T4 headphone amplifi er

Owner’s Manual

beezar audio

ecp audio

This page intentionally left blank.

Published by Beezar AudioMarch 2019

Copyright 2019, Beezar, L.L.C.All Rights Reserved

http://www.ecpaudio.comhttp://www.beezar.com

http://www.beezaraudio.com

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Voltages exceed 300V inside the amplifi er. Never open the case or remove the lid (for changing tubes) without turning the amplifi -er off and unplugging the wall power. Never operate the amplifi er with the case lid off or not fi rmly screwed into place. Except for changing tubes, there are no user serviceable parts inside. Always ensure that the ampli-fi er is plugged into a grounded outlet with a properly grounded power cord.

Do not allow foreign objects or any liquid to fall into the cooling slots or the tube holes. If a foreign object or liquid falls into the ampli-fi er, immediately switch off the power and disconnect the amplifi er from the wall outlet. Do not touch the unit until it is completely disconnected. If you are unable to clear the object by removing the amplifi er top, return the unit to Beezar Audio for servicing.

Caution Warning - High Voltage!

SAFETY

Foreign Objects

Vacuum Tubes and Heat

Do not touch the tubes while the amplifi er is operating. The tubes can attain temperatures higher than boiling water. If changing tubes, allow suffi cient time for the tubes to cool. Do not leave the amplifi er unattended while turned on or turned on for extended periods.

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Do not connect the amplifi er to any power source other than the type and voltage as specifi ed on the rear of the amplifi er.

Power Sources

If the unit is left unused for an extended period, disconnect the ampli-fi er from the wall outlet.

Non-Use

The amplifi er is set up as either 110VAC or 220VAC, NOT BOTH. Connecting to an improper outlet at the wrong voltage may severely damage or destroy the amplifi er.

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The T4 diff erential hybrid parafeed headphone amplifi er, custom as-sembled by Beezar Audio, was created by ECP Audio. The T4 continues in the tradition of its predecessor, the ECP Audio/Beezar Torpedo III. Its circuit and confi guration are totally unique in the world of headphone audio. The T4 combines tubes with a fully diff erential solid-state out-put, feeding into custom-manufactured Lundahl output transformers for the fi nest in single-ended, zero-feedback output from a headphone amplifi er. The result is perhaps the fi nest tube headphone amplifi er available anywhere at this price point.

Amplifi er Design Description

INTRODUCTION

The tubes are confi gured in a long-tail pair that results in a fully diff er-ential output. From there, a fully diff erential solid-state buff er is used, terminating in output transformers confi gured into a parafeed ar-rangement, where the diff erential signal is combined back into a single ended connection at the headphone jack. Because of the fully diff er-ential circuit, common mode distortion is fully cancelled out. At the same time, the solid-state buff er output after the tubes results in more power than would be available from the tubes themselves. The output transformers assist with this, ensuring that ample current and voltage are available, regardless of the impedance of the load.

ECP Audio designed the T4 headphone amplifi er to utilize the ubiq-uitous 12A*7 audio tube family. Specifi cally, the T4 is designed for the 12AY7 or 12AT7 tube, but others can be used that meet the general 12A[T, U, V, X, Y, Z]7 tube specifi cations. There are many, many other tube types that will work, too. Refer to the tube section of this manual for a list.

The T4 includes a “Z” switch that allows switching between low and high-impedance loads (75 to 300 ohms). This switch may be thrown at any time - even while music is playing and headphones are plugged in.

Note also that with a true, output-transformer-coupled amp, there is no need for any kind of power-on or power-off headphone protection.

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• Custom machined and fi nished casework, laser-etched• Hand-oiled, solid-hardwood sides• ECP Audio custom-designed Lundahl output transformers• ECP Audio custom-designed, toroid power transformer• New thin-fi lm Vishay/Beyschlag resistors throughout• Special Vishay low-noise nickel chrome tube plate resistors• Genuine ALPS “Blue Velvet” volume control• Large, custom-machined solid-aluminum volume knob• Neutrik 4-pin XLR headphone jack, compatible with 4-pin XLR

balanced headphone connectors• Advanced thermal bar heat rejection through the casework

Components List

Specifi cations*

Measurement Item 300R 78R 61RFrequency Response, 20-20kHz ±0.4dB ±0.4dB ±0.4dB40-15kHz ±0.3dB ±0.3dB ±0.3dBNoise Level, dB (A-weighted) -94.6 -94.5 -97.1Dynamic Range, dB (A-weighted) 94.6 94.4 97.1THD, % 0.014 0.089 0.169IMD + Noise (A-weighted), % 0.009 0.051 0.096Stereo Crosstalk, dB -79.7 -81.4 -83.1

Power, mW, 1kHz 290.4 314.1 239.0Vpp 26.4 14.0 10.8Vp 13.2 7.0 5.4Vrms 9.3 4.9 3.8I,ma 31.1 63.5 62.6

Power, mW, 500Hz 290.4 314.1 239.0Power, mW, 100Hz 290.4 314.1 239.0

Note that performance measurements are only a guide to the basic capability of the amplifi er. Actual measurements are almost entirely dependent on the tubes and can vary widely, depending on the type and quality. These measurements were taken with NOS (New Old Stock) Mullard CV4024 tubes using RMAA software and an M-Audio Firewire Audiophile. Power measurements were estimated using static resistor loads (value indicated) and an oscilliscope at the point just prior to visibly distorting the output wave (clipping). 12AX7 tubes were used for the power mea-surements to provide suffi cient gain for clipping.

*

7

11 11

11 22

11 33

11 11 11 22 11 33

4-pi

n XL

R H

eadp

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Jack

(out

put)

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ters

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ones

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low

.

Amplifi er Physical Description

Front Panel

8

11 22

11 33

11 4411 5511 66

11 77

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11 11 11 22 11 33

T4 H

eadp

hone

Am

plifi

er S

eria

l Num

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RCA

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Cool

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Fuse

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Rear Panel

9

11 33

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11 77

11 66

11 55

Top Panel

10

11 11 11 22 11 33

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Ther

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ght (

8) u

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at m

ust b

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ten-

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*

11

OPERATION

Installation/Break-In

Location/Ventilation

Ensure that the amplifi er is located on a solid footing. Provide suf-fi cient room for the power cord and ensure that the cord has a secure, grounded connection with the wall outlet. Tubes are unshielded devices and we recommend that the amplifi er is located away from interfering sources such as computers and cell phones. Do not place the amplifi er on top of another heat-producing device.

The amplifi er is provided with cooling slots on the rear and on the top of the amp, in addition to the tube holes themselves. Provide at least 12 inches of clear space above the amplifi er and at least 4 inches in the rear for proper cooling. The amplifi er can become warm if operated for more than a few hours, especially if some of the higher heater current tubes are used (see Recommended Tube List). Turn the amplifi er off if it’s not being used and do not allow the amplifi er to run unattended.

Tube Warmup

Generally speaking, the tubes are suffi ciently warmed up in about a minute after turning the power on. Contrary to many reports, great listening can be achieved very quickly after powering on the amplifi er. It may be true that best results are obtained after a few more minutes, but Beezar Audio and ECP Audio do not necessarily subscribe to rec-ommendations you may see for hours of operation before achieving optimum performance.

Note that some tubes – particularly genuine NOS Mullard or Brimar tubes, will “fl ash” upon initial turn on. They will then act like any other tube and achieve a constant glow once the heaters are warmed up (30 sec. – 1 minute). This “fl ash” is completely normal for those tube types and there is no cause for alarm. Note that newly manufactured tubes with the Mullard brand are not the same and will not present this be-havior (neither will almost any other tube).

Break-In

Other than the tube warmup mentioned above, no special treatment is needed for amplifi er break-in. You may notice some subtle changes in the fi rst hour or two, but we do not recommend the hours and hours of burn-in that you may see discussed elsewhere.

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Tubes

General Care

Vacuum tubes, or sometimes referred to as electron tubes, are manu-factured of glass. They heat up and provide some light from the heat-ed parts inside. That said, they are not entirely like old incandescent light bulbs. The glass is much thicker than a light bulb, but they can still break. They also get just as hot as an old incandescent light bulb.

A vacuum tube break will often occur at the tip or somewhere at the juncture of the pins and the glass. Some breaks or cracks are not obvi-ous. However, tubes come with a silver patch somewhere around the top of the tube. This patch is a chemically reactive substance referred to as the “getter fl ash.” It is used to catalyze any remaining gas mol-ecules in the tube to create a more perfect vacuum. If the tube is bro-ken and has lost vacuum, this silver patch will become frosted white. If that occurs, do not use the tube.

• Use the tube boxes if the tubes are not plugged into the amplifi er. They provide isolation and cushioning. Many of the NOS tubes that we use have been successfully stored in these small boxes for several decades.

• Protect the tube tips. Never place anything on top of the amplifi er that may break off the tube tips.

• Heat is radiated from the tubes during operation. If the tube is dirty, this radiation is impaired and the tube will overheat. Keep your tubes clean. Use glass cleaner and/or a soft, non-scratching cloth to keep the glass clear and clean. (Do not use alcohol, it will remove the branding labels on the tube.) Never, ever attempt to clean a tube when it is hot or operating.

• Ensure that the pins are clean and can provide good electrical contact. Careful use of a small wire brush can usually clean off any corrosion. Alcohol may also be used, but as noted above, be care-ful to limit it to the pins, not the tube itself or you will remove the branding silkscreen.

Specifi c Recommendations

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• Use a tube pin straightener to keep the pins straight and aligned. Some are even newly manufactured today. Here are a few exam-ples:

Replacing/Removing Lid & Tube Sockets

“Tube Rolling” is one of the more interesting features of owning a tube amplifi er. This is especially evident on a headphone amplifi er, where you can easily hear every diff erence and every nuance. Unlike most solid-state devices, tubes are almost organic – diff erences in sound sig-nature abound. Not only do diff erent tube types have slightly diff erent signatures, but you will be able to distinguish diff erences between brands of the same tube type. There were many manufacturers back in the day when tubes were king. These manufacturers used slightly diff erent construction methods and parts to construct the tubes that ended up with the same designation. As a result, there are diff er-ences in sound signature. “Tube Rolling” is the general term for trying diff erent tubes in an amplifi er to either tailor the sound signature to your liking, or to fi nd that magical tube that brings out the optimum performance of the T4 headphone amplifi er.

NOTE: Under no circumstances attempt to change the tubes while

the amplifi er is on and plugged in. There is danger of shock even

if the amplifi er is turned off . Unplug the amplifi er before ever at-

tempting to remove the lid.

A New Old Stock (NOS) tube pin straightener made by the General Cement Company

An outstanding NOS tube pin straightener made by Hytron (both NOS pin straigteners can be found on ebay from time to time)

A brand new tube pin straightener from Riverstone Audio - even available on Amazon!

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In order to change tubes in the T4 headphone amplifi er (or replace them if they go bad), the lid must be removed. Refer to the Top Panel diagram on p. 9 and the description in that section.

There are 8 Phillips head screws that must be removed in order to re-move the amplifi er lid. These screws are quite small and have special, undercut heads in order to fi t fl ush to the top surface. They are special order and not generally available in local hardware stores. Contact Beezar Audio for replacement screws if you lose them.

Once the screws have been unscrewed, remove the lid. (You may fi nd it convenient to not actually remove them, but to let the counter sink hold the screws while you lift out the lid.) You will note that the lid is assembled with close tolerances and is almost a press-fi t into the case. Use the tool provided with your amplifi er for popping the lid out from the case. Or, use something that can hook underneath one of the tube holes or cooling slots (something that will not scratch), and lift the lid. You should only pop the lid up enough that you can get your fi ngers on the edges and remove it the rest of the way.

Tube Sockets

Unplugging tubes are easy – simply lift them out with a good tug. Plugging tubes in is somewhat diff erent. The sockets are often stiff , especially in a brand-new amplifi er. It can be diffi cult and a little bit concerning to forcefully push on a glass tube in order to plug it into the socket. Beezar Audio/ECP Audio recommends the spiral method for plugging in tubes. This is much safer and easier on the tube pins than trying to rock the tube back and forth when plugging it in.

As shown above, line up the gap in the tube pins with the gap in the socket. Slowly use a gradual twisting motion in a circular/spiral direc-tion while pushing down. Ensure that the tube is seated fi rmly on the tube socket. Grip the tube by its sides while you are plugging the tube in. Do not press down on the tube tip.

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Finally, adjust the tubes so that they are aligned to the center of the holes when replacing the lid. You can easily make this adjustment by wiggling the tube slightly into position after the lid is replaced.

Tube Type Recommendations

T4 Headphone Amplifi er Recommended TubesMajorTubeType

MinorTubeType

Amplifi ca- on

Factor

PlateVoltage

Heater Current

maComment

12AT7 60 250 150Many choices, including new manufactureElectro-Harmonix, JJ, etc.

ECC81 60 250 150 European version of 12AT7: iden cal

CV4024 60 250 150

Mullard version is Beezar default for highest performance; Expensive, but price-perfor-mance ra o is jus fi ed

6201 60 250 150 Military or industrial 12AT7

5965 47 150 225

Industrial 12AT7; inexpensive high-perfor-mance T4 choiceDo not use for long periods - heat buildup

6414 42.5 180 225Tall tube, 10,000 hr ra ngDo not use for long periods - heat buildup

6829 39 150 225Tall tube, very similar to 6414Do not use for long periods - heat buildup

7728 60 250 150 Very rareECC801 60 250 150 European rare and expensiveE81CC 60 250 150 European rare and expensive

12AY7 44 250 150

Good alterna ve to 12AT7, generally non-audiophile prices,New manufacture available

6072 44 250 175

Low noise, industrial version, some Europe-an tall versions can be expensive, may sound lean depending on manufacturer

12AV7 41 150 225Inexpensive, but may be low performance;Do not use for long periods - heat buildup

12AZ7 60 250 225

Inexpensive, high-performance choice for T4;Do not use for long periods - heat buildup

12AU7 20 250 150

Gain too low, may be OK with highly-sen-si ve headphones/strong sources; many, many variants, including new manufacture

5963 21 150 150Excellent inexpensive 12AU7 variant, low gain

12AX7 100 250 150High gain, may have high frequency drop-off , not ideal

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The T4 headphone amplifi er can utilize any line-level source that termi-nates into RCA left and right jacks. The gain may be less than optimal with higher-level sources, but this can still be adjusted by selecting a tube with less gain (amplifi cation factor). For instance, a 12AU7 pro-vides very small gain in the T4. However, it may be suitable if you have a combination of a stronger-than-normal source and very effi cient headphones.

Sources

Most medium-to-high effi ciency headphones, both high and low im-pedance, will have no issues with gain using the recommended tubes. In fact, with the tested resistor loads (61R, 78R, and 300R), the ampli-fi er cannot be driven into clipping with industry-compliant line-level sources. (The power tests on p. # were accomplished using the high-gain 12AX7 tubes.)

The amplifi er is optimized at the Hi-Z switch setting for 300 ohm headphones such as the Sennheiser HD800/s and the HD650/600/580 family. At the Lo-Z switch setting, the amplifi er is optimized for 75 ohms. This is ideal for headphones such as the Focal Clear, AKG 701 family and the inexpensive Koss KSC-75. As can be seen from the power specifi cations in the table on p. 6 (78R), the T4 Headphone Am-plifi er actually supplies more power at the Low-Z switch setting for 75 ohms. However, power will progressively drop with lower impedances. Nevertheless, low impedance headphones that are reasonably effi cient will work very well, such as Grados or the Massdrop THX-00.

Headphones To Use (Impedances)

XLR Connector and Adapter

The T4 headphone amplifi er uses a 4-pin XLR connector for the head-phone jack. The 4-pin XLR jack is a professional audio standard. It provides a superior non-shorting method of headphone connection. Adapters are available from Beezar Audio to convert from ¼” TRS stereo jacks to XLR. However, use of this adapter on other headphone amplifi ers is not recommended.

Note that a balanced, 4-pin XLR-terminated headphone may be plugged into the T4 without conversion. (The headphone’s XLR termi-nation must be compliant with professional audio wiring standards for a balanced, stereo signal.)

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Voltage Setting - 120V or 240V

The T4 headphone amplifi er will be set for the correct line voltage in your area when you receive it. However, you may want to change that voltage if you move or sell your amplifi er to a headphone enthusiast where the line voltage is diff erent. There are a series of pins, labeled A, B, C, and D where one or two jumpers set the line voltage for the amplifi er. By using these jumpers, you may change the line voltage of the amplifi er to either 110/120VAC or 220/240VAC

WARNING! Do not attempt this under any circumstances unless the amplifi er is completely disconnected from a power supply!

WARNING! Do not attempt this unless you follow these instructions exactly! You can easily destroy the amplifi er if you do this incorrectly.

PowerTransformer

Area

T4 Headphone Amplifi er PCB Layout

PCB location for line voltage jumpers

The PCB layout of the T4 headphone amplifi er is shown on the preced-ing page. The amplifi er line voltage is set with jumper(s) in the high-lighted area. Two jumpers are supplied with your amplifi er. Depend-ing on the voltage setting, either one or two jumpers are required.

The diagrams below indicate the correct positions of the jumpers for the two voltages that may be set.

110/120VAC 220/240VAC

Two jumpers,One on A-B,One on C-D

One jumper onlyon B-C

FUSE

If you change the voltage setting, don’t forget to also change the fuse at the IEC inlet. This is a small plug-in “drawer” in the middle of the IEC inlet. Two plastic tabs at the top and the bottom hold the “drawer” in place. The end of the fuse drawer with the metal prongs is the active space. The other space is for a spare fuse, if desired

Fuse drawer at IEC inlet

Active fuse at space w/prongs

Space for spare fuse, if desired

T4 Headphone Amplifi er

Fuses

Size: 5x20 mm

110/120 VAC 250 ma

220/240 VAC 125 ma

About ECP Audio/Beezar Audio

Support

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ecp audio

ECP Audio offi cially began in 2012, but traces back many years with sterling examples of tube and solid-state amplifi er construction and DACs. With a rich heritage in tube design, the L-2 parafeed headphone amplifi er was the fi rst offi cial off ering from ECP Audio. Many outstand-ing products have resulted since then, including various versions of the DSHA, the Black Diamond, and the Torpedo (T1), Torpedo 3 (T3) and fi nally, the T4 headphone amplifi er. While earning a reputation in tubes fi rst, ECP Audio has perhaps become better known for revolu-tionary applications of audio transformers - both with tubes and solid-state components.

Besides its collaboration with Beezar Audio, ECP Audio continues to produce many custom-built high-end designs to the audiophile com-munity. Contact them at http://www.ecpaudio.com.

beezar audioBeezar Audio (http://www.beezar.com) and its companion DIY site, diy-forums.org (http://www.diyforums.org) has been selling DIY parts and kits for the headphone world since 2007. Beezar’s collaboration with ECP Audio began with the Starving Student, using the ECP Audio PCB design based on Pete Millett’s original creation. Further work with ECP Audio resulted in the Torpedo parafeed tube amplifi er and the Torpedo 3. The T4 is the latest and greatest iteration of that collaboration and the fi rst design to be sold exclusively as assembled, production units.

We trust the T4 headphone amplifi er will provide you with thousands of hours of trouble-free audiophile performance. However, if an issue arises, please contact Beezar Audio at service@beezar.com.

Warranty

The ECP Audio T4 Headphone Amplifi er is warrantied for a period of 1 year from the date of purchase. This warranty covers parts and labor (except shipping costs) for repair of manufacturing defects – excluding tubes, normal wear and tear, or operator-induced damage.

Repairs will include either new or refurbished parts, of equal perfor-mance quality as intended when the amplifi er was new.

Once repaired, the amplifi er assumes the remaining warranty of the original purchase or 180 days from the date of repair, whichever is longer.

While this warranty excludes tubes, NOS tubes can sometimes be sus-ceptible to unpredictable defects or failure. Beezar Audio will replace tubes with like quality that are proven defective upon receipt of a newly purchased T4. Beezar reserves the right to replace tubes found to be defective with our choice of tubes.

To obtain warranty service or if you are in receipt of a defective tube(s), you must fi rst contact Beezar.com at service@beezar.com . We will help you to determine the problem and the most appropriate solution.

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Check out the matching (to the T4) Walnut X DAC, available soon at beezar.com! The Walnut X DAC features the following:

• ECP Audio DSHA-style fully diff erential buff er output• Lundahl high-quality output transformers (no capacitors)• Fully linear-regulated power supplies• Cirrus Logic/Wolfson WM8741 DAC chip - fully diff erential• Amanero-based, asynchronous USB to 24-bit, 192kHz

ECP/Beezar Audio Walnut X DAC

beezar audioMarch, 2019