Audio Products Review
Tubebuilder Product Reviews

EL84SE-4.5 Single-Ended Amplifier

     This is one of the best mini-amps I have listened to in a while. The soundstage was incredibly accurate, and each and every instrument was well defined. Very natural were the horn of Miles and the voice of Tracy Chapman. This amp performs well with jazz, classical and even reggae. It demonstrated the uncanny ability to handle quiet and extremely dynamic passages very well. Fortunately, I was able to do some long term listening.

     I got the amp with new tubes, and was able to discern the sonic differences as the tubes burn in. Very subtle yet very distinct were the tones as the burn-in period ended. The amplifier actually sounded better by the minute.

     Figure 1 shows the result of the spectral analysis (Hanning Method -1kHz signal) done on the amplifier in the triode mode with the SV83 output tube. You can't help noticing the 2^nd harmonic content. I think the EF86 made some significant contributions to this.

Some unique options offered with this amplifier are:

1. Headphone jack
2. Triode or pentode operation
3. Zero or variable overall negative feedback
4. Ability to use an EL84 or SV83 output tube

     You can pick what suits your ears. I reviewed the amp with zero feedback and triode mode and the Svetlana SV83 output tube (Class A) and also the Svetlana EF86 input tube. What a combination!

     The amplifier also comes with a custom Toroid Power transformer which is very quiet. The SOWTER output transformers are oversized, which account for the excellent LF response.

     Figure 2 shows the 10 kHz square wave response, which is very good considering there is no feedback applied on this test amp.

     Figure 3 shows the 1 kHz square wave response. The EF86 (wired in triode mode) used in the input stage is a tube I call the “unmentioned hero”. This tube has given the EL84SE its unique tone and a midrange that you never get tired of listening to.

     On the matter of distortion, I really need to point out some details. This measurement is highly dependent on the output tube. I have tried various brands that gave rather interesting results ranging from 0.8% to 3.0% distortion with no feedback. Brands from Sovtek and PentaLabs preformed quite well. These gave the 1.9% distortion with less clarity in the midrange. The Svetlana SV83 came in at 1.5% distortion (specified) and sounded very detailed. The absolute best performer is the Bugle Boy EL84 from Richardson Electronics. Distortion was under 1.0 %. I was very impressed with the clarity and tonal balance these tubes exhibited. These are expensive, but it brought the little amplifier to life. I recommend only the tube brands mentioned above for use in this amp.

     With fairly efficient speakers, this little giant will overwhelm your sense of hearing with very natural tones and bring your favorite musical performer right to your living room. The chassis is hand polished deep drawn aluminum that is about 1/10th of an inch thick.

     Also comes with gold plated speaker terminals and RCA input jacks - very stylish. With an asking price of $599.00, this is the best deal of all small single-ended amplifiers in its class. You will walk away with a very exquisite finish and very good performance.

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SPECIFICATIONS

Power:
4 watts Pentode 5 watts clipping
2 watts Triode 3 watts clipping

Distortion:
0.9% @ 1 Watt, Triode mode
1.5% @ 1 Watt, Pentode mode

Frequency Response:
9Hz to 35 kHz @ -3dB

Sensitivity:
0.75 V

Signal to noise ratio:
63dB, 2mV output

Channel Separation:
65.5 dB

Power consumption:
59 Watts - Idle
60 Watts - Full Power

Tube Compliment:
1) 6CA4/EZ81 Tube rectifier
2) EF86/6201 Input Tube (Svetlana)
3) SV83 Output Tube (Svetlana) Note - The 6BQ5/EL84 can also be used.

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EL84SE KIT

     Assembly of the EL84se kit takes very little effort. I was able to put the kit together in one night. It is supplied with a point-to-point board that make all your wiring tasks quite simple. You can pre-wire the board, then mount it in the chassis, so all the awkwardness of using a soldering iron under the chassis is eliminated.

     Picture 4 shows the internal wiring of the amp. You will notice the low component count. The ease of construction of this kit is perfect for the first time tube builder. All the components are well laid out with ample space between them.

     The only potential problem I see with this kit is the possibility of placing the wrong value resistors in a certain place. The metal film resistor supplied with the kit has color bands that look similar, especially for the 1K, 10K and 100K ohm values. To work around this, take actual resistive measurements for each resistor before you install them.

     After wiring your point-to-point board, you secure it with six screws on stand-offs. You then run your signal wires, terminate your Output Transformer wires, High Voltage wires, Heater Wires and you are done. Easy! I gave this kit high marks for simplicity.

 !! FINISHED PRODUCT !!