Transcendent Sound       Vacuum Tube Audio Amp Kits

The Evermore OTL

The Only OTL Amp That Uses

Common Guitar Amp Tubes

Power Output With EL34 Tube Family: 10 watts into 8 ohms, 18 watts into 16 ohms

Power Output with 6550 Tube Family: 12 watts into 8 ohms, 20 watts into 16 ohms

Price: Full kit only $1499 for Monoblock Pair, without tubes

The new Evermore amp ushers in a new age in OTL amplification.  By utilizing common, easy to obtain guitar amp tubes, owners will never have to worry if tubes will be available years from now.  So long as the guitar amp industry exists, tubes will be available for this amp.  The amp is hardwired to accept one of two families of tubes.  The change only requires changing out one diode and one resistor (both supplied), which is very easy to do.  The amp must be used with the selected tube family unless the two parts are swapped out.

The Evermore will work with ANY EL34 or 6CA7 type tube from any manufacturer.  It will also work with the JJ KT77, as well as any big bottle EL34’s.  It will work with any 6550 type tube from any manufacturer but the tubes must be the straight bottle type.  This includes the Electro-Harmonix KT90EH.  Flared and Coke bottle type tubes are too big to fit.  Tubes must be less than 2 inches in diameter.

For the first time, tube rolling in now an option.  Want a different sound, use different tubes.  The EL34 version captures all of the midrange liquidity that it is famous for.  It tends to push vocals forward.  The 6550 version sounds more like the traditional sound of an EL509 push-pull OTL.  The choice is yours to make.  The low cost of the EL34 is a considerable upfront saving.  Please note:  The amp is not being supplied with tubes because customers can obtain them much more cheaply than we can provide them.

Using guitar amp tubes required a complete redesign from previous models.  This amp has a new output stage that improves performance and simplifies circuitry.  Speaker protection has also been improved.  These tubes require higher voltages, so to better protect the speaker, a transient surge diode has been included that will clamp the output at lightning speed in the rare event that a tube shorts.  The clamping action will cause the output fuse to instantly blow, thereby protecting the speaker.  

Guitar amp tubes are rugged and built to take some serious abuse.  During extensive testing, the amp was pounded hard and no tubes failed.  We blew some fuses, but the tubes survived.  DC stability is also excellent with these tubes.  The output easily adjusts for 0V DC offset and the adjustment stays put.  These tubes experience little temperature drift.  Set and forget it.

As with any of our OTL’s, this amp is fast, clean and stable.  Take a look at the square wave responses.

The image on the left is a 10kHz square wave into 8 ohms at 4 volts peak to peak.  It’s nearly perfect without any ringing or phase distortion.  The image on the right is 100 Hz signal with the same loading.  The slight tilt indicates a slight low frequency roll off.  Again, this is excellent performance.

The above image is the noise spectra in RMS volts with an active input.  The first spike 60 Hz filament noise at a low 600 microvolts.   The next one is 120 Hz power supply ripple at a very low 70 microvolts.  The third spike is power supply 180 Hz third harmonic ripple at 570 microvolts.  The fourth is fifth harmonic 60 Hz at a very low 220 microvolts.  Then nothing.  No annoying buzzing.  The primary noise spikes are very low and occur at frequencies of low hearing sensitivity.  They are essentially inaudible.

If you have hesitated to purchase an OTL because of the need for expensive or exotic tubes, those reasons have now been eliminated.  Transcendent Sound has worked for 20 years to bring OTL amplification from the realm of the exotic to the practical world of everyday listening.  This new amp is the culmination of that journey.

Tube compliment for each amp:

8-EL34 or 6550



Power consumption at idle (each amp):

160 watts for the EL34 version

205 watts for the 6550 version

Output impedance: 0.4 ohms

Bandwidth: Flat from 20 Hz to 60 kHz.

Power consumption for two amps: 320W for EL34 and 410 watts for 6550.

Footprint: 17 inches wide and 10 inches deep for each amp

Power required: 120V 60 Hz or 230-240V 50Hz.