re: Gratewhitehuntr
The 6P31S and 6CM5 are only 10 Watt plate dissipation tubes, not exactly the right stuff for a 500 Watt amp.
On that 6JH5, I think you mean 6HJ5. 6JH5 is a HV beam triode (rarely useful).
6HJ5 is $4 here: 6C to 6LY8
A nice tube for a 75 to 100 Watt home Amp. (no plate cap)
You should also consider 36LW6 (40 Watt Pdiss) for $11 here:
Tube List range 13CW40 - 90C1 @ ESRCVacuumTubes.com
I think George has gotten 250 Watts from two of them. In any case its the biggest sweep tube around for cheap. (there is also the similar 6KG6/EL509/6P45C too, which might well be cheaper in quantity, and uses a standard 6.3V heater, check Epay for 6P45C)
That 2x600 Watt Amp was intended for PA use. (limited low freq.) The OT doesn't look big enough for a Bass/Sub Amp. Rather minimal looking power supply too. The idea of just building stackable output stages with a master driver is interesting.
As you mentioned, the OT secondaries would need additional taps if the load Z is always the same speaker (versus # of amps in parallel). I think the PA amp was designed for a matching variable # of speakers in parallel too. (So each amplifier always sees the same loading. Equivalent to N # of individual amplifier/speakers, just saving on cabling by paralleling up the speaker wires.)
The 6P31S and 6CM5 are only 10 Watt plate dissipation tubes, not exactly the right stuff for a 500 Watt amp.
On that 6JH5, I think you mean 6HJ5. 6JH5 is a HV beam triode (rarely useful).
6HJ5 is $4 here: 6C to 6LY8
A nice tube for a 75 to 100 Watt home Amp. (no plate cap)
You should also consider 36LW6 (40 Watt Pdiss) for $11 here:
Tube List range 13CW40 - 90C1 @ ESRCVacuumTubes.com
I think George has gotten 250 Watts from two of them. In any case its the biggest sweep tube around for cheap. (there is also the similar 6KG6/EL509/6P45C too, which might well be cheaper in quantity, and uses a standard 6.3V heater, check Epay for 6P45C)
That 2x600 Watt Amp was intended for PA use. (limited low freq.) The OT doesn't look big enough for a Bass/Sub Amp. Rather minimal looking power supply too. The idea of just building stackable output stages with a master driver is interesting.
As you mentioned, the OT secondaries would need additional taps if the load Z is always the same speaker (versus # of amps in parallel). I think the PA amp was designed for a matching variable # of speakers in parallel too. (So each amplifier always sees the same loading. Equivalent to N # of individual amplifier/speakers, just saving on cabling by paralleling up the speaker wires.)
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As stated I didn't understand the inherent challenges of low frequencies when starting this thread.
6CM5 is highly documented and cheap. I didn't have it in mind for 500w, rather something newbish. They were in the Philips amps Mississippi linked to.
Thank you for clarifying 6JH5 vs 6HJ5.
Are we of the opinion that ESRC, VT.net are always more desirable than an ebay seller with what appear to be NOS? (excellent boxes all straight pins)
What % premium would you be willing to pay when buying from ESRC, etc?
I like the 36LW6!
SMPS would be a must for any monster amp.
PL509 @$30 ea vs 36LW6 @$10 ea is enough to buy a 36v supply for the heaters with the savings from a single tube.
Also easier to get amperes @36v, assuming something like this is acceptable 180W 36V 5A Single Output Switching Power Supply for LED Strip Light AC to DC | eBay
Heater current is .45A on 36LW6, would there be problems with something in that class driving 6 heaters?
I expected those PA amps were driving large obnoxious horns that sounded like Charlie Brown's teacher.
In the case of dual voice coil speakers it would be simple to connect one amp to each coil. No changes.
Yeah I'm way behind the ball but less of what I'm reading looks like Greek, even compared to yesterday.
6CM5 is highly documented and cheap. I didn't have it in mind for 500w, rather something newbish. They were in the Philips amps Mississippi linked to.
Thank you for clarifying 6JH5 vs 6HJ5.
Are we of the opinion that ESRC, VT.net are always more desirable than an ebay seller with what appear to be NOS? (excellent boxes all straight pins)
What % premium would you be willing to pay when buying from ESRC, etc?
I like the 36LW6!
SMPS would be a must for any monster amp.
PL509 @$30 ea vs 36LW6 @$10 ea is enough to buy a 36v supply for the heaters with the savings from a single tube.
Also easier to get amperes @36v, assuming something like this is acceptable 180W 36V 5A Single Output Switching Power Supply for LED Strip Light AC to DC | eBay
Heater current is .45A on 36LW6, would there be problems with something in that class driving 6 heaters?
I expected those PA amps were driving large obnoxious horns that sounded like Charlie Brown's teacher.
In the case of dual voice coil speakers it would be simple to connect one amp to each coil. No changes.
Yeah I'm way behind the ball but less of what I'm reading looks like Greek, even compared to yesterday.
Too late to edit, I meant LESS LIKE GREEK sheesh
FRom TubeCad Journal
" Your last issue addressed low cost or "free transformers". I think I have found another source of cheap power. My latest amp used 4 36LW6 (AES has them on sale) sweep tubes. The filaments are connected in series and driven with a bridge rectifier and cap directly off the line. You can find "industrial transformers" on ebay for about $20 for a 500 watt unit. You need one with a 480 volt primary and 120 volt secondaries. Hook it up backwards. This results in about 450 - 500 volts with a choke input filter and 600 volts with a cap input. 600 volts will drive the 36LW6's to over 100 wpc. I am currently experimenting with cathode feedback and direct coupled screen drive with these tubes."
http://www.tubecad.com/october2000/page23.html
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NEVER do this. I know that these tubes were designed to have their heaters powered directly from the AC line. They were also designed when TV's were housed in plastic or wood boxes with insulated knobs. You are looking to build an amplifier which could be made of, or connected to something metal that the user would touch, a turntable, CD player, or even an electric guitar. If the tube develops an internal short (not uncommon) the wall outlet will be DIRECTLY connected to whatever is plugged into your amp.
Powering the 36 volt tubes from a 36 volt SMPS is a good idea, and is exactly how I plan on feeding my 35LR6's or 36LW6's. Note that tubes suck a lot more than their rated current when first turned on, so you need to use an oversized SMPS. A 5 amp supply should work with 6 tubes.
This works, and is exactly how I built the power supply in a big amp I made. I used a 480 volt industrial control transformer feeding a vacuum tube voltage doubler to make 1100 volts for a pair of 845 tubes.
You can also just use one of these to power an amp up to 250 watts continuously forever, or a bigger amp fed with normal music. When 13GB5's were $1 each I bought a bunch. They will run fine on a 12.6 volt (or two 6.3 volt) heater windings and make about 100 watts per pair on 550 volts.
AS-4T475 - 400VA 475V Transformer - AnTek Products Corp
I plan to use 3 of these (or similar toroids) to power my 1KW (500 WPC) tube amp. Big, yes. Heavy, well, with about 70 pounds of transformers...........
Really, I would suggest building something like Petes big red board, boosted to 100 or 125 watts per channel for a first try. It is a proven design that works and has a high probability of first time success. Spend some time searching this and other forums to find out how many people have actually built tube amps over 100 WPC. very few if any of them are first time builders. The probability of success goes down, and the cost of failure goes up quickly as the power level goes up, and the knee in the curve starts getting steep when you go past a pair of KT88's (about 75 wpc).
Read through the entire red board thread for a good education on sweep tube amps.
http://www.diyaudio.com/forums/tubes-valves/151206-posted-new-p-p-power-amp-design.html
OK I won't.
Electric guitar is on the list of probabilities. (easy to build separate tonestack preamp or use some pedals ) I've seen some guitar safety circuit but that wouldn't cover other devices.
donh safety circuit
I've used thermistors to protect filaments from inrush current. They might be a nice $0.32 protection for the heater PS also.
I've been reading like crazy, a steep learning curve has this one 😀
I haven't yet gotten to understand how "output impedance" works. Not load impedance, but reading the OTL threads has muddied the water about output impedance. (and there's a bunch of BS artists)
"Feedback" also seems to get endless use with little distinction between types or locations.
I do have 13GB5 and 25DN6.
Jon at Antek is great, very quiet transformers and reasonably priced.
By looking at a challenging design a person can get a better idea of what the real issues are, IMHO.
For example, considering weight constraints of large amps made SMPS seem like the obvious choice. Why not the same for small amps?
12v power supplies are almost free since LED cam into vogue.
I know it isn't what a purist would do.... I'm not that guy....
Electric guitar is on the list of probabilities. (easy to build separate tonestack preamp or use some pedals ) I've seen some guitar safety circuit but that wouldn't cover other devices.
donh safety circuit
I've used thermistors to protect filaments from inrush current. They might be a nice $0.32 protection for the heater PS also.
I've been reading like crazy, a steep learning curve has this one 😀
I haven't yet gotten to understand how "output impedance" works. Not load impedance, but reading the OTL threads has muddied the water about output impedance. (and there's a bunch of BS artists)
"Feedback" also seems to get endless use with little distinction between types or locations.
I do have 13GB5 and 25DN6.
Jon at Antek is great, very quiet transformers and reasonably priced.
By looking at a challenging design a person can get a better idea of what the real issues are, IMHO.
For example, considering weight constraints of large amps made SMPS seem like the obvious choice. Why not the same for small amps?
12v power supplies are almost free since LED cam into vogue.
I know it isn't what a purist would do.... I'm not that guy....
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