RS1003 in SE triode-UL monoblocks
 

Just finished monoblocks with RS1003 ( SRS551) tube in SE-ClassA triode (option UL) connection. For drive tube I use EL803 (EL83 or EL803S) tube in triode connection. Also build in switch for LOW/HIGH output power for spare tube life time. Output power is 11W or 15W in triode connection, and 16W or 22W in UL connection. UL tape is at 25% turns of output transformer (closer to pentode connection), so I must use SHADE-feedback to reduce gain and distorsions.

My comment is only about safety.
I notice you lift the connection to Earth at the chassis! This makes it unsafe,
If you want to break ground loops, lift the (-) on the input, nevet the Safety Earth!

On the back side of chassis, there is terminal for separate wire for grounding.
Also, You can see previous version of frame.

Great job Davorin ... please tell more about your impressions how it sounds ...

Sonds very good, more like some other bigger transmitting tubes with direct heating, not like 2-3 paralell connecteed EL34, KT88 or GU50 tubes.
In triode connection sunds like 811A or 812A, but with less distorsion. UL-connection provide much more power, and can drive less sensitive speakers. Less detail than triode connect, but with BIGG sound for rock, metal and simphonical music.

Nice one...

Hello!
I love this lamp RS1003 and congratulations for this achievement.
What would be equivalent to EL803, or could be replaced this lamp???
What about the scheme designed by me?
EF80 is galvanic coupling advantage is a very good response in low frequencies.
The disadvantage is that the anode voltage to be coupled after the tubes were heated

Do you have a link to a spec sheet on this tube? Looks pretty interesting.

these data will be helpful?

or equivalent to RS1003 is SRS551 find here:

Scheidig Rhrensammlung: Senderoehren: SRS 551 Letztes Update: Sat Jan 10 13:14:01 2009

EF80 is good drive for UL connection output tube, but in triode connection there is much more capacitance (total input capacitance of RS1003~150pF including Miller) , and You need tube with less internal resistance for drive.
Good substitute for EL803(S) is EL83, 6CK6, and cheep russian 6P15S. Also new production (actual) is SV83 (SVETLANA).
Gain of output tube in triode connection is ~20-21x, and for normal input sesitivity (~1Veff) You need drive element with total gain about ~12x(including SHADE feedback). You can use 1/2 double-triode tubes(6SN7, 6CG7, 6FQ7, E80CC etc.; russian 6N6P and 6N30P) and many tubes with single triode in sistem with same caracteristic like 6J5GT.
At first, I try with triode connection E80F(~EF86) and 5879 tubes with very good sounds at low power, but more distorsions at higher levels as triode conection output tube. Also try triode connection EL84(6BQ5) and 6BW6(noval version of 6V6). Booth have perfect caracteristic and sound, but too low gain (~6-8x).
You can try 6CL6, caracteristics in triode mode are near EL83, and any video output pentode/tetrode from old B&W-TV sets.