Why a single-ended power amp with a 400-watt triode?

“ Single-ended” is currently the only circuit design where the input signal (in this case the electric guitar) is not split into a positive and a negative half wave and then mixed together again, but is amplified as a whole. In this form the guitar signal from instrument to speaker is kept in its entireity.
Crossover distortion, which inevitably occurs with the common push-pull operation, is simply out of the question in single-ended-operation, that’s why this amplifier always sounds good at low or high volume levels whilst delivering an accurate and detailed tone.
Negative feedback, that normally reduces crossover distortion, does not exist, giving the over-all sound an airy and more transparent reproduction.
The audible end result of using this single-ended power amp without negative distortion, is a crystal clear and nuance rich reproduction of the original signal even at low and high volume levels, and all that whilst still retaining an unbelievable dynamic.
Sound changes caused by temperature fluctuations or badly paired power amp tubes cannot occur with the use of this circuitry and only one power amp triode


“Triode” as power amp tube – it likes it harmonic

The first special feature of a triode compared to a pentode is the evenly produced harmonics, which are amplified by the single-ended-operation. Primarily it is the second harmonic that is formed, equivalent to an octave above the fundamental note.
(Even harmonics sound pleasant to the human ear, uneven sound enharmonic and thus raspy.) The end result in using a real triode is a harmonious, contour rich and high-resolution sound.
With the “400-watt triode” 833 it has been possible to realize all the above benefits with a power output of 100 watts, making this amplifier suitable not only for club gigs and studios but also for big live concerts.
The somewhat “muddy” sound that partly adheres to the conventional tube amps that no longer achieve the specified performance doesn’t occur with this amp due to the extreme long life of the power tube whose performance stays constant over a very long time.
(The 833 are a tube developed for radio that has a constant operation with 400-watt anode performance. In ERUPTION it’s only burdened with 300 watts!).
They are made in Russia and China and are still being used in small radio stations.
They are still available through leading distributors.
The price is comparable to a selected quartet EL34 / 6L6 power tube set.

Active LC-EQ with tube technique- as always still effective with analogue.

For this amplifier a new kind of EQ-control circuitry with LC- filters has been developed that works in active circuitry together with a double triode ECC81
Here the LC-filter, similar to those by MANLEY MASSIVE PASSIV, comes to use.
To achieve the strong increases and decreases of the frequencies that are important for a modern guitar sound an active circuitry was chosen. Because of the LC-filters that are used the frequency response can be efficiently and differentially influenced.
These filters are designed as standard to be pluggable for every channel, thus it is possible by swapping the filters to change and adapt the sound characteristics for every individual sound concept the guitarist may have.
Because the LC-filters for each channel affect the ECC81 at only one point in parallel and not in series (one behind the other) the occurrence of phase shifting is very low, thus the excellent sonic properties of the power amplifiers will not be degraded by the pre amplifiers.

Fewer pre-amps – guarantor for dynamic tone. 

To achieve a highly dynamic and faithfully detailed signal only so many tube systems as deemed necessary are used for each pre-amp. This way, unnecessary tube type compression, and thereby under some circumstances a breaking up of the guitar signal, is consequently avoided.
In addition to the above-mentioned attributes the amp is rewarded with a very good noise ratio, and often neglected for electric guitar amps, ambient noise.

Weight / Cost price

The single-ended-technique can only be realised in pure class-A operation, this necessarily demands a high-energy input and consequently an increase in weight,
(power transformer and output transformer.)
To provide a hum-free circuit voltage, elaborate and cost intensive circuitry is necessary.
All this, plus a higher than standard set of features and quality workmanship (hand made in Germany) has naturally its price.

  • Single-ended-triode-technique with 100-watts power output.
  • No crossover distortion.
  • No negative distortion of the power amplifier.
  • Very low hiss, hardly any background noise.
  • No selected power amps and driver tubes necessary.
  • Consistently balanced sound even at low volume levels.



  • In all channels, high dynamic and very fast attack.
  • Crystal clear, high-resolution reproduction of the guitar signal in clean channel.
  • Stable sound quality over a long time period and under any conditions.
  • Efficient, exact on the channel (Clean, Crunch, Lead) balanced EQ.
  • Filters individually swappable via slots for each of the 6 EQ’s.
  • 6 separately independent channels.