I would NOT build it the way I did either. That was just a "test" amp that was together for about a week to determine the feasibility of the design. Every time that it was on the Lexan shield was there, except for one picture that was taken in "autowinder" mode while I was in the next room. Yes the amp looks hazardous, but I understand what would have happened if the guitar got too close to the HV. Hence the big piece of Lexan and the extra fire extinguisher.
It did have a "sound" that I have never heard before. I still want to build that 200 watt SE guitar amp, and I have collected all of the parts. But like I have stated here a RELIABLE amp of that caliber would require special techniques that would take a lot of time and money to pull off. When I have the time and can commit an entire workbench for a month or more I will build it. I need to think of a construction technique that would show off that glowing tube without posing a DEATH hazard. Maybe a clear Lexan amp head with forced ventilation.
Another issue with using the 833A for guitar amps is the fragillity of the filament, especially after it has been used for a while. I am sure you know how roadies treat these things! Most musicians will toss even the coolest amp if they have to fix it before each show. I have "inherited" a few pieces of equipment that way. It is also far too loud to use in the studio. I think that it would eat a "Power Soak" (resistive attenuator) for lunch!
When I find some output transformers that work good enough for HiFi that I can afford, I want to build "the big one" but that is also pretty far down the project list.
SE or P-P? How much power? The 807 is closely related to the 6L6. Find and old stereo or two old organ, PA, or guitar amps that used any of the 6L6 variants. If you go the organ, PA, or guitar amp route the frequency response may not be good enough for HiFi. I have had good luck though. I also see "Schumaker" guitar amp transformers go on Ebay relatively cheap. Even though these were designed for guitar amps I bought a pair, and tested them. They were good to 19KHz. I contacted the seller (several years ago) and bought a large quantity. I have been using them in HiFi amps ever since. I have a pair in my 300B push pull amp.
There are military surplus output transformers out there. Avoid these unless the frequency response is explicitly stated on the transformer (or you have the oportunity to test it). They are often limited to speach frequencies.
The Motorola base station power supply had a few oil filled 2500 volt caps on it which was not enough to handle the current drawn when driving the amp with a low frequency tone.
Look at the first picture of the "breadboard" on my web site. To the left of the current meter, behind the 833A is a large oil filled capacitor, 16uF 7500 volt. It came from an old cardiac defibrillator unit. It is still not quite large enough to handle the current drawn under low frequency operation. Caps of this size can be found in the surplus market, although some may contain toxic substances. You can still but them new but they are several hundred dollars each!
This is again one of those cases where "specialized" components are required. If considering an amp of this magnitude, consult an older ham radio operator who built high power vacuum tube transmitters "back in the good old days" This is flea power to them. The old ARRL handbooks (up to the early 1980's) had detailed plans to build these monsters. I built a 1 KW transmitter in the 1970's.
Look at the first picture of the "breadboard" on my web site. To the left of the current meter, behind the 833A is a large oil filled capacitor, 16uF 7500 volt. It came from an old cardiac defibrillator unit. It is still not quite large enough to handle the current drawn under low frequency operation. Caps of this size can be found in the surplus market, although some may contain toxic substances. You can still but them new but they are several hundred dollars each!
This is again one of those cases where "specialized" components are required. If considering an amp of this magnitude, consult an older ham radio operator who built high power vacuum tube transmitters "back in the good old days" This is flea power to them. The old ARRL handbooks (up to the early 1980's) had detailed plans to build these monsters. I built a 1 KW transmitter in the 1970's.
For the rock'n rollers, how about a double pole, etc power switch? What goes on, is that that the secondary 'off' position is actually a passively connected drain switch/circuit,and a timer circuit for cooling the innards of the sensitive bits.
Then a 'rule' where the ultra sensitive tube is removed, put in package for safe transport, and then re-assembled before use?
You'd be down to a timed wait for shutdown and storage, and a simple tube re-install before use. Use deadman (switch) techniques/(drainage systems) on the hardware side to ensure safety. The tube itself in boxed 'suspended' holder type device. This box is inserted in and out of the chassis. Or even a slider on the chassis or the like for creating an internal shipping suspension system, much like a CD player, TT, etc. then the tube and etc, are all internal and no prying hands inside. For that crew of artists, the size and complexity is not an issue. Safety and reliability is.
I know little about this amp, but if it's cool and works like a monster, then they might go for it.....As stated, I'm speaking out my butt on this one, just throwing thoughts out there, it might make it on stage/studio/record yet. I just smell something highly viable here, in terms of being a element of desire for the 'recording' crowd.
Then a 'rule' where the ultra sensitive tube is removed, put in package for safe transport, and then re-assembled before use?
You'd be down to a timed wait for shutdown and storage, and a simple tube re-install before use. Use deadman (switch) techniques/(drainage systems) on the hardware side to ensure safety. The tube itself in boxed 'suspended' holder type device. This box is inserted in and out of the chassis. Or even a slider on the chassis or the like for creating an internal shipping suspension system, much like a CD player, TT, etc. then the tube and etc, are all internal and no prying hands inside. For that crew of artists, the size and complexity is not an issue. Safety and reliability is.
I know little about this amp, but if it's cool and works like a monster, then they might go for it.....As stated, I'm speaking out my butt on this one, just throwing thoughts out there, it might make it on stage/studio/record yet. I just smell something highly viable here, in terms of being a element of desire for the 'recording' crowd.
833 Amp from Unison845
Unison845,
Your 833 amp is a lot more compact that all others out there and I am very impressed that you can use the same circuit to drive the Eimac 250TL tubes in your other amp.
I like the simplicity of the drive circuit developed by Tubelab.com:
http://www.tubelab.com/833SE.htm
bur would like to compare how your design differs from his before I embark on a full-fledged build.
Would you mind sharing the schematic with the folks here?
Thanks,
-- josé k.
Unison845,
Your 833 amp is a lot more compact that all others out there and I am very impressed that you can use the same circuit to drive the Eimac 250TL tubes in your other amp.
I like the simplicity of the drive circuit developed by Tubelab.com:
http://www.tubelab.com/833SE.htm
bur would like to compare how your design differs from his before I embark on a full-fledged build.
Would you mind sharing the schematic with the folks here?
Thanks,
-- josé k.
step down interstage
Hi Triod Lover
remember that the ratio's work differently.
A step-up/-down of 2 means multiply by 4;
A step-up/-down of 4 means multiply by 16 !
So your proposed interstage with a 3 K / 800 ohm tranny will have a ratio of just 2. And at the 833-grid you need a much mor lower impendance ! That's why i opted for a ratio for tranny which gives me 3K2 / 200 ohm !
Regards,
Reinout
Hi Triod Lover
remember that the ratio's work differently.
A step-up/-down of 2 means multiply by 4;
A step-up/-down of 4 means multiply by 16 !
So your proposed interstage with a 3 K / 800 ohm tranny will have a ratio of just 2. And at the 833-grid you need a much mor lower impendance ! That's why i opted for a ratio for tranny which gives me 3K2 / 200 ohm !
Regards,
Reinout
Hello..Reinout
Thank you so much for your kindness and give me the information of interstage,Your 833A amp is such a beautiful and looks great to me that i like to built one,i plan to use 6SL7 to drive 300B. and then interstage to drive 833A.,but now am not quite sure about bias the 833A.Could i use a variable power suply that can deliver the voltage of 18-20 VOLT to the secondary of interstage and the other lead go to grid of 833A?,and i have the output transformer 5K:8 ohm/200 ma. is it safe to use on 833A.?
Best Regards,
Triod Lover.
Thank you so much for your kindness and give me the information of interstage,Your 833A amp is such a beautiful and looks great to me that i like to built one,i plan to use 6SL7 to drive 300B. and then interstage to drive 833A.,but now am not quite sure about bias the 833A.Could i use a variable power suply that can deliver the voltage of 18-20 VOLT to the secondary of interstage and the other lead go to grid of 833A?,and i have the output transformer 5K:8 ohm/200 ma. is it safe to use on 833A.?
Best Regards,
Triod Lover.
Hi again Triod lover,
the 6SL7 - 300B combination is a classic. No funnies there; altough the 6SN7 - 300B seems more logical. The gain of the 6SL7 is more than needed and the output impendance of the 6SL7 is lower (always better).
Nevertheless.....NO problems with either the 6SN7 or the 6SL7 as the first stage.
The second stage with the 300B proofs to work also. My amp is the actual proof; and rest assured....that rocks !
The 833 is simply great.
I use my 833 as a zero-bias tube. Not very common, but it spares me again a complete power supply line for the bias of the 833. Of course you can use a classic negative bias and you can have a more stable/directed/forced/ bias which makes it less depended on the driver. But the zero-bias schematic is well proven (in transmitters). Not very common in audio amps; but for me that was no reason not to go for it.
Did some maths:
Anode voltage / output impendance / milliamperes anode current:
- 3000 V / 20 K / 100 mA;
- 2000 V / 10 K / 150 mA;
- 1500 V / 8 K / 200 mA;
- 1000 V / 5 K / 250 mA;
- 650 V / 2 K / 290 mA.
All above measurements were proven in practice (from the Wavac 800 ~850 V to the 2400 V Lumley amps. And of course all the DIY-833-amps).
So your 5K / 200 mA seems a bit flimsy if you're going to use 1000 V. And going higher on voltage makes it easier for the windings (less current to transport); but leaves you with an impendance missmatch. And going lower on voltage leaves you with a very stable tranny (somewhat higher on impendance makes it stable on the cost of some efficancy) but will leave you with a serious problem with current !
The Electra-Print CU5KB is a good example of the basic 833-tranny. Still you need to discuss the required voltage with your winder.
Happy building,
Reinout
the 6SL7 - 300B combination is a classic. No funnies there; altough the 6SN7 - 300B seems more logical. The gain of the 6SL7 is more than needed and the output impendance of the 6SL7 is lower (always better).
Nevertheless.....NO problems with either the 6SN7 or the 6SL7 as the first stage.
The second stage with the 300B proofs to work also. My amp is the actual proof; and rest assured....that rocks !
The 833 is simply great.
I use my 833 as a zero-bias tube. Not very common, but it spares me again a complete power supply line for the bias of the 833. Of course you can use a classic negative bias and you can have a more stable/directed/forced/ bias which makes it less depended on the driver. But the zero-bias schematic is well proven (in transmitters). Not very common in audio amps; but for me that was no reason not to go for it.
Did some maths:
Anode voltage / output impendance / milliamperes anode current:
- 3000 V / 20 K / 100 mA;
- 2000 V / 10 K / 150 mA;
- 1500 V / 8 K / 200 mA;
- 1000 V / 5 K / 250 mA;
- 650 V / 2 K / 290 mA.
All above measurements were proven in practice (from the Wavac 800 ~850 V to the 2400 V Lumley amps. And of course all the DIY-833-amps).
So your 5K / 200 mA seems a bit flimsy if you're going to use 1000 V. And going higher on voltage makes it easier for the windings (less current to transport); but leaves you with an impendance missmatch. And going lower on voltage leaves you with a very stable tranny (somewhat higher on impendance makes it stable on the cost of some efficancy) but will leave you with a serious problem with current !
The Electra-Print CU5KB is a good example of the basic 833-tranny. Still you need to discuss the required voltage with your winder.
Happy building,
Reinout
Attachments
Hello...again Reinout!
Thanks again for your patient...one more question please!!!
and if iwould like to connect the 833A in zero biasing,all i need to do is just connect one of the output(200 ohm) interstage to ground is that correct?
P.S Reinout,Phuket island the place i live is a beautiful beach and crystal clear water if you would decide to take a vacation here i would be grad to welcome you and be your host!!!,anyway you can see and listen to my amp 833A sing a song!!!
Bgrs,
Triod Lover.
Thanks again for your patient...one more question please!!!
and if iwould like to connect the 833A in zero biasing,all i need to do is just connect one of the output(200 ohm) interstage to ground is that correct?
P.S Reinout,Phuket island the place i live is a beautiful beach and crystal clear water if you would decide to take a vacation here i would be grad to welcome you and be your host!!!,anyway you can see and listen to my amp 833A sing a song!!!
Bgrs,
Triod Lover.
Hi Guys,
Interesting thread,
I was messing with a 212 the other day, again !!! and thought to myself I wonder what that ornament of an 833 would sound like?
So I plugged it in and was quite supprised just how easy it was to set-up. I finished at 800V, 0 bias, 170ma
It's driven by my PX4 amp straight off the output transformer which works out to 20:1 ratio.
I could do with something more like a 4:1 for more gain, but hey, it works, and quite well too.
So I tried it off my 1W 6EM7 amp and that works too, but a little low on volume I have to say. Sounds good though.
Best wishes
Darren
Interesting thread,
I was messing with a 212 the other day, again !!! and thought to myself I wonder what that ornament of an 833 would sound like?
So I plugged it in and was quite supprised just how easy it was to set-up. I finished at 800V, 0 bias, 170ma
It's driven by my PX4 amp straight off the output transformer which works out to 20:1 ratio.
I could do with something more like a 4:1 for more gain, but hey, it works, and quite well too.
So I tried it off my 1W 6EM7 amp and that works too, but a little low on volume I have to say. Sounds good though.
Best wishes
Darren
Hi Triod lover,
Not sure what you're asking?
You can follow my ongoing build here, feel free to ask again, Best wishes
Darren
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=17
Not sure what you're asking?
You can follow my ongoing build here, feel free to ask again, Best wishes
Darren
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=17