Does any one have any success using a 6HV5A in position V1 in a cap coupled, two stage amplifier? I understand that this is a difficult tube to tame since it is happiest wtih a high voltage on the plate and multiple grids.
lotsmorebetter,
I am curious . . .
Why are you wanting to use the 6HV5A?
You have one
You like the way it looks
You like the high u of 300
. . . or a combination of the above.
The 6HV5A was intended to be used as a high voltage pulse regulator.
Low duty cycle, short pulse width, high pulse current, high plate power dissipation.
The high u, and low plate impedance of 4,600 Ohms are most likely only available with at, or near to, -4.4V bias, and 3,500V on the plate.
With a more moderate plate voltage of an audio amplifier (perhaps 350V), you are correct, the tube will be difficult to use as the input stage of a 2-stage amplifier.
And the filament requirement of 6.3V, 1.8 Amps, 11.3 Watts; and plate dissipation of 35 Watts, will probably be one of the highest dissipation audio input stage tubes ever.
You can use the plate at much lower dissipation, but the filament is going to take lots of power, even if you run it at 5V.
Why does anyone climb Mt. Everest, because they can;
Why does hardly anyone climb K2, because it is too dangerous.
Reminds me of attaching the original Volkswagen bug engine onto a 10 foot wingspan balsa and cloth based construction airplane.
Just my opinions.
I am curious . . .
Why are you wanting to use the 6HV5A?
You have one
You like the way it looks
You like the high u of 300
. . . or a combination of the above.
The 6HV5A was intended to be used as a high voltage pulse regulator.
Low duty cycle, short pulse width, high pulse current, high plate power dissipation.
The high u, and low plate impedance of 4,600 Ohms are most likely only available with at, or near to, -4.4V bias, and 3,500V on the plate.
With a more moderate plate voltage of an audio amplifier (perhaps 350V), you are correct, the tube will be difficult to use as the input stage of a 2-stage amplifier.
And the filament requirement of 6.3V, 1.8 Amps, 11.3 Watts; and plate dissipation of 35 Watts, will probably be one of the highest dissipation audio input stage tubes ever.
You can use the plate at much lower dissipation, but the filament is going to take lots of power, even if you run it at 5V.
Why does anyone climb Mt. Everest, because they can;
Why does hardly anyone climb K2, because it is too dangerous.
Reminds me of attaching the original Volkswagen bug engine onto a 10 foot wingspan balsa and cloth based construction airplane.
Just my opinions.
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The answer as to why use one:
I have one and I can use it with the 1kv plate voltage of V2 without dropping resistors.
But if you are saying that it is more like climbing Mt. K2, then, ok.
Would it be any better/easier to use it at lower voltages like around 500v?
I have one and I can use it with the 1kv plate voltage of V2 without dropping resistors.
But if you are saying that it is more like climbing Mt. K2, then, ok.
Would it be any better/easier to use it at lower voltages like around 500v?
I think we need someone who has a high voltage curve tracer that can go to 1kV, who also has access to a 6HV5A tube.
If they can post the family of curves, we would know a lot more of how useful that tube would be as your amplifier input tube.
. . . Curve tracer people, can you help?
Single ended amplifier, right?
What output tube are you going to use, and what is the grid bias voltage (grid, to cathode / DH filament voltage)?
Is this for Class A1, or for Class A2 operation of the output tube?
What are the output voltage(s) of your signal source(s)?
It takes a lot of data to know if all the bases are covered.
I am reminded of what got me back into vacuum tube amplifiers . . .
Seeing the light, and hearing a 2 stage amplifier that used 1250V B+.
A single triode of a 6SN7 and plate load resistor to 1250V; was RC coupled to a direct heated Western Electric 212E triode.
Looked great, and sounded even better.
If they can post the family of curves, we would know a lot more of how useful that tube would be as your amplifier input tube.
. . . Curve tracer people, can you help?
Single ended amplifier, right?
What output tube are you going to use, and what is the grid bias voltage (grid, to cathode / DH filament voltage)?
Is this for Class A1, or for Class A2 operation of the output tube?
What are the output voltage(s) of your signal source(s)?
It takes a lot of data to know if all the bases are covered.
I am reminded of what got me back into vacuum tube amplifiers . . .
Seeing the light, and hearing a 2 stage amplifier that used 1250V B+.
A single triode of a 6SN7 and plate load resistor to 1250V; was RC coupled to a direct heated Western Electric 212E triode.
Looked great, and sounded even better.
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In terms of tube tracer and curves, see here: http://vinylsavor.blogspot.com/2011/07/tube-of-month-6hs5.html
Single ended, class A, output tube would be 845; 500v (preferred) up to 1kV.
Output voltages of signal source: 2v.
Yes, those reminders that brought you back are those things that are keeping me involved with tubes. Wonderful inventions.
Single ended, class A, output tube would be 845; 500v (preferred) up to 1kV.
Output voltages of signal source: 2v.
Yes, those reminders that brought you back are those things that are keeping me involved with tubes. Wonderful inventions.
Lotsmorebetter,
There are few schematics using the 6HV5 as a driver online with a search which should be enough to get your started.
I used one to drive a 211 SET amp with a B+ of 1,200V. Worked quite well but crawling infants meant I deconstructed it years ago and I cannot find my notes. I'm sure the 6HV5 was choke loaded and cap coupled. I had a few high voltage bench supplies so I experimented with some A2 designs. I ran it as a spud amp for awhile.
There used to be an Italian tube site, Anza High Tension, that I can no longer find, he offered a few 6HV5 schematics as did Jack Eliano of Electra-Print. You might be able to unearth those on the Way back machine. Thomas Mayer on his blog has a few as well, <https://vinylsavor.blogspot.com/search/label/6HS5>
Matt
There are few schematics using the 6HV5 as a driver online with a search which should be enough to get your started.
I used one to drive a 211 SET amp with a B+ of 1,200V. Worked quite well but crawling infants meant I deconstructed it years ago and I cannot find my notes. I'm sure the 6HV5 was choke loaded and cap coupled. I had a few high voltage bench supplies so I experimented with some A2 designs. I ran it as a spud amp for awhile.
There used to be an Italian tube site, Anza High Tension, that I can no longer find, he offered a few 6HV5 schematics as did Jack Eliano of Electra-Print. You might be able to unearth those on the Way back machine. Thomas Mayer on his blog has a few as well, <https://vinylsavor.blogspot.com/search/label/6HS5>
Matt
Wow! What creative designers there are.
It looks to me like you have a project on your hands.
Be careful, Safety First!
Prevent the "Surviving Spouse Syndrome".
Happy designing, building, and listening.
It looks to me like you have a project on your hands.
Be careful, Safety First!
Prevent the "Surviving Spouse Syndrome".
Happy designing, building, and listening.
Thank you for your suggestions. I know of Jack Eliano's use of the 6HV5A in his 845 configuration and I also know that he no longer uses it for some reason. I also read Thomas Mayer's blog a while back, but I could not find a schematic.
Do you know how the tube will work at 500v? Are there any considerations for it at such a low voltage?
Thanks
Lotsmorebetter,
You have the tubes just start playing around. As you drop plate voltage you may have to go grid positive to get the plate current you are shooting for. If you have a bench supply its easy, or it can be done with batteries to get a feel for operating parameters. I ran the grid positive for my spud amp utilization which was around 450V, but my memory could be off. Grid positive changes things upstream of the 6HV5 as you build a circuit as you expect. Good luck.
Matt
You have the tubes just start playing around. As you drop plate voltage you may have to go grid positive to get the plate current you are shooting for. If you have a bench supply its easy, or it can be done with batteries to get a feel for operating parameters. I ran the grid positive for my spud amp utilization which was around 450V, but my memory could be off. Grid positive changes things upstream of the 6HV5 as you build a circuit as you expect. Good luck.
Matt
Piero,
Thank you for the link to Ansa's site. I'm not sure why I couldn't find it but I've loved his experiments and builds over the years.
Matt
Thank you for the link to Ansa's site. I'm not sure why I couldn't find it but I've loved his experiments and builds over the years.
Matt
Thank you for your schematic. I have some questions about your parts, but before I get to them, can you tell me if any part of this schematic be redesigned to allow for a pos/neg. (dual) power supply? I am, like everyone, concerned about Surviving Spouse Syndrome. (Mind you, 100v at a high enough current can still kill).
Thanks.
Thanks.
As mentioned in post #10, if the plate to cathode voltage goes much below 500 volts you will need to drive the control grid positive to get much plate current. In the region near zero volts on G1 it's impedance will vary greatly with the incoming audio input signal. This makes a low impedance drive voltage mandatory. Many years ago I simply connected the headphone output of a Sony Discman between the cathode and G1 while wiring a power supply and OPT between the cathode and the plate. This was truly a minimal parts spud amp but it took all 650 volts of my power supply to drive the distortion down to a listenable level. Power output was three to five watts based on a loudness guess and probably drive level limited. The tube used was not a 6HV5, but it was another version of the same tube with similar curves, probably a 6JD5. There are 5 or so different flavors of these beam triode regulator tubes that only vary in pinout and plate dissipation, 35 or 30 watts.
If that's the case, then perhaps the 845 can use a pos/neg power supply and use another tube in v1, like maybe a 7905. I know my question was originally about using the 6hv5 but now I am rethinking it because I like the idea of a pos/neg/ power supply-- it simplifies many design problems.
I don't know what you have in mind, but I don't see how a bipolar power supply would make things simpler. I ran my 845 amp on 1050 to 1100 volts of B+ to make a little over 30 watts of power with the last 5 to 10 watts well into the A2 region (grid current). It took over 300 volts peak to peak of drive to get that power level. I used a 45 tube running into a CCS load with a plate voltage around 300 volts and a mosfet follower buffer to drive the grid of the 845 to get there. The 45 was driven by a 5842. The whole driver was simply a TSE board.
A lower voltage, lower powered amp would need less drive, but you are still looking at 200 volts peak to peak or more. A single stage triode would need a near ideal load and a Mu of well over 100 to get there. The 6HV5 could work, but a lightly loaded pentode like a 6V6GT, EL84 or maybe an EL34 would be where I would start.
Any time you run a single tube at high gain you run the risk of microphonics. Pentodes are worse than triodes, and physically larger tubes are worse than small ones. They should not be bad at gains in the 100 V/V range. I made a pentode stage in a guitar amp with variable gain. At gains in the 1000 range it will pick up your voice if you talk to the input tube. It is useless at that level due to acoustic feedback. The tube is an 18FW5 (an 18 volt 6AU6) running into a gyrator load.
I ran this thing foe a couple years in Florida where there were no young kids to get near the amp. Its main drawback was the 500+ watts of heat it put into the 100 square foot room. Here I have curious grandkids that haven't got a clue what my stuff is, so the deadly tube amps are well hidden or gone. After sitting around unused for over 15 years, I just sold the whole 845 amp for $200 at the Dayton Hamfest.
A lower voltage, lower powered amp would need less drive, but you are still looking at 200 volts peak to peak or more. A single stage triode would need a near ideal load and a Mu of well over 100 to get there. The 6HV5 could work, but a lightly loaded pentode like a 6V6GT, EL84 or maybe an EL34 would be where I would start.
Any time you run a single tube at high gain you run the risk of microphonics. Pentodes are worse than triodes, and physically larger tubes are worse than small ones. They should not be bad at gains in the 100 V/V range. I made a pentode stage in a guitar amp with variable gain. At gains in the 1000 range it will pick up your voice if you talk to the input tube. It is useless at that level due to acoustic feedback. The tube is an 18FW5 (an 18 volt 6AU6) running into a gyrator load.
I ran this thing foe a couple years in Florida where there were no young kids to get near the amp. Its main drawback was the 500+ watts of heat it put into the 100 square foot room. Here I have curious grandkids that haven't got a clue what my stuff is, so the deadly tube amps are well hidden or gone. After sitting around unused for over 15 years, I just sold the whole 845 amp for $200 at the Dayton Hamfest.
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I cannot answer your question.
I am writing in English by translating my thoughts into Italian through an automatic translator, which often distorts what I want to say.
The project I published is not mine, but a project I saved in a personal archive of other audiophiles' DIY projects I found on the net.
I cannot say anything about the goodness of its design: it could be a valid and well-tested design, as well as a hypothesis of some improvised DIYer.
The post only wanted to underline the fact, now established by many who have used the 6HV5A tube as a driver in amplifiers with 211, 845 and other tubes with similar characteristics, that for hi-fi audio use the tube needs to be used with a minimum voltage of 900 volts.