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NAD-1981 Deluxe Reverb. opinions wanted for improvement

Discussion in 'Glowing Bottle Tube Amp Forum' started by Sterence, Jun 2, 2017.

  1. Sterence

    Sterence TDPRI Member

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    This was in "
    How is your Silverface Deluxe Reverb set up?" thread and I wanted to move it here not to derail that thread.

    It is here! My folks packed it up in a towels and put it a suitcase and schelped it up here on Alaska Air and it seems to have arrived intact.

    It is pretty sweet. Much louder and brighter than my Princeton as expected, but there are some issues that I want to address that I think will make it sound better. So, any and all advice is appreciated.

    Someone though it was a good idea to make it SS state rectified. ugh. Seller did not disclose it when I talked to him on the phone and my dad does not know what to look for when he picked it up. According to the guy I purchased the amp from the amp came to him with the a SS rectifier. There is a gob of Shoe Goo looking stuff over the rectifier tube socket (another ugh). If I do switch back to tube rectification I plan to replace the socket and go with a GZ34 as that seems to be the preferred setup. I know it is not what the original was designed for. But is there a big difference between SS rect. and GZ34? From what I understand the GZ34 s one of the "stiffer" rectifiers. It doesn't look like a hard thing to reverse and I plan on playing it bit before I mess with that.

    I think it could use a speaker up grade. It flubs out pretty bad after low A. Especially power chords. So advice on speaker (maybe a Neo ) that accentuates that Mids and Low end and brings down the highs would be great. And I am probably gonna clip the bright cap. This thing is bright! Cannbi

    Looks like the filter caps are new. That is good!

    Reverb is kinda noisy. Not sure what that is about. And it kinda goes from nothing to lots of verb right at 2.5 on the knob. It would be great to smooth that out.

    It has what look to be a new set of JJ 6v6's but smorgasbord of preamp tubes. There is a EH, a few GTs, a Sylvaiana and some I don't recognize. Not really sure where to go with this. Any advice here would be especially helpful.

    And since I have only played a handful of DR I am not really sure what to expect, but it gets pretty gainy and over driven at ~3-4 on the volume and not much louder after that (but oh boy it is loud) on both channels. Kinda like my Princeton. I was expecting more clean headroom. Is that normal? Is this function of my funky preamp tubes?

    At rehearsal last night it ran really well. On the Vibrato Channel, Vol 1.5, Verb 2.5, Bass 7, Treb 4, it sat well with 4 horns, drums and bass. Never used the bridge PU in my Tele as it was too bright for my ears. Open chords where kinda lost but anything above the 5 fret popped right out. I was standing only 5-7 feet away from the amp so that may have been part of the problem. I am gonna do gig Saturday, I will bring a backup to the gig (a friends Deluxe VM). I see this amp as a great starting place, as I paid $580 for it, to make an awesome gigging rig.

    I have more pics of the guts if that is useful. Thanks[​IMG]

    [​IMG][​IMG][​IMG][​IMG]
     
  2. Sterence

    Sterence TDPRI Member

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    Some close ups of the SS rectifier.
    IMG_7429.JPG
     
  3. theprofessor

    theprofessor Poster Extraordinaire

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    Hey @Sterence - I'm so glad you got this. Very cool! It looks like it's in fantastic shape to me! However, I am not an expert on the insides of amps, so for that kind of stuff, you'll need to wait on the comments of others. However, I'll offer these things:
    • At $580, that is an absolute steal! You should be thrilled. Even if there's stuff going on that you'll need to fix (I'm not saying that there is; I just don't know), that's basically a "silverface" Deluxe Reverb with a black face plate. That is something to be proud of.
    • It's nice that whoever replaced the filter capacitors used F&Ts (Fischer & Tausche). As long as they're the right values, they're supposed to be the best in terms of holding their values and in terms of durability.
    • I'd probably ditch the solid state rectifier, as you're thinking of doing. As far as tube rectifiers go, the GZ34 is the closest thing you can get to a solid state rectifier in a tube. However, the spec tube is a 5U4GB, and I'd definitely use one of those. Provided that the schematic for the pull-boost models hasn't changed since 1976/1977, I think yours would be exactly like those (others can confirm or deny this). One good thing is that those later SF amps are designed to run on 120V A.C. at the wall, which is standard today. But they also have slightly beefed up power transformers, and the voltage runs higher than the older BF Deluxe Reverbs. So in my opinion, the stock rectifier is the way to go. Mine had a GZ34 in it when I got it, so it's definitely do-able. But I am of the opinion that you need to get those voltages down rather than keeping them up. If you do want a slightly "stiffer" sound with a GZ34, I highly recommend sticking with those JJ6V6S power tubes. They can handle the high voltage.
    • If you switch the rectifier, you'll need to re-bias your power tubes. If you simply substitute a 5U4GB for a solid state rectifier and turn on the amp, I guarantee the amp will sound sterile and bad. You'll have to up the tube current to get things sounding good again.
    • I'd probably think about getting a better speaker than the Utah/Pyle that likely came with it (that's what it looks like to me). I don't consider it an absolute necessity, but it will definitely sound better with a better speaker. If you're looking for a classic Jensen C12N sound, I think that Eminence did a great job with the GASC-64. However, for just the reasons you mentioned (brightness), many folks love the Eminence Cannabis Rex in a Deluxe Reverb. Others suggest another hemp-cone speaker: the Tone Tubby 40/40. You may want to give one of those a shot. The Cannabis Rex is cheaper, but is a high-quality speaker (it's an Eminence!). The Tone Tubby is probably a little more articulate and retains more sparkle, but it's not cheap.
    • Your comment about the reverb: Mine is not noisy like yours, but mine does exactly the same thing--kind of "nothing" until 2.5, where it kicks on. And there's a lot of increase in reverb between 2.5 and 3 on the pot! I have no idea why it does that; I'm wondering about that myself. But for noisy reverb, first try replacing valve 3 [V3] (from the right) with a fresh 12AT7. I highly recommend the investment of a Mullard CV4024 from the 1980's. They are worth it. Wonderful sounding, and the tubes in V3 that drive the reverb take a lot of abuse.
    • As for preamp tubes, I suggest pulling out those GT's and finding others. I'm guessing that they're most likely JJ's, which I'm not a fan of in the preamp stage. You can leave any working tube in V5, though, since all it does is run the tremolo. I really like Sylvanias. I'd see what it is. Is it one of the 12AX7's? I'd probably keep it in, if it's anything other than a long gray plate. If it is a short gray plate or short black plate 12AX7, that could contribute to the early breakup. Both the SBP and the SGP Sylvania 12AX7's are characterized by early breakup, though the SPB is more articulate than the SGP.
    • Make sure you have a nice, balanced 12AT7/ECC81/CV4024 in V6--the phase inverter. Again, I highly recommend Mullards there. But you can also find a balanced vintage RCA 12AT7. Those sound very nice and should add some warmth. They're also cheaper than Mullards.
    • Check the fuse, just to make sure it's the right value. That's one place where people sometimes go "full dummy" by putting a higher value in there if they have problems. The fuse must be the spec value.
    • I'd say stick with the JJ power tubes for now, until you figure out what you want for sound. They're not my favorite, but they're pretty good and very tough. DR's are tough on tubes, and you need to make sure your voltages are good before going back to vintage tubes.
    • As far as the amp sounding loud and bright, that can be very typical of Deluxe Reverbs. It is even more typical of SF models, when one combines the DR design with the higher voltages from the transformer and also some of the parts used in the inside of the chassis that tend to sound more brittle. Using the bridge pickup on a tele can be a real bear with a bright DR. A lot of people like "juicing" their amp and getting the gain up. I prefer the opposite. If you want more pleasing tone and clarity, I suggest trying to get the gain down. This is one reason that I recommend switching away from the JJ6V6S power tubes, if at all possible. The treble is kind of "hard," the bass is boomy, and they make the amp sound kind of "juiced." Also: try plugging into input #2. You'll get clarity without being so strident. As far as overall effect, it will be similar to putting a lower-gain tube in V2 or whatever, like a 12AY7. I've begun plugging into the low input (input 2) instead of the high input, and I really like the effect. I also play a tele, so I know what you're dealing with!
     
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  4. Ringo

    Ringo Poster Extraordinaire

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    It's possible that you could pull the glob of silicone off cleanly and reuse the rectifier tube socket, I'd certainly try to do that.
    Either way if you can salvage the socket and rewire for a rectifier tube, or have to use a new socket, I'm sure you'll need to rebias , and as mentioned don't use a GZ34, a 5U4B is what you need for that amp, there are a lot of those available NOS or even used old stock.

    Personally I'm not of the opinion that you have to use NOS Mullard tubes to get good tone, and not all Mullards are the same either for that matter.If you choose to get NOS tubes that is fine of course, there are plenty of NOS and again good used 12AT7 and 12AX7 tubes around. RCA, Sylvania, Phillips, pulls from old organs which may be labeled Baldwin , Hammond etc...
    But some new production 12AX7s and 12AT7s sound good too.

    Another trick is try a 5751 tube in place of a 12AX7 for the normal or reverb channel ,it helps smooth things out a bit IMO.

    A lot of folks clip or desolder one leg of the bright cap on the reverb channel volume pot to tame the brightness, I haven't done that yet on my 79 but I may the next time I pull the chassis out. I did it on the last DR I had and felt that it improved the tone a lot.

    I'd say get the rectifier tube sorted out, rebias and then you can see about swapping tubes, even now you can try different 12AX7s that you have in different positions to see if you prefer one brand over another, the first and second 12AX7s are the normal channel and then the reverb channel preamp.

    That's a really clean amp and you got a good deal on it, even if it needs some TLC.

    That looks like the same speaker that was in my 79, apparently it is a Pyle speaker, and they sound pretty good.
     
  5. mad dog

    mad dog Friend of Leo's

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    Great post from the Professor! Excellent suggestions. Especially on the rectifier. DRs sound better to me with slightly lower plate voltage. The GZ34 works well, but can make the OD sound a bit harsh. A better speaker can make all the difference. I'd try a Celestion Heritage 12-65 first, based on experience with similar amps. The CRex would be another excellent choice. Almost any NOS tubes beat the newer stuff in these amps. I'm talking preamp here. JJs are a great choice for power tube, though it is a more hardass type of sound than more traditional 6v6s. But still a good sound.

    Reverb is the luck of the draw on these amps. Some tanks are great, others not so. If you have a known good sounding reverb tank from another amp, it would be worth a try here. My BFDR had so so reverb. Others I heard from the same vintage, much better. Could just be the variability in tank quality, is my guess.
    MD
     
  6. JDRNoPro

    JDRNoPro Friend of Leo's

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    That's a great amp and a great deal!

    Good advice and info from others above. I would want to go back to a tube rectifier too. A couple other points: 1) Whatever tubes you use, you need to check bias of power tubes to hear the amp at its best with those particular power tubes. It can make a big difference. 2) V2 preamp tube position has the most tonal influence. Put your best 12ax7 there.

    Some additional comments: While I like to use old glass, I also like the reissue Tung Sol 6V6 and 12ax7 tubes pretty well. As far as speakers, is that one an Oxford? Whatever it is, box it up and hang onto it for "originality." I have a Weber 12F150 in my 74 SFDR, but if I was doing it again, I'd probably go with a 12" WGS "Jensen C12N copy" with ceramic magnet - WGS G12C. I really like those speakers and they are very reasonably priced.

    Congrats and enjoy!
     
    Last edited: Jun 5, 2017
  7. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    The Pyle speakers are very hit or miss. After changing output tubes and biasing it if it still farts out I'd replace the speaker; don't worry about saving it, they don't help maintain value.

    Tube rectifier is highly recommended both for tone and amp health. Try to get hold of some preamp tube shields to help keep noise down. The professor covered everything well!
     
  8. Sterence

    Sterence TDPRI Member

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    IMG_7495.JPG IMG_7493.JPG Well I have played a gig with it and another rehearsal. I am very pleased with the tone and volume I am getting out of it, especially with my Washburn 335 copy. Had it miked up for the gig in small bar with ~80 people (it was a wedding reception) but never had to use it. Vol was just 1.5, Treb 5 Bass 7, and man the tone was clean. Used a TS10 for leads and RMC wah. Everything sounded great. the band has an outside gig next week ans I am looking forward to seeing how will will sound in that setting and if it will need to be miked or not.

    The combo of a mid hump OD pedal with Fender BF/SF mid scooped amp is pretty killer. I never really liked my TS with my Princeton but that might be because the Princeton is very mid focused. I just OD from cranking the Princeton up and using the Volume on my guitar. I need to experiment with my other OD pedals (soul food and old Rat) and the DR. I kinda feel Like a whole new world has opened up to me!

    I also got my hands on a RCA 12au7 for V3 and 5U4GB for the rectifier, hoping to get some more NOS tubes from this source. Putting the lower gain tube in V3 made reverb much more usable and less noisy. Great suggestion. Aslo pulled V1 as I do not use the normal channel. That does seem to thicken up the effects channel nicely. I have not got rewiring the rectifier from SS back to tube. I am going to do it after I get done with the run of gigs we have this month.

    But it brings me to my first question:
    Is the tube rectifier socket on my later version of the DR (A1270 I think) wired differently than the AB763? I can very easily understand the "layout" diagrams but have trouble with "schematics" and there does not me seem to be a Layout diagram for the later DR.

    And second question is:
    Does punting lower gain preamp tubes in V2 give more head room and lower volume? I would like to get more usability out of the volume control. I dont need more volume just less sensitivity on the volume dial.

    And finally:

    What are the options for the push pull function? It sounds awful, worse than I expected. It sounds like a hive of bees on the loose. I am kinda surprised anyone thought that it was a good idea. So are there any mods than can be done to make the push/pull functionality useful? Or should I just ignore it and move one.

    Thanks again!
     
    Last edited: Jun 8, 2017
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