AC30 Clips - Modded vs Stock

Discussion in 'Builder's & Retailer's Forum' started by Lyle Caldwell, May 7, 2008.

  1. Lyle Caldwell

    Lyle Caldwell Member

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    Directly recorded guitars through the amps using a re-amping setup. This ensured the performance was the same each time.

    Edit: clips redone without added hiss.

    Both amps were set the same. Top Boost channel, volume at 10:00, Bass and Treble at 2:00, EQ set to Standard on the stock CC (not applicable on the modded AC30, which is permanently set to the "standard" setting). Reverb and tremolo both off. Cut set to 11:00.

    The modded amp has power scaling and a pre-phase inverter drive compensation control, while the stock amp just has the basic post phase inverter master volume. I set them to comparable output levels, but there is no direct correlation between the control positions.

    My mods include taking the circuit to JMI specs, upgrading the components in the power supply, installing Sozo caps, putting in a Mercury Magnetics "Woden" output transformer, and some voicing tweaks throughout the amp, to make it sound like an idealized JMI - the old amps vary so much due to component drifiting that I took some values I found in actual good sounding JMIs, even though they are not what was in the JMI schematic. Tubes were new JJs throughout.

    The stock amp was literally pulled out of the shipping box 15 minutes before the clips were done. Bone stock brand new AC30CC. Two Tung-Sol preamp tubes, one generic Chinese preamp tube, EH output tubes, Sovtek GZ34. Both amps were played through the same speakers, with the mic in the same position.

    Speakers were a Weber Blue Dog and Weber Silver Bell. I don't have a stock cab with stock Blues or Wharfedales here to compare. You'll have to trust me - the Webers sound better. I'll do that comparison when next I get a chance.

    Mic was an SM57, about a foot out in front of the cab, so as to favor neither speaker. The mic ran into a Mackie 1202VLZ and then to a MOTU 1224.

    The only computer processing I did was to normalize them all so people didn't just perceive the louder amp as sounding better. Oh, and MP3 encoding, of course.

    I'll let people judge the clips without knowing which amp is which.

    Ten short clips, each in pairs of the same U2 style part (no delay though), followed by six clips doing more of a blues/rock thang, going through some different pickup positions.

    http://psionicaudio.com/audio/AC30-U2-1A.mp3

    http://psionicaudio.com/audio/AC30-U2-1B.mp3

    http://psionicaudio.com/audio/AC30-U2-2A.mp3

    http://psionicaudio.com/audio/AC30-U2-2B.mp3

    http://psionicaudio.com/audio/AC30-U2-3A.mp3

    http://psionicaudio.com/audio/AC30-U2-3B.mp3

    http://psionicaudio.com/audio/AC30-U2-4A.mp3

    http://psionicaudio.com/audio/AC30-U2-4B.mp3

    http://psionicaudio.com/audio/AC30-U2-5A.mp3

    http://psionicaudio.com/audio/AC30-U2-5B.mp3

    http://psionicaudio.com/audio/AC30-Blues-1A.mp3

    http://psionicaudio.com/audio/AC30-Blues-1B.mp3

    http://psionicaudio.com/audio/AC30-Blues-2A.mp3

    http://psionicaudio.com/audio/AC30-Blues-2B.mp3

    http://psionicaudio.com/audio/AC30-Blues-3A.mp3

    http://psionicaudio.com/audio/AC30-Blues-3B.mp3
     
  2. hdiddy

    hdiddy Supporting Member

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  3. riker4208

    riker4208 Member

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    awesome Lyle.....I'm digging this
     
  4. Lyle Caldwell

    Lyle Caldwell Member

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    Had a computer crash, so I will be redoing the clips this afternoon. Sorry for the continued hiss. Thanks for all the kind words.

    I will soon have a section on my website with prices and full explanations of the various options available. In the meantime, please contact me at info@psionicaudio.com if you are interested.

    If I post prices here, and later have to increase them due to parts costs rising, etc, then Google will have the old prices listed in this old thread and confusion will ensue. I think it's better to have the prices on my site instead.
     
  5. Secret Ingredient

    Secret Ingredient Member

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    Dumb question, but how do we know if we prefer the modded version if we don't know which clip is which?
     
  6. dayn

    dayn Silver Supporting Member

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    A=modded B=Stock?

    I liked A better. More chime and "kerrang" as they say.
     
  7. Lyle Caldwell

    Lyle Caldwell Member

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    I wanted people to judge just on the merits of the clips, first. Some would be inclined to prefer the modded amp ahead of listening, while others would be biased against any "boutique mods" before listening. To a large degree, people hear what they want/expect to hear. Hence the initial blind comparison.

    In all the "A" clips you're hearing the modded amp, and the stock amp is the "B" clips.
     
  8. thudle

    thudle Member

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    The mods do make a huge difference in the sound. The stock AC30 sounds much more thin/tinny/has less character and resonance as the modded one. Great job!
     
  9. Woozy

    Woozy Member

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    Very nice!
    I listened to clips without knowing which was which (good idea, btw).

    The mod really makes a difference.
    Now I just need a AC30...

    Great work!
     
  10. OccTone

    OccTone Supporting Member

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    The "A" clips clearly sound better, more open, smoother top end, more pleasant break-up where applicable.
    I would love to hear the stock amp with JJ tubes in it though, comparing the 2 with JJ's in one and EH in the other makes it harder to see the difference in just the mod part of what you do, really very nice work though:):AOK
     
  11. Lyle Caldwell

    Lyle Caldwell Member

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    I'll do that soon.

    Next up are:

    Stock amp with JJs.

    Amp with JJs and my standard mods, but without the OT and powerscaling.

    Amp with JJs, standard mods, OT, but no powerscaling.

    If anyone wants to lend me a couple of hundred dollars worth of Mullards, I'd be glad to do clips with those. ;)

    There isn't a huge difference between the Tung Sols and JJ ECC83s. The JJs are just a bit darker (a good thing in an AC30) and not as prone to microphonics (I've had bad luck with Tung-Sols in this dept). The EH EL84s are brighter and a bit harsher than JJs, but it's not a night and day thing.

    The one big tube difference is in the rectifier - JJ GZ34s put out about 15V more on the B+ than the generic chinese GZ34, and a bit more than the Sovteks the amps ship with now. My preference is for the JJ or the Weber WZ34 Copper Cap, which does not fail and runs cooler.

    "Sag" is not really an issue with these amps, no matter the rectifier tube. You can view the AC30 as an amp that never sags, or as an amp that always sags by the same amount. Now, the output tubes and output transformer compress at high volumes (as do the speakers), so there is some behavior that is sag-like, but it's not coming from the rectifier.

    I love the sound of NOS tubes, but I cannot recommend them to my clients for regular gigging use. Just too expensive in an amp that runs tubes so hard. I tell clients to save Mullards, Brimars, etc, for recording sessions. JJs are great tubes for gigging.
     
  12. nibus

    nibus Supporting Member

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    Huge difference! How much is the mod Lyle? I might be shipping you my AC30.
     

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