I am forever lurking the forum with very little contribution, so the time has come for me to participate a wee bit more.
I have wanted to build an amplifier based on the 807 tube, and after pondering many designs, mine as well as many on this forum, I decided the "Vixen" by Miles Prower was an intriguing and exceptional design.
So my first build thread will be this on of the Vixen. I contacted Miles and made sure I was working with the latest information possible and to make sure I he was aware of this project.
One thing I want to do, is to add the delay power on circuit to the high voltage rather than have separate switches. This might be way of a timed relay allowing the heaters time to warm, or possibly a delay relay based on the temperature at the base of the 807's.
I have the Iron on order through Edcor, XPWR108 and 2 of the CXPP30-6.6K, Chokes will be Thordarson NOS 20C54 8H 150mA, and a separate 12.6Vct 2.5 Amp filament out of the junk box here.
Most of my tubes are sitting in a storage unit some 1300 miles away, so I have ordered a couple of matched quad sets of the 807, going to try some USSR tubes as well for comparison. Everything else is NOS RCA/ Tungsol/ Sylvania. I will probably pick up a few other's to play with, and also ordering a few different brands of audio caps. Auricaps among the group as it is specified.
I am very interested in Miles screen regulation circuit, along the lines of another amp I want to build (later) solving the issue with the regulation of the 6146B screen voltage problems.
I am impressed with the phase-splitter incorporated here, and I am looking forward to listening to the sum total of of Miles work here.
Other than a time delay on power up, I do not wish to make any other changes to this circuit.
In my early days I used the 807 in my transmitters as an amateur radio operator, fiddled around with other tubes and always came back to the solid performance I got from the 807. The 6146B being the only other tube that performed to my liking. I did play with the 6293's in the stead of the 6146's for a while and will have to place that one in the pot for my future experiments. On the other side I also fell in love with the RCA 45's and the Sylvania 71A's. Otherwise I did not play around much further.
I do not believe there will be much activity on the project for another couple of weeks, while waiting for the parts to arrive, and planning the chassis for a pair of mono blocks, single separate power supply.
My only regret is that I was unable to tackle this sooner than now, but with retirement settling in, and the promise to myself that when I do retire, I will be able to focus on a proper build.
I welcome all thoughts, suggestions, and critique and look forward to hearing everyone else's thoughts. If all goes well, I should be able to start the fun part of assembly by Christmas time.
Harlan ( I go by Tim to my Friends)
Tim
I have wanted to build an amplifier based on the 807 tube, and after pondering many designs, mine as well as many on this forum, I decided the "Vixen" by Miles Prower was an intriguing and exceptional design.
So my first build thread will be this on of the Vixen. I contacted Miles and made sure I was working with the latest information possible and to make sure I he was aware of this project.
One thing I want to do, is to add the delay power on circuit to the high voltage rather than have separate switches. This might be way of a timed relay allowing the heaters time to warm, or possibly a delay relay based on the temperature at the base of the 807's.
I have the Iron on order through Edcor, XPWR108 and 2 of the CXPP30-6.6K, Chokes will be Thordarson NOS 20C54 8H 150mA, and a separate 12.6Vct 2.5 Amp filament out of the junk box here.
Most of my tubes are sitting in a storage unit some 1300 miles away, so I have ordered a couple of matched quad sets of the 807, going to try some USSR tubes as well for comparison. Everything else is NOS RCA/ Tungsol/ Sylvania. I will probably pick up a few other's to play with, and also ordering a few different brands of audio caps. Auricaps among the group as it is specified.
I am very interested in Miles screen regulation circuit, along the lines of another amp I want to build (later) solving the issue with the regulation of the 6146B screen voltage problems.
I am impressed with the phase-splitter incorporated here, and I am looking forward to listening to the sum total of of Miles work here.
Other than a time delay on power up, I do not wish to make any other changes to this circuit.
In my early days I used the 807 in my transmitters as an amateur radio operator, fiddled around with other tubes and always came back to the solid performance I got from the 807. The 6146B being the only other tube that performed to my liking. I did play with the 6293's in the stead of the 6146's for a while and will have to place that one in the pot for my future experiments. On the other side I also fell in love with the RCA 45's and the Sylvania 71A's. Otherwise I did not play around much further.
I do not believe there will be much activity on the project for another couple of weeks, while waiting for the parts to arrive, and planning the chassis for a pair of mono blocks, single separate power supply.
My only regret is that I was unable to tackle this sooner than now, but with retirement settling in, and the promise to myself that when I do retire, I will be able to focus on a proper build.
I welcome all thoughts, suggestions, and critique and look forward to hearing everyone else's thoughts. If all goes well, I should be able to start the fun part of assembly by Christmas time.
Harlan ( I go by Tim to my Friends)
Tim
sser2:
I will make a reference to older threads here where I came upon this circuit. The second of which also has a more current update zip file. I know if you message Miles, he would make sure you get the right version.
Once I get Miles permission to post the schematic (with values) I will be happy to put that up here. I won't assume though when it is another person's design.
Higher power amps using 807's or 1625's
RH807 push pull ?
Also there is an article Miles wrote here on the forum on the 807:
Featured Vacuum Tube: The 807 - diyAudio
I really like his design especially with the phase-splitter and excellent screen regulation, something the 6146 requires, as well as the 807.
I hope the threads help and maybe Miles will post a link to the schematic here as well.
Tim
I will make a reference to older threads here where I came upon this circuit. The second of which also has a more current update zip file. I know if you message Miles, he would make sure you get the right version.
Once I get Miles permission to post the schematic (with values) I will be happy to put that up here. I won't assume though when it is another person's design.
Higher power amps using 807's or 1625's
RH807 push pull ?
Also there is an article Miles wrote here on the forum on the 807:
Featured Vacuum Tube: The 807 - diyAudio
I really like his design especially with the phase-splitter and excellent screen regulation, something the 6146 requires, as well as the 807.
I hope the threads help and maybe Miles will post a link to the schematic here as well.
Tim
That is an unusually well thought out amplifier. We will all be very lucky to see a schematic with populated values, as some of the design details are rather complicated.
I would be very curious about the choice of DC heating everything in the amp. That's a decent amount of additional cost/complication in an amp that should be quiet without it (but maybe not?). You could leave space for the rectifying components, heatsink, etc. but build the amp with AC heaters first, then revisit the DC option if hum is a problem (or if Miles comes in here and tells me I'm wrong).
I would be very curious about the choice of DC heating everything in the amp. That's a decent amount of additional cost/complication in an amp that should be quiet without it (but maybe not?). You could leave space for the rectifying components, heatsink, etc. but build the amp with AC heaters first, then revisit the DC option if hum is a problem (or if Miles comes in here and tells me I'm wrong).
The rise of SS rectified B+ supplies can be "softened: by adding a negative temperature coefficient (NTC) inrush current limiting thermistor between the diodes and the PSU filter. Candidate parts are (IMO) the CL-90 and CL-130.
audiowize:
I am not planning on DC heating at this time, like you say is something I can consider if hum is present. I sent Miles a PM inviting him to come chime in during this build, so hopefully he will also share his thoughts.
Eli: I have ordered the CL-90's and thinking have them here to test with as well.
Kenneth: My first goal here is to maintain the design, listen to it and consider future changes based on performance. The transformer I will use is the Edcor CXPP30-6.6K which does not have any extra winding's, (cathode Bias, feedback, ..) and it will be hard not to tinker too much until after completing the build, but I do want to stick to the design until the completion. In the long run the build will take on a life of it's own, and with careful study, testing and listening, I am sure that improvements can be found with any design. I like your input here, some things to consider and test during the exploration phase of the circuit and as audiowize mentioned, this is an unusually well thought design, so I am very excited to explore as much as I can and learn what the Vixen has to offer. As an engineer, the tinker bug is always prevalent, and as a musician the ear is always reminding the tinker bug to behave.
This is going to be fun!
Tim
I am not planning on DC heating at this time, like you say is something I can consider if hum is present. I sent Miles a PM inviting him to come chime in during this build, so hopefully he will also share his thoughts.
Eli: I have ordered the CL-90's and thinking have them here to test with as well.
Kenneth: My first goal here is to maintain the design, listen to it and consider future changes based on performance. The transformer I will use is the Edcor CXPP30-6.6K which does not have any extra winding's, (cathode Bias, feedback, ..) and it will be hard not to tinker too much until after completing the build, but I do want to stick to the design until the completion. In the long run the build will take on a life of it's own, and with careful study, testing and listening, I am sure that improvements can be found with any design. I like your input here, some things to consider and test during the exploration phase of the circuit and as audiowize mentioned, this is an unusually well thought design, so I am very excited to explore as much as I can and learn what the Vixen has to offer. As an engineer, the tinker bug is always prevalent, and as a musician the ear is always reminding the tinker bug to behave.
This is going to be fun!
Tim
That'll be fine. I didn't do it because it's such a PITA, and so made text parts lists.
The Vixen was the first hollow state design I did. Everything else was always solid state, and transistors don't have heaters. DC heater power isn't necessary here because the signal levels aren't all that low, and the Vixen doesn't use any DH types. I did another hollow state project that uses AC on the heaters, with a floating secondary and it doesn't have hum issues.
Tim, We've been waiting for a year to hear how your Magnavox project turned out. 20
Hey 20to20:
No worry! see, everyone confuses me with others, in fact I confuse me with others too!
Hope you will stick around for this build, even though..... it is gonna be rather slow at first here. Going to spend some time working up the schematic with values and the small additions I would like to implement, still wagging between the MOV and a high voltage Relay with time delay. Either gets the relay so just pondering the realms.
Miles, thank you and of course I agree on it being a Real PITA, but I am gonna do it anyway for my notes so, just as well share for the sake of the forum and the readers.
Now what I did accomplish, I can see the workbench! and trust me that was an accomplishment. Playing around with some ideas on layout, sorting through what few boxes I did grab during a move, so taking final inventory. Making sure I will have everything at hand by December, except the Russian parts, but that is not an issue. Will work with my old stock first anyway.
So that's the reality of the moment.
Tim
No worry! see, everyone confuses me with others, in fact I confuse me with others too!
Hope you will stick around for this build, even though..... it is gonna be rather slow at first here. Going to spend some time working up the schematic with values and the small additions I would like to implement, still wagging between the MOV and a high voltage Relay with time delay. Either gets the relay so just pondering the realms.
Miles, thank you and of course I agree on it being a Real PITA, but I am gonna do it anyway for my notes so, just as well share for the sake of the forum and the readers.
Now what I did accomplish, I can see the workbench! and trust me that was an accomplishment. Playing around with some ideas on layout, sorting through what few boxes I did grab during a move, so taking final inventory. Making sure I will have everything at hand by December, except the Russian parts, but that is not an issue. Will work with my old stock first anyway.
So that's the reality of the moment.
Tim
I am almost done with entering the schematics with values, learning curve since I am working with a new schematic program. I should get that posted soon, and will post this with no changes at first as a reference. Adding the time delay or other surge control will follow.
I had another delay though that just had to take precedence in a nice pair of Klipsch Heresy speakers in good shape, for a pittance of value. At 99 dB advertised sensitivity, it was something I could not pass up.
Tim
I had another delay though that just had to take precedence in a nice pair of Klipsch Heresy speakers in good shape, for a pittance of value. At 99 dB advertised sensitivity, it was something I could not pass up.
Tim
Quick update
I made the changes to add a delay relay to the high voltage lines, and positioned the MOV to be series to the line. This allows using the filament winding for the delay board and maintains the 12.6 Vct transformer for the filaments.
I will do a PCB layout for the relay board, and I chose the RTE24005F relay with a max switching of 400VAC. Still looking for a more durable solution there.
For the FQPF1P50 I had to go with a FQB1P50TM due to availability.
Now to wait for everything to get here. I need the time though to finish changing things here to open up more bench space and add the speakers.
All goes well Ill be building before Thanksgiving, hopefully sooner.
Tim
I made the changes to add a delay relay to the high voltage lines, and positioned the MOV to be series to the line. This allows using the filament winding for the delay board and maintains the 12.6 Vct transformer for the filaments.
I will do a PCB layout for the relay board, and I chose the RTE24005F relay with a max switching of 400VAC. Still looking for a more durable solution there.
For the FQPF1P50 I had to go with a FQB1P50TM due to availability.
Now to wait for everything to get here. I need the time though to finish changing things here to open up more bench space and add the speakers.
All goes well Ill be building before Thanksgiving, hopefully sooner.
Tim
Attachments
Quick update:
Parts are rolling in now, so a little light to the project. Waiting mostly now on Iron, meters, and cable/wire. I ordered special connectors for power supply to mono-block cabling and that estimate is right around Christmas.
Working on a couple of PCB Drawings, meter control boards, power supply, bias boards, and then will finalize Miles schematic with the minor changes.
I am considering going 5R4 rectification as well, just not sure yet, but would help the time factor to high voltage enable. Plus it adds that (as miles would say) that glassy glowing shiney part.
Having to revamp my little bench and area, to incorporate the new Klipsch Heresy's, but they make a perfect addition and companion to an amp like the Vixen.
Tim
Parts are rolling in now, so a little light to the project. Waiting mostly now on Iron, meters, and cable/wire. I ordered special connectors for power supply to mono-block cabling and that estimate is right around Christmas.
Working on a couple of PCB Drawings, meter control boards, power supply, bias boards, and then will finalize Miles schematic with the minor changes.
I am considering going 5R4 rectification as well, just not sure yet, but would help the time factor to high voltage enable. Plus it adds that (as miles would say) that glassy glowing shiney part.
Having to revamp my little bench and area, to incorporate the new Klipsch Heresy's, but they make a perfect addition and companion to an amp like the Vixen.
Tim
Some things that I have done when delay is necessary but I don't want to stuff the chassis full of boards/parts:
1. Get a rotary switch with at least 3 positions and 2 poles. For the first position, just send power to a heater transformer to warm up your tubes. For the second position, send power to both the heater transformer and HV transformer. The last time I bought such a switch, it was about $8.
2. Use tube rectifiers. You can get some rectifiers that take considerable time to warm up, and this will generally provide sufficient delay.
3. Do nothing. 807s are tough buggers, they aren't going to mind the stress that comes with turnon, and they frankly aren't particularly expensive to replace if you need to.
1. Get a rotary switch with at least 3 positions and 2 poles. For the first position, just send power to a heater transformer to warm up your tubes. For the second position, send power to both the heater transformer and HV transformer. The last time I bought such a switch, it was about $8.
2. Use tube rectifiers. You can get some rectifiers that take considerable time to warm up, and this will generally provide sufficient delay.
3. Do nothing. 807s are tough buggers, they aren't going to mind the stress that comes with turnon, and they frankly aren't particularly expensive to replace if you need to.
If you want a startup delay but also want to avoid complication, here's a two switch scheme. Doesn't matter which switch you throw first.
https://3.bp.blogspot.com/-g7SWDsqQ7pc/UGtx4nACCkI/AAAAAAAAXVM/LS7gcf8PWvM/s640/dual_switch.gif
John
https://3.bp.blogspot.com/-g7SWDsqQ7pc/UGtx4nACCkI/AAAAAAAAXVM/LS7gcf8PWvM/s640/dual_switch.gif
John
Nice thoughts, yes things I am exploring. I will get a schematic up of the power supply this weekend, it's just been kinda hectic here, inventory all the smaller parts that came in yesterday from Mouser. I really made a mess of things when I decided to put speakers in here, so am still working at relocating items that had storage. I am really liking the 5AR4 thought since it slows things down naturally and I really think it will add to the look of the supply. I found a relay that is within the spec's of the high voltage for switching and time delay there is no big factor. I agree the 807 tubes are rugged brutes and very forgiving but, there is no reason for me not to be nice to them either, I do have the time to make sure things are right. I might even go 5AR4 plus a relay and for giggles, a switch for power, then another for heaters, then one more for high voltage, but only after the relay kicks in and sounds an alarm that the heaters are warmed, alarm hmmm... lets see an old school bell.. ok enough of my weird humor.
I was sort of leaning towards the single switch thing and walk away, so is the why I was thinking the delay relay but as I pondered on other things, it gnawed on me that we never thought of delay a lot in the old days, and I remember when we started converting transmitters from tube to SS rectifiers was when we had issues if we did not have switching to the plates.
Anyway Thank you Audiowize and nerdorama, appreciate the input , and keep it coming.
Ill get that schematic up hopefully by tomorrow and we go from there.
Tim
I was sort of leaning towards the single switch thing and walk away, so is the why I was thinking the delay relay but as I pondered on other things, it gnawed on me that we never thought of delay a lot in the old days, and I remember when we started converting transmitters from tube to SS rectifiers was when we had issues if we did not have switching to the plates.
Anyway Thank you Audiowize and nerdorama, appreciate the input , and keep it coming.
Ill get that schematic up hopefully by tomorrow and we go from there.
Tim
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