GU50 8w Monoblock Amplifier

$998.00 US

SKU: N/A Category:


Get ready for the amazing sound of a Single Ended Pure Class A amplifier.  Clarity defines Class A and with clarity we get a great stereo image and with those two key things we get a wonderful soundstage!

We’ve carefully selected every part and component. From the Solen coupling capacitors to the solid Cherry Wood Plinth and Hand Brushed Aluminum Top Plate, to the Universal Hammond power transformer.

The GU50 comes as a Full Kit that includes all parts and an unfinished Solid Cherry Wood Plinth and Finished 3/16″/ 5mm Aluminum Top Plate. Or as a Light Kit, without a top plate or wood plinth, for those of you who’d rather build your own enclosure.

Build Information will include a Color Schematic of the Power Supply and Amplifier, also a Build Series of Videos will be available on YouTube (Mellow Tone Kits).  The videos are the Build Manual.


SE (Singled Ended) Pure Class A (no Negative Feedback)
Rated Output Power: 8 Wrms
Universal Power Transformer
Household Voltage 100-240vac
Input Sensitivity: 5.45 Vrms
Signal To Noise Ratio: 64 dB
Input Impedance: 470 Kohm
Output Impedance: 4 Ohm / 8 Ohm
Power Consumption: 73W

Tubes – Driver: 1 x 6N6P or 6N6P-I
Power: 1 x GU-50

Sound Signature:  Musicality, Drive, Natural Bass, Magical Midrange and Treble with Amazing Detail, Clarity, Stereo Image & Soundstage.

System Compatability:  Feed the GU-50 with any of our Quality Preamp Kits and Drive any medium to higher efficiency speakers of  about 87dB or more.   Fun Fact:  I run custom open baffles (dipoles) that are about 93dB efficient and for the full volume “Live” test, I needed to wear hearing protection and 1/2 volume was already too much!

Build Complexity:   Medium – if you already make stuff, and are a thoughtful careful person, who can focus for an hour – You Can Build this Kit Amp.

Shipping Extra (to check on rate, make an account, place item in cart and go to check out page)

Discount Codes – don’t work on Kit Amps – the margin is too tight to offer discounts.

Not included:  Tubes, IEC power cord, solder


6N6P Preamp/Driver Tubes

GU50 Power Tubes

IEC Power Cords


Full Specification Sheet

Frequency Response

Frequency Sweep

Power Supply Schematic

Amplifier Schematic

Build Videos – (coming soon) follow along with Jim on YouTube as he guides you through the build process step by step.  Note:   Link brings you to the Yuri Build Series, a similarly constructed amp.

Recommended Tools:  Link to Tools in the Store*

Temperature controlled solder station (I use: Lonove 926LED III available at Amazon)

Electrical Solder  63/37 tin/lead rosin core 0.8mm/.031” (Kester “44” 24-6337-0027)

Rosin Soldering Flux (I use: Caig “no clean” paste RSF-R39-2)

Volt/Ohm Meter (CAT III 600v – minimum) c/w probe & clip-on leads

Variac  0-130vac/20A or 0-260vac/10A  (helpful but not required)

Hot Glue Gun – a mini craft type will work just fine

1/4″ Socket Wrench & Deep Sockets 3/16″ &  7/32″ c/w  3″ (75mm) extension

*Wire Stripper

*Solder Sucker

*Needle Nose Pliers

*Side Cutters

*Ratcheting Crimper (Note: this is NOT your standard red/blue/yellow crimper)

*Mini Hot Air Gun (very very useful)

*Mini Utility Knife

*Mini 1/8″ Slot Screwdriver

*Torx Driver T15


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