"Upgrading" to a 3-Spring Reverb Tank. Is this hurting my Vibrolux?

[teddycaster]

Hey all Ted here.

I'm a reverb freak. I drench a lot of my tones in it and I have found the Fender "Custom" Vibrolux Reverb (CSR 8) to be the amp for me. I know it gets a lot of shade for its various idiosyncrasies, but it just happens to work great for me. One thing I noticed however was the reverb was a little lacking in comparison to the traditional blackface designs. I don't know much about much but I looked at my reverb pan, 4AB3C1B, and with the code convention I figured if I just updated the "4" to a "9" and leave the impedance values the same I would theoretically get a 3-spring version of what I previously had. I've been using it for ages and as far as I know haven't had any issues and to me it's much lusher and sounds great. I just realized last night after watching an Uncle Doug video on reverb units that the impedance completely changes when it's a 3-spring vs 2-spring. Welp I'm an idiot. Whatever. SO, I recently picked up another Vibrolux and I want to throw a 3-springer in there. I had that "what you don't know can't kill you" mindset before, but now I'm worried that I could be doing something bad to the amp. It's a 8 ohm (2-spring) vs 10 ohm (3-spring) difference from what I understand.

My question is: With the impedance difference, am I doing something bad or is it "acceptable" like running a higher ohm cab. I know I may get flak for that statement but just looking for opinions, no matter how pointed or chill.

Thanks!!

[Bieworm]

That tank isn't going to do much. There is info online on how to fix the reverb with the CVR . I remember changing some cap value in the circuit, which is a pita by the way,and the reverb was lush and splashy.  With the standard tank...

Link attached.. don't do the NFB loop mod because it will kill the raunchy sound to a bland sad charactreless tone
http://www.eaelec.com/ea_sound/amp_article2.htm

That amp has the best tremolo ever on any amp!!! Played mine for 20 years, but since I have my vibro king... well.. it became obsolete

[sluckey]

Nothing bad or unacceptable about what you want to do. The difference between 8Ω and 10Ω is no big deal. Just do it. Let your ears be the sole judge. Ignore all net babble.

[teddycaster]

Bieworm,

I've read a lot about this mod and am thinking about doing it to my other Vibrolux which I currently have the board out of. Question regarding the outcome of this process: Which channel will the reverb live on after this mod you sent? the Normal or Bright? Apologies if I overlooked something. I'm a huge fan of the bright channel and just want to make sure that's where it lives.

Thanks!

[PRR]

....t the impedance completely changes when it's a 3-spring vs 2-spring.

No. Same coil. They measure it at a different frequency. And as said, 8 versus 10 is no real difference.

[Bieworm]

Bieworm,

I've read a lot about this mod and am thinking about doing it to my other Vibrolux which I currently have the board out of. Question regarding the outcome of this process: Which channel will the reverb live on after this mod you sent? the Normal or Bright? Apologies if I overlooked something. I'm a huge fan of the bright channel and just want to make sure that's where it lives.

Mine lived at the bright channel. It was really nice. That mod is worth every drop of sweat. People that didn't play the amp for years are not even closely aware of hox good it is.
One other mzin ingredient is the blue alnico speakers. They add a lot of low end to this lightweight amp.
I ended up modding the hell out of that amp.. even changed the power tx to add a tube rectifier. But the reverb is the most important mod.
I sold it to my co guitarist who owns a 1966 twin reverb. He agreed the CVR was superior and had to have it..

Thanks!

[Bieworm]

Oh and don't waste your time on eliminating the hiss. That hiss is a consequence of what makes it sound so great. Hot amps hiss...

[teddycaster]

Oh and don't waste your time on eliminating the hiss. That hiss is a consequence of what makes it sound so great. Hot amps hiss...

Oh I have no problem with the hiss. I love how gritty and dirty this amp is and how it works with my single coils to really drive and compress them naturally. Im just looking for a little richer verb is all and it sounds more and more like this is something I'm interested inn checking out.

[2deaf]

I just realized last night after watching an Uncle Doug video on reverb units that the impedance completely changes when it's a 3-spring vs 2-spring.

Somebody on some other forum once said that if you could team Uncle Doug up with a fact checker, then you would really have something (no, it wasn't me).

All tank impedances are specified at 1KHz.  The type 4 and type 9 have the same number of turns in their input coils, but the type 9 has a longer core length resulting in a higher inductance.  Inductance is proportional to impedance, so the type 9 has a slightly higher impedance. 

[sluckey]

Somebody on some other forum once said that if you could team Uncle Doug up with a fact checker, then you would really have something (no, it wasn't me).

I don't think I said it but I've certainly thought it lots of times.   

[Bieworm]

Somebody on some other forum once said that if you could team Uncle Doug up with a fact checker, then you would really have something (no, it wasn't me).

I don't think I said it but I've certainly thought it lots of times.   

Nevertheless I find him very entertaining. God I miss Rusty!!!😃

[teddycaster]

I just realized last night after watching an Uncle Doug video on reverb units that the impedance completely changes when it's a 3-spring vs 2-spring.

Somebody on some other forum once said that if you could team Uncle Doug up with a fact checker, then you would really have something (no, it wasn't me).



All tank impedances are specified at 1KHz.  The type 4 and type 9 have the same number of turns in their input coils, but the type 9 has a longer core length resulting in a higher inductance.  Inductance is proportional to impedance, so the type 9 has a slightly higher impedance.

To clarify, it wasn't Uncle Doug necessarily saying it, he featured a breakdown from a manufacturer showing the impedance values and that's when I realized that they are different. Admittedly my phrasing "completely changes" may have been a stretch but it does in fact change based on the document.

Now, he was also saying that at an 8Ohm impedance being the standard because the circuit is essentially a mini amp, you could swap out the pan for a speaker and I suppose get an amplified signal out of it. The reason I questioned this was because I'm not 100% in the know on impedances and I know if your amp asks for an 8ohm load and you throw a 4ohm at it you could screw with the output transformer among other thigs, the difference between 4 and 8 seems small in a grand scheme, but I have no frame of reference when talking about reverb pans, hence the post. Is 8 to 10 a big jump? will that hurt the reverb driver or whatever?? I didn't know but I appreciate all of the input and insight around this. Thanks again.

[PRR]

....All tank impedances are specified at 1KHz.  ......longer core length resulting in a higher inductance. ....

I sit corrected. Obviously true.

[2deaf]

Now, he was also saying that at an 8Ohm impedance being the standard because the circuit is essentially a mini amp, you could swap out the pan for a speaker and I suppose get an amplified signal out of it.

Yes.  This is done sometimes to trouble shoot reverb problems.

Is 8 to 10 a big jump? will that hurt the reverb driver or whatever?

No.  Some people use their amps for years with no tank connected at all and it does their reverb driver no harm. 

[glass54]

Hi teddy
At the risk of presenting useless info see attached doc 
There is a lot of info on various models of spring rev units including input/output impedance's (@ 1kHz  ).
Kind regards
Mirek