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Old 19th February 2012, 12:09 PM   #11
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I've given up using such low-gm pentodes like 6V6, 6L6 etc as triodes. It's not worth it. Horizontal beam deflection tubes make wonderful triodes. Even better are tubes like EL156, F2a, E130L etc.
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Old 19th February 2012, 01:57 PM   #12
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Терпенье и труд все перетрут>>

Does this translate as "patience and hard work poison everything"?
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Old 19th February 2012, 02:12 PM   #13
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I was once besotted with a free spirit - a young Norwegian painter - who used to say "Fornuft ødelegger alt". Sounds like a similar kind of sentiment!

Andy
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Old 19th February 2012, 02:40 PM   #14
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Andy, I absolutely see what you want to point out. And honestly, you're right about that. I don't want to badmouth everything from the very first. But a bit of rationality will keep you away from disappointment.

I have a bunch of 1625 and started with a SE in triode connection. I was absolutely unsatisfied with the output power and first thought something else was wrong. But no...you only get a bit over 1W. Yepp...a single watt from a 25W triode. The output power tenfolded when connected as pentode. I liked the increased dynamic range due to the power reserve much more than the triode sound.
The extremely good STC datasheet shows nearly all topologies with that tube: www.tubezone.net/pdf/807stc.pdf

So, no triode bashing from my side, just don't be suprised when the triode power of your 1624 won't be sufficient.
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Old 19th February 2012, 06:42 PM   #15
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Quote:
Originally Posted by 316a View Post
As a triode 1624 has Ra 2.5k mu 10 so it's like a beefed-up 6V6 . Good for a watt or so SE with 8k output transformer . Two in parallel would be more interesting and could use a 3.5k-4k output transformer but very inefficient , a single 2A3 would do better . Ultra linear probably a better application for this valve .

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The best application (other than as a Class B or Class C RF amp) is PP, pentode. That's what it was designed to do. If it requires any help, then you can always add local NFB and/or gNFB to take off however much "edge" these produce as PP audio finals.

Getting a watt or two from a tube rated for Pd= 25W that'll have to run at Vpp= 600V is absurd. You'd be better off sticking with actual audio triodes (45, 2A3, 6A3) or vertical deflection triodes. If you're not a "sand-o-phobe", then RF power triodes also become a possibility. The horizontal deflection pents wired as pseudotriodes would also be much better.

If you just have to do it, and can live with the results, well, there have been crazier things done.
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Old 19th February 2012, 08:40 PM   #16
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Miles - there is indeed a bit of an ominous silence about using the 1624 in triode. Mountains of them about and if it really were a directly heated 807 then surely somebody would have published a few schematics. But they haven't. Mind, nobody used the 2E22 much and that was a much better choice in triode.

It's looking more like a driver in triode if it's anything. I was debating whether to go on with trying this or using 2a3/6B4G outputs exactly like you say, and frankly it's looking like the 2a3s unless anybody has some bright ideas. I'm still curious to lash up something and have a listen, but motivation is getting a bit rocky!!

Andy
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Old 20th February 2012, 02:47 PM   #17
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Wait and second,

I thought the 1625 was the equivalent to the 807 besides the 6v verses 12v???

I have not researched the 1624. But my amps are based on the specs of the 1625 tube.

Am I missing something?

Here are the specs for the 1624 and nowhere does it say refer to the 807 for specs?

NJ7P Tube Database Search


Now if you look at the 1625 it will refer you to the 807 specs.

NJ7P Tube Database Search

Scott

Last edited by WildOne; 20th February 2012 at 02:50 PM.
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Old 20th February 2012, 04:07 PM   #18
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The 1625 is like a 807. The 1624, though it looks like a 807, biases differently. The 1625 and 1624 are quite different!!

andy
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Old 20th February 2012, 04:43 PM   #19
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Oh Good!

I thought I may be on the wrong track with my 240w mono blocks.

Scott
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Old 1st August 2013, 06:23 PM   #20
yangmei is offline yangmei  China
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Default how many RAC 1624 do you have now?

Quote:
Originally Posted by andyjevans View Post
I have a bunch of 1624 I haven't used, and when considering a 2a3 PP amp I wondered about 1624 in triode instead. Information I have so far is:

- 2.5v filaments at 2A. about 2K Rp in triode, mu about 8-10 (??)
- Operating points are like 1619 or 6V6, not 807 as often suggested.
- Max plate dissipation looks like 15 to 16W, not more.
- Can't find triode curves, so presumably 6V6 in triode is closest?
- Steve Bench reports good results with starved filament
- Can be used as low voltage driver (HT about 200v)
- Some users report microphonics, and also loose plate top caps
- Not sure what value grid leak to use - maybe lower?
- Sound reported as warm and smooth but that's anecdotal
- Probably needs 8K A-A OPT in PP. Maybe 6.6K?

Has anyone any experience of this in triode, and any other information, curves, operating points, OPT values, applications etc?

Andy
hi:
how many RCA 1624 doyou have now? are they all new in original box?
how much are they? if Tthe price good ,I want to buy all of them ,please contact me :yangmei191@hotmail.com
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