need advice re buying new fleawatt SE amp

Audionut

Next Round Is On Me
You’ve done well @rogerfederer ! Loving the amps toggle option between 2a3 and 45, I wish my bottle head had that option between 2a3 and 300b. Those cabinets have a sweet color scheme and making me look hard at a set of similar jbl dual sub cabs locally.
 

paulbottlehead

Active Member
It's very difficult to make an amp optimized for two very different DHTs. Between at 45 and a 2A3, at least the filament voltages are the same, but otherwise the two tubes want very different output transformers and standing current. The compromise is just to plug a 2A3 into a 45 amp and maybe increase the operating current a little bit, but it's hardly an optimization for a 2A3.

Going from a 2A3 to a 300B is incredibly difficult. The filament voltage and current are very different between the two tubes, the available B+ should usually be a lot higher for a 300B compared to a 2A3, but at least the output transformer primary impedance is less of an issue. The compromise here is usually to accept a significant reduction in power with the 300B option, but who wants a compromised 300B amp?
 

Audionut

Next Round Is On Me
It's very difficult to make an amp optimized for two very different DHTs. Between at 45 and a 2A3, at least the filament voltages are the same, but otherwise the two tubes want very different output transformers and standing current. The compromise is just to plug a 2A3 into a 45 amp and maybe increase the operating current a little bit, but it's hardly an optimization for a 2A3.

Going from a 2A3 to a 300B is incredibly difficult. The filament voltage and current are very different between the two tubes, the available B+ should usually be a lot higher for a 300B compared to a 2A3, but at least the output transformer primary impedance is less of an issue. The compromise here is usually to accept a significant reduction in power with the 300B option, but who wants a compromised 300B amp?
Very well put, now I have an excuse to buy a 300b amp!
 

rogerfederer

Junior Member
tube question of the day:
i have been on the hunt for 45 and 46 tubes and have a small rag-tag collection. which is more important, matching tube structure (getters, etc) or strength (via tube tester)?
 

Salectric

Senior Member
I have roughly 30 different 46 tubes all bought off Ebay from private sellers. I have never encountered a dud. I don't have any tube testing equipment other than my ears, but I can say all of the 46 tubes have sounded consistent within their brands and types. I.e. RCA tubes sound like other RCAs, same with Raytheons, GEs and Sylvanias. Cunninghams are a bit of a mystery---some of them sound like RCAs and others sound different. My suggestion is to buy a couple of each of the major brands and figure out which ones sound best in your equipment, then order some more to have as spares.

For what it's worth, my favorite is RCA ST type from the mid to late 1930s. (There is a website somewhere that has info on how to date the RCA and Cunningham tubes.)

The only problems I have ever run into with 46s concern residual hum and this was only with some Cunninghams. With several Cunningham ST type and one Cunningham globe, there was a slightly higher hum level than any of my other tubes. They still sounded nice and the hum wasn't bad (much less than a 300B with AC heating), but compared to the usual nearly dead silent background of the other 46 tubes with AC heating the Cunningham hum was a surprise.
 
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