Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dpm309 on August 15, 2011, 10:56:59 am
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Has anyone performed the "Omega Mod" on a Fender Hot Rod Deluxe? This mod is supposed to give a richer and fuller sound on the clean channel and more drive and sustain on the other channels. There is very little information on this mod, must be a proprietary thing. I did find some other information on hot rod mods that involve changing out components with higher quality components in the PI section and changing a couple of cap values and replacing other caps with higher quality caps such as Orange Drop. Here is one quote:
"If you're interested in trying your own solution, look into the following: change C23 to .0022uF or .0047uF, and add good quality caps of the same values for C18, C5, C6, C7, C2, C10, C24, C25, C26, and C27. Also, add a couple of lower gain tubes in V2 and V3 and your drive channels ought to both be pretty usable."
Others also mention replacing the Master Volume pot with an audio taper pot and putting a NOS 12AV7 in V2. All of these mods would be fairly inexpensive and easy to perform If anyone has any additional information on this mod, please let me know.
Thanks,
Dan
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IMHO the stock HRD sounds cold & sterile clean, with an unpleasant drive tone. After substantial mods, it now sounds like a proper Fender amp. Here's the mods I did (mostly from Justin's Unofficial HRD site):
mods I did to the HRD:
* input jacks > SwitchCraft, chassis mounted
* speaker upgrade > Celestion Greenback, made in England + 2X 10" vox Bullgogs in a custom built (by me) matching ext'n cab
* 12at7's in V 1 and V2
* power tube upgrade > TAD short bottle 6L6's
* carbon comps in the signal path
* orange drops in the signal path
* 470R 5w resistors > 330R 5W (the stock resistors were burning the PCB)
* SAG mod switchable > 150R 25W inductive metal housed power resisitor in the B+ rail
* Plate resistors & 220K power tube mix resistors > carbon comp
* Master Vol pot > audio taper & jumper the attenuating resistor R45
* Mid pot jumper mod (see Unofficial HRD website)
* .022 orange drops in the tone stack; silver mica 250pf cap
* lead mode bass boost
* jumper R102 bright mod for drive channel
* bypass caps for Vol & drive pots
* reverb mods
* diode in B+ rail & .22 orange drop across the last filter cap
* C1 > 4uf
* 22uF cathode bypass cap added to V1b
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I agree with jjasilli, but do the mods incrementally starting with the easy stuff--the tubes. The amp already sounds like a ghetto fuzzbox so reduce noise and fizz by simply subbing a 12AT7 or 5751 in V1 to start. You will get focus and pick sensitivity. Listen to the neck pickup cello sound now. The TAD 5881's
are a great output tube--they have a big round sound, attenuate the ice pick highs, and breakup starts early but gently. The speaker is the next thing--easy but very significant mod. Two Greenbacks in parallel will net 50 watts and will not hold up unless you use an extension like jjasilli suggested. I think a pair of Celestion Vintage 30's would work nicely. Jim