Yes, if you look at the datasheets, these output transformers don't perform that bad when used at 5k or 2.5k.
Max DC bias seems to be around 90mA, which is quite substantial.
So for near symmetrical bias, something around 8-10W output power will do.
With the 5k impedance you could get a bit more output power (about 10-17W), although with a little less low-end (see Hammond datasheet).
In that case just find a nice tube with a max plate dissipation of around 35-40W
Or with the 2.5k impedance you could get little less power (7-9W or so) but with better low end.
In this case we are limited by the max DC current of the output transformer.
So you won't get much more from a tube with a plate dissipation more than 25W.
So something like a EL34 or similar will work fine around 250-270V or so.
I am sure there are some very nice television tube equivalents that can be used here as well!
I just don't know them all by heart.
It depends on if you care where the tubes were made and if they use a plate cap or not. US and Euro tubes tend to cost more than Soviet or Chinese tubes.
Personally, I'd probably use 12AV5GA (Octal) or similar, strapped as triodes, running 300V - 320V B+ and connecting a 4R load to Black and White on the secondary (reflected load 1k25) with an idle of 80mA for 24W dissipation and about 10W out.
Other good choices are 12GE5 (Duodecar), 12GT5 (Novar), 12BQ6 (octal with plate cap), etc.
Basically, any sweep tube with a Pd of 24W strapped as a triode will work here.
Koda
Personally, I'd probably use 12AV5GA (Octal) or similar, strapped as triodes, running 300V - 320V B+ and connecting a 4R load to Black and White on the secondary (reflected load 1k25) with an idle of 80mA for 24W dissipation and about 10W out.
Other good choices are 12GE5 (Duodecar), 12GT5 (Novar), 12BQ6 (octal with plate cap), etc.
Basically, any sweep tube with a Pd of 24W strapped as a triode will work here.
Koda
The A Number One problem with these types is that the most linear part of the characteristic lies well within red plate territory: see, for example: 6BQ6GA. This is why the specs don't mention any audio usage. The HD types work best as Class AB, push-pull pairs. The other problem is the low screen voltage that males using them as pseudotriodes (or in ultralinear) difficult.
As for pseudotriodes, your best choices are probably the 6AV5 or 6BQ6 since both types are very similar with the only difference between them is a plate top cap (6BQ6). They seem to be able to take over screen voltage without poofing, and the pseudotriode characteristics are quite like the 2A3.
The most linear portion of the characteristic of many audio triodes is firmly in red plate territory too.
Vertical deflection pentodes can normally take screen voltages approaching the plate voltage. They may do better trioded. But the biggest ones I know of are 19 watts dissipation, and most of them 12 to 14. Quite a few vertical deflection triodes out there with some pretty damn high perveance, and will get you close to pentode efficiency. Might be maddeningly short of 6-8 watts single ended though, as the typical dissipation limit is 9 or 10 watts. The 4-5 watt level should be easily do-able.
Vertical deflection pentodes can normally take screen voltages approaching the plate voltage. They may do better trioded. But the biggest ones I know of are 19 watts dissipation, and most of them 12 to 14. Quite a few vertical deflection triodes out there with some pretty damn high perveance, and will get you close to pentode efficiency. Might be maddeningly short of 6-8 watts single ended though, as the typical dissipation limit is 9 or 10 watts. The 4-5 watt level should be easily do-able.
Hello Stenak:
there are a few to chose from. SmokingAmp has provided some Triode curves for a bunch (in this Thread). Attached is a great document to use as a reference when choosing a tube. I have a small stash and will likely use the 6he7 tube. Don has indicated the rectifier section can be avoided and the tube should be able to dissipate in the range of 20W. I think it is worth an experiment given the price.
Another proven yet less power is the 6lu8,@ 3W triode, ~5W UL.
Good luck.
there are a few to chose from. SmokingAmp has provided some Triode curves for a bunch (in this Thread). Attached is a great document to use as a reference when choosing a tube. I have a small stash and will likely use the 6he7 tube. Don has indicated the rectifier section can be avoided and the tube should be able to dissipate in the range of 20W. I think it is worth an experiment given the price.
Another proven yet less power is the 6lu8,@ 3W triode, ~5W UL.
Good luck.
Thanks for all the nice and good information. Have tested the 125SE for Hammond and I "feel" after many listening sessions, that they are NOT "worse" or better than Edcor's SE output transformers, Hammond's 16 series, are audibly better than the 125 series, but they are also sold at a completely different price . I'm going to sit down just over the New Year and check what old TV tubes are available, and how they fit with the transformers I have, and then I'll see what I can find in terms of schematics. Thank you all very much for all the help and good advice. Have a Merry Christmas and a Happy New Year. I really do not care where they are built, cause I am not going to speak to them!
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6P45S, 6KG6, EL509........ in triode or 6C4C or 4P1L in parallel, 12/6AV5GA, 6CB5/A
https://www.bartola.co.uk/valves/tag/6c4c/
https://www.diyaudio.com/community/threads/2a3-versus-6b4g-6c4c.399150/
from dissident-audio.com:
Had a trip to ebay and looked at tubes that were once made for use in TVs. Found, among other things, 12AV5GA, which was recommended. If I'm going to buy a pair with shipping from the USA, where most of the TV tubes are produced?, then a pair costs 1200 NOK, which is around 120 USD. Maybe not so cheap anymore to buy TV tubes? Have to check European sellers to see what is available here in Europe.
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TV tubes were produced in Europe in great quantities as well and some can still be found cheap.
PL36 works great in triode. It has a 300mA heater (25V) and topcap anode connection. There are also 6,3V versions with and without topcap. You pay more for these. Dissipation rating is similar to the 6AV5 (12W vs 11W).
EL/PL504 is a bit bigger, but needs a magnoval socket.
The big EL/PL509/519 is getting expensive.
PL36 works great in triode. It has a 300mA heater (25V) and topcap anode connection. There are also 6,3V versions with and without topcap. You pay more for these. Dissipation rating is similar to the 6AV5 (12W vs 11W).
EL/PL504 is a bit bigger, but needs a magnoval socket.
The big EL/PL509/519 is getting expensive.
Hello again Stenak:
looking back at your post 1842. It seems to me you are interested in the entire family of Horizon Sweep tubes. That is a pretty big list to consider. Attached is a spreadsheet that was developed by P.Millett (I think) a few years ago. It will give you many options to consider. For 6-8Watt output I speculate something in the range of 20Watt+ dissipation should do the trick. If you go with odd ball heaters the tube price will be quite a bit less. Finding a proven circuit will be tricky. You may need to develop your own, or get help from the group here.
sorry about the pdf it was the only way I could attach it. It should get you started at least.
looking back at your post 1842. It seems to me you are interested in the entire family of Horizon Sweep tubes. That is a pretty big list to consider. Attached is a spreadsheet that was developed by P.Millett (I think) a few years ago. It will give you many options to consider. For 6-8Watt output I speculate something in the range of 20Watt+ dissipation should do the trick. If you go with odd ball heaters the tube price will be quite a bit less. Finding a proven circuit will be tricky. You may need to develop your own, or get help from the group here.
sorry about the pdf it was the only way I could attach it. It should get you started at least.
Those are $5 tubes at the major online sellers in NA that have them. 6AV5GA are $8. Don't shop on ebay if you want a deal.
jeff
The way to get BQ6’s is the 17 or 25 volt version from RES. They are cute little tubes. The innards are tiny - not any bigger than a 50C5 inside. But the math says they can do 30W per pair off cheap iron without doing anything crazy. Not really a single-ended solution though, unless you’re looking for 4-5 watts (and then SE iron still costs because a $20 power toroid is out). For that, there are better.
