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tube fanatic

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That picture is neat Mike!  You're more of a "mad scientist" than I am with that set-up! :D   Nice to see you using the Heath p/s.  I sure remember those- very versatile.  For years I've wanted to build a variable B+ supply but just can't find the time with all of the other projects going on.  As far as DHTs go, would you believe that I've never bothered building an amp with one?  My ears can't hear differences between actual triodes and triode strapped pentodes anyway, so I stick with the latter since they are easier to deal with!

 

Maynard 

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That picture is neat Mike!  You're more of a "mad scientist" than I am with that set-up! :D   Nice to see you using the Heath p/s.  I sure remember those- very versatile.  For years I've wanted to build a variable B+ supply but just can't find the time with all of the other projects going on.  As far as DHTs go, would you believe that I've never bothered building an amp with one?  My ears can't hear differences between actual triodes and triode strapped pentodes anyway, so I stick with the latter since they are easier to deal with!

 

Maynard 

 

Thanks, I appreciate comments like that. The retired EE friend turned me on to bread-boarding...it's a quick way to check out different tube amplifier circuits, provided the test circuit is not over the B+ voltage of the supply.

I bought that Heath PS-4 supply about 7-8 years ago for 50 bucks. That little supply has been one of the handiest items I bought for the applications involved. Versatile nails it completely.

The guy I bought it from did replace a couple caps in the supply, but I need to go through and freshen things up a bit. I've used it quite a bit over the years. I like it because it is light, and you can move it around.

 

With your interest in single ended tube circuits, and the amount of time you've been doing this sort of thing, you never lashed up a triode of any sort as a output tube?

Not even something like a 6EA7? I think a guy can almost get a watt with one side driving the other. Of course, a 6EA7 isn't directly heated either...

 

I've tried strapping pentodes or beam tubes in SE circuits, like 6BQ5 or 6L6, and I was never really too thrilled with the strapped pentode sound. My experiences are light however, and I never used any feedback...just straight strapped pentode/beam. They always had a more noisy sound, with more accentuation in the midrange.

 

I seem to favor a pentode connected as a pentode, with a bit of feedback. Done properly, the overall sound seems more balanced to my ears. DHT triodes always have a touch of accentuation in the midrange as well. My DHT 2A3 amp has it's compromises, (a slight filament growl, and the slight midrange accentuation) but it puts out a larger open "sound". Same with the bass...more open/larger sounding than a strapped pentode in my small experiences.

 

I should revisit the strapped pentode/beam tube idea again, but I'll try 6V6 this time.

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With your interest in single ended tube circuits, and the amount of time you've been doing this sort of thing, you never lashed up a triode of any sort as a output tube?

Not even something like a 6EA7? I think a guy can almost get a watt with one side driving the other. Of course, a 6EA7 isn't directly heated either...

 

I've tried strapping pentodes or beam tubes in SE circuits, like 6BQ5 or 6L6, and I was never really too thrilled with the strapped pentode sound. My experiences are light however, and I never used any feedback...just straight strapped pentode/beam. They always had a more noisy sound, with more accentuation in the midrange.

 

I should revisit the strapped pentode/beam tube idea again, but I'll try 6V6 this time.

 

Mike, it's only the DHT types which I haven't bothered with (between wanting to use a regulated filament supply with extremely low ripple, and having to provide huge amounts of drive, I don't consider them worth the trouble).  I've done lots of cathode type SETs using the typical vertical amplifier type tubes which I always had around in abundance for the TV repair.  Types like the 6AH4, 6CK4, 6BL7, 6BX7, 12B4, and so on.  They're fine, but in comparison with the triode strapped pentodes, I can't hear any difference.  And, with these types getting a bit more expensive, it's easier to just strap a pentode.  For a more "purist" approach, I've used the 6GK6 which brings the suppressor out to the tube base instead of internally connecting it to the cathode.  That makes it easy to strap both the screen and suppressor to the plate making the tube an actual triode.  I never use any feedback in the triode amps.  Something which I haven't yet played with is this idea which Deckert promotes:

 

http://www.decware.com/newsite/paper145.htm

I'm a bit skeptical, but it's easy enough to try it and hear what (if anything) it does for myself.  It's on the list for when I have more time!

If you have some, the 6W6 or 6Y6 are better choices for triode strapping than the 6V6 or its variants.  Both of those will give you more output with less plate voltage.  It's possible to get very low distortion from them as well.

Maynard

Edited by tube fanatic
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Hi, Maynard

You mention DHTs being "not worth the trouble." But.....they are a great love of mine despite some of the 'issues' associated with cathode/filament triodes. There are some very interesting looking variants beyond the now seemingly ubiquitous 2A3, 300B, 45. With careful grounding, it's possible to get quite good performance using AC filaments, which I have come to prefer over unregulated or even regulated DC (despite the fact that DC on directly heated cathodes is arguably more free of hum). AC just sounds better to me.

Happy New Year to you!

Erik

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Hi, Maynard

You mention DHTs being "not worth the trouble." But.....they are a great love of mine despite some of the 'issues' associated with cathode/filament triodes. There are some very interesting looking variants beyond the now seemingly ubiquitous 2A3, 300B, 45. With careful grounding, it's possible to get quite good performance using AC filaments, which I have come to prefer over unregulated or even regulated DC (despite the fact that DC on directly heated cathodes is arguably more free of hum). AC just sounds better to me.

Happy New Year to you!

Erik

Hi Erik, and HNY to you also!  I trust you're enjoying your vacation break.  I should have qualified my statement more by saying that the DHTs are not worth the trouble to me.  No question that careful routing of AC filament wiring, combined with good balancing and grounding, can keep hum issues from being a nuisance.  It was no different back when I did p-p amps.  Some friends loved long tailed pair phase inverters, and other "more complicated" types, while I always leaned toward the cathodyne.  Also, in regard to my not hearing differences between actual triodes and the triode strapped pentodes, I've always made the comparisons using the same output transformers, at the same impedance, and with listening levels matched as closely as reason allowed.  Otherwise, it's not possible to know exactly what is causing differences that are audible.  Another manifestation of my ocd when it comes to this stuff!  :)  Glad you joined this discussion.  Now you need to post some nice glowing filament pix of those DHTs for all of us to enjoy!!!

 

Maynard  

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Maynard

Among my favorites is the AVVT meshplate 2a3, the single largest version of that triode I have seen. The amp I use them in has been undergoing some modifications over the past several months, one of which is replacing the worn four pin sockets with new. When that's finished, I'll post a picture of it. I was active on the forum between 2002 and about 2012 approximately and have not really posted any images recently after the website changes here. Is it possible to upload pictures from a cell phone or iPad? (Probably sounds like a dumb question!)

I can share an image of an RCA 2a3 with the AVVT to share the difference between the two.

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Among my favorites is the AVVT meshplate 2a3, the single largest version of that triode I have seen.

I can share an image of an RCA 2a3 with the AVVT to share the difference between the two.

 

 

A very brief, somewhat random, listening session with the Moth Audio si2A3 using a set of AVVT Mesh Plate 2A3 tubes back in the late 1990's probably was responsible for triggering my desire to explore single-ended triodes about eight to ten years later.  

 

I see AVVT Mesh Plate 2A3 tubes come up for sale a couple of times a year; however, each time, the price has gone beyond my budget selling at ~ $1,000 a pair. Most of my 2A3 listening has been using KEN-RAD 2A3 with the dual parallel plates (looks like two 45 plates in the tube), a pair of Tung-Sol single plate 2A3 and the more mainstream RCA and Tung-Sol black and grey plate tubes.

 

Over the years I've had the Welborne Labs Moondogs, Wright 3.5 monos, the Wright mono 10s (push pull) and the Bottlehead Stereomour.  I also have a couple of examples of the Shannon Parks "Get*Set*Go" single ended amplifiers that use the 6B4G tube (very similar output to the 2A3).  I've posted pictures of the Moondogs and the Wright mono 10s that include the wiring underside to the Amp Porn thread.

 

While many do not consider the Sophia Electric a true mesh plate, they glow nicely in the dark.  Then there is this Type 10 triode that shines like a light bulb.....

 

 

 

 

 

 

glowing tube 2A3 Sophia Electric 2.jpg

 

 

glowing tube type-10-single-ended-amp.jpg

 

 

KEN-RAD 2A3.jpg

 

 

 

glowing tube 2A3 Sophia Electric.jpg

 

 

glowing tube Chinese 2A3.jpg

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Edited by Fjd
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