SuperBee
7137 posts
Mar 20, 2025
1:37 PM
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Recently took my Sonny Jr 2 for service.
Amp is 25 years old now.
I also have a Princeton Reverb which is coming up 47 years.
I think the SJ2 had never been serviced before.
Tech said time to replace some filter caps.
The quandary is, in this particular case the original marketing made a big deal about how every component choice was made in a considered way with lots of A-B testing and decisions taken based on the ears of the designer.
So when it comes time to replace a 40uF Sprague filter cap, do you go with the exact same component, or do you listen to the tech who says the F&T product is better quality and less than half the price?
Oh but also, F&T don’t make an exact 40uF replacement. You can have a 47 or a 30. You might notice a difference in response, or not.
Oh, and then there’s this to consider; component values have a +50%/-10% tolerance factor anyway, so oils ain’t oils necessarily, but then again they could be.
Seems to me that people face this kind of decision all the time when they are maintaining their tube amps. Sometimes they probably aren’t even asked for their input.
Whoever is making the decision, for sure there’ll be a range of decisions taken.
My old Princeton Reverb isn’t even particularly elderly. There’s still a bunch of amps in use that are older than it.
So when you look at old amps, really two examples of the same model could be rather different.
Now I’m going to go fire up the old Sonny Model 2 and see how it goes. I doubt I’ll be able to tell anything other than whether I like it. It’s been probably two years since I last used it. It’s been in the shop since last July!
Maybe I’ll go for a walk with Mr Spaniel before I get too much into it though.
Another milestone today;
About 3 years ago I noted we were about to play a 70th birthday for the first time.
Tonight we are doing an 80th.
I think our amps are all younger than the band members. Probably need a bit of preventative maintenance there also.
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Prento
91 posts
Mar 20, 2025
2:23 PM
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Hi Dave, I think there’s a lot of snake oil when it comes to the marketing of valve amps for different purposes, i.e harp amps. You will notice no difference between a 40uf filter cap and a 47uf filter cap. From what I know, F &T caps are the go now. Sprague are over priced and not necessarily the same quality that they were renowned for. Good luck with the 80th birthday gig.
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SuperBee
7139 posts
Mar 20, 2025
7:06 PM
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Hi Prento. Amp sounds alright to me. I might use it tonight. Or maybe not. It’s such a big lump of a thing and there’s a long flight of stairs to traverse.
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Prento
92 posts
Mar 21, 2025
10:15 PM
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You’ve got to consider the tone vs weight ratio when making these decisions
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