[L0rdGwyn]

It's also a beast of a tube in size. Next to a 6C5 for reference

Gotta have big plates to handle big power! Looks to be a pretty linear tube as a triode.

 

[UntilThen]

For current production, these tubes are actually very good sounding. Wish I had rotate them in more.

 

[whirlwind]

I am going to try! All is dependent on Elma sending my selector switch on time, I will start bothering them about it now it is scheduled to ship 9/5, maybe I can have them push it back a few days.

I will look over the datasheets at be sure these tubes are compatible, all about their bias point and ensuring no ratings are exceeded in my circuit. There are a few oddball pentodes that bias too hot in this amp. But I want to exhaust the tubes that do not need adapters first before trying others, top of the power tube shopping list right now is a pair of Tung-Sol 6550. I would also like to try the RCA 6L6GC. Honestly NOS KT88 are so expensive, I may not even bother.

@Zachik if the timeline is met, I will send it to Zach who will bring it with him to CanJam not practical for me to fly out and back for one day unfortunately given my work schedule.

This amp will use many different power tubes that you can get decent deals on and without going the crazy route of GEC KT88, which are at insane prices, really insane. Much more money than most would spend to have in the amp daily.
There are numerous EL34 tubes that sound fantastic without going overboard and getting into the metal base variety.
At some point the price of a tube is just not worth the risk of using them, there are some tubes that are just basically in the collector's status in my opinion.
Some people may use them, but most of the people will never even bother when they can buy numerous tubes for an even lesser price.
I am sure at one point these tubes were a decent price, but not anymore.

 

[triod750]

If you buy the most expensive tubes and let them warm up continuously for a month they will sound glorious, trust me ! You won't be able to stop listening.

 

[whirlwind]

If you buy the most expensive tubes and let them warm up continuously for a month they will sound glorious, trust me ! You won't be able to stop listening.

Oh yes, you are correct, thing is the law of diminishing returns is at it's highest....most all pentode tubes sound good.

 

[L0rdGwyn]

This amp will use many different power tubes that you can get decent deals on and without going the crazy route of GEC KT88, which are at insane prices, really insane. Much more money than most would spend to have in the amp daily.
There are numerous EL34 tubes that sound fantastic without going overboard and getting into the metal base variety.
At some point the price of a tube is just not worth the risk of using them, there are some tubes that are just basically in the collector's status in my opinion.
Some people may use them, but most of the people will never even bother when they can buy numerous tubes for an even lesser price.
I am sure at one point these tubes were a decent price, but not anymore.

You're absolutely right Joe, there does come a point where the ultra rare tubes just aren't worth it. Unless a happen across some insane deal, I will most likely pass on GEC KT88, and the metal base Mullards are out of the question. Lots of other tubes to try. Probably the highest up the rare tube ladder I want to go is a pair of Tung-Sol 6550, and likely some other Mullard EL34. If the amp / circuit is good, most any tubes will sound good in it. Right now I am listening to the Visseaux 6V6GT, they are relatively inexpensive and sound phenomenal. I've thought about grabbing some GEC KT63 / 6F6G too, which aren't too pricey.

 

[L0rdGwyn]

Part of the reason I am interested in trying something from the KT88 / 6550 family is simply to see how they perform in the amp and take some real-world measurements. All for the sake of science of course I can't bring myself to buy a new production KT88 though, probably what I will eventually do is try one of the variants that is only available new production, KT90, KT120, or KT150. Assuming they are drop in replacements for KT88 and will bias similarly, the amp should be able to use any of them, it has the heater current available to do so. But I will check the datasheets just in case. The KT150 would look hilariously huge in this amp though lol probably would go for the KT90 or KT120.

 

[triod750]

Oh yes, you are correct, thing is the law of diminishing returns is at it's highest....most all pentode tubes sound good.

The more diminished the more valuable the result. Eventually one will experience something nobody else has (not) heard since they haven't yet got that far

 

[L0rdGwyn]

The more diminished the more valuable the result. Eventually one will experience something nobody else has (not) heard since they haven't yet got that far

For the cost of collecting extremely rare and valuable NOS tubes, the buyer could commission an entirely new amplifier, which would have much more drastic effects on listening experience than swapping tubes. There is an entire 300B thread right now where people are spending thousands of dollars on 300B tubes. Why not hold onto that money and commission a custom 300B amp as opposed to an off-the-shelf model? Just my opinion, but the money would be better spent that way. I think there is a misconception from tubehead audiophiles that the tube model makes the amp, but IME that is not the case, the totality of the circuit is more important and tubes are just another circuit element.

Take a 300B amplifier with a resistor loaded cathode biased input stage, cap coupled, and cathode biased output stage with an 60Hz AC filament supply and listen to it side-by-side with a CCS or inductor loaded fixed bias input stage, cap or transformer coupled, and a fixed bias output stage with a proper DC filament supply. There would absolutely be no comparison, the cheapest 300B tube in the latter circuit would slay the most TOTL 300B tube in the former.

 

[triod750]

I'm just joking. The designer of my Triod750 amp always said 'It's not the tube, it's the design'. Use the right tube for the design or use the right design for the tube. But what did he know?!

 

[L0rdGwyn]

I'm just joking. The designer of my Triod750 amp always said 'It's not the tube, it's the design'. Use the right tube for the design or use the right design for the tube. But what did he know?!

Oh I know you are joking! I am agreeing with your sarcasm

 

[L0rdGwyn]

I'll just add if you already own your dream amplifier and have the cash to spend on TOTL rare NOS tubes, then more power to ya but I think there are instances where people could get better performance by changing amplifiers instead. For many of these commercial 300B amps, I suspect the manufacturers are spending more on the cost of the chassis than they are on what's inside.

 

[L0rdGwyn]

RCA 5691 have arrived. Yeah these are good sounding tubes, and pretty to look at. Paired with the RCA 5R4GY and Mazda 6V6GT. I have been taking a break from the ZMFs and listening to the HD650. It's a headphone that really scales with good amplification, can still be downright impressive and very enjoyable tone.

 

[UntilThen]

I'll just add if you already own your dream amplifier and have the cash to spend on TOTL rare NOS tubes, then more power to ya but I think there are instances where people could get better performance by changing amplifiers instead. For many of these commercial 300B amps, I suspect the manufacturers are spending more on the cost of the chassis than they are on what's inside.

Haha if you've not already gotten your NOS tubes then it's probably too late already unless you're willing to spend big bucks. I was fortunate to have met a private collector who owns a Leak amplifier and have amassed an amazing collection of lovely NOS tubes. We became kind of friends the more we corresponded and I bought my NOS tubes much much cheaper than on the open market or eBay.

Was it worth buying all the NOS tubes for Odyssey? You bet. I love all of them and they add different flavors. Take for instance the EL12 spez. They are as good as the others and I have 3 pairs new in Telefunken boxes.

I'm done buying tubes for Odyssey but I'm entering a next phase with 300b amp. I look around at the commercial offerings and decided that I will still go with a custom 300b amp. If those pentode NOS tubes are expensive, good 300b tube prices will make them pale in comparison.... unless I go cheap with a pair of Psvane 300b tubes. Now I'd like to hear that it doesn't matter what 300b tubes I use, it's in the amp design but die hard 300b amp owners will tell you that's not true.

 

[L0rdGwyn]

Haha if you've not already gotten your NOS tubes then it's probably too late already unless you're willing to spend big bucks. I was fortunate to have met a private collector who owns a Leak amplifier and have amassed an amazing collection of lovely NOS tubes. We became kind of friends the more we corresponded and I bought my NOS tubes much much cheaper than on the open market or eBay.

Was it worth buying all the NOS tubes for Odyssey? You bet. I love all of them and they add different flavors. Take for instance the EL12 spez. They are as good as the others and I have 3 pairs new in Telefunken boxes.

I'm done buying tubes for Odyssey but I'm entering a next phase with 300b amp. I look around at the commercial offerings and decided that I will still go with a custom 300b amp. If those pentode NOS tubes are expensive, good 300b tube prices will make them pale in comparison.... unless I go cheap with a pair of Psvane 300b tubes. Now I'd like to hear that it doesn't matter what 300b tubes I use, it's in the amp design but die hard 300b amp owners will tell you that's not true.

It's fortunate for you to have come across such a stash, I'm sure they are lots of fun to play with

I think you are right to go with the custom amplifier, of course you know the quality will be better. There are certain commercial designs that are poor IMO selling for over $10K USD, but since they use 300B, like moths to the flame the audiophiles are drawn. I don't doubt for a second that there are gains to be had using higher quality 300B tubes, but I think the person willing to spend 3-4K on their commercial 300B amplifier and another 4K on 300B tubes would be better served consolidating that money into a higher quality custom amplifier and one or two good pair of 300B. Of course there is the wait time to deal with, but quality takes time.