Shiny Eyes EML300B – C3g single ended amplifier

Here is my latest creation inspired by the beauty of a pair of EML300B that was lying unused.

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As always, I try to create 2 stage SE amps for many reasons. Hard to do 2 stages with low gain power DHTs. One of the few tubes that have the advantage of high gain, great linearity and still a bit of headroom to be able to let the 300B signature be predominant. The 300B starts clipping at 8W or so and that corresponds to a 1.65Vrms input. The C3g starts clipping at 2.3Vrms input. This allows a headroom of 2.9dB which is not a lot, but still way better than no headroom and better than many designs out-there with drivers that will go into clipping before the 300B.

Anyway, the 300B will distort above 2% at 4.5W and in my opinion the listening levels for a 300B amp should be at 2-3W and that allows a 6-4.2 dB power headroom and therefore creates a more realistic 7.4 dB signal headroom for the C3g.

I was a bit reluctant to built it in one case, but many audiophile are looking for single enclosure amps as more convenient use of space. It ended up weighting more than 50lbs.

The big challenge, when building a tube rectified DHT amp in one enclosure, is to keep it quiet. This amp is dead quiet on my 96dB speakers and my 100dB headphones.

The power supply uses the LL1651 and two LL1673 10H chokes in common mode. The B+ is around 475V. This time I didn’t use the famous Coleman regulators because of lack of space. The 300B filaments and the C3g filaments are powered using LD1085V regulators.

The amplifier is transformer coupled using the LL2753 and the output transformers are Jack Elliano’s Electra-Print 3.5K to 8Ohms low IMD. The tubes are self-biased and decoupled with Elna Cerafine. All the resistors for biasing the 300B are Mills MRA-12. The 300B is biased at 380V/-80V/75mA and the C3g at 225V/-3.5V/17mA.

The amp has an input sensitivity of 1Vrms for 3W output. The frequency response is 20Hz to 25kHz at -0.8 dB and the damping factor of 2.3 which calls for easy to drive, full range drivers.

This amp sounds great on my TangBand and Mark Audio speakers. The bass is well defined and under control, the mids are superb and the high are clean and crisp.

 

Shiny Eyes SE UL EL34-6SL7 tube amplifier

Shiny Eyes SE UL EL34-6SL7 tube amplifier

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Despite the fact that my love stays with DHTs, I’ve designed and built this amp to fill a gap that I thought it was worth the effort: making an amp in one enclosure, small enough but able to put out more power than a 45 or a 4P1L could do. I’ve also wanted to compare the sound with the 300B amp  I was building at the same time.

It all started while I was trying to figure out what amp to build with my last pair of James6123HS. I breadboard the EL34 and tried many drivers and configurations. I’ve ended up liking  the 6SL7 paralleled and using a small amount of global NFB, just enough to bring the distortions down, while widening the frequency response and increasing the damping factor.

This amp measure good as well as sounds very nice. It gives a max 8W at 1.7% ( 0.58% at 1W, 1% at 3W and 1.25% at 5W). The input sensitivity is 1Vrms for 5W output. The frequency response is 10Hz-40kHz @ +0.25dB for 3W output. The damping factor is about 7.

As expected this amp has a predominant 2nd harmonic and the sound is very pleasant. Dear reader, please remember this is still a low power, single ended amp and  will do the right thing if it is used with the right type of speaker ( easy to drive, preferably full range) and music.

I am very pleased with the sound of this amp and considering the cost of tube replacement, I am kindly recommend it for ever is looking for a decent cost SE tube amp that will sound as close to a DHT as possible.

I’ve used all good quality, audio grade components: James 6123HS output transformers, TungSol tubes, Heyboer custom order main transformer and choke, quality Made in Japan sockets, Cardas binding posts, Kimber RCAs, Obbligato Premium Gold coupling caps, Vishay and Takman resistors, Elna Cerafine decoupling caps. The power supply is using CREE Schottky diodes, CDE lytics  and DC regulated filament supply for the 6SL7.

This is a well build amp that will last for a long time and give a rewarding sound. It is self-biased so there is no need for any adjustments throughout the life time of the tubes.

All the equipment is attached to the 1/8″ top aluminum plate that sits on a hardwood wooden case made with the outstanding Brazilian cherry, light oil and urethane coated ( 4 coats).

The amp weights 37 lbs and measures 13x13x9″.