Shiny Eyes SE UL EL34-6SL7 tube amplifier
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″.
This is Fullrangeman greetings.
Always nice to see a good tube amp.
I noted choke and power trafos are much bigger than Inspire and Decware amps, always a good thing to run cooler and long life.
Do this amp can run KT77/88/90-?
This amp could use 6D22(half wave) or 5C8S as rectifiers?
It could add more sound quality or no?
Thanks and wish you a great 2019.
Click to access 6d22-svetlana.pdf
It can run KT77 that is pretty similar to the EL34.
Yes, I could’ve used tube rectifiers but I was restricted by the size of the top plate and proximity.
Thank you and Happy New Year to you too!
“I’ve also wanted to compare the sound with the 300B amp I was building at the same time.”
And how did they compare?
The SEUL EL34 is a very good sounding amp delivering about the same power as a 300B amp.
However, the 300B if designed right, it is more musical and refined. Better mids and more air.
If I were to choose I would definitely go for the 300B.
If you don’t care about less power and lower damping factor, then use EL34 in triode mode. Closer sound to a DHT.