Amp/Speaker pairing questions

Discussion in 'Amp Central Station' started by ryguy76, May 23, 2020.

  1. ryguy76

    ryguy76 TDPRI Member

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    Hey,

    I have a 1st gen (MIA) HRDx amp that is completely stock and so has the "specially designed for Fender" Eminence speaker.

    I don't have any issues with this amp in terms of it's clean sound. It's quite nice for my style of playing.

    I also have a BJ IV with the Celestion Type A in it. That amp is beyond bright for my liking. I am in the ballpark of where I'd like to be with Fat switch of, master vol cranked, bass on 12, treble at 1 and mids at 3-4 depending on the guitar. While I am content with the sound using these these settings, it leaves virtually no wiggle room for tonal shaping with the mids/highs before it becomes ice-picky. I am contemplating a speaker change to a Cannabis Rex in the BJ which would leave me with a perfectly fine Celestion Type A.

    I see the newer HRDx's come with the Celestion Type A stock now. So I'm wondering of anyone has experience with the original "Fender by Eminence" speaker vs the Celestial Type A in the HRDx before I go to the hassle of swapping it. I'm also on the fence with whether or not I want to spend the money on the Cannabis Rex for the BJ. I think I would like it better, but not sure if it's needed. If I know the HRDx would be an improvement with the BJ's Celestion, then I'll pull the trigger as it'll most likely be a win-win for both amps.

    Thoughts/opinions most welcome.
     
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  2. Wally

    Wally Telefied Ad Free Member

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    Save some money...buy an Eminence Legend GB128 for the Blues Jr. And keep the Celestion away from any amp!! LLol......duck for cover, Wally! Hint: you can sell the Celestion with no problem. That is the best thing about a modern Celestion, imho.
    If you have not had your HRD biased as warmly as it will allow, do that. Install a 5751 or 12AY7 in V1....much better amp then, ime.
    Worry about the speaker later if needed.
    The Gb128 is a very good sounding speaker in any amp in which I have placed it...bargain time, imho!
     
  3. dougstrum

    dougstrum Tele-Afflicted

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    I have GB-128 in two different amps and think it is a great speaker.
    I have a Crex that sits on the self. I've tried it in different amps, but never seem to like it. I lot of folks do, guess everyone is different.
     
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  4. Dacious

    Dacious Poster Extraordinaire

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    Before you do that - do this.



    It will transform the amp's brightness, harshness and crap sounding reverb and distortions. And it makes the notoriously touchy 1.8 off, 2.1 too loud volume tameable.

    We've done this to Hotrods and s Blues Deluxe.

    A lot of people spend $100-150 on a speaker finding meh or indifferent results. This is the main cause of what people hate about these amps other than chintzy construction.

    There is nothing wrong with the Eminence in the amp.

    In these amps Fender married a 50s Tweed preamp section to solid-state rectified power section and digital reverb - those original amps had a 12AY7 preamp tube, which is a lot lower gain. Fitting a lower gain preamp tube drops gain through the amp and basically it's sweeter and more controllable

    I used to hate my bandmates HRDx and BD - muddy, or too loud and incredibly harsh. Now they sit in the mix just great.
     
    Last edited: May 23, 2020
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  5. PhredE

    PhredE Tele-Meister

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    Last edited: May 23, 2020
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  6. Dacious

    Dacious Poster Extraordinaire

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    Also - if you have a first generation 90s amp - it's due for some service. Fender used underspecced 450volt filter caps in early ones. Take the back panel off, check for this
    images (32).jpeg

    If you see these big caps in the middle and they say 450 not 500 volts consider getting the amp serviced and those replaced. The carbon film resistors on the power tube daughter board also give trouble and should be inspected and maybe changed before they melt something.
     
  7. ryguy76

    ryguy76 TDPRI Member

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    I watched the video and will be ordering a new preamp tube after writing this! You're saying it'll improve the onboard reverb too? I don't use the gain channels on this amp as I find it requires a radical re-EQ of preamp settings to get something useable.

    You mentioned 12AY7 in your post but the video is referring to 12AT7's. Am I wanting the AT7's, not AY7's?

    Should I buy another for my Blues Junior then too? Just needs the one there too?

    Thanks!
     
  8. ryguy76

    ryguy76 TDPRI Member

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    Interesting. Guessing mine will have these caps. I think I bought mine in 1999. Would this be an issue if not playing at loud volumes these days? I used to gig with it back when it was originally purchased but now it's just being used as a living room amp and goes no louder than 2.
     
  9. Wally

    Wally Telefied Ad Free Member

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    The circuit in your amp is based on the 5F6A circuit, which had a 12AY7 in V1. The 12AY7 has a gain factor of 40 compared to a 12AX7’s gain factor of 100. A 5751 has a gain factor of 70 and is better suited to a tone processing position compared to a 12AT7, which also has a gain factor of 70 but has other specs that are different because the 12AT/AU7 tubes were designed as drivers. This difference is why Leo Fender never used a 12AT7 in a tone processing position but used that tube only for the reverb driver and the phase inverter positions. Yes, a 12AT7 will function where the 12AX7/12AY7/5751 tubes function and vice versa; but how they function is another matter. And yes..,you might prefer a lower gain tube in V1 of any of the Blues/Hot Rod series amps.
     
  10. ryguy76

    ryguy76 TDPRI Member

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    I re-read your initial post and must have missed the 12AY7 recommendation as I was focussed on the speaker portion.

    I don't need a ton of gain as I have pedals for that when needed so dropping to the 12AY7 with a much lower gain factor is fine by me as long if the tone has been improved. Sounds like it's worth trying at least.

    Any recommendations on which AY7 to buy for both these amps? Would you recommend keeping the AX7's in V2 and V3 for now and just focus on V1?
     
  11. Dacious

    Dacious Poster Extraordinaire

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    Yes - as Wally said the 12AY7 or a 5751 is the preferred tube in preamp slot 1, which is the most critical , as it takes the signal off your guitar cable and boosts it through the amp.

    I have personally fitted a 12AT7 to three amps and the owners all agreed it was an improvement and kept them,. But AY7 or AT7 would achieve the same aim possibly slightly nicer. JJ makes decent 5751 and AY7, plus Ruby and one or two others.

    To be fair to Fender, when these amps and 65 Reissues were introduced the only new production tube was the 12AX7 - 12AT7s didn't come back until the mid Noughties and 12AY7s and 5751s only the last 4-5 years.

    The issue with a 12AX7 in the front slot of these - it 'overloads' the eq section. It's like having a tube screamer, on, plugged in. Reducing gain in front of the eqs gives you the ability to produce a clean signal until you want to make it dirty; for instance instead of a 1.8-2.1 range on the volume, you can now run 3-6 which gives finer control. And the sound passed to the reverb circuit is cleaner, meaning it's cleaner coming back to the level control which is a mix between dry un-verbed and reverbed signal.

    Ditto the distortion. Believe me, I hated the Drive and More Drive, and you're right, it was hard getting a good on-the-fly sound. Wait until you try it with the tube swap. You now have a decent classic crunch and a Mesa-ish medium drive. They're much less nasally and more meaty without pushing volume to gonzo levels. Only need to drop guitar volume slightly.

    Really transforms the amp.

    As far as the caps go, the plate volts on the schematic are 446, I measured 445 on my friends HRDx - that's very close to the wind rated 450 volts. Coming off standby it probably spikes.

    There's been a lot of fails. It's easy to check, five screws and don't touch inside.

    What you're looking for is this:

    images (33).jpeg

    That goop dries and leaks, the caps stop working. Not only does the amp hum but it affects tone and volume.

    Being '99 you're probably OK. I'm pretty sure it was the earlier ones my friends 2003 was 500 volt caps. If there's no leaks visible and the amp's quiet you're good. Just have a squiz at the power tube mounts too - a little bit of browning is normal but any blackening or cooking, get it seen to.
     
    Last edited: May 25, 2020
  12. ryguy76

    ryguy76 TDPRI Member

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    This is great info! thanks. I'll have a look at my caps and see what I can see.

    You mentioned to re-bias my amp as warm as it can be. Aim is to get as close to achieve a specific ma by turning the bias pot inside?

    Looks like I can get Groove Tubes or Electro-Harmonix 12AY7 tubes easy enough. I can order the JJ's too, but shipping costs etc so would be twice as expensive. Worth it?
     
  13. ryguy76

    ryguy76 TDPRI Member

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    Capacitors all look good. No sign of leakage on top or bottom. Amp is quiet so I guess I'm good there.

    Different than pictured above with the 450v caps. I have 500v caps so obviously not from the 1st generation. (Need to figure out how to date this amp next.)

    I didn't notice any browning around the power tube mounts but did notice some slight browning around the 3 components in the 2nd pic.

    All good to just keep on keeping on with it until it gives me reason for a service?
     

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  14. PhredE

    PhredE Tele-Meister

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    Those are the ceramic wirewound power resistors (in the 2nd pic).
    I'll let one of the other folks who know more about their function in your amp chime in about those. I had an old Fender SS amp that literally burned through a pair of those several years ago. They can take some beating and keep working ok in most cases.
     
  15. Dacious

    Dacious Poster Extraordinaire

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    I think you're good to go. If the amp is quiet the caps look fine. Those big cement bath resistors down the bottom are dropping resistors to the preamp and they do generate a bit of heat which can loosen the solder joints but a bit of browning is normal especially after a long time. If that happens you will notice reverb and channel switching going flaky and odd noises. If no symptoms like that you're good.

    If in doubt about that, with the amp unplugged and powered off, just put a finger on top and gently waggle it side to side. If it feels firm all good. If it feels like a loose tooth needs resoldering.

    All the modern tubes are OK and fairly similar. I haven't tried those particular ones.
     
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  16. ryguy76

    ryguy76 TDPRI Member

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    Awesome! Thanks for sharing your wisdom. Will get a 12AY7 and report back with my findings once able.

    cheers!
     
  17. ryguy76

    ryguy76 TDPRI Member

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    Well, I bought the 12AY7 and have new issues now. Hoping someone can shed some light on what I'm experiencing.

    I unplugged the amp, pulled the AX7, popped in the new AY7. All was good. I switched into the Drive channel, which I rarely used before to check it out and it was sounding great for a moment until it started to pop a couple times where the drive channel lights were going out entirely and/or dimming. Then it settled for awhile but returned. I was worried it was something with the new tube so put the old one back in and same thing.

    At this point, I can switch into the drive channel and the lights don't illuminate nor any sound is heard. Going back to clean channel gets me sound, but even there it's now getting quieter/louder randomly.

    I read there's a muting circuit that gets enabled when switching between clean and drive channels. Could this be faulty and is it something that I might have caused when switching the tube or just really bad coincidental luck?
     
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