300B should be biased at 60 to 75 mA (per Tubelab description). B+ voltage will drop as you increase the bias.rknize said:
The blue glow looking like that is from the gas inside of tube as I was told. It shouldn't interfere with the tube's performance unless it floods the inside like fog which is said to be a sign of leakage (someone correct me if I'm wrong).
By the way, are those Sophia mesh tubes?
You are right about the bias. I was being very conservative with them, as they are not my tubes and I didn't want to have to replace them should something go wrong. This breadboard amp has at well over 100 hours on it now using 45s, so I guess I shouldn't worry.
The tubes are Shuguang's aptly-named "300BS". They are borrowed from a well-to-do friend who isn't using them anymore. He bought these after his set of vintage WE's got weak. He since bought a pair of the new WE's and so these were sitting idle. I was talking to him about my projects, so he offered to let me borrow the pair.
I've seen plenty of harmless blue glow in other tubes, mainly Sylvania beam tetrodes and a few others (SED EL34s are neat). I don't think it is gas if the blue glow is only projected onto the glass, which is the case here. I don't see any glow inside the open space of the envelope. I suspect that electrons are just blasting through the mesh in places and hitting the glass. I've just never seen glow from any DHT before....
The tubes are Shuguang's aptly-named "300BS". They are borrowed from a well-to-do friend who isn't using them anymore. He bought these after his set of vintage WE's got weak. He since bought a pair of the new WE's and so these were sitting idle. I was talking to him about my projects, so he offered to let me borrow the pair.
I've seen plenty of harmless blue glow in other tubes, mainly Sylvania beam tetrodes and a few others (SED EL34s are neat). I don't think it is gas if the blue glow is only projected onto the glass, which is the case here. I don't see any glow inside the open space of the envelope. I suspect that electrons are just blasting through the mesh in places and hitting the glass. I've just never seen glow from any DHT before....
rknize said:
To keep the B+ down on my Tubelab SE, I use a choke input configuration ( 10Hy). That puts my B+ right at 275 volts with both 45 and 2A3, when I use a 5AR4 rectifier. My tranny is a flat mount Utah something I bought for a buck or two at a hamfest.
It is dead quiet with 45's on 96 dB/watt speakers.
I seem to recall George writing that the 2A3 sounds best in the low to mid 300's, but I haven't tried that.
I don't think 2A3's are all that. I have both RCA 2A3, and Sylvania 2A3W/5930, and just haven't found the right setting yet, I guess. I always seem to go back to 45's.
I don't own any 300B's.
Win W5JAG
OK, I put the spurs to the 300B's tonight and let rip for about 5 hours at 80mA per tube. Holy crap could this things get loud on my 98dB speakers. Serious wall shaking power. At more sane listening levels, I would say they have less detail than the 45s but it could be my ears ringing...
The 660VAC winding was pulled down exactly to spec: 660VAC. B+ sagged to around 370-375 VDC. Supposedly this is the ideal spot for the 300B. I suppose running the tubes well short of the rated plate voltage will help them last longer. Given the price of 300Bs....
After 5 hours, the transformer was a bit warmer than before but not hot by any means.
So overall I am happy with it. The only change I would make is to drop the B+ taps down to 250VAC for "45 mode".
The 660VAC winding was pulled down exactly to spec: 660VAC. B+ sagged to around 370-375 VDC. Supposedly this is the ideal spot for the 300B. I suppose running the tubes well short of the rated plate voltage will help them last longer. Given the price of 300Bs....
After 5 hours, the transformer was a bit warmer than before but not hot by any means.
So overall I am happy with it. The only change I would make is to drop the B+ taps down to 250VAC for "45 mode".
I guess that I haven't found the magic setting yet either. I have a few RCA's (all twin plate) a pair of Shuguangs and a pair of Sovteks. I tried to find something that I liked in the RCA's and Shuguangs, but they are my least favorite of all the DHT's that I have stuffed in my amp. I have tried B+ voltages from 225 to 375 volts with 3K and 5K OPT's. They definitely sound different than the other tubes. Yes, I tend to prefer high voltages and higher load impedances than most users, but 300 volts is over the line for most 2A3's.
I got the Sovteks in response to an issue that a customer found. The Sovtek 2A3's arent really 2A3's they are mini 300B's with 2.5 volt filaments. To me they sound more like 300B's than the others. Like the 300B's these tubes sounded best when fed 375 volts into a 5K load. The filament current is higher than the 2.5 amp spec which annoys the regulator IC. It can also drag the input voltage to the regulator down near dropout causing hum.
That is my opinion too. The 45 is the best sounding tube that I have ever used. My only problem is its low power. The speakers in my lab are 87db so the 45 won't rock the house. The 300B gets them loud enough to get "turn it down" comments from my wife in another room.
I have run my Tubelab SE on a variable power supply and found that 370 to 400 volts all sounded good. I had a Tubelab SE with a big Hammond transformer (I don't remember the #) that provided 375 volts. I took it apart. I have one Tubelab SE that I use daily. It has a B+ of 320 volts and I run 45's or 300B's. I have about 10 45's of various flavors that I have collected over the years. They all seem to be happy on 320 volts. They make about 2 watts at 30 mA. 300B's make about 5 watts at 70 mA in the same amp.
I will order one of these transformers in the next few weeks. Despite the state of the company our division actually got a bonus check, so I finally got a modern TV. I gave away the 320 pound monster, and now I have a bunch of space where it used to be. This means that I need to put a tube amp there. My big "old radio cabinet" speakers have been connected to the TV set
because there was no room for a real amp. The speakers are two way, so a Tubelab SE with 45's for the HF is a given. LF is undecided yet. Maybe one of these transformers has enough juice to run two amps? I guess some experiments are in order. 5.1 with a few more old radios? Maybe. I didn't build a single amp during 2008, and only managed a few simple experiments, so its time........
I decided not to try to cover the 2A3 with the heater as well because it feels like a compromise to me anyway. If I am going to make the effort to support a 300B and spend the money on a pair, why would I want to run 2A3s too? Maybe I'm just too simplistic and there is something lovely about the 2A3 I am missing...I dunno. I have heard at least one amp that uses them, but it wasn't a situation where I could compare it to anything else.
OK, so one odd thing about this amp with 45s...it is not obvious when the amp starts clipping. Maybe it is an SE-vs-PP thing, but usually an amp sounds good until I can start to hear the crunching. Perhaps my line stage needs more gain, but I can "dime" this amp and I don't get any of that. I do notice a drop in detail and sound stage before ear fatigue sets in, so maybe it is clipping and introducing harmonics, but it's not obvious.
It does have a hard time driving my BA A70s, which are acoustic suspension, when I start to push it with the 45s. The 300Bs can rock those suckers, though. The KLF-10s are driven to uncomfortable volumes with the 45s, so no problem there.
Good to hear. The axe was poised to swing again here, but it hasn't at us just yet. Everyone is holding their breath...
Two might be pushing it, but I guess it depends what demands the 2nd amp will have. The heater winding would be overtaxed at the very least....
tubelab.com said:
OK, so one odd thing about this amp with 45s...it is not obvious when the amp starts clipping. Maybe it is an SE-vs-PP thing, but usually an amp sounds good until I can start to hear the crunching. Perhaps my line stage needs more gain, but I can "dime" this amp and I don't get any of that. I do notice a drop in detail and sound stage before ear fatigue sets in, so maybe it is clipping and introducing harmonics, but it's not obvious.
It does have a hard time driving my BA A70s, which are acoustic suspension, when I start to push it with the 45s. The 300Bs can rock those suckers, though. The KLF-10s are driven to uncomfortable volumes with the 45s, so no problem there.
tubelab.com said:I will order one of these transformers in the next few weeks. Despite the state of the company our division actually got a bonus check, so I finally got a modern TV. I gave away the 320 pound monster, and now I have a bunch of space where it used to be. This means that I need to put a tube amp there. My big "old radio cabinet" speakers have been connected to the TV set
Good to hear. The axe was poised to swing again here, but it hasn't at us just yet. Everyone is holding their breath...
tubelab.com said:
Two might be pushing it, but I guess it depends what demands the 2nd amp will have. The heater winding would be overtaxed at the very least....
Are the Electra print's worth the extra $, as George mentioned them as tops especially for the OT's? What about Lundahl's?
Has anyone tried to wind their own? I want quality , but can't afford to spend lot's of $. I ran across a thread to Susan Parker's designs on winding Trans. She also has quite the simple Amp design! Could hand winding be as good as factory if one has the time?
Thanks Very Much
Randy
Has anyone tried to wind their own? I want quality , but can't afford to spend lot's of $. I ran across a thread to Susan Parker's designs on winding Trans. She also has quite the simple Amp design! Could hand winding be as good as factory if one has the time?
Thanks Very Much
Randy
If you have access to an oscilloscope it is an interesting exercise to hook one up to the speaker outputs. Most SE amps can be run well into cliping on transients before the distortion is heard. It is not an SE vs PP thing. It is usually a feedback or no feedback thing.
In an ideal zero feedback design the amp simply limits the output during cliping. The total amplifier gain drops slightly since the increased input does not produce more output. When the transient passes everything returns to normal. Small signal details are lost during the overload period since the output is slammed against the rail (clipped). The ear usually does not hear fine detail during loud sounds (the masking phenomenon that brought us MP3's), so the lost detail may not be missed.
In an ideal amplifier with large amounts of global negative feedback (typical SS amp) the amp may have an open loop gain of 60db. This may be reduced to 30db by applying 30db of NFB. When the transient pushes the amp into clipping the feedback loop causes the gain to increase until the excess gain is used up. The amps gain will aproach the open loop gain in an attempt to avoid clipping. This can drive multiple stages to their rails leading to long recovery times, IMD distortion and a bunch of other ugly sounding phenomenon.
Obviously there is a lot more to it than this, but it is possible to build a push pull amp with similar clipping behavior as the Tubelab SE. My 300Beast can be pushed well into clipping before it becomes obvious, but it is a class A all triode design with no feedback. It unfortunately no longer works, and will be rebuilt, but that is a new story yet to unfold.
We hear similar rumors. Something unplesant happens coincident with the quarterly earnings (not) report.
Yeah, I am just dreaming out loud for now. I want to experiment with some more push pull stuff before I build the final design. I have come to realize that no amp is ever completly done. I keep taking them apart and rebuilding them. I only have two amps that have been left alone since they were built. The Lexan Tubelab SE and the "industrial" Simple SE. The industrial amp is a bit too small and it gets too hot especially since I have it set at 100 mA per tube. I decided that I would rebuild it when it blows up. It hasn't missed a beat since I said that, so it remains untouched.
I got a pair of "10 watt 5K SE OPT's" made by Jack a few years ago for $100 each. At that time I decided that they were the best transformers that I have owned. They are on my Lexan amp which is the only other amp that I made that I liked well enough to leave alone. That amp still sounds very nice especially with 45's in it and it has been to a few auditions where it held up well next to some real expensive amps.
The Electra - Print transformers are considerably more money now, so I can't say whether they are the best value for the money today. I have not tried Lundahl's or any of the other higher priced OPT's. If I had to pick an "under $100 OPT today I would go directly for the big Edcors (CXSE series). I got them after the Lexan amp was done so I have never done a direct comparison with the Electra-Prints yet.
I have tried to wind my own, but so far all of my attempts (3) have sounded bad. There are people on this forum who have made their own transformers though. I must say that a SE OPT especially one of a fairly high impedance ratio is one of the hardest transformers to get right.
tubelab.com said:
Ah, that makes sense. Thinking back, I think this is the only amp that I ever had for any length of time that has no feedback. I've tried remove the feedback on my Thomas amp that I have had forever, but it sounded gutless when I did (OPTs, I'm quite sure). I do have a "scope", but it needs to be connected to my computer to function and so I generally only use the signal generator in that case.
The cats were away this evening, so I let this amp go full throttle with the 300Bs. It rattled stuff on the shelves on the second floor from the basement. Serious bass...it was awesome. I love these speakers.
Nothing makes you want the company to succeed more like the perpetual threat of layoffs.
Murphy's law. It won't until you decide you want to keep it.
Just another follow-up on the transformer. I clamped my squangle to the heater regulator heat sink so I could remove the little fan I was using to keep it from shutting down. I had a hunch that the nearby air movement was cooling the transformer as well. After a few hours it did get pretty warm, but I could still put my hand on it and leave it there as long as I liked so i am not concerned.
Russ
Uk version available?
Hi All,
I am looking to build a Simple SE to start and maybe a SE after. Would this universal transformer be suitable for both amps?
Also do they have a UK 240v version?
Used with a pair of CXSE25-8-5K i would like to try, 6l6gc, kt88 and maybe some 807 ( just they look so cool ) Then maybe 300b down the line. I just want to reuse as much as possible.
Do Edcor also make chokes?
Over in the UK all I seem to find is Hammond, and from what i have read the quality is slipping.
Many thanks
Ian
Hi All,
I am looking to build a Simple SE to start and maybe a SE after. Would this universal transformer be suitable for both amps?
Also do they have a UK 240v version?
Used with a pair of CXSE25-8-5K i would like to try, 6l6gc, kt88 and maybe some 807 ( just they look so cool ) Then maybe 300b down the line. I just want to reuse as much as possible.
Do Edcor also make chokes?
Over in the UK all I seem to find is Hammond, and from what i have read the quality is slipping.
Many thanks
Ian
This transformer should suffice for most Simple SE configurations. You'll get about 370-400V B+, depending what your bias current is. I'm not sure about your goal here...are you planning to use the same 3 transformers for both a SSE and a TSE? If so, then this should work for you.
Otherwise if you are getting different iron for each, I would get the XPWR035 for the SSE, which gives you 430-460 B+ (depending on your load). It can crank out plenty of current if you want to run some KT88s hard at 100mA without breaking a sweat. The XPWR035 is rated 740VCT @ 200mA while this one (XPWR131) is rated for 660 @ 175mA.
I believe that Edcor does make chokes, though these two Tubelab amps uses a CLC filter which does not tax the choke very much. You can get away with any properly rated cheap old choke and it will work just fine.
Otherwise if you are getting different iron for each, I would get the XPWR035 for the SSE, which gives you 430-460 B+ (depending on your load). It can crank out plenty of current if you want to run some KT88s hard at 100mA without breaking a sweat. The XPWR035 is rated 740VCT @ 200mA while this one (XPWR131) is rated for 660 @ 175mA.
I believe that Edcor does make chokes, though these two Tubelab amps uses a CLC filter which does not tax the choke very much. You can get away with any properly rated cheap old choke and it will work just fine.
Uk version available?
Hi Russ, thanks for the reply.
The Simple SE is the priority, i need to get the right iron to make the best of it. But if i could also use it for the SE, then even better. I will order both PCB's.
I already have a couple of 6l6gc's and want to try some KT88's, and when funds allow some 300b's.
I was trying to clarify if the universal Edcor was suitable for both Simple SE and SE, And if they do a 240V version for the UK?
Also with the choke, if Edcor do a suitable product.
If I am going to the trouble of ordering the iron from the states I may as well buy all of it from one place.
If someone knows a UK supplier of decent, good value iron???
Was also looking for the Ebay transendars mentioned in a few posts, couldnt locate them?
Thanks very much
Ian
Hi Russ, thanks for the reply.
The Simple SE is the priority, i need to get the right iron to make the best of it. But if i could also use it for the SE, then even better. I will order both PCB's.
I already have a couple of 6l6gc's and want to try some KT88's, and when funds allow some 300b's.
I was trying to clarify if the universal Edcor was suitable for both Simple SE and SE, And if they do a 240V version for the UK?
Also with the choke, if Edcor do a suitable product.
If I am going to the trouble of ordering the iron from the states I may as well buy all of it from one place.
If someone knows a UK supplier of decent, good value iron???
Was also looking for the Ebay transendars mentioned in a few posts, couldnt locate them?
Thanks very much
Ian
Re: Uk version available?
The best thing to do would be to talk to them on the phone. Being in the UK, you have some choices...I'm sure someone else can chime in. Sowter comes to mind, but I think they are pricey.
The SSE is a great choice and can run on a lot of tubes. You'll probably want to use the TSE for a tube like the 300B. The TSE is a more complex design and also uses 5842 tubes for the input stage. They are starting to get expensive, even on eBay, but they are not hard to find. I personally think the TSE is more suited to a smaller, higher-quality transformer. I think part of the detail I feel is missing from the SSE versus the TSE is that my SSE uses these big, honkin' Edcors (CXSE25-8-5K) and some fine detail is lost in all of that iron. My TSE has One Electron UBT-2s.
If this is your first SE amp, then I would build the SSE first since it is the easiest to build and doesn't require any special tweaking to dial it in. The only thing that is "adjustable" is the bias resistors. The TSE is a different kind of amp...less power but more detailed. The way I am, I don't think I'd be happy with only one amp at a time.
What I'm trying to get at is that you may want to have both amps ready to go, depending on your mood, and so you probably would want to have iron for both. So getting back to your original question: the transformer that this thread is about (XPWR131) will work in an SSE but the XPWR035 is even better because it will give you more B+ and more current capability should you want to run some big tubes hard. However if that is not in the budget, then you should be fine with just this set.
Also, strictly for appearances, the XPWR035 is exactly the same size as the CXSE25-8-5K. They go well together.
http://www.diyaudio.com/forums/showthread.php?postid=1820073#post1820073
webby said:
The best thing to do would be to talk to them on the phone. Being in the UK, you have some choices...I'm sure someone else can chime in. Sowter comes to mind, but I think they are pricey.
The SSE is a great choice and can run on a lot of tubes. You'll probably want to use the TSE for a tube like the 300B. The TSE is a more complex design and also uses 5842 tubes for the input stage. They are starting to get expensive, even on eBay, but they are not hard to find. I personally think the TSE is more suited to a smaller, higher-quality transformer. I think part of the detail I feel is missing from the SSE versus the TSE is that my SSE uses these big, honkin' Edcors (CXSE25-8-5K) and some fine detail is lost in all of that iron. My TSE has One Electron UBT-2s.
If this is your first SE amp, then I would build the SSE first since it is the easiest to build and doesn't require any special tweaking to dial it in. The only thing that is "adjustable" is the bias resistors. The TSE is a different kind of amp...less power but more detailed. The way I am, I don't think I'd be happy with only one amp at a time.
What I'm trying to get at is that you may want to have both amps ready to go, depending on your mood, and so you probably would want to have iron for both. So getting back to your original question: the transformer that this thread is about (XPWR131) will work in an SSE but the XPWR035 is even better because it will give you more B+ and more current capability should you want to run some big tubes hard. However if that is not in the budget, then you should be fine with just this set.
Also, strictly for appearances, the XPWR035 is exactly the same size as the CXSE25-8-5K. They go well together.
http://www.diyaudio.com/forums/showthread.php?postid=1820073#post1820073
oldmanStrat said:
I just picked up a pair of the 5K Transcendars on ebay about two weeks ago; Gery is now selling them with UL taps for $5 more than the non-UL version. You can also order transformers directly from Gery/Transcendar (no ebay needed) if you want multiple output taps, etc. I inquired about this several months ago.
Thanks for the great info.
The xpwr35 is a 120v version, i count find a 240v version with the same rating on the site. which 240v transformer would be the closest match?
I have looked at all the UK suppliers I can find, they are a lot more expensive.
Maybe I should start a new thread asking for UK users to chime in?
Thanks for the advice.
Ian
The xpwr35 is a 120v version, i count find a 240v version with the same rating on the site. which 240v transformer would be the closest match?
I have looked at all the UK suppliers I can find, they are a lot more expensive.
Maybe I should start a new thread asking for UK users to chime in?
Thanks for the advice.
Ian
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