Vacuum Tube Sound for the 21st Century

Mapletree Audio Design offers a unique range of products designed and hand crafted by Dr. Lloyd Peppard, a retired electronics engineering professor. The goal is to increase your enjoyment of recorded music through the use of vacuum tube amplification and signal processing. 

Click on these tubes for more information ^^^^^^^^^^

Quick Find:    Headphone Amplifiers   |   Preamplifiers  |   Other Products (line routers, Dynaco driver board, power amplifiers)

New! SUPER STEALTH + Monobloc Power Amplifier with 20 Free Watts!*

* The Super Stealth + monobloc power amplifier features the same proven Mullard circuitry as the 10 W Super Stealth but offers 30 W power output using EL34 tubes with uprated power supply and output transformers--all for the same price as the Super Stealth (introductory offer).


Tube complement: 12SJ7/12SJ7GT, 12SC7, 2 x EL34 matched pair
Rectifier: full-wave solid state with ultra high-speed silicon diodes
Output configuration: Class AB1 ultra-linear push-pull with self bias (EL34 matched pair
Driver circuit topology: Mullard type with pentode voltage amplifier (12SJ7) and
cathode-coupled phase inverter (12SN7)
Rated power output (8 Ohms): 30 W
Frequency response at 1 W output: 20 Hz–20 kHz –0.5 dB
Gain: 27 dB (22.2) or 0.7 V input for 30 W output
Input resistance: 100 kOhms with input level control
Output resistance: < 1 Ohm
Noise: < 0.7 mV (87 dB below rated output)
Dimensions: 6"W x 11" D x 6" H overall
Weight: 15 lb

User's Manual download (pdf)

The Mapletree Engineered To Order (ETO) Concept

Customers often have specific requirements that can be met with custom features and modifications to existing Mapletree products. Usually, these can be accommodated at nominal extra cost. Let us know if ETO can tailor a product to the particular needs of your system. The LR 1 shown on the left has custom features that were implemented at no extra cost.  The L2X preamp with PSX power supply (right) is a compact derivative of the Line 2C/PS2C with customizable features including maximum gain (unit shown is configured as a unity gain buffer), level control, heater voltage switch, second input, etc. Base price (single I/O, level control, heater voltage switch) with PSX power supply  is $670.


FREE! Pair of NOS 12SN7GT tubes–with purchase of Ultra 4C or Line 2C preamps while supply lasts. Many different internal structural versions of the 12SN7GT were made over the years, including samples from the same manufacturer. I have accumulated a bunch of 'orphan' 12SN7s that make excellent backup tubes for owners of the Mapletree preamps. Where possible, tubes will be of the same brand, or at least the same manufacturer with different branding. Internal structures, physical dimensions, etc. may differ.

Free shipping continues!  Free Expedited Mail delivery of Ear+ HD, Super II, Line 2C, Phono 3C, Ultra 4C, and LR 1/SP 1 orders to N. American locations during April, 2016. A shipping discount is applicable for international orders.


Ultra 4A SE Phono/Line preamp with PS 2 power supply–Dr. P's original personal system unit, surplus to needs, completely refurbished.

Premium components and custom features: Noble volume control, Auricap and Multicap coupling caps, two phono inputs with stereo-mono switch on rear panel, RCA NOS 12SC7s, Sylvania 'chrome top' 12SN7GTs. Selling for $600 USD, which is 35% less than the current Ultra 4C. Free shipping to N. America applies.


Stealth 60i prototype/demo - Fully refurbished integrated version of the Stealth 60 stereo power amplifier. The original Stealth 60 design is enhanced with the addition of a preamp stage, level control, and provision for output bridging for use as a mono subwoofer amplifier. The power amp utilizes EL34s in class AB1 ultra linear with a Mullard long-tailed phase inverter (6SL7GT) and a pentode voltage amplifier (6SJ7/5693). The preamp stage is a common cathode 6SN7GT. The power transformer is a heavy duty unit from Triode Electronics, made in USA. The output transformers are Hammond, made in Canada. The EL34s are fully tested Electroharmonix. The low-level tubes are premium types: brown-base Westinghouse 6SL7GTs, Sylvania special red 5693s (6SJ7), and a GE brown base NOS 6SN7GT. A built-in meter allows for easy bias adjustment.

For more detailed information, you can download the User's Manual.

You can steal this unit for $800 USD plus shipping (120 VAC only), which is less than half the normal selling price.

6SN7GT TUBE SALE! I have accumulated a small stock of "orphan' 6SN7s that are ideal for tube rolling with the Mapletree preamps. These days,. even single used 6SN7GTs sell for more than many customers are willing to pay. I am offering tubes from my stock to Mapletree customers, past and present, at reasonable prices. The first batch for sale are described below. Most are strong used samples but some are NOS, as noted. Shipping, any quantity is $5. All prices USD.

1. GE 6SN7GTB USA, grey parallel plates.
2. GE 6SN7GT Canada, black plates.
3. GE 6SN7GT Canada, smoked glass.
4. GE 6SN7GTA USA NOS, grey parallel plates.
5. GE 6SN7GTB Canada, micanol base, grey parallel plates.
6. Marconi 6SN7GT Canada NOS, black plates, similar internal structure to 2.
7. RCA JAN 6SN7GT, USA NOS, smoked glass.
8. KEN-RAD 6SN7GT USA, offset plates.
9. GE 6SN7GTB USA, grey parallel plates.
11. GE and RCA 6SN7GTB USA NOS, coin base, grey parallel plates.
$20.00 (pair)



A comparison of the Mapletree/SugarMaple headphone amplifiers

Ear+ HD Headphone Amplifier ---- still the gold standard after 10 years

"Now I have to listen to all my CDs all over again. I have a decent stereo system but with the Ear+ it sounds like a $20,000 setup".

Reviews Customer feedback

• Outstanding performance with a wide range of headphone impedances and drive requirements.
• 2 x 12B4A NOS and 1 x 5751/12AX7/ECC83 tubes.
• High and low impedance headhone jacks.
• Premium passive components include Panasonic polypropylene output capacitors and Alps volume control.
• Ultra high-speed rectifier diodes.
• Line source output or passive preamp output.
• Dual switched source inputs.

• Available with red/black/white/yellow/blue/green chassis top with anodized aluminum side panels.
• Dimensions: 6" x 10" footprint x 5" tall
• Weight: 8 lb

Ear+ HD Super II  Headphone Amplifier

Customer feedback

The use of  6BQ5/EL84 output tubes in the Ear+ HD250 was popular with customers who aprriciated its wide availability. Like the HD250, the HD Super II  utilizes the EL84 with triode connection in cathode follower mode (as is the 12B4A in the Ear+ HD). The 12AX7/5751 drivers are configured in SRPP topology. The power supply is constructed on a separate chassis to obtain the lowest possible noise floor and to minimize heat buildup in the main amplifier chassis, thus increasing component life expectancy. Both units are a compact 5" wide. Appearance is distinctive with brushed aluminum and chrome trim.  Wood side panels are not available as both chassis have ventilation holes along the sides. The two chassis can be stacked, positioned side by side or even located on different shelves. A 1 ft power interconnect cable is supplied; longer cables can be requested. Available with 240 VAC wiring at no extra cost.

provides three inputs and a passive output.

                           RM 2 REMOTE VOLUME CONTROL MODULE for HD Super II
The RM 2 remote volume control is housed in a chassis to match the HD Super II and its power supply. It features a Bent Audio motorized Alps potentiometer with remote handset. Available with 4 inputs, a source output (which can be used as a passive preamp output), and dual power jacks to provide connections to both the Super II power supply and amplifier chassis. No modifications to the existing chassis are required.  A wall power supply can be added if desired. Priced at $400 with motorized Alps control.  Please inquire about other options including a
motorized DACT stepped attenuator.

SugarMaple OD300 Headphone Amplifier

This is the first product developed by Mapletree Audio Design Associate, Dr. Al Freundorfer, under the new SugarMaple banner. The OD300 (Octal Duo) Headphone Amplifier employs an all-octal tube lineup including a 6080 (6AS7G equivalent) output and a 6SL7GT triode driver stage. Polypropylene output caps are standard and circuit refinements ensure a perfectly flat frequency response from 20 Hz to 20000 kHz. The high output power (over 1 W into 16 Ohms!) and low driving impedance of the 6AS7G easily handle any headphone sensitivity and impedance characteristic. For more details and complete specifications, you can download the User's Manual.

"The OD300 sounds great after settling in and combines musical dynamism with a lovely euphonic quality."

SugarMaple Sidewinder Headphone Amplifier

NEW! Customer feedback on the SugarMaple Sidewinder.

The latest take on the Ear+ HD theme features ultra-low output impedance and ample opportunity for tube rolling with new and NOS 6DJ8 and 12AX7 tubes and variants. For more details, download the User's Manual.

  A comparison of the Mapletree/SugarMaple headphone amplifiers


Line 2C Line Preamplifier                  Review of Line 2B SE by Tim Smith at wall of sound.

Customer feedback

• Premium passive components include polypropylene film coupling capacitors and Alps volume control.
• Optimized circuitry for lowest distortion and noise.
• 3 inputs, 2 outputs, rec output, volume and balance control.
• 2 x 12SN7GT with switch for 6SN7GT tubes.
• Separate PS 2C power supply (with tube/fast diode hybrid rectification) included.

- Line 2C RM now available with Bent Audio/Alps remote volume control - 

Also available—Line 2C HT with Home Theater bypass. The source input switch is modified to select Line1, Line2, or HT. In HT mode, Line2 (front channels) is routed to the output completely isolated from the preamp circuitry (preamp can be powered off).


Ultra 4C Phono/Line Preamplifier

Customer feedback


 • Premium passive components include
polypropylene film coupling capacitors and Alps volume control.
• 48 dB phono gain, three 18 dB line inputs, two line outputs, rec output.
• Volume and Balance controls.
• 2 x 12SN7GT (switchable for 6SN7GT) and 2 x 12SC7.
• Separate PS 2C power supply included.

- Ultra 4C RM now available with Bent Audio/Alps remote volume control -

Power Supply  
Supplied with Line 2C, Line 2C RM, Ultra 4C, and Ultra 4C RM

Newest version of the PS 2 power supply uses a 6X4/EZ90 rectifier tube in place of the 6X5GT of the PS 2. The latter tube is getting harder to source and has a reputation for premature failure due to shorts (not experienced with the PS 2 but definitely a weakness). The 6X4 is easier to source and the equivalent EZ90 is currently manufactured. The tube is enclosed in the PS 2C chassis as are the filter capacitors. Specifications are unchanged.


 Phono 3C Phono Preamplifier


For a number of years, customers have asked about a phono preamplifier that embodies just the phono stage of the Ultra 4. The issue was always that the Ultra 4 was really a phono preamp with line inputs, so there was little price or sonic advantage in going to a dedicated phono version of the Ultra 4 by omitting the volume/balance controls and source selector switch. The phono gain of the Ultra 4 is around 48 dB which is suitable for MM cartridges driving a typical tube or solid-state power amplifier. The new Phono 3 preamplifier incorporates the low-level gain and equalization stages of the Ultra 4 without the output b
uffer and with around 10 dB less gain. Thus, it is suited to drive the line input of a preamp or integrated amplifier with at least 5-10 dB of additional gain. The Phono 3 output has a driving impedance of around 2.5 kOhms, which can drive a reasonable length of interconnect without compromising the high frequency response. Noise at full output is less than 2 mV. Like the other Mapletree preamps, the Phono 3 is designed to use a separate power supply. Normally, for stand-alone use, this is the compact PSX unit shown. However, the Phono 3 is fitted with an extra power jack on the rear panel to permit connection of the PS 2 power supply to both the Phono 3 and Line 2 preamps without any modification. Two switched phono inputs are provided, which can be ordered with custom loading specs. A power switch on the rear panel allows powering down the Phono 3 when just the Line 2 preamp is needed in a shared power supply setup. Details and full specifications can be viewed by downloading the User's Manual from the "Users Manuals" page.         


SugarMaple BB (Black Buff) Line Level Buffer Stage

You can now sweeten the sonics of your DAC or other digital source with the Black Buff  line stage. It features unity gain, 100K input impedance, <500 Ohms output impedance, and includes  a volume control and heater voltage switch for use of either a 6SN7GT or 12SN7GT tube (supplied). Tube heater glow is visible through opening in chassis. Download the User's Manual  for complete specs.


Dr. P spins some 78s on his mini system. Photo by Christian Keresztes
For more information or to place an order, please telephone or email Lloyd Peppard at
(613) 387-3830

Lloyd Peppard
Mapletree Audio Design
158 Seabrooke Rd
R.R. 1, Seeley's Bay, Ontario, Canada K0H 2N0

Al Freundorfer
SugarMaple product line

PayPal LogoCredit card payments through PayPal are highly recommended. Registered PayPal email addresses are or