Help me solve a Fender Deluxe mystery.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by brad347, Mar 4, 2006.

  1. brad347

    brad347 Member

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    Some background: OK so for those of you who have seen my thread about the shoddy repairs to the Deluxe I bought today know that I have two deluxe non-reverb amps now.

    Anyway, my FEI deluxe has the awesome original Jensen speaker, the FMI one I got today has a replacement... an oxford from the early 70's. The FMI has also had some shoddy repairs and is chock full of crappy chinese and bottom-of-the barrel russian tubes... including some incorrect 5881s (should be 6V6). My amp has all Mullard preamp tubes and brand new NOS Marconi/Westinghouse 6V6s which are awesome.

    The mystery begins here... that deluxe I got today... with a not-so-hot speaker and crappy tubes and shoddy repairs... sounds better than mine, much to my surprise and dismay! I'm trying to figure out why this is... I have a theory which I want some input on, discussed below...

    All of the circuit board electrolytics on the FMI have been replaced. My FEI has two (or three, depending on how you count the two-in-one on the right) that are still original and way past their life expectancy. See pic...

    [​IMG]

    I also tried switching the speakers on the amps... all that did was make the FMI sound even better-er than the FEI.

    I should also say that my FEI has at some point had the power trans. replaced with a newer Fender replacement (supposedly OK), but according to some other threads this shouldn't make much difference in tone anyhow... or should it...???

    Or maybe the Deluxe (or me) just likes the 5881s instead of 6V6s... can anybody give their own opinion one way or the other on this?

    SOOO (sorry for the long post) my main question is, as someone who's just getting into the technical side of things, what do those electrolytics on the board do? How do they affect the sound when they are failing? When they are new?

    Any other ideas? I know you all are thinking "just keep the one that sounds good and ditch the other one" but I sort of have an attachment to my amp (I know it sounds dumb) and I want to make it all that it can be. Changed transformer and all, I love it. I have always thought it sounded amazing, until this other one came along!!

    Thanks in advance guys.
     
  2. BozoTone

    BozoTone Member

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    Uhhh, OK, got to start somewhere. How does the FMI sound better than your FEI...more thump?..sweeter?..rawer?...You do have one "given". You have already proved that the speaker in the FEI is better than the Ox in the FMI, so that is a mute point. Do you know how the 5881's are biased (like 70% dissapation, lower, higher) and is the FEI w/6V6's biased about the same %. Two things come to mind on your FEI. First the OT. OT's do play into the overall sound. Maybe your replacement ain't as "good" as the one in the FMI. Second, the old caps in your FEI. They can certainly hurt signal and tone if going or gone. I would take the good Mullards and speaker out of your FEI and stick them in the FMI. This should??? make the FMI one killer MOFO w/no cost to you. As long as your swappin' tubes, put the cheapies in the FEI one at a time to see where it takes it. Sometimes "thars magic in them thar cheap bulbs"....
    BZT
     
  3. brad347

    brad347 Member

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    FMI has a 'sweeter' tone to it... not as "round" as the FEI but a little sweeter and more complex.

    Not sure about how they are biased. Haven't checked that far yet...

    Thanks for the reply.

    PS... how do OTs play into the overall sound? Headroom type issues only, or does it go deeper than that?
     
  4. BozoTone

    BozoTone Member

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    OT's are like tubes. How and what they are wound with, air space, paper, magnetic material, etc.. As many people will say a good sounding OT is just snake oil, as they will say about old tubes vs. new tubes. I think a good OT makes as much difference as good tubes, and in the same ways. More headroom, more complex and richer...tube terms...lol...snake oil. If I were a bettin' man, I would say the 5881's bias is whacked, probably hotter. The bad caps will also mess with all of the above in signal degeneration....I don't think I answered anything...Hmmm.....
    BZT
     
  5. brad347

    brad347 Member

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    sorry, not OT's.... I mean PTs. How do power transformers affect the sound? I assume it's not as drastic as the difference an OT will make. Am I wrong?
     
  6. phsyconoodler

    phsyconoodler Member

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    Here's how to find out why it sounds better.
    1) measure all the voltages of both amps and record them on paper.
    2) check the value of all filter caps.record your findings
    3) check the bias of both amps.Record it.
    5) take the tubes out of one and try in the other one
    (only if the voltages are near the same.)
    Don't skip any voltage readings.Even the heater voltages are important.
    Just because the tubes are chinese does not mean they won't sound good.your amp might sound better if you can duplicate the results.Whenever someone converts an amp to a solid state rectifier,it makes me wonder why.I am thinking the power transformer may not have enough voltage with the tube rectifier and the guy may have added the diodes to get it up to spec.It also may sound better because it's overbiased,and the tubes are on the ragged edge of burnout.Sometimes an amp sounds it's best just before it's ready to pop.A set of mismatched power tubes can sound better in the right circumstances.So you see,there are lots of reasons why it may sound better,but not all may be good for the amp.Check and re-check everything.
     
  7. John Phillips

    John Phillips Member

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    As I said in the other thread, you may just prefer the tone of the hacked-about one... your tone descriptions of the original amp being 'rounder' and the hacked one being 'sweeter' make total sense.

    Here's why: you may not believe this, but the Deluxe and DR are badly designed in the sense that the original OT ratios are incorrect for 6V6s, and a better match for 6L6s (of which 5881s are a variant), with an 8-ohm speaker. Really. The difference in tone is quite substantial - the better match gives more power, more (and tighter) bass, and a more balanced sound. That 'classic' Deluxe tone when pushed - soft and flubby, touch-responsive but also easy to push into mush - is very characteristic of an output stage driven into too low an impedance, and not so much of 6V6s in general, even though everyone thinks the DR is the perfect example of a 6V6 amp!

    Also, the 5881s may not be biased correctly (they require more supply voltage than the amp will deliver without changing some components in the bias circuit, even if you max out the trimmer) but since they are much higher rated they may take it without you noticing that the amp is in fact running much hotter. DO NOT simply swap the tubes from one amp to the other, the original amp will not like having 5881s put in it without rebiasing.

    Secondly, the solid-state diodes bridging the rectifier in the hacked amp will give it more crunch, at the expense of smoothness, because there will be very little sag when the amp is driven harder - like the difference between a Tweed Bassman and a 50W Marshall (though there are other differences with those two amps too, that's just an illustration). This could be what you're describing as 'sweet and complex' vs. 'round'. Tube rectification is not better, just different.

    The changed PT on the original amp may make some difference (is it a recent replacement or a SF one, BTW?), but not all that much usually - although the old filter caps might.

    Don't necessarily think that the more original amp 'must' sound better. That isn't always the way it is, especially as your tastes may not be the same as other people's. That's the whole reason amp design evolves - some folk are dissatisfied with what they have and want to improve things... though to others they were better the way they were.
     
  8. fullerplast

    fullerplast Senior Member

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    Those caps are cathode bypass caps, 25uF, 25V pairs in one package. They are usually replaced with modern single caps (much smaller too) like the pair that are between the two you outlined. They will affect the (frequency dependent) gain of stages if they are failing and are important components to the overall healthy tone and gain of the amp.

    As for the differences between amps, as John and others have pointed out, there are far too many variables between the amps to draw any specific conclusions. Start with trying the same tubes (with proper biasing) in both amps and use the same speaker if you want a better idea of what else may be changing the tone.
     
  9. wilder

    wilder Member

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    Are the power filter caps on your clean Deluxe original? If they are it will never sounds as good as one with newer filter caps. Have you pulled the cap cover and looked at those?

    Chris
     
  10. BozoTone

    BozoTone Member

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    Great bunch of info John...
    BZT
     
  11. brad347

    brad347 Member

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    Thanks for all of your replies. I'll work from the bottom up:

    The power filter caps on my FEI have been competently and professionally replaced (not by me).

    I'll consider replacing those cathode bypass caps.

    The changed PT is a new reissue replacement... I didn't put it in there. I never would have put it in there... however it always sounded okay to me, so I never worried about it.

    I read this article on Mercury Magnetics webpage... is it true, or just exaggerated hogwash so they can sell more iron...?

    http://www.mercurymagnetics.com/pages/articles/misc/WayneReno.htm

    interesting re: the 6L6s being more appropriate for the amp than 6V6s. I've heard this before...

    Finally, psychonoodler's advice is sound. The fact of the matter is, I'm no amp tech, in fact i'm a full-time pro player with music degrees and no electronics degrees! I know my limitations. I can change caps and solder well, etc, but I'm no tech and don't want to hurt myself probing about for voltages. In fact, I'm not even sure which ones I should measure. Thanks for the sound advice though.

    So... should I pop for a new Mercury PT in my old FEI deluxe??
     
  12. Blue Strat

    Blue Strat Member

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    Sorry if I'm repeating stuff, but I didn't have patience enough to read the whole thread.

    1) Until you've tried your amp with a SS recto and 5881s, you haven't compared the amps

    2) Once you've done this and decided that the new amp is still better, compare all power supply and plate voltages. This will eliminate your replaced PT as a suspect.
     
  13. brad347

    brad347 Member

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    I A/B'd the amps again today after sleeping on it... my conclusion today is that both sound great, just different. The difference is actually smaller than I remembered, but the FMI with 5881s does have a touch more sweetness and warmth. The FMI with 6V6s and better quality tubes has a touch more roundness and depth. The one with 5881s isn't any louder though... it probably is biased weird as you have suggested. I haven't checked its bias out yet. The two amps have their own personalities, I wish I could keep both but I can't. I'll sleep on it again and compare again...
     
  14. Geetarpicker

    Geetarpicker Member

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    I also have two non-reverb Fender Deluxe amps. Mine are both FEI, Oct. & Sept. '64 both without logos. They sound different too. They both have all original circuit components except one has a changed volume pot, and both have had the caps under the can swapped for Blue Atoms. I have Jensen reissue C12Ns in both. Even swapping the same tubes from amp to amp yields a slightly different tone. I attribute that to tolerance of original components and also some caps and resistors have probably drifted with age in different ways. When I got my second Deluxe it didn't have the fatness of my first, but was clearer on top. However just changing the PS caps under the can brought it to life. Still that amp is a little more articulate on top then the other, but now the low end is there fat and big just like the other. That said I usually gig with the darker sounding one.

    Great amps. I've owned 4 of these over the years, and 3 reverb ones. Recently I just decided to get two and keep them. Done. I've tried various speakers over the years in these amps. Vintage 30, DBL D120, EV, original Oxford, etc. I'm very impressed with the Jensen reissue C12Ns in these amps, and they are dirt cheap.

    I noticed your amp in the pics has a small hole drilled. I always look at Deluxe amps with a hole over there wondering if it could be the first Deluxe I ever owned (which had a master added on the back) which was back in like '76-'80 or so. Does that amp have an added logo on the front, put too close to the corner? My first Deluxe was a non logo one, and at the time I thought they just forgot to put it on! They made quite a few of these amps though, and I may never actually find the actual one I owned way back when not that it really matters... CHEERS

    I run mine in an A/B wet/dry rig with my 1974x. Note the stacking platform.


    [​IMG]
     
  15. Big Dan

    Big Dan Member

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    I'm just an amp novice myself, but it seems to me the biggest factors that I would suspect are:

    1) SS/Diode recified vs. tube rectified.

    2) Different type power tubes.

    3) The amp you just bought has weird oversized caps (You posted the pic in the other thread). What value are these and what are they replacing?

    4) The bypass caps in your old amp need to be replaced.

    These things can easily account for the tonal differences you are hearing.

    Dan
     
  16. brad347

    brad347 Member

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    Geetarpicker: no, the amp with the hole doesn't have a logo on the front, but oddly enough the other (FMI) one, DOES have a logo and it is too close to the corner!

    Strange coincidence...
     

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