Modding a HRD for bass.

Discussion in 'Shock Brother's DIY Amps' started by cqmurphy, Mar 19, 2009.

  1. cqmurphy

    cqmurphy TDPRI Member

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    As it's too big to bring around to most guitar gigs I do (and thus taking up space) and it already sounds too bottom heavy for my taste, I am opting to turn my Hot Rod Deluxe into my main bass amp. The reverb is currently busted and I have used it for quiet home rehearsals for bass before (and LOVED the results more than any bass amp I have owned), so I figure now's the time.

    Right now the only mod I was planning on making was a speaker swap for something that would allow me to use it at medium-sized gig volume. (still deciding whether I should get a new 12" or go 2x10")

    Without going overboard (replacing power transformer, heavy board mods), are there any smaller mods I could/should to make this an even more serviceable bass amp for small to medium gigs?
     
  2. marshman

    marshman Poster Extraordinaire

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    Well, I dunno how well you're gonna like it, but here's a few simple suggestions:

    Replace V1 with a 12AY7. That will significantly reduce the front-end gain.

    Replace V3 with a 12AT7. That will reduce the signal strength hitting the power tubes, allow the 6L6s to breathe a little easier.

    If it's still too gainy, you can try a 5751 or another 12AY7 in V2, but I dunno how much that'll help.

    Of course, neither of those suggestions are gonna change your output level much--it's still gonna be 40ish watts, which ain't all that much in bass circles.

    I've heard that the Winged C (=C=) tubes are one of the most popular new production 6L6GC for bass, so maybe a set of those, biased a bit on the cool side, would improve your tone a bit, but that might just be the most subjective thing in the world..."Which tubes sound best in this amp?"...threads can rage forever.

    If I remember correctly, there's space on the circuit board for another big filter cap--that might help a little with the bass response, too, but be warned, if you don't know what you're doin' in there, those electrolytics can KILL YOU, no lie.

    It's not likely that the speaker is gonna be real happy with high-power bass tones comin' through it, but at something like 101dB, you're not gonna be terribly likely to find anything capable of kicking out sound pressure in that range that likes bass frequencies. Most modern bass cabs are closed back, as well, driving all the sound energy out a port of some sort in the front. You an try to close it off, but that'll really trap all the tranny & tube heat inside the cab, which isn't good for anything in there.

    You're fightin' a seriously uphill battle there, my friend...good luck.
     
  3. tele12

    tele12 Friend of Leo's

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    I think you should probably close the back of it and put a real bass speaker in
     
  4. backalleyblues

    backalleyblues Friend of Leo's Silver Supporter

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    A separate cab would be better for bass tones, otherwise go 2x10" with a new baffle, and don't close the back in-Marshman's right, you'll cook the guts right quick and toast the amp completely...

    Franc Robert
     
  5. Ben Harmless

    Ben Harmless Friend of Leo's

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    I think there are two good options:

    1. Replace the speaker (or go for a 2x10 if you can) and then play with the tubes. Go for a beefy, overrated bass speaker - simply because there's no closed back to cushion the thing.

    2. Sell the amp and use that money plus what you would have spent on the speaker and/or other mods, and pick up a used Peavey bass combo.

    It's a gamble on what's going to sound best, but I've gotten some great bass tones out of guitar amps. Seems like most modern bass amps are so focused on giant lows and super-scooped bass-specific midrange that they just can't do what an old Dual Showman or something can do.

    There is a third option, as mentioned above - and that's to pick up a small bass cabinet. It would probably be your best bet if you like the overall tone of the amp. That's assuming you're willing to carry the extra junk though.
     
  6. wnorcott

    wnorcott Tele-Holic

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    If it were my amp I would just change the speaker to a 12" bass driver, for example like this one that is designed for a vented cabinet. It is an easy swap no baffle work or anything and is replacing the Fender 50 watt 8 ohm speaker with the Fane 300 watt 8 ohm speaker. Just swap speakers and leave the back open like it is.

    http://www.fane-acoustics.com/pdfs/Sovereign12-300_SpecSheet.pdf

    A guy on ebay is selling these for $70 plus shipping. it was Fane Sovereign series 12-300. I think that will be your biggest bang for the buck.

    The speaker is not going to do extreme low bass on 40 watts of tube amp. The speaker is pretty flat from 60-4000 Hz. So it seems like a good match. These are very efficient speakers 100 dB/1 watt which is as efficient as any guitar speaker, so it is going to squeeze about all you will get out of a Hot Rod Deluxe. A speaker has a lot more to do with the perceived volume than adding another 5 watts.

    In my experience playing a bass through a guitar head into a bass speaker, still sounds like a bass.


    Bill
     
  7. cqmurphy

    cqmurphy TDPRI Member

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    thanks all for the many different opinions. I spent some time this afternoon researching the 2x10 option. i have read in a few a places that jensen mod10's are good replacements for ampeg 8x10 cabs and the like. BS or not?

    if it's true, i am considering getting to 8ohm versions of those and running them out of the speaker out/ext speaker outs on the back.

    i am not looking for a particularly "subby" or scooped bass sound. round and clear are what i need; and in my little experience of using this amp at LOW practice volumes, it sounds great.
     
  8. marshman

    marshman Poster Extraordinaire

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    The Mods are pretty ineffecient, so you're not gonna get a whole lot of volume out of them, but I can't actually comment on their tone...I'm stuck in the land of 'more power' as bass goes, and for what it's worth, you'd probably have better results out of a single Jensen Neo 15 than a pair of 10" Mods. But that's totally conjecture, I haven't tried any of them myself.

    A quick scan of AES' website says, however, that a 15" neo will cost about the same as 4 10" Mods. But it might just fit in the HRD cab with a new baffle. Thinkin' out loud, here.
     
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