Other Amps

5E7 Bandmaster(Thanks Ethan)

26

I did not build this amp. It was made by a small Dutch boutique builder who has high reputation (for a reason). So I'll get a new pair of power tubes as I need them as a spare anyway. Any of the modern ones you can recommend? And forgive my ignorance: What's the significant difference between 5881s vs. 6L6s?

27

Not a lot. 5881s are smaller and reportedly have slightly less low end but that probably depends on manufacturer. I believe the 5881 was a military tube whereas the 6L6 was designed for the consumer.

For tubes I usually get JJ because most of the new Russian tubes are all made by Sovtek. I have never found a Sovtek power tube which has inspired me. All the modern "Mullards", "Tung Sols", Groove Tubes - they're all badge engineering. I like JJs because they have nothing to do with New Sensor Corp (who helped to destroy the original St Petersburg Svetlana tube company by using their name on inferior tubes in the USA). Real Svetlanas - "winged C" were great tubes but no longer available.

So I like to buy quads of matched tubes from places like Tubesandmore.com or Tubedepot.com - they're very affordable and available matched. Then I have two new tubes for my amp and another matched pair for backup which I should be ok to use without rebiasing.

FWIW your amps looks to be very well put together Sascha. I might have used different parts here and there but that's up to the builder and taste. I don't use carbon comp resistors despite missing out on their massive mojo value because they can add noise and drift in value. I'm happy using carbon film. I can't hear a difference and hopefully they'll last forever. Carbon comp are usually fine, it's what was used in the original amps and most of the time they work just fine!

If the amp was mine I would have cut the transformer wires shorter rather than bundling them but that's more because of my anal neatness than anything else!

28

Sascha, in my experience the odd crackle/seemingly broken speaker noise can also be dirty tube pins/sockets. Worth carefully taking out your tubes one by one, squirting a tiny little bit of WD40 on a Q-tip, and getting any dirt or oxidation off of the tube pins, and cleaning out the tube sockets.

29

Thanks, guys. You're the best. I'll order a matched quartet of power tubes and check this out. The noise doesn't sound like a broken speaker but more like a tiny high frequency explosion. I'll look at the sockets and pins, too. I never got deeper into amps but I like knowing my gear. So this is both informative and fun.

30

One more question: Do I necessarily have to re-bias the amp when swapping power tubes to a matched set or is it okay to give it a listen and decide then???

I guess it's a must when switching from 5881s to 6L6s, right?

31

Do I necessarily have to re-bias the amp when swapping power tubes to a matched set

Yes

32

Matching is the tubes matched to each other. The amp needs to be biased to work with them too. However, if you buy a matched quad and use only a pair you should be fine to use the other pair without rebiasing in an emergency. It is always best practise to check the bias whenever you change output tubes.

Bear in mind this is only for a fixed bias amp. Cathode biased amps like a 5E3 Deluxe or Vox AC30 don't need to be biased. (Although you can bias a cathode biased amp with surprising results - but it's uncommon)

33

So my understanding is that I cannot check myself if it's actually a bad power tube and I need to get the amp to a tech in any case since I can't re-bias myself. Ouch.

34

If you get a bias meter it's really easy to do if the amp has a bias pot. Biasing tubes takes 5 minutes. And a bias meter might cost the same as a visit to a tech!

Have you tried emailing the builder?

35

Sascha, in my experience the odd crackle/seemingly broken speaker noise can also be dirty tube pins/sockets. Worth carefully taking out your tubes one by one, squirting a tiny little bit of WD40 on a Q-tip, and getting any dirt or oxidation off of the tube pins, and cleaning out the tube sockets.

– WB

Play safe. WD40 can cause a whole host of problems if left in a tube socket. Use this.

https://caig.com/deoxit-d-s...

36

Quick update: I contacted the builder and while I know online diagnosing is a difficult thing he is very helpful with any question I have. I can highly recommend Jack and his business. http://www.tubeking.nl/

My amp is very sensitive to the power environment. The room is in the basement of a modern industry building. 16A fuse, one circuit only, unfortunately. If someone switches on the light in the floor room the amp makes a slight crackling noise already. So I wonder if a power conditioner would help. Something like this: https://www.thomann.de/gb/f...


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