I own (and enjoy) a Velleman K4040 Power amp. I have performed some recent work on improvement (with the help of some experts…lol) and a question came up I am unable to answer.
The core question is “how does this amp achieve 90wpc in its configuration”. According to my ‘experts’ they cannot see how it achieves anything even approaching 50wpc due to its configuration. They have said that it appears to work in triode mode (though Velleman say Ultra Linear) and that what they see Per the tube manuals, a pair in pentode mode is good for 55w with 450v on the plate and 400v on the screen. A pair in triode mode with 400 volts on the plate is good for 12.5 watts. A quad in push-pull-parallel, which this amp runs, would be good for darn close to 25 watts based on those operating parameters
So they are thinking 25wpc. I do not believe Velleman would inflate the numbers as many experts have worked on these with various modifications; I think one of the would have noticed if the WPC were far off.
Can I get someone from TECH SUPPORT to explain exactly how it achieves the listed wattage ? I have indicated that its in ultra linear mode which may account for it but they have said that requires special taps on the output transformers (which perhaps it does). So if you can give me the ultra technical explanation, it would be a great help in my getting further assistance from my ‘experts’…lol I thank you in advance.
The tubes do not run in triode but in penthode mode (see diagram).
Sorry, but due to limited time and staff, we have to limit our support to helping people getting their amps to work.
Providing in-dept circuit descriptions is unfortunately not a service we can offer (although we would like to)…
I understand…but I thought it says it runs Ultra Linear…? The taps are there. when you say see diagram, you mean the schematics ? That is what they are looking at.
Yes, it runs in penthode mode, hence the taps.
They are at 1/3 2/3 if I remember correct.
The device has been developed almost 20 years ago, so the available info is quite limited.
Thank you…I understand it is an older product - so am I …LOL
I just have a bunch of ‘experts’ who can’t wrap their minds or the schematics around the 90wpc.
Now I have almost every piece of data on the internet on this unit. People who created modifications, in-depth …and no one at any time ever questioned the wpc. I think they would have so they seem to know something about the configuration that I cant get across to these folks…
Anyway, thanks again, anything you can provide (if anyone knows) would be helpful…
Basically the issue is this; a PUSH pull pair of 6L6GC or EL34 is approx. 20watts (they say) So two pairs per side would only net 40wpc. Even in UL mode, it would be almost double that, would still not reach 90wpc. And they can’t see that it is in UL mode
Can you tell me in technical terms (that I can share) how it achieves 90wpc output ?
One of the comments I have received
[i]Anyway, power output differences between the EL34 and the 6L6GC still exist. The Sylvania book gives 34 watts in class AB1 push-pull ultralinear operation for the EL34 at 2.5% THD, or 20 watts at 0.34% THD. Those appear to be cathode bias figures too. Figure double that for PPP operation vs PP, and you’d see some more in fixed bias vs cathode.
I’d still like to see a real honest to goodness power, frequency response, and THD measurement on one of these. Someone here has this quote in their sig. I can’t remember who, nor who said it, but “one accurate measurement is worth 100 expert opinions”. A bit of time with the appropriate test gear would tell the story way better than any of us could by quoting stuff out of old books.[/i]
If someone could JUST EXPLAIN how it achieves it and at what THD…Thanks