Porkchop61,
Ag ja (darn, must you have such an appetising nom-de-plume), main problem with much of the reasoning in Electron Stream is that field strength progression from cathode - anode in tubes is not as simple as assumed there. Grid contribution is also dependent on density of wire mesh vs a solid plate, etc. I have accurately measured electrode distances for several power tubers and they do not correspond to what was given there somewhere, etc. etc.
Leave the diode out. The G2 always draws current, so it gives no more than a continuous but unreliable little voltage drop. Assuming that it passes dc and not ac is nonsense.
Tubelab,
Oh yes? (regarding wire-wound load resistors). Thanks, I will then have a look at that myself (vs non-inductive R). Perhaps another new year's resolution is to build a 100W equivalent loudspeaker load.
AND, AH YES! REGARDS AND LOADS OF FORTUNE TO ALL FOR THE YEAR 1111101100! (Jeepers, am I that old?)
Ag ja (darn, must you have such an appetising nom-de-plume), main problem with much of the reasoning in Electron Stream is that field strength progression from cathode - anode in tubes is not as simple as assumed there. Grid contribution is also dependent on density of wire mesh vs a solid plate, etc. I have accurately measured electrode distances for several power tubers and they do not correspond to what was given there somewhere, etc. etc.
Leave the diode out. The G2 always draws current, so it gives no more than a continuous but unreliable little voltage drop. Assuming that it passes dc and not ac is nonsense.
Tubelab,
Oh yes? (regarding wire-wound load resistors). Thanks, I will then have a look at that myself (vs non-inductive R). Perhaps another new year's resolution is to build a 100W equivalent loudspeaker load.
AND, AH YES! REGARDS AND LOADS OF FORTUNE TO ALL FOR THE YEAR 1111101100! (Jeepers, am I that old?)
In order to make a meaningful and repeatable measurement of an amplifiers performance a purely resistive load should be used. Yes the amplifier will be operated into a speaker system which is far from a resistive load. Since every speaker system behaves differently, which one do we use as a "standard" for measurement? A speaker system with a complex crossover network may appear inductive, resistive, or capacitive at a given frequency, and this is not even considering back EMF effects.
If you are performing any measurements on an amplifier a pure resistive load should be used to obtain true readings. Why? Consider a frequency response test. an inductive load would have an impedance that rises with increasing frequency. It may be 8 ohms at 1 KHz and 10 ohms at 10 KHz. A tube amplifier will generally produce a higher output voltage across a higher load resistance, so the amplifier would show an increase in output as the frequency is increased. This would lead to a frequency response plot that has an upward tilt throughout the audio range.
I did some frequency response, power output and efficiency testing on my 833A amp a few years ago. http://www.tubelab.com/833SE.htm
During that testing I claimed a 51% efficiency at 212watts output. You can see the large 500 watt wirewound load resistor on the right. I was informed that those measurements might be in error due to the load resistor. Since I do not have any other load capable of withstanding the output of this amp (and I dissassembled this WMD before it could cause harm) I decided to do some testing on a lower powered amp. I found two sources of error. The inductive load caused the output voltage reading to be high by about 1 or 2 % at 1KHz even though it measured 7.95 ohms. The cheap DVM that I was using to measure the output voltage is off by 3 or 4 % compared to 60Hz. The error is not linear across voltage levels either. So these two error mechanisms caused my 212 watt reading to be optimistic by 5% or so. The resistor alone probably caused the slight upward rise in the mid band frequency response plot shown.
Are these errors a big deal. For the average DIY amp builder probably not. So your readings are off by 2 or 3%. They generally make your amp look better than it really is.
I have since constructed a load bank using premium (TO220 case) resistors mounted on a large heat sink, and I got my HP8903A audio analyzer fixed. I use this "good stuff" to make final measurements on a known good amp. I still use my indestructable 500 watt loads and a cheap DVM during the experiment phase and whenever something could go wrong.
Hi George,
I know this is old thread...but I have a questions about simple SE and the operation in triode/pentode/ultralinear mode when its comes to the sonic qualities. Can you comment on the sound, not just power? Are there any audible differences besides the total output power? What is the prefered mode for hifi?
ed
I know this is old thread...but I have a questions about simple SE and the operation in triode/pentode/ultralinear mode when its comes to the sonic qualities. Can you comment on the sound, not just power? Are there any audible differences besides the total output power? What is the prefered mode for hifi?
ed
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ummm...seriously, here, DO NOT FLIP THE DAMNED SWITCH WITH THE AMP ON.
you're playing with the b+ supply to the power tubes here, straight off the output transformer, and the voltages are LETHAL. just cuz someone "got away with it with some junk tubes" does not excuse obviously unenlightened experimentation like this. THIS COULD KILL YOU or your amp, as well...just DON'T DO IT.
you COULD however, do it with the amp on standby, as at that point, the B+ is disconnected and the only thing that SHOULD be recieving voltage is the heaters of the tubes. i would reccomend, particularly if you're not intimate with the circuit in question (and never knowing what someone before you might have done inside it) to do this with the amp off.
not to be insulting, but someone could die doing the afforementioned behaviour. don't let that dumb person winning a darwin award be YOU.
you're playing with the b+ supply to the power tubes here, straight off the output transformer, and the voltages are LETHAL. just cuz someone "got away with it with some junk tubes" does not excuse obviously unenlightened experimentation like this. THIS COULD KILL YOU or your amp, as well...just DON'T DO IT.
you COULD however, do it with the amp on standby, as at that point, the B+ is disconnected and the only thing that SHOULD be recieving voltage is the heaters of the tubes. i would reccomend, particularly if you're not intimate with the circuit in question (and never knowing what someone before you might have done inside it) to do this with the amp off.
not to be insulting, but someone could die doing the afforementioned behaviour. don't let that dumb person winning a darwin award be YOU.
If it is a metal shell switch in which the shell is in contact with the chassis (earth) there is no safety issue that I see.
That said, I don't know of any switches rated for this type of operation short of vacuum switches.
Operating a 250VAC switch with 350V DC on it is a sure recipe for destroying the switch due to contact arcing.
At some point in the switching operation you will lose the connection to the screen, which is a good way to destroy the tube and possibly burn up your OPT.
That said, I don't know of any switches rated for this type of operation short of vacuum switches.
Operating a 250VAC switch with 350V DC on it is a sure recipe for destroying the switch due to contact arcing.
At some point in the switching operation you will lose the connection to the screen, which is a good way to destroy the tube and possibly burn up your OPT.
never assume, unless you've been inside an amp, that it's wired right. i've seem amps come in for repairs where people had the chassis hot after "converting" them to grounded mains leads or "installing" new 2 conductor wires, etc.
people make mistakes..even people that have done this for decades.
as the gimp said as well, it could easily arc the switch as well...if that switch shorts, say goodbye to your output transformer as well.
imho, better to be safe...i've been bit enough times that i prefer to be pretty anal about safety. 500+ volts across the chest can make your heart beat kinda funny for a while.
just not a good practice. again, your mileage may vary. but to me, that's not a particularly smart thing to do...but by all means, feel free if that's what you choose to do.
peace
Hi George,
I know this is old thread...but I have a questions about simple SE and the operation in triode/pentode/ultralinear mode when its comes to the sonic qualities. Can you comment on the sound, not just power? Are there any audible differences besides the total output power? What is the prefered mode for hifi?
ed
I know this is old thread...but I have a questions about simple SE and the operation in triode/pentode/ultralinear mode when its comes to the sonic qualities. Can you comment on the sound, not just power? Are there any audible differences besides the total output power? What is the prefered mode for hifi?
ed
Quite the attitude. #1 it's not your thread #2 questions about Tubelab products belong in the Tubelab forum
Most SE amp lovers will tell you that triode mode sounds best. I have had my SSE for about 7 years now and I agree. Some even go so far as saying UL isn't worth listening to. I won't go that far.
Triode mode has the best sonic accuracy, offers the best damping factor, but gives me about 8 watts in my KT88 SSE. UL boosts the power to about 14 watts but gives up some accuracy (detail) and the bass is less defined with my big speakers. I can improve things a bit by engaging the Cathode Feedback switch. I prefer triode mode without any feedback at all. That is where the switch stays for most of the time. I use UL with CFB when loudness is more important than detail. Pink Floyd, Jimi, or Metallica is usually involved.
I experimented with pentode mode when I designed the SSE and decided that the sonic penalties weren't worth the small power increase over UL mode. CFB did not improve the sound enough to warrant its use. If you are using an OPT without a UL tap, it might be worth trying to see if it works with your speakers, but it didn't with any of mine. Some type of global feedback is probably needed which is possible with the SSE, but I still didn't like it.
This forum is for and about people who usually build their own amps. We tend to put safety in high regard, and so do I on my web site. If an amp is properly built the way it is explained here, flipping the switch isn't going to kill anyone. Nevertheless no one is advising anyone to flip the switch with the amp on. I advise against it in the amps I design that incorporate a switch.
Operating an AC rated switch on DC will cause contact arcing in many cases. In this case we are switching the screen voltage which is over 400 volts DC, but the current is 5 to 15 mA and that isn't going to arc weld a 10 AMP AC switch.
You lose connection to the screen at least for a moment every time you flip the switch since they are break before make. In any audio tube that is in good enough condition to be listening to, the tube current will go to zero when the screen grid circuit is opened (a really gassy tube may be an exception). The screen grid draws current and its voltage will drop to zero, or even slightly negative when open, killing the tube current. That said flipping the switch at full tilt, with a fairly high tube current, will attempt to drop the current through the OPT to zero. That IS a possible way to blow up an OPT since you can NOT immediately cease the current through an inductor. Even this should not cause damage in an OPT with a loudspeaker load since the magnetic energy stored in the OPT will be dumped into the speaker causing a loud pop, which may not be good for expensive sensitive fullrange drivers, or tweeters.
That said, I have been building tube amps for nearly 50 years. I have blown up more tubes and silicon than most of the builders here combined. I subject my amps to far more abuse than I expect the users to since I want to find the weak links before I sell them. My SSE has been alive for 7 years and it still has the same pair of EH KT88's that have been in there for about 5 1/2 of those years. I have played my guitar through it driven to well beyond clipping, flipped every switch on it while doing this, and the only thing that has ever blown is the solid state diodes in the power supply.
I still DON'T RECOMMEND flipping the switch with the amp on, but it isn't going to kill anyone, an isn't likely to kill a well designed amp either. Don't blame me for zapping your Lowthers though.
This may be true but this thread started long before there was a Tubelab forum, or even before Tubelab was a company.
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That maybe true but post #24 was made long after there both a Tubelab forum and a Tubelab company. There is no reason post #24 could not have been handled as a new post in the Tubelab forum with a link to this thread, if that was even necessary.
I'm putting "The Switch" in my amp.
In fact, I'm putting four switches in it. There are two switches per channel.
One pair of switches selects between UL and Triode mode. (I thought about adding two more switches to allow for Pentode mode also, but gave it up.)
The second pair of switches select between Triode strapped pentode input with current source in anode, and Mu Stage input (Triode strapped pentode in bottom, Pentode in top).
In fact, I'm putting four switches in it. There are two switches per channel.
One pair of switches selects between UL and Triode mode. (I thought about adding two more switches to allow for Pentode mode also, but gave it up.)
The second pair of switches select between Triode strapped pentode input with current source in anode, and Mu Stage input (Triode strapped pentode in bottom, Pentode in top).
Everything said here applies to all amps, not just one of mine. I think that it has been brought up in my forum, but not as many people read my forum.
This ain't one of my amps.
I have a few extra switches too, and even two knobs. One of the knobs allows for variable cathode feedback. I thought it would be a cool idea, but I found that I either turned it all the way up, or all the way off.
Another, attempted to dial from pentode, to variable UL, to triode. There was a thread here somewhere called adjustable split load....something. It worked OK on the bench, but never sounded quite right in the real world, so I cut the wires on that one.
The switch to turn on the solid state rectifier gives a 30 volt boost in B+, good for a little power boost and a bit better bass control. Flipping that one repeatedly at full power while listening for the A/B sound difference test.....does tend to kill the diodes! Again.....DONT DO IT.
No George.
It is one of my abominations.
6P41S SE output with Mu stage input.
I added switches to allow me to change to a triode mode input with LED bias and Current Source anode load just in case.
This one:
http://www.diyaudio.com/forums/tubes-valves/190797-another-se-amp-design-2.html
It is one of my abominations.
6P41S SE output with Mu stage input.
I added switches to allow me to change to a triode mode input with LED bias and Current Source anode load just in case.
This one:
http://www.diyaudio.com/forums/tubes-valves/190797-another-se-amp-design-2.html
Well,
In the past I have fitted Triode, UL, Pentode switches. Yes they are/were AC rated. Fitted with a B+ kill switch because I was fed up with opening and soldering the amp over and over again. And they were minature toggles as well...shock horror..They worked perfectly fine for 10 years.still have the amp and it still works. 100W per channel PP...dual pole switches two on each side one for triode/UL and one for Pentode...even more shock and horror..450V B+. How /why can they work...because I switch off load. The switches I used are not the same switches in the link however look at the insulation spec for contacts ect as an example. The problem is on opening and closing any contact while on load. If you do this mod its at your own risk..and YMMV. If they flash over well it could stuff the TX then again if an EL 34 flashes over it could stuff the Tx yes it has fuses in the B+. Never switch while playing or with B+ on...The switches were fitted on the back of the amp so they could not be switched by others buy accident or with B+ on..you had to reach over the hot tubes and it was a pig to get to. I should add they were bolted through an earthed chassis. (So the toggle is at Earth potential.)
http://docs-europe.electrocomponents.com/webdocs/01a6/0900766b801a6714.pdf
Regards sound...yes there is a difference and it depends on your mood and if you want to listen to Rock pop or classical. I could switch between all and it spent most of its time set to triode also with a pot on each side to set feedback. Then again triode with all grids to triode connection sounds different as well (True triode). <<to much hassle. soldering required. I also understand why some people prefer pentode its "crisper" not so warm in the sound.
Regards
M. Gregg
In the past I have fitted Triode, UL, Pentode switches. Yes they are/were AC rated. Fitted with a B+ kill switch because I was fed up with opening and soldering the amp over and over again. And they were minature toggles as well...shock horror..They worked perfectly fine for 10 years.still have the amp and it still works. 100W per channel PP...dual pole switches two on each side one for triode/UL and one for Pentode...even more shock and horror..450V B+. How /why can they work...because I switch off load. The switches I used are not the same switches in the link however look at the insulation spec for contacts ect as an example. The problem is on opening and closing any contact while on load. If you do this mod its at your own risk..and YMMV. If they flash over well it could stuff the TX then again if an EL 34 flashes over it could stuff the Tx yes it has fuses in the B+. Never switch while playing or with B+ on...The switches were fitted on the back of the amp so they could not be switched by others buy accident or with B+ on..you had to reach over the hot tubes and it was a pig to get to. I should add they were bolted through an earthed chassis. (So the toggle is at Earth potential.)
http://docs-europe.electrocomponents.com/webdocs/01a6/0900766b801a6714.pdf
Regards sound...yes there is a difference and it depends on your mood and if you want to listen to Rock pop or classical. I could switch between all and it spent most of its time set to triode also with a pot on each side to set feedback. Then again triode with all grids to triode connection sounds different as well (True triode). <<to much hassle. soldering required. I also understand why some people prefer pentode its "crisper" not so warm in the sound.
Regards
M. Gregg
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