[Neogeo333]

Are you using it solely as a headphone amp or does it also double as speaker amp?  The transformers I had in mind are vintage Tango HS5 with sec taps to 4,8,16,and 32ohms.  Since it's going to be doing double duty.   Most of my cans are low impedance. 
 
Yes, at first Glenn also tried to steer me away from the 45 and suggested 300b.   Seeing how masterfully David's amp came out i feel it put a spell on me.   Hence I wanted the 300b.   I'm sure with the right components a 45 is hard to beat.   But then it still wouldn't have the lows a 300b produces or be able to drive lower than 95db speakers.   Is there such a tube?   As liquid as a 45 but also great low end as a 300b?   

 

[No_One411]

  Are you using it solely as a headphone amp or does it also double as speaker amp?  The transformers I had in mind are vintage Tango HS5 with sec taps to 4,8,16,and 32ohms.  Since it's going to be doing double duty.   Most of my cans are low impedance. 
 
Yes, at first Glenn also tried to steer me away from the 45 and suggested 300b.   Seeing how masterfully David's amp came out i feel it put a spell on me.   Hence I wanted the 300b.   I'm sure with the right components a 45 is hard to beat.   But then it still wouldn't have the lows a 300b produces or be able to drive lower than 95db speakers.   Is there such a tube?   As liquid as a 45 but also great low end as a 300b?   

 
Perhaps 2A3s? It seems like 45s are pretty limited due to what they can actually power, hence the limitations with driving some equipment. 

 

[MoatsArt]

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[Xcalibur255]

  Are you using it solely as a headphone amp or does it also double as speaker amp?  The transformers I had in mind are vintage Tango HS5 with sec taps to 4,8,16,and 32ohms.  Since it's going to be doing double duty.   Most of my cans are low impedance. 
 
Yes, at first Glenn also tried to steer me away from the 45 and suggested 300b.   Seeing how masterfully David's amp came out i feel it put a spell on me.   Hence I wanted the 300b.   I'm sure with the right components a 45 is hard to beat.   But then it still wouldn't have the lows a 300b produces or be able to drive lower than 95db speakers.   Is there such a tube?   As liquid as a 45 but also great low end as a 300b?   

 
Don't believe what people say about 45 not having great lows.  My 45 has the best bass of any amp I have ever personally heard, tube or ss.  It's the whole package, weight/slam AND speed/control.  45 tubes have amazing bass when the amp is designed right.  It's still the thing that surprises me the most when I listen to mine.  Hearing bass string instruments is a treat because you hear so much texture in the notes that other amps can't bring out but the weight and power of the notes are still there too.
 
Mine is solely a headphone amp, running Lundahl LL1664 OPTs.  They only have an 8 and 16 ohm secondary so Glenn used the 16 for the output.  I don't know if upping the Z out to 32 would salvage the ability to run stuff like the HD800 or not, Glenn would know better than me for sure.  But on paper it seems like a nice setup with your Tangos.  You have the 4-8-16 taps for speakers and the 32 for headphones.
 
The 2A3 kind of sits right in the middle between those two choices too, something worth considering.  But the 2A3 doesn't seem to have the magic tone and transparency the 45 has.  I had a 6B4G amp for a short while, same tube as the 2A3 only with 6.3V filaments.  It sounded very nice, but was overtly colored in a way.  The 45 has a purity of tone that makes a lot of other things feel untrue to the music.

 

[Xcalibur255]

  Would multiple 45s in parallel increase power output without sacrificing their beautiful sonic qualities?

 
Possibly.  This is what Eddie Current does.  But I don't think you get the extra power for free if you know what I mean.  Some designers don't like to do parallel output and there must be a reason why.
 
The logical solution in my mind is to have a custom made output transformer with two secondaries, one at 20 ohms and the other at 200.  Then do a low/high switch.  But I'm not sure if you can get away with no feedback for both, and it might come with a sonic penalty of its own.
 
I just resigned myself to the fact that headphones with impedances in the triple digits are basically off limits on my 45 amp.  With great stuff like the HE-560 out there that's not so hard to live with, but I see a recent trend of everything go to higher Z including the orthos and it does worry me.

 

[No_One411]

  Would multiple 45s in parallel increase power output without sacrificing their beautiful sonic qualities?

Eddie Current uses 4 45s in his design. I'm not an expert with tubes at all, but I'd imagine that you'd get an increase in power output by parallel output tubes, but will also need a larger driver stage to get the necessary current to the output stage. 
 
Expensive, more parts, etc. There are so many tradeoffs in these designs. I think Glenn is of the clean and simple camp, which I think is the correct and most elegant design. 

 

[Xcalibur255]

The C3g is definitely up to the challenge of driving the harder load.  I mean Yamamoto does a headphone amp that is single stage, just the C3g (or maybe it was the C3m) by itself and it produces basically the same 1.5 watts the 45 can.  The C3g is a really amazing tube, both from a specification and a practical application perspective.
 
The question is, does paralleling the output stage give you more voltage swing, or just more current?  It's the former problem that needs solving.

 

[Neogeo333]

Or go push pull.   Not much to scratch in that department.  Only one 45 pp the Dejavu one with Acrosound irons.   But parallel and pp will never sound like a se and vice versa.   In my opinion the 45 should always be se and as simple as it can be.  

 

[Xcalibur255]

  Or go push pull.   Not much to scratch in that department.  Only one 45 pp the Dejavu one with Acrosound irons.   But parallel and pp will never sound like a se and vice versa.   In my opinion the 45 should always be se and as simple as it can be.  

 
I think people have done it.  No reason not to consider it among your options.  It's sort of like using pentode drivers, lots of purists turn their nose up at the idea but if you look at the DIY scene people get some really great results from them.  I guess it all depends on the specific circuit implementations and your goals for how you want it to perform.

 

[No_One411]

  The C3g is definitely up to the challenge of driving the harder load.  I mean Yamamoto does a headphone amp that is single stage, just the C3g (or maybe it was the C3m) by itself and it produces basically the same 1.5 watts the 45 can.  The C3g is a really amazing tube, both from a specification and a practical application perspective.
 
The question is, does paralleling the output stage give you more voltage swing, or just more current?  It's the former problem that needs solving.

Ah yes, I forgot how amazing of a tube the C3g is. It's great how Glenn is able to find these "non-audio" tubes and produce such great results from them. This includes the 6BL7s and tv damper diodes. Looking at the specs for these, they were built to much higher standards than some audio tubes. It's just up to someone like Glenn to work his magic and get all the optimal bias points. You really can't just throw any of these tubes in your design and expect them to work perfectly. 
 
Seems like Glenn isn't a huge fan of push-pull or "balanced" designs. It's essentially almost doubling the components, output impedance, complexity and cost. I know some people center tap the secondary windings of the transformers for balanced operation...

 

[Xcalibur255]

I would say, for what it's worth NeoGeo, that unless we can solve the drive limitations of the design without losing the magic of the sound, it's probably better and safer to stick with 300B in the long run.  It's quite a sticking point being locked out of half the headphones on the market, and if you want to run speakers you have to have super high sensitivity and take special care to eliminate any noise sources to use the 45 in that application.  The 300B seems like a better fit from a practical point of view, and it's not like you are settling in terms of sound.  Driven correctly the 300B sounds awesome.  It's gotten its reputation for being syrupy because so many designers use driver stages that aren't up to the job (like the 6SN7).  The C3g solves that problem.
 
Or, just go with your gut.    I did 45 not because it was the smartest choice but because it's just what I wanted.  I fell in love with the idea of the tube and wanted to see it to fruition.

 

[Neogeo333]

  I would say, for what it's worth NeoGeo, that unless we can solve the drive limitations of the design without losing the magic of the sound, it's probably better and safer to stick with 300B in the long run.  It's quite a sticking point being locked out of half the headphones on the market, and if you want to run speakers you have to have super high sensitivity and take special care to eliminate any noise sources to use the 45 in that application.  The 300B seems like a better fit from a practical point of view, and it's not like you are settling in terms of sound.  Driven correctly the 300B sounds awesome.  It's gotten its reputation for being syrupy because so many designers use driver stages that aren't up to the job (like the 6SN7).  The C3g solves that problem.
 
Or, just go with your gut.    I did 45 not because it was the smartest choice but because it's just what I wanted.  I fell in love with the idea of the tube and wanted to see it to fruition.

If I haven't fallen in love with speakers again I would most certainly get the custom transformers for my 300b with two  sec instead of only 40ohms.  Oh well.   At least they are fairly efficient.   But who knows what will happen next.   Maybe I'll be amazed by the 300b that I'll forget about the 45.  Can't wait to try them.   

 

[rosgr63]

  This is my Good Friday gift to you all.
 

That's great Nathan, thanks.

 

[rosgr63]

One of my amps uses 45's or VT 52's which are an upgraded/special 45.
 
Even though I have a nice selection of Globe 45's including Raytheon Box Plates, Arcturus Blue Glass etc, I am hooked on the VT 52's.
 
It's true that 6SN7's can't drive the 300B's as good as other tubes like some pentodes strapped in triode mode like WE328, WE310, C3g's etc.
However, some 300B's driven by the right 6SN7's can sound great too, my AVVT 300B's driven by RFT 6SN7's sound excellent.
 
The biggest problem is finding good/strong tubes.
 
This is what I find out with my headphone systems and preferences.

 

[Xcalibur255]

My holy grail tube for 45s is probably the EverReady Raytheon 4-Pillar box plate, either globe or ST would be fine.  I saw a pair on eBay with original boxes and regret not taking the plunge and just doing it.  I mean I blew $400 on TS BGRP 6SN7 back in the day, and the return on investment on the 45s is higher arguably.
 
My other moment of regret was passing up an absolutely pristine pair of in original boxes DeForest Audion 445s.  I think those went for $500 and given what they were and their condition that was probably a fair price. 
 
But then I think about a tube suddenly dying or becoming noisy and the high costs begin to feel less justifiable.  Honestly the cheapest 45 tube you can find (probably because they were the last ones made), the early 50's era Sylvania print base, is easily one of my favorites out of what I have heard so far.  It has a sweeter, more playful tone and a great sense of rhythm and drive.  I'm also digging what I heard last night from my Ken-Rad UX-245 globes.  I'm going to turn the bias up a little bit on them next time and see how well they can sing, but they were satisfying as they were in that first listening session.