Grateful Dead Music Forum

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 #121092  by Mosfed
 Fri Nov 16, 2012 7:27 pm
Has anyone tried this? Success? Issues?
 #121097  by GeneralGoldilocks
 Fri Nov 16, 2012 8:51 pm
I have a jbl e-120 in a hot rod deluxe, which looks like a very similar chassis cabinet, etc.... should be no problem. switching a speaker out in that chassis is kind of annoying, you have to remove the amp chassis section of it entirely to get to the speaker, I also had to buy some different bolts to fit the jbl e 120, but mine had a celestion in it already. It makes the rig pretty heavy, those jbl e 120s are heavy (about 20 lbs), but sounds great.
 #121113  by Jon S.
 Sat Nov 17, 2012 7:09 am
FWIW, here are the differences between the HRD & the BD (the HRD would be the better choice for Jerry tones). Credit to amp tech Steve Dallman:

The first stages are classic Fender except the BD uses a 22uf cathode bias cap while the HR uses a larger 47uf, which will create a bit more low end.

Coupling cap next is .01BD Vs .022 in HRD. Still a little more low end in the HR. The bright switch in the BD is next. This is a non-standard Fender design, which bypasses a 100k resistor with a 750pf cap. As the 100k resistor is attached to the 250k-volume control, it is only effective in clean mode. The drive control in the HR is between the first and second stage.

The second stage is unbypassed in both amps. In the HR the bright switch is a .068 cathode bypass cap that is non-functioning in drive mode.

The tone stack follows the second stage. They are identical except the HR uses a 130k mid slope resistor, while the BD is 100k. This will create a little less low end in the HR.

The drive control precedes the 3rd stage in the BD, a standard Fender bypassed gain stage. The 3rd stage is used in both clean and drive in the BD.

In the HR the 3rd and 4th stages are used in drive only. This tube is unbypassed. In More drive a 1uf-bypass cap is switched in on the 3rd stage and a 22uf bypass cap is switched in on the 4th stage. (The 4th stage is not used in the BD, but is just waiting to be modded in.)

Note on bypassing. The gain in a tube stage is set by 3 components, the plate resistor, (typically 100k in Fenders, larger for more gain) the cathode resistor, (typically 1.5k in Fenders, smaller for more gain) and a bypass cap that bypasses the cathode resistor. The cathode cap is not always used but when it is, it will increase gain in different frequency ranges. 22uf will increase gain across the entire guitar spectrum. Smaller will only raise gain in higher frequencies.

The master for the drive channel follows in both amps. From there the amps are nearly identical, except the HR has somewhat fuller reverb due to the design of the reverb return. (The reverb circuit and the effects loop are solid state.) The HR has an extension speaker jack that uses the 4-ohm speaker tap on the output transformer. The BD has this tap but it is not used (but could be added by a tech.)

In general these amps are similar. The BD will not stay as clean at higher volumes due to the 3rd stage always being active. The HR has “improved” distortion (drive) with “more drive” added. The HR has fuller reverb and an extension speaker jack. Both are good designs with plenty of classic Fender tone.

May I add that improvements can be made to the Blues. The earliest Blues Deville's used the 2nd stage of V2 as a cathode follower just before the PI. In all but the earliest, the 2nd half of V2 isn't used. This can be modded into the drive channel for huge improvement. (See the Blues Deluxe mod in the Technical section at Duncan Amp Pages...)

The reverb can be improved by clipping C50. Bias adjust can be easily added.
 #121126  by JonnyBoy
 Sat Nov 17, 2012 4:13 pm
I use a K120 in HRD and had an E120 in it before the K score. Both speakers make a HUGE difference towards a Jerry tone. The stock speakers suck for that application. You can happily and successfully use either speaker in your Blues Deluxe, and it made a huge difference for me!! Good luck!!!
 #121131  by Mosfed
 Sat Nov 17, 2012 6:02 pm
Thanks to all.

John that's a great post that I read from you on the Gear Page - when the OP completely ignored it and went on his merry way...

My worry was needing to cut a new baffle - 12" speakers are not always the same - so I was happy to get the confirm that at least in the HRD that must have the same baffle - it worked.

I am changing the pot that controls the volume, the tubes and the speaker so I hope it's going to make a good difference. Already banning the drive circuit has made a huge difference in the tone. It would be nice to have something a little more portable than my Bandmaster Reverb / 2 x D120f rig.
 #121430  by Winterland
 Mon Nov 26, 2012 8:02 pm
I did it. Sounds great. way better than with the stock speaker. My Brother in law did a quick mod on it to. I acually sounded good with it but wasn't quite powerful enough. It broke up to soon so I went back to the twin with Weber Californias.
 #122351  by James-T
 Wed Dec 26, 2012 10:17 pm
That's a great rig. I've done the same mod to my Blues Deluxe but with a D120F which fit like a glove. Love the JBL and the amp. Great for pub gigs! I could not believe the fender speaker that came out of my amp, compared to the JBL it looked like a toy, but I did love the way it broke up. The JBL is night and day however, with a really tight bottom end.

I've got a E120-8 sitting around and plan to make an ext cab for it. Got it for $125 when I picked up the D120F.