The xCW5's appears to be a family of miracle tubes. In the 1960ies German musical instrument manufacturer Hohner squeezed 45 watts of output power out of just one pair of PL84's/15CW5's in an organ amplifier. Screen supply was 200 V, but plate voltage was higher by far. Sorry, don't know more Hohner Orgaphon 50 details.
We Europeans only know of UL84, EL86 and PL84 as members of this family.
Best regards!
We Europeans only know of UL84, EL86 and PL84 as members of this family.
Best regards!
My "daily driver" amplifier of the last few years has been a 6CW5 push pull with a 6n2p input and concertina. I'm running power toroids as outputs, garter bias and a regulated screen voltage on the output stage. It's been lovely 
They behave like a little sweep tube almost, great little things.
They behave like a little sweep tube almost, great little things.
Yeah, you look at those curves and one has to wonder why anyone bothered with the EL84 for the 17 watt application (Even for guitar). You can run these ultralinear at 200 volts, too, so I don’t see a downside. How the hell they do this with the same heater power is what one has to wonder about. Dilithium crystals inside the bottle? I can understand about the 6W6 and it’s variants pushing decent current with the 1.2 amp heater. It’s gotta have as close a spacing on the G2 as the big 1-amp horizontal sweeps.
That 45 watt organ would need to be running up at 330V, with 4K a-a. It would be running right at the 12 watt rating (at full power). Regulated G2 is always how you get the most watts (and lowest distortion) in pentode.
Now we’ve got to figure out which small signal tubes to use for the front end. No cheating - can’t just grab a 12AX7 - gotta be one from “the box”.
That 45 watt organ would need to be running up at 330V, with 4K a-a. It would be running right at the 12 watt rating (at full power). Regulated G2 is always how you get the most watts (and lowest distortion) in pentode.
Now we’ve got to figure out which small signal tubes to use for the front end. No cheating - can’t just grab a 12AX7 - gotta be one from “the box”.
My preliminary testing shows at least for DC conditions in triode mode they are very, very close on the Salas preamp PCBs, with no changes other than swapping the tubes over. One would think they are down to just the typical variance among tubes of the same type. Pentode mode I'm not sure.
Once I set up my Behringer UCA-202 I can swap them in/out of my 6CW5 amp and compare distortion I suppose. Would be an interesting comparison.
Once I set up my Behringer UCA-202 I can swap them in/out of my 6CW5 amp and compare distortion I suppose. Would be an interesting comparison.
The 6P43P looks like a significantly cheaper alternative to the 6CW5, even if it biases up a little differently. If the heater draw is similar to the 6CW5, it might be as muscular. I had some 6CW5s go red plate on me on one amplifier build, but then again, I was trying out several risky concepts jammed together, generally asking for trouble...
It looks like the filament draw on the 6P43P is a little lower than the 6CW5...
It looks like the filament draw on the 6P43P is a little lower than the 6CW5...
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George has some thoughts on various 6CW5/EL86 versions. It looks like some versions are more muscular than others.
http://tubelab.com/designs/tubelab-spp/applications/
Apparently the PhilipsECG version from the 1980s is not a keeper. Burns up at only 200V plate and screen, while Amperex and GE worked fine for him.
http://tubelab.com/designs/tubelab-spp/applications/
Apparently the PhilipsECG version from the 1980s is not a keeper. Burns up at only 200V plate and screen, while Amperex and GE worked fine for him.
I was impressed getting over 10 WRMS out of a pair of 6P43P in triode until I got 38WRMS in the same circuit using 6P31S as triodes (and a different bias point). So far, I haven't seen a tube that comes close (ok maybe 6P45S or 6P36S but they are much larger tubes). 6DQ6/12AV5/12GE5/12GT5 (and the like) all only make 24WRMS in the circuit.
No idea how long they would output 38 WRMS sine waves without melting, but for music they are great
Surprisingly, the real world testing shows the same results as VTADIY calculator!
As you can see, I run the tube way out of spec LMAO but J'men câlice! (I don't care but more vulgar).
No idea how long they would output 38 WRMS sine waves without melting, but for music they are great
Surprisingly, the real world testing shows the same results as VTADIY calculator!
As you can see, I run the tube way out of spec LMAO but J'men câlice! (I don't care but more vulgar).
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Yeah, and I’m guessing they make an 8 volt/450mA. Perhaps a buck or two cheaper, too.
There's a schematic ready for download at www.radiomuseum.org. It says plate voltage is 460 V at idle or 370 V at full power; screen voltage is 250 V at idle and 220 V fully driven. No regulation at all
. And, of course, no details on the OT.Best regards!
That’s not as severely overloaded as Koda is doing with his little 6P31’s. That little GT form factor isn’t much bigger than a mini 9-pin, and they’ve been known to stuff the same guts in both from time to time.
I generally don’t like to go overloading tubes in terms of current or dissipation - at least not in something I’m going to keep. When they get older and lose emission you notice it more if you’re trying to get every available mA out of them. With $3-5 TV tubes an extra pair (and pair of sockets) isn’t much of a hardship compared to doubling the size of the TRANSFORMERS, which you simply can’t cheat or it runs up against a wall.
I generally don’t like to go overloading tubes in terms of current or dissipation - at least not in something I’m going to keep. When they get older and lose emission you notice it more if you’re trying to get every available mA out of them. With $3-5 TV tubes an extra pair (and pair of sockets) isn’t much of a hardship compared to doubling the size of the TRANSFORMERS, which you simply can’t cheat or it runs up against a wall.
Got a link to the exact schematic?There's a schematic ready for download at www.radiomuseum.org. It says plate voltage is 460 V at idle or 370 V at full power; screen voltage is 250 V at idle and 220 V fully driven. No regulation at all
Best regards!
They are only overloaded if you believe the datasheet... It was a horizontal sweep tube for B&W sets, the usage of which is a much harsher working condition than an AB audio amp. I find all sweep tubes to have an underrated Pd for audio service.
They are only "fragile" if the plate cap comes off while it's on (screen melts).
Think it's this guy-
https://www.diyaudio.com/community/threads/what-do-you-think-about-this-tube-schematic.309342/page-3
If so, isn't that output combined for both channels?
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Yes, this amplifier features the very same PSU and output section as the Orgaphon 50, but isn't identical completely.
To achieve any schematics from www.radiomuseum.org, you need to search at the website. It isn't possible to provide download links from there, and you're limited at three downloads per day .
Best regards!
To achieve any schematics from www.radiomuseum.org, you need to search at the website. It isn't possible to provide download links from there, and you're limited at three downloads per day
.Best regards!
I had some custom PP-UL OPTs wound by Toroidy and built a Tubelab SPP with PL84s. There are lots of different maximum characteristics available in different manufacturer's data sheets, and I suspect that an EL86 is actually a tougher valve (built to specifications) than a PL84 (built for purpose). Depending on the tube source, max anode and screen can be 170V, 200V or 220V. So if you are building for a tube you have to use the lowest common denominator.
The other snag is that the B+ for the power stage is not enough headroom for the driver and phase splitter, at least not in the design I was adapting. So that turned the project into a power supply exercise. To use my power transformer and get the B+ down to an acceptable level (with no redplating as I had the first iteration) I had to have a low value capacitor/choke input for the lower B+, and then a conventional CRC in parallel for the other stage, which worked fine, but with the right transformer a doubler is probably the best solution.
The other snag is that the B+ for the power stage is not enough headroom for the driver and phase splitter, at least not in the design I was adapting. So that turned the project into a power supply exercise. To use my power transformer and get the B+ down to an acceptable level (with no redplating as I had the first iteration) I had to have a low value capacitor/choke input for the lower B+, and then a conventional CRC in parallel for the other stage, which worked fine, but with the right transformer a doubler is probably the best solution.