Princeton 6G2 - 25 watt OT?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by pete12string, Nov 7, 2018.

  1. pete12string

    pete12string Supporting Member

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    I'm looking at getting a Princeton 6G2 clone and am considering a 25 watt version over the usual 12 watt. Are there any problems using a larger OT (25 watt) with the 6G2 circuit? I'd like the increased volume/headroom but don't want to introduce any problems by using a larger OT.

    Any assistance, comments, opinions are appreciated!

    Thanks for your help!
     
  2. Tron Pesto

    Tron Pesto Member

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    Nope - no problems - assuming it can fit! And assuming you have the correct primary impedance and your secondary impedance is matched to your speaker impedance.
     
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  3. UsableThought

    UsableThought Supporting Member

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  4. pdf64

    pdf64 Member

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    How are you planning to increase the power output to 25 watts?
     
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  5. pete12string

    pete12string Supporting Member

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    Basically, by asking the builder. :D I'm having an amp built and I have the option of 12 or 25 watt.
     
  6. UsableThought

    UsableThought Supporting Member

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    @pete12string, I'm realizing from pdf64's question & your reply that I misread your initial question. The thread I referenced isn't relevant & you can disregard it.

    And when I go back & reread your initial question more carefully -
    - it seems to me that if the builder is modding the original circuit to produce a 25-watt version, then it's not really a question of "a larger OT (25 watt) with the 6G2 circuit"; what you will be getting if you go for that version is a larger OT with a modified circuit, not the original.

    So you probably would want more details from the builder. E.g., will he keep the preamp the same & just mod the power amp? Has he done this before? (Hopefully yes.) How does the modded version sound vs. the original, in terms of headroom or whatever else is important to you? Etc. If you get some solid details as to the mod, you could post them here - it would give folks on this forum more to go on than just a 25W OT being involved.
     
    Last edited: Nov 8, 2018
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  7. monkmiles

    monkmiles Supporting Member

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    Seems like it ought to sound close to the 6g3 to me. But I don't know all the differences in the two cicuits.
     
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  8. pete12string

    pete12string Supporting Member

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    Thanks for the information. Very helpful! I'll check with the builder again. He has a "12 watt" already built and said if I wanted the 25 watt it would just be a matter of swapping the output transformers.
     
  9. UsableThought

    UsableThought Supporting Member

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    I did a quick Google for "Princeton 6g2 25 watts" and found a site for Lil Dawg Amps, w/ a clone called the "ChocoPrince." Is this guy your builder? http://www.littledawgamps.com/the-chocoprince/

    If so his description of the tube set provides a clue:
    What he seems to be saying is that although the original circuit uses a pair of 6V6GT's for the power amp, he is able to tweak things so as to use the 6L6GC instead - a tube capable of much higher output. And although the phrase "match your need" is cryptic, it seems very likely that the 25W OT is offered solely to accommodate the 6L6's. There would need to be other tweaks to the circuit as well (e.g. bias and a large-enough PT), but that's over my head since I've never made a similar power tube swap on anything I've built (although I have certainly thought about it).

    In terms of tone differences, you might find that the tube swap (6V6 vs. 6L6) plus OT swap would carry more weight than just an OT swap alone. For starters you might check out this thread on the regular Amps & Cabs page: "6V6 vs. 6L6"; there are also generic articles like this one, but they wouldn't be specific to the basic Princeton 6G2 circuit. And if Lil Dawg really is your builder, he has an entire page on his site on his impressions of the 6V6 vs the 6L6.

    Anyway whether it's him or someone else, you can always ask. (The amps & cabs forum thread above mentions another clone brand w/ the same feature, the Louis Electric Princetone.)
     
    Last edited: Nov 8, 2018
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  10. pete12string

    pete12string Supporting Member

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    Yes, L'il Dawg amps - Jim Nickelson. I bought one of his WonderDawgs (like a blackface deluxe) so I'm comfortable with his abilities - fabulous amp. From what I'm hearing, I think I will go the 25 watt route. What would the resulting increase in volume be like with a 25 W OT using 6V6's (if any)? Or would this just offer more clean headroom over the smaller OT? Your help on this whole thing has been great and I really appreciate it!

    Thanks!
    Pete
     
  11. Darkness

    Darkness Member

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    I’ve got a 25watt OT Chocoprince. It’s the first one Jim made. This amp is my favorite bedroom amp. I don’t have a 12watt OT version to put it up against. All I can say is my Chocoprince has golden tone at any level. No problems whatsoever.

    Jim is awesome.
     
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  12. UsableThought

    UsableThought Supporting Member

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    Just to clear up some terminology: You ask about "headroom," but strictly speaking, headroom isn't to do with the OT, but with when a preamp or power amp starts to clip the signal (move from clean into distortion). For OTs, the usual jargon for the introduction of distortion is "compression" and/or "saturation"; and for speakers it seems to be "breakup." For an amp overall, I suppose you could use any of these terms; but I find it more helpful to restrict them to the parts of the amp they affect.

    So to slightly rephrase your question: Might the bigger OT in the 12W/6V6 version of the Chocoprince give you the rough equivalent of "more headroom" by staying cleaner at higher volumes? For this, I recommend reading comment #3 in the thread I first referenced. My (possibly wrong) interpretation is that yes, the over-sized OT might in fact do so - possibly because it would be relatively more efficient at similar power levels than a smaller OT, i.e. it would resist "compressing." And perhaps for the same reason (greater relative efficiency), it might sound slightly louder, too.

    However my guess is that any perception of increased volume would be moderate; a 12W amp is a 12W amp. Plus if it's loud you're after, speaker choice might be more important for you, since from what I read, loudness can be heavily influenced by speaker efficiency. Or you could just go w/ the 25W/6L6 version of the Chocoprince as you say you are planning to do.

    Anyway these are all things you can ask Jim about.
     
    Last edited: Nov 9, 2018
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  13. eolon

    eolon Silver Supporting Member

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    Just from experience, I can tell you that the 6G2 is easily capable of 22 Watts without modification. I have a 1962 brown Princeton that has the voice of angels. The modern line voltage @ 123 VAC raises all the B+ voltages. The 6V6GTs are TAD, designed for higher plate voltages (as are the JJ "S"). The measured static dissipation is 22 Watts. Although the 6G2 circuit is original, someone at some point added reverb and master volume. Well done, the modifications were unobtrusive; the two pots were mounted on a little bracket inside the cabinet. Part of the tone wonderfulness comes from the original transformer working to keep up with 22 Watts.

    The amp was modified in the '80s, so it has been performing flawlessly for almost 40 years. Another indicator of the robustness of early Fender amps!

    Best Regards,
    Don
     
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  14. UsableThought

    UsableThought Supporting Member

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    Yes, somewhere in the low 20W range seems quite possible, from what I've read about extra-hardy 6V6 variants such as the JJ 6V6S. But 25W as a standard for new builds seems a stretch. And even 20W or 22W might not be a go if it meant customers had to confine themselves to a narrow range of tube choices. Along these lines I wrote the following (but then deleted as irrelevant) as part of my response to the OP:

    Remember that I am still only speculating that based on the description on Jim's web site, the default for the 25W Chocoprince is to use 6L6 tubes in combination with the 25W OT. But it's a fair speculation. A designer can push a pair of 6V6 tubes pretty hard, but subject to correction, I'm dubious that they can be pushed all the way up to a legitimate 25W output in a class A/B amp. Whereas with 6L6 tubes, 25W output is a snap.​
     
    Last edited: Nov 9, 2018
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  15. HotBluePlates

    HotBluePlates Member

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    @Jim Kelley might disagree with you, as his 4x6V6 amps made 60w RMS.

    That said, getting the 6V6 up to higher power outputs requires a good bit of B+ voltage, and juggling of voltage, output transformer impedance, bias, and phase inverter drive levels.
     
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  16. Steppin' Wolfe

    Steppin' Wolfe Member

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    “The measure static dissipation is 22 watts”.....
    Is this in reference to the plate dissipation number at idle? If so, that is not a measure of the power output from the OT, is it?
     
  17. Jim Kelley

    Jim Kelley Supporting Member

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    Yep, and screen grid current limiting.

    https://www.jj-electronic.com/en/6v6s
     
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  18. jnickel

    jnickel Member

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    First I want to thank the folks in the forums for being so kind to me over the years as they've helped me stay busy with my amps, & for that I'm so grateful.

    I seldom post on any forum as there are so many different opinions on most any subject. Rather than argue one side or the other I prefer to stay out of the middle of them but once in a while I feel it would help to clarify something so here's an excerpt from my website explaining the transformer options that you're discussing now.

    "Regarding the output transformer ratings, I need to clarify how to interpret them. I use the manufacturer's specifications in the description of various builds, but I don't guarantee that you actually get that output in every instance as the actual output can vary from one circuit to another. For example, a 6V6GT in a single ended amp will only have an output of 5.5 watts regardless of the output transformer used. An 8 or 12 watt output transformer will give you more headroom and a bump in volume over a 5 watt unit, but it'll never exceed the ability of the tube itself. When you get into the push-pull circuits like the 5E3, then the output of the two 6V6GTs can go up accordingly with some of the larger output transformers but still may not yield the rating of the output transformer. So please keep that in mind when looking over the amps and feel free to ask questions if you need to."

    The same would be applicable to the questions of 12 watt OT vs. 25 watt OT in the 6G2 circuit. There is no claim to the 25 watt OT producing 25 watts with 6V6GT's, just more clarity & detail which some consider headroom as well as a "bump" in volume which to one person may be slight but to another more pronounced. Everyone's ears are different so the results do vary from one to another.

    I also use an oversized power transformer in my 6G2 builds which can easily support the use of 5881 or 6L6GC power tubes so with those you would be closer to the 25 watt output if that's what you're looking for.
     
  19. UsableThought

    UsableThought Supporting Member

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    Well, I hope I didn't steer the OP too far wrong - I'm a layperson wading through the shallow end of the pool & so generally I qualify what I say as being limited to that perspective. At least what @jnickel writes reassures me that I got the basic OT/tube matches correct for his Chocoprince.

    Beyond that, I suppose one could make a distinction between designs which tweak or play with vintage circuits, or which follow fairly standard practice, vs. more advanced practice that has a lot of experimentation behind it? It's certainly over my head.
     
    Last edited: Nov 9, 2018
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  20. jnickel

    jnickel Member

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    Each & every tube stands on it's own as far as it's voice & output. Matching the power tubes helps put a pair together that work well but they don't necessarily need to be the same brand, & each pair will have their own unique tonal character. That would hold true for the vintage 6V6GTs or current production 6V6GTs, and sometimes the best sounding tube set will be a a mix of new & old. The JJ 6V6S is a more robust tube that can handle the higher plate voltages much better than a lot of others, and while some put it into the 6L6 family I don't hear that myself & consider them to be a fairly stout example of the 6V6 character. When the amp is built the voltages should be in line with what the era of the power tubes require. For example a vintage 6V6GT would be happy with a plate voltage up to 350VDC, but above that it's service life will be compromised some. The JJ 6V6S can handle up to 450VDC easy enough, so there's more room to tweak the circuit for the needs of the individual as far as his playing style & music genre are concerned.

    Once again, everyone ears are different so what holds true to my ears may not be the same for someone else's.
     

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