UGS-muse preamp GB

Hi there,

The design topic is here : UGS - Muse edition sur le forum Amplis et Préamplis du site - 30058092 - 1056

The other thread is for GB preparation.

I don't have time to read it all thouroughly, but the design looks great.
They aim to upgrade Cheff's All Inclusive UGS. So they keep the enclosure, all connectors and connectors PCB, frontplate.
They redesign the rest (uC board, display, motherboard)

They do use a lot of SMD components, including the uC.

They may launch the GB with the uC, nothing looks definite yet.
Basically, it's an upgrade project

Hope it helps
Hi All. Preamp is dual mono, using the UGS gain module (PassLabs UGS DIY module, as describded into this very forum,

The original intent was to supply the necessary PCB set (2 channel PCB + new controller PCB) to upgrade the original UGS preamp, but it seems now the GB is going in the direction of a complete preamp PCB set.

The original complete UGS preamp contains the following PCB:
-External Supply PCB
-Left & Right channel gain, input selection and Relay Step attenuator PCB (called motherboard since the UGS module plug on it)
-Front uP controller and display PCB
-2 I/O RCA/XLR PCB, again full dual mono, one per channel for the rear panel.
-3 smaller pcb (2 for remote trigger, there is 7 of them...) and one for the supplies input

This thread is showing the first UGS preamp GB:

The controller software is so sophisticated that it matches if not exceed the functionality of the best preamp such as Mark Levinson and others.

Most of the functions can be programmed, and the source code was available so you could play with it ;)

For example to name just a few:
-Each channel name programmable, SE/BAL selection, reference level that can be adjusted, each channel can be selected has bypass to the output (Home theater bypass), variable gain separate subwoofer output, volume speed adjustable, Relay step attenuator click delay, mute level, mute message programmable, etc...Almost everything is easily programmable, including the IR remote learning code mode ;)

The user software menus were extensive.

Preamp source selection was done by front panel push button, and volume and menu navigation was done using an optical encoder. Naturally the preamp support RC5 full remote control, with remote code learning.

I can provide to this site users a translated menu. I compiled the Menu document in French. It won't be a big deal.

The new preamp GB includes the MUSE Volume chip to replace the relay step attenuator, new LDO SMD regs and surface mount design, improved analog/digital supplies insulation, improved PCB layout and ground plan, and the uP controller supports now OLED display, Wifi smartphone app, even I2S digital input to support a DAC if you wish. It is very sophisticated.

So far the GB is only for the PCB, you need to buy the part yourself. From my past experience everything can be bought from the Mouser & Digikey. The PCB fit a case from HiFi2000, the rear panel is done by Front Panel Express and I have the design file. You need to make your own front panel.
External power supply fits also nicely into an other Hifi2000 smaller enclosure.

Naturally using UGS module, you need access to rare and precious K389/J109 or matched K170/J74 JFET...

The rest of the parts are easily available.

See my preamp pictures


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Here example of the original preamp documentation schematics, pcb layouts, and some other preamp case versions


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Images of this GB PCB. Even if the GB is only for the two channels and processor PCB, the rest of the PCB are quite easy to do yourself using the supplied Gerber, or send them to a small PCB manufacturing shop.

The Volume MUSE chip used is the JRC MUSE72320


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Previous Preamp Menu structure

Menus ‘User Preferences’, version 2.01

Volume Settings
Volume Balance, default 0.00dB II 0.00dB
Startup Volume (Preset, Last, Minimum Volume), default Preset Volume
Mute Level (off, -94.5dB à 0dB), default off
Volume Display (dB, Decimal, Binary, BarGraph Display), default dB Display
MBB Turn Off Delay (0 to 4.080mS), default 960uS
MBB Turn On Time (0 to 255uS), default 32uS
IR Volume Speed Up (Normal, No, Fast Speedup), default Normal Speedup
Encoder Stepping (1,2,4,8), default

Input Setup
Input N°1 setup
Input Name, input name using characters table, default ‘Grammophone’
Input Type (Balanced Input, Unbalanced Input)
Add 6dB to Volume (same volume, add 6dB), default same volume
Note: This choice doesn’t appears in ‘Unbalanced’ mode
Volume Trimming, trim range -6.00dB to +6.00dB , default 0.00dB
Activate Trigger (Trigger Off, Trigger On), default Trigger Off
Input N°2 setup, same as No.1
Input N°3 setup, same as No.1
Input N°4 setup, same as No.1
Bypassed Input (No Bypass, Input No.1,2,3 & 4), default No Bypass
Startup input (Preset + Input No.1,2,3,4 & Bypass ou Last), default Preset Input No.1

Display Settings (LCD Display Setup)
Brightness (0-255), default 200
Contrast (0-30), default 20
Idle Brightness (0-255), default 0
Idle Timeout (15s,30s,1,2,5-55min by step of 5min, 1 Hour ou Never), default 15 sec
Led Brightness (Switch Led Off, Keep Led On), Keep Led On

Messages Setup
Power On Message, Default: UGS Preamp V2.01 / Thanks Nelson
Mute Message, Default: Ce silence est aussi/Sponsorisé par NP..
ByeBye Message, not defined

Manage Settings
Restore Defaults, then ‘Are you sure’, ‘Realy sure?’, press ‘Menu’ one last time…
Settings –» Mem 1, idem…
Settings –» Mem 2, idem…
Mem1 –» Settings

Remote Control: IR remote codes programmation
System ID: Test to check if the UGS can decode the remote:. Default 16
Standby/On : Press "mode", then standby key on the remote to program this function, thens press "mode" again to save.
Mute Output : Same for the Mute function
Volume +, Volume – etc…
Balance left, Balance right
Input 1, Input 2, Input 3, Input 4
Bypass UGS
Brightness +, Brightness –
Contrast +

Naturally every setup was saved in non volatile memory.
Hi CeeVee, hello Portugal :),
I've just discovered this project thanks to this thread :)

Yes, it's too soon for now.
I suggest you follow the trend, to get the PCB, they are not too expensive and are the main pain to get for a good price.

As it is an upgrade, the components will not get you to bankrupcy ^^

Ah, one thing to know, you will have to change your Xformers
Joined 2006
Paid Member
Hi CeeVee, hello Portugal :),
I've just discovered this project thanks to this thread :)

Yes, it's too soon for now.
I suggest you follow the trend, to get the PCB, they are not too expensive and are the main pain to get for a good price.

As it is an upgrade, the components will not get you to bankrupcy ^^

Ah, one thing to know, you will have to change your Xformers


No Problem with BOM as i intend to build a completely new one.

I have 2 pairs of UGS3 modules built and calibrated, so i intend to build 2 , one for me and one for my son who has caught the bug from me :).

I had a few MUSE modules sent over from Japan since i have friends there but now you can buy the chips at Akouo ( 25€ each )

But worth every penny.

Ofcourse if one could buy a batch from Japan as GB they would probably be much cheaper.

Some colleagues here don't know what they are missing....if they are good enough for PASS XS preamp......:cool:
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