Supro Delta King 10 Reverb

mjrpieces

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I decided to try a speaker swap in my Delta King and when I fired it back up the reverb sounded completely different. I knew it wasn't due to the speaker so I checked and discovered I had accidentally swapped the leads to the reverb tank. I read through a write-up on the "amplifiedparts" website ( https://www.amplifiedparts.com/tech-articles/spring-reverb-tanks-explained-and-compared ) to try to understand reverb tank circuitry a bit. Looks like there are multiple ways to ground or not ground the tank and its input and outputs so I have no way to know how Supro's reverb circuit is wired. But here's the kicker. I haven't been impressed with the sound of reverb on the amp and have read posts from others that also didn't care for it. But with the wires swapped it sounded really good! It came on faster as you turned up the knob but sounded so much more like a spring reverb should sound. I returned the wires to their "correct" position but am inclined to put them back reversed if I knew it wasn't going to damage anything. Looking for possible explanations and whether it would be OK to swap the leads back again. Thanks
 

mjrpieces

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Wildeman, Don't think it's a phase issue as the signal just goes in and out of the reverb tank from the opposite ends with the wires swapped. What is different is the impedance characteristics for the tank's input and output transducers and the fact that they are then mated to the wrong ends at the send/receive circuits after the swap. I don't know how different the two transducer's paramaters are and why it appears to then totally change the nature of the reverb when swapped. It sounds so much better it's almost as if Supro made an error in the way they wired it up. I'd be curious if anyone else would like to try the swap and report back on what they hear, the difference is very dramatic.
 

Phrygian77

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I'm guessing that's an opamp driven tank. Since other people seem to have issues, maybe you're on to something. I would check to see which cable/jack (does it even have jacks?) is actually sending signal.
 

mjrpieces

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I made a couple of measurements and noted the labeling on the amp's circuitboard reverb connections. It uses RCA plugs (male on the leads to the tank). Measuring into the reverb tank the red lead has a DC resistance of 78 Ω and the white lead reads 223 Ω. On the PC board the white plug is labeled drive and the red is labeled return. I don't want to go much further making any measurement on the amp circuitry and have no idea what this all means. I hooked it back up incorrectly and played some more and then back correctly. After considering what I heard after going back and forth a few times I think what I may have been experiencing is the increased sensitivity making me think it was sounding better. Like when two speakers are A/B'd and the louder one will often sound "better". Oh well, I think I'm done with my accidental experiment.
 

redhouse_ca

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May 13, 2022
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I decided to try a speaker swap in my Delta King and when I fired it back up the reverb sounded completely different. I knew it wasn't due to the speaker so I checked and discovered I had accidentally swapped the leads to the reverb tank. I read through a write-up on the "amplifiedparts" website ( https://www.amplifiedparts.com/tech-articles/spring-reverb-tanks-explained-and-compared ) to try to understand reverb tank circuitry a bit. Looks like there are multiple ways to ground or not ground the tank and its input and outputs so I have no way to know how Supro's reverb circuit is wired. But here's the kicker. I haven't been impressed with the sound of reverb on the amp and have read posts from others that also didn't care for it. But with the wires swapped it sounded really good! It came on faster as you turned up the knob but sounded so much more like a spring reverb should sound. I returned the wires to their "correct" position but am inclined to put them back reversed if I knew it wasn't going to damage anything. Looking for possible explanations and whether it would be OK to swap the leads back again. Thanks
Thanks for sharing that link. That’s the first I’ve seen that and it’s a goldmine of good info.
 

Scooby9261

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Mar 10, 2017
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Interesting. Thanks for posting this info. I am looking into the 12in model and its always good to read up as much as possible about the amp your looking into. Love this site :)
Has anyone messed around with different tube brands etc in theirs ?
 




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