Disclaimer: as usual this is just subjective BS to be taken with a bit of a pinch of salt. It is, however, what I perceive to be true. You may find otherwise and Goran certainly did. Many thanks to Goran for helping me source the valves.
Here's a few thoughts on the Tesla RD27AS.
I waited for a pair of 100% RD27AS before comparing to a pair of 100% Tesla AD1 - date code OJ as documented earlier in this thread.
The RD27AS were made in 1979 and 1980, so not the same year but pretty close. One looked new, the other shows some sign of use.
Let me say I spent an entire evening listening to the RDs and I really enjoyed it. So in its own right it is a good valve. But there are quite a few good valves around.
I was going to write a detailed review of various tracks comparing AD1 to the RDs but the problem was this. For me, after just playing two tracks on the RDs and then following up with AD1, I just thought it would be a pointless exercise.
The reason for this was I instantly found AD1 to be preferable. So why do I make this statement?
Even without matching volume levels i.e. I could play AD1 louder or quieter than the RDs, I found AD1 to be cleaner, more resolved. As I wrote to Ked yesterday privately, AD1 just knows what it is doing. RD sounds a bit echoey and diffuse by comparison. The RDs throw a big soundstage but it is less precise in its image definition. AD1 clearly "knows" where everything is and there's a better sense of everything being separated in the acoustic.
There's another area where AD1 wins too. The bass is more tuneful and better defined.
The system I used to evaluate this for those who don't know is a pair of Apogee Duetta Interstella loudspeakers, a modern Apogee based on the original Duetta and a Luxman M-800a and matching Lux pre C-800F. Playback was via a Lampizator Big 7 which has been heavily modified and is far superior to the original product supplied by Lampizator, even though it retains the original DAC board. It has a 4V 2A switch position which is the heater spec for both these valves, though RD is actually quoted as 2 to 2.3A for some reason.
The output caps I used were Dueland copper foil 0.47uF rather than the other choice, Jupiter 2.2uF copper foil.
So RD is a nice addition to the collection and it is awesomely made. Despite being large and therefore more susceptible to microphony, it is kept to low levels. But it is not as low as the AD1, which is an absolute champion on this parameter.
RD fought as well as it could. Next up I will probably do AD1 versus Loewe AD1/400. Winner takes on Osram Marconi PX25.
Here's a few thoughts on the Tesla RD27AS.
I waited for a pair of 100% RD27AS before comparing to a pair of 100% Tesla AD1 - date code OJ as documented earlier in this thread.
The RD27AS were made in 1979 and 1980, so not the same year but pretty close. One looked new, the other shows some sign of use.
Let me say I spent an entire evening listening to the RDs and I really enjoyed it. So in its own right it is a good valve. But there are quite a few good valves around.
I was going to write a detailed review of various tracks comparing AD1 to the RDs but the problem was this. For me, after just playing two tracks on the RDs and then following up with AD1, I just thought it would be a pointless exercise.
The reason for this was I instantly found AD1 to be preferable. So why do I make this statement?
Even without matching volume levels i.e. I could play AD1 louder or quieter than the RDs, I found AD1 to be cleaner, more resolved. As I wrote to Ked yesterday privately, AD1 just knows what it is doing. RD sounds a bit echoey and diffuse by comparison. The RDs throw a big soundstage but it is less precise in its image definition. AD1 clearly "knows" where everything is and there's a better sense of everything being separated in the acoustic.
There's another area where AD1 wins too. The bass is more tuneful and better defined.
The system I used to evaluate this for those who don't know is a pair of Apogee Duetta Interstella loudspeakers, a modern Apogee based on the original Duetta and a Luxman M-800a and matching Lux pre C-800F. Playback was via a Lampizator Big 7 which has been heavily modified and is far superior to the original product supplied by Lampizator, even though it retains the original DAC board. It has a 4V 2A switch position which is the heater spec for both these valves, though RD is actually quoted as 2 to 2.3A for some reason.
The output caps I used were Dueland copper foil 0.47uF rather than the other choice, Jupiter 2.2uF copper foil.
So RD is a nice addition to the collection and it is awesomely made. Despite being large and therefore more susceptible to microphony, it is kept to low levels. But it is not as low as the AD1, which is an absolute champion on this parameter.
RD fought as well as it could. Next up I will probably do AD1 versus Loewe AD1/400. Winner takes on Osram Marconi PX25.
Last edited:
