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Dirty-South Blues Harp forum: wail on! >
Clean Up/Update Class A Amp (Silvertone 1471)
Clean Up/Update Class A Amp (Silvertone 1471)
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jplpagan
6 posts
Apr 06, 2016
11:02 AM
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Hey everyone,
Looking for info on cool stuff I could maybe do to improve a little 5w amp.
I think this may be my very first topic post here... I've read a lot of good stuff already on Class A amps on this forum, but thought I'd post about my specific question anyway, in case there was more to learn (isn't there always?).
I have a Silvertone 1471. It is (I believe) a Class A 5w amp similar to the Fender Champ of its day. One 12ax7, one 6v6, and a 6x4 rectifier. Volume knob, tone knob, 8" speaker. Pretty simple. I brought it in to an amp tech recently because it just didn't seem loud at all compared to other amps with similar specs (this is the only amp I own, but I've A/B'd against others).
The amp tech isn't a harp guy, but he did confirm the output was very weak. He's trying to figure out the issue now and, while it's "on the bench", I thought I'd ask the group for suggestions on good fixes or updates to make. For example, I've asked for a line out from the speaker output (as if I know that that means). I've also been told a speaker replacement would probably improve the sound (possible even a 10" speaker?).
Any other thoughts or suggestions? I know it's a pretty simple amp, I'm not looking to make it something it isn't. But I'm also not a purist/collector type—I just want it to be a really good harp amp.
Thanks in advance!
JP
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Barley Nectar
1191 posts
Apr 07, 2016
4:42 PM
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http://www.geocities.ws/rdiubaldi/Silvertone1471.jpg
Replace the power supply caps of course. I'd go with 40, 20, 5 @ 450VDC if you can get them.
You can also use 1n4007 diodes to replace the rectifier tube. This will give you more voltage thruout the circuit. More power, less sag.
Apply cathode bypass caps in parallel with R4 & R7, use 25/25 ecaps.
Replace C1 & C2 with .047/600 signal caps. I like Mallory 150's
Remove C5 (death cap)
You might try a different value on C3
Install 3 wire power cord and ground the chassis on a transformer bolt.
If you go to a 10" speaker, the Eminence Ragin Cajun is very efficient (loud as hell). Don't worry about running a 50W speaker in a 5W amp. If you stick with an 8" go with an Eminence 820H.
BTW, if you do all of this the amp will sound totally different. You may or may not like it???
OR...Go find a Fender VibroChamp, (great amp) and get a standard tuneup on the Silvertone. Good luck...BN
Last Edited by Barley Nectar on Apr 07, 2016 4:51 PM
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jplpagan
7 posts
Apr 08, 2016
8:49 AM
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Thanks for the tips, Barley. Hadn't heard of the Cajun before, I'll have to check that out!
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rainman
197 posts
Apr 08, 2016
8:59 AM
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I have that amp and use a harp tone+ with it and it's a great harp amp without mods. I would recommend removing the death cap for safety reasons.
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markdc70
167 posts
Apr 08, 2016
9:43 AM
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FWIW, My approach would be to definitely change the power supply caps and remove c5. I would change out c1 and c2 to .1uF caps. Then install 220k resistors at the inputs of v1b and v2. Do this in a way as to create voltage dividers there, halving the input voltage. Lastly, install a cathode bypass cap at r11 of 25 to 50uF range, this alone could boost your volume. These mods would allow a little more preamp voicing and volume knob sweep before feedback.
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jplpagan
8 posts
Apr 08, 2016
1:43 PM
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What does replacing the power supply caps do?
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