Gr8 Fish: Nest Theater Part Ten - Rollin', Rollin', Rollin' 24May20

Sunday, May 24, 2020

Nest Theater Part Ten - Rollin', Rollin', Rollin' 24May20

I rolled tubes in the pre-amp section of the 300B SET Kit 1 today. My amp came with a modern Electro Harmonix 6SN7, which was excellent, but I replaced it with a NOS 1951 RCA 6SN7GT Grey Glass Short. I'd have preferred late 40's but those were 2X the price. That swap delivered a wider sound stage but not much measurable difference (see graph); I kept going on the pre-amp and replaced the stock GE 5687 tubes, also excellent, with desirable matched NOS 1958 Tung-Sol 5687s. The new pre-amp sounds better to me, and measures slightly flatter and extended but as measured it is very correlated to the prior tube set. I conclude that the pre-amp has less impact on sound in my system than do other things - well, WTF, what are those other things... search on.

Original Pre-Amp

New Pre-Amp

Comparing SPL Sweeps of OG & New Pre-Amp

My DRC-BLHs (D37) were built to allow "rolling" of the full range 6.5" drivers. I did that today for the first time by replacing the keen original Fostex 168E𝜮s with some somewhat less efficient 6.5" Tang Band W6-2144 full range drivers. In firing up the new drivers I had plenty of power (which was a concern replacing 94dB sensitive drivers with 89dB ones - NP). After balancing the system for the new drivers I was very pleased and impressed. Drivers make a difference but not as large a one as I'd expected. The TB does seem to shout less and have a smoother high end behavior (I imagine it is the center plug). I can see that the enclosure of a full range driver is the most major factor in what sound is delivered to my ear (other than source material quality); this makes sense but was not what I fully understood till today. Handmade enclosures take a lot longer to swap - I'm staying with the DRC-BLHs for now. I don't know if further driver swaps or new rectifier or power tubes will change my already astounding sound for the better. I need to cogitate but both of these drivers are excellent - especially when tamed with some EQ.