Nazaroo,
Only my thoughts..
I completely agree with your comments..
However anyone can just trawl the internet and get circuits for everything from ecc83 to 211 ongaku..IF we do a two second search we get:
http://www.electra-print.com/300bdrd.php
700V rails..
Perhaps exclude the power supply section until the end of the thread..this is the dangerous bit<<if someone builds this it’s their own fault.
Then people can at least simulate the circuit and see what you are doing.
I think you have to also take into account that ..
You put a disclaimer something like..
Tube amps can kill!
This amp contains lethal voltages. Do not attempt to build this if you are not a competent engineer. If you attempt to build this, it is at your own risk! This is a theoretical build only.. I accept no responsibility for any injury or damage incurred by such a build.
IF YOU ARE NOT CONFIDENT AND COMPETENT DO NOT BUILD THIS CIRCUIT!
ON the top of the drawing..
Then it’s important to see what the moderators think..
It would have to be accurate with correct values, Then again the choice is yours.
Even a search on this forum will give amps containing HV at all levels..
If we all decided that HV is to be banned (to protect people from themselves) then this forum and many others would not exist..
I regard this as a discussion thread..and very interesting it is too.
I for one have an issue with HV and HC <<linked to high values of B+ smoothing. (instant high current available)
Perhaps the way forward is post the schematic add the warnings..
do the discussion.
Its interesting to note SVT bass amps had this reputation.
Regards
M. Gregg
Only my thoughts..
I completely agree with your comments..
However anyone can just trawl the internet and get circuits for everything from ecc83 to 211 ongaku..IF we do a two second search we get:
http://www.electra-print.com/300bdrd.php
700V rails..
Perhaps exclude the power supply section until the end of the thread..this is the dangerous bit<<if someone builds this it’s their own fault.
Then people can at least simulate the circuit and see what you are doing.
I think you have to also take into account that ..
You put a disclaimer something like..
Tube amps can kill!
This amp contains lethal voltages. Do not attempt to build this if you are not a competent engineer. If you attempt to build this, it is at your own risk! This is a theoretical build only.. I accept no responsibility for any injury or damage incurred by such a build.
IF YOU ARE NOT CONFIDENT AND COMPETENT DO NOT BUILD THIS CIRCUIT!
ON the top of the drawing..
Then it’s important to see what the moderators think..
It would have to be accurate with correct values, Then again the choice is yours.
Even a search on this forum will give amps containing HV at all levels..
If we all decided that HV is to be banned (to protect people from themselves) then this forum and many others would not exist..
I regard this as a discussion thread..and very interesting it is too.
I for one have an issue with HV and HC <<linked to high values of B+ smoothing. (instant high current available)
Perhaps the way forward is post the schematic add the warnings..
do the discussion.
Its interesting to note SVT bass amps had this reputation.
Regards
M. Gregg
HV circuits are posted here all the time. No problem at all, and there's already a disclaimer in the tube forum heading. The only thing forbidden by forum rules is direct mains connection with no isolation.
IN the spirit of the last few posts expressing concern for extra-high voltage required by the main design, I'm going to begin a build that avoids that danger for 90% of the build.
The strategy is simple:
We will build the lower part of the amp,
and test it using a 'dummy' powersupply,
which will allow the circuit to fully function as an ordinary amplifier,
so it can be tested in its basic operation and performance,
then build the real power supply with CCS and PSRR, containing the High Voltage in a separate chassis,
with special instructions to avoid the bulk of the danger in that build.
Then the two projects can be combined to give the desired performance, after each is safely built and tested.
I hope that will satisfy safety concerns as best as can be done.
Any safety suggestions will be welcome as we proceed,
because you can never have enough safety!
regards,
Nazaroo
The strategy is simple:
We will build the lower part of the amp,
and test it using a 'dummy' powersupply,
which will allow the circuit to fully function as an ordinary amplifier,
so it can be tested in its basic operation and performance,
then build the real power supply with CCS and PSRR, containing the High Voltage in a separate chassis,
with special instructions to avoid the bulk of the danger in that build.
Then the two projects can be combined to give the desired performance, after each is safely built and tested.
I hope that will satisfy safety concerns as best as can be done.
Any safety suggestions will be welcome as we proceed,
because you can never have enough safety!
regards,
Nazaroo
Jus' ventin' in da middle of da night.
You know, I asked for a complete schematic in post #13. On rereading that post I was a little harsh, though I didn't mean to be. I just really wanted to build the amp. And Gregg is right. With a complete schematic we would know it was our mistake and not the design if it didn't sound right. Besides, the MU follower isn't new. And if we were all capable of designing the amp from scratch what would we need the forum for? I suffer from Asberger's so my social skills are somewhat questionable. And being an amateur I'm easily dismissible.
One thing I find suspect about this amp is its inefficiency. As output power increases so does distortion. So why go to the trouble of building a twenty watt amp? Build a simple, clean, hundred watt amp and drive it moderately I say.
And is there really a difference between being electrocuted by three hundred volts and 800? For FUN I build and race cars. On the back stretch at Mid-Ohio doing 160 do I think about every nut and bolt? (hell yes!) But, "if you're born to hanged you'll never drown." Looked at phenomenologically you can't prevent your own death.
Wavebourn, thanks for the 6P15P schematic. Now I have something to do with all those Russian tubes I bought.
You know, I asked for a complete schematic in post #13. On rereading that post I was a little harsh, though I didn't mean to be. I just really wanted to build the amp. And Gregg is right. With a complete schematic we would know it was our mistake and not the design if it didn't sound right. Besides, the MU follower isn't new. And if we were all capable of designing the amp from scratch what would we need the forum for? I suffer from Asberger's so my social skills are somewhat questionable. And being an amateur I'm easily dismissible.
One thing I find suspect about this amp is its inefficiency. As output power increases so does distortion. So why go to the trouble of building a twenty watt amp? Build a simple, clean, hundred watt amp and drive it moderately I say.
And is there really a difference between being electrocuted by three hundred volts and 800? For FUN I build and race cars. On the back stretch at Mid-Ohio doing 160 do I think about every nut and bolt? (hell yes!) But, "if you're born to hanged you'll never drown." Looked at phenomenologically you can't prevent your own death.
Wavebourn, thanks for the 6P15P schematic. Now I have something to do with all those Russian tubes I bought.
Forgive my tardiness to this thread, but I have to ask, how is "today's world" different from 50'years ago, WRT high voltage use in tube amp design?
There are lots of dangerous activities, and people continue to do them, even in today's world.
I've read all 25 pages and can't make heads or tails of this thread.
No, but there's a difference between being alive and being dead (I think). 300 volts didn't manage to kill me, 400 volts showed me the doors to heaven, 800 volts should get me there (I think).
The schematic is complete. I just think Naz forgot about the resistor values. Read his post about what happens when you build an amp being stoned. It should give you a clue.
My humble proposal. Attached is a schematic that has been modified from a John Broskie design and from Walt Jung's article (http://waltjung.org/PDFs/Sources_101_P2.pdf)on constant current sources. This is just a first draft, please feel free to comment. The idea is a low cost testbed using fairly standard components. Power output will be fairly low, maybe 3 or 4 watts per channel, but the tubes are only running at a fraction of their design limit. It can fairly easily be switched back to a conventional push-pull by re-arranging the output transformer leads (a single DPDT switch per channel may be able to do it) and changing the bias.
The LED array should be 6 parallel strings of 3 LEDs, assuming the average LED that drops 2v across it. That is according to the Phillips EL84 datasheet that gives a bias of about 6v at 40ma and 220v in triode mode. This may need to be adjusted. The OPT and capacitor value: I would try a 12v CT power toroid and at least a 10uF 400v film cap.
For the CCS in the first stage, I would use a LM334 in place of a LM317 (just reverse the pinout) and bias according to the datasheet, or use a 30K resistor. I would also use a regulated power supply, probably a simple source follower, since the PSRR of the concertina is fairly low.
The LED array should be 6 parallel strings of 3 LEDs, assuming the average LED that drops 2v across it. That is according to the Phillips EL84 datasheet that gives a bias of about 6v at 40ma and 220v in triode mode. This may need to be adjusted. The OPT and capacitor value: I would try a 12v CT power toroid and at least a 10uF 400v film cap.
For the CCS in the first stage, I would use a LM334 in place of a LM317 (just reverse the pinout) and bias according to the datasheet, or use a 30K resistor. I would also use a regulated power supply, probably a simple source follower, since the PSRR of the concertina is fairly low.
Attachments
Once alive does anything ever really die? But that's a MUCH bigger question than we can answer here.
I've built a few amplifiers and preamps and know that tiny differences can alter the sound of the component. And Nazaroo has, I'm sure, done a lot of experimentation. I would give anything to come up with something truly original.
When I was four I heard a blood curdling scream from the basement. When I ran downstairs I found my older sister laughing maniacally. She handed me a straightened out safety pin and said, "stick this in there." Unaware of my beloved sister's murderous intent I did. I flew across the room and hit the opposite wall. She laughed even harder.
Then, when I was about eight I was standing on the stove and put my hand on the ungrounded refrigerator. As I flew across the kitchen my baby brother, being fed in his high chair watched me. His mouth dropped open and applesauce drained out. I hit the back door. Hard.
I learned that lesson at an early age. Twice!
I've built a few amplifiers and preamps and know that tiny differences can alter the sound of the component. And Nazaroo has, I'm sure, done a lot of experimentation. I would give anything to come up with something truly original.
When I was four I heard a blood curdling scream from the basement. When I ran downstairs I found my older sister laughing maniacally. She handed me a straightened out safety pin and said, "stick this in there." Unaware of my beloved sister's murderous intent I did. I flew across the room and hit the opposite wall. She laughed even harder.
Then, when I was about eight I was standing on the stove and put my hand on the ungrounded refrigerator. As I flew across the kitchen my baby brother, being fed in his high chair watched me. His mouth dropped open and applesauce drained out. I hit the back door. Hard.
I learned that lesson at an early age. Twice!
Being a contrary curmudgeon. What would happen if you were to build Fenris's amp without the CCS? I prefer amps with unregulated power supplies, no transistors, FETS or LED's. From my understanding a CCS is meant to keep the current in the circuit very high so it can be delivered quickly. But it also drives the power supply very hard, like a single ended amp. How much difference would it make, sonically, to have the power supply deliver current on demand, as in an older amp design?
Also, what type of output transformer is being used here? Is it a standard non-ultralinear? Or a single ended?
Also, what type of output transformer is being used here? Is it a standard non-ultralinear? Or a single ended?
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Actually, the CCS is there to keep the current constant and provide a nearly infinite AC impedance to the load, which in theory makes a triode as linear as possible. It actually makes the power supply work less since the demand is constant and therefore the power supply can be optimized to work at one single point. Large current surges drag down the PSU and can shift the bias points or impart noise into other parts of the circuit.
The transformer ideally would be a standard push pull type (no UL taps needed) or even a single primary transformer - no need for an air gap because there's no DC current flowing.
Nothing is critical. Just bridged pair of SRPP amps. Bridging is good when driving speakers directly from an amp powered from low voltage battery. Otherwise it is meaningless. When pair of tube amps is bridged it is contrary to what is needed for tube amps: bridging increases twice required transformer ratio making it much more expensive for given frequency range.
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I did. What has that got to do with your comments WRT "today's world" and "using high voltage for the sake of building with tubes"?
There is a saying in motorcycle racing, "stupid hurts", and it should!
My electronics career started at about age 5. That's when the paper clip met the wall outlet. The black stain remained on the outlet for years to remind me why I was forbidden to play with wall outlets......What does a kid do when he is forbidden to play with something???? He graduates to kite string, aluminum foil, and POWER LINES!
There are lots of dangerous activities that humans engage in for fun or profit. Look at the guys jumping off cliffs in wing suits.
I used to build and drive race cars although my fastest one only went 154. At age 60 I no longer have the reflexes to be a compettive driver (not that I ever was, just autocrossed and drag raced).
I have also built some rather large electronics devices for fun or profit. The largest was a power supply for a Gates 5KW transmitter, 7000 volts at just over 1 amp. Back in the 80's I built a little CB radio that used a 4-400 for an output stage and ran on 2 KV. There is a little prototype SE guitar amp on my web site that runs on 1.5 KV. It only existed for a week to prove out the concept and test the OPT. I decided that it wasn't practical and I decided not to build it. Over the last 2 years I have sold, given away, or trashed about 90% of the electronics "stuff" that I have collected over the past 50 years. Without planning it, it seems that all the major components for that build are still here, so I might just build it.
I am comfortable with both endeavors and have the knowledge to understand my limits and work within them. It is IMPERATIVE in any potentially life threatening endeavor to understand the risks, plan for every possible screw up, and be prepared to meet and deal with them. Anyone contemplating building or tinkering with a tube amp, at any voltage level, should understand the risks, and the different ways that you can get fried. At least read the safety information on my web site.
The SRPP output stage is not new. Note the schematic included in the Mullard data sheet for the EL86, vintage 1960. Philips was using this circuit in radios in the 1950's. I did a CCS loaded output stage several years ago. It worked very good, but was extremely innefficient.
Active Loaded SE Output Stage
Electrical Safety
Safe Meter Use
Equipment Grounding
The 833A SE Amp Prototype
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