Fender Hot Rod Deville

[azrael]

I had an HRD on my workbench this weekend, had to do a few repairs for a friend.
While it was there, I did a few mods.
I wanted to:
increase the treble on the cleans
tighten up the bass
improve the reverb usability
improve drive, make it less harsh, more usable and thicker
So here's what I did:

-removed filter network on reverb control (C52, R103)
-changed the way the mids control was wired
-reduced the 47uF cathode bypass cap on V1 to 10uF
-reduced R9 to 100K to allow more highs and signal
-increased C23 to 10nF to thicken drive
-decrease C2 to 22nF to tighten up overall signal
-remove R105
-change TL072 to OPA2134
-changed master volume to log pot

I think it sounded a lot better, but the drive is still a bit muddy. Cleans were gorgeous though.


Any other thoughts?

[groovtubin]

I had an HRD on my workbench this weekend, had to do a few repairs for a friend.
While it was there, I did a few mods.
I wanted to:
increase the treble on the cleans
tighten up the bass
improve the reverb usability
improve drive, make it less harsh, more usable and thicker
So here's what I did:

-removed filter network on reverb control (C52, R103)
-changed the way the mids control was wired
-reduced the 47uF cathode bypass cap on V1 to 10uF
-reduced R9 to 100K to allow more highs and signal
-increased C23 to 10nF to thicken drive
-decrease C2 to 22nF to tighten up overall signal
-remove R105
-change TL072 to OPA2134
-changed master volume to log pot

I think it sounded a lot better, but the drive is still a bit muddy. Cleans were gorgeous though.


Any other thoughts?

increase last stage cathode to 3.3K, and run a .0047 coupler on that stage. Try running a old fender pi set/up and NFB, pres control doesn`t work the best, but it sure snds great!

jim@Omegamps, home of the HRD mod!!

jim@Omegaamps

[Tberg]

Put a bright-cap, say 100-300pF depending on how much brightness, across the Drive-volume, from signal in to wiper. That should bring back alot of harmonics the that muddy drive. Normally, I'm not too happy with brightcaps all over the place, but here it does the job.

[honeydip]

Hi,

I think you had good ideas. To me it's that simple: The amp is not a great design! The 47uF at the first stage is far to big, so any preceeding stage cannot handle the bass. So good that you lowered that value (try 4.7uF). Another problem with the design is the position of the eq after the second stage, eg lots of signal level but not much you can do with it. BTW the tone stack is not wired the right way. You might try to alter the slope resistor to standard 100K or you might raise to 150K (more mids).

To brighten up the sound it could help to remove all series resistance in the signal chain. You could play around with all cathode bypass caps. For instance if you go lower than 10uF, say 4.7uF at all stages you gonna get some really good sound from the amp. If you are not satisfied with the OD Channel, play around with the coupling caps behind the OD Stages to dial in your sound.

If you want to get really experimental you can implement a marshall eq (HRM) after the OD to shape your OD sound. But that is hard work in an amp on PCB

Send some soundfiles, so we know what you achieved.

Regards
HoneyDip

[Tonegeek]

Don't forget speakers. I had an HRD on my bench a while back and when I used it with my 2x12 cab with G12H-65 speakers it was a different amp. It was fatter and tighter sounding, and not as spikey or harsh as with the stock speakers. It did tame the highs a bit (for good or bad). Some of the change was the cab too, but my cab was open backed and maybe had a bit more cubic inches than the combo.

[Bob-I]

Jeez, I see almost everything you did, but I can't locate C23.

I've heard some really nice tones come from these amps after mods. Post some clips.

[azatplayer]

These are great sounding amps stock! I saw Mike Landau using a pair of 2x12's recently, i assume they were hired backline, therefor stock. Sounded killer.
I had an unmodded 4x10 on my bench a year ago with burned out load resistors on the PI. Fixed that and his ass about speaker wiring he had done, and the thing was very addictive. I think its the best thing fender are doing.
So if you have not replaced the pissy half watt plate R's on the PI, then thats a must. They see the same voltage as the screens.

[martin manning]

Jeez, I see almost everything you did, but I can't locate C23.

Right off of V1a's plate. Who assigned those numbers?!!

[Bob-I]

Jeez, I see almost everything you did, but I can't locate C23.

Right off of V1a's plate. Who assigned those numbers?!!

Ahhh... There it is... Wtf?

[josetxu]

Hi everybody!

I was searching for hot rod deluxe mods and I've seen this post.

I have a 2002 hrdlx with the standard speaker and I'm looking for a more cleanish (and clearer) blackface sound and more headroom (I don't care for the drive channels). I've done the following:

- C1 changed to 22uF: a little more cleaner bass but I not a lot of difference.
- TAD 6L6WGC (short bottle) power tubes biased at 70mv, a little too low with 430Vdc plate voltage, isn't it? but I don't know why everybody recommend bias about 68mv (Fender even 60mV). Anyway with the bias pot maxed I can only reach 75mV (I'll have to check this)
- Tungsol RI 12AX7 in V1 and V2, TAD 12AT7 in V3.
- Changed C5 to 0,047uf
- I also changed R12 to 100K and C7 to 390pf but I think this changed goes in the wrong direction (more bass and, although more high-mids, less mid scoop, isn't it?)
- A wire between the middle and up lug of the mid control

After the mods I didn't seen a lot of difference. I've got break-up at 3 and at that volume it isn't a lot of volume (my '63 vibroverb RI sound a lot louder I think). Yesterday I tried cutting R105 but I think the lows are "cleaner" with it (a very subtle difference anyway). I've thought the following mods:

- My amp has the C56 0,47uf cathode resistor in the second gain stage, reduce it to 22uF.
- R12 and C7 to the stock values
- R9 to 100k
- Add a switch that puts another 0.022uf cap in parallel with C6 for a 0,044uf value (near to the 0,047uf of blackface tonestacks) so I can switch from 0,022uf (more bass) and the other value.
- Reduce R69 (NFBL) to maybe 10K or even less.

What do you think of this mods? any another suggestions?