs equipment, so yes. The original UGS Preamplifier started to float around the diyaudio community in the mid 00's. I think I did a fare job of explaining why and how I arrived at the UGS-Muse Edition.

Project | Homebuilt Hi-Fi - A user submitted image showcase of high quality home built hi-fi components.

I'm not going to investigate the first UGS preamplifier since the later and updated one is fully realized.
The board kit could be an option as I mentioned. We will know when my version is fully developed.


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