6v6 Tweed style - check my numbers?

Discussion in 'Shock Brother's DIY Amps' started by jsnwhite619, Sep 1, 2021.

  1. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Hmm. Is there a setting — one maybe I already set? If I click 'watch thread' mine appears defaulted to 'without email.'

    6736A38F-FF5D-4457-8056-D66980372651.jpeg
     
    Last edited: Sep 7, 2021
  2. Wally

    Wally Telefied Ad Free Member

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    maybe I need to take a look at my personal settings although I have never requested email notification. I forget to go to ‘more options’ at the lower right and click ‘no email’.
     
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  3. mountainhick

    mountainhick Tele-Meister

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    Wally, go to your username on the top menu bar (on a computer, I don;t know about the phone setup) to the drop down menu and select "Preferences". (Not "Alert Preferences"). all of the selections have an option for email notification, you can uncheck the boxes. This is a global not per thread way of shutting it off.
     
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  4. jsnwhite619

    jsnwhite619 Friend of Leo's

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    I just had a thought. I copied from an 18W Lite IIb for my inputs - #1 runs paralleled and #2 is a "normal" Fender #1 value. In this setup they share a single plate resistor. Assuming has the same effect as a Fender-style 820R shared cathode resistor and doubles the value when shared between the two plates, the original 100k plate resistor would have been equivalent to 200k, and the current 47k is equivalent to 94k in operation?

    Am I correct here?
     
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  5. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Bump. Now that the account settings are sorted out, any feedback on the last question or clips?
     
  6. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Well, the 5u4 arrived today long with a Jensen C10Q RI. I started with the 325v taps and the 5u4, and it sounded great - huge improvement over the 5Y3, but the voltage was higher than I wanted - biasing between 410v- 415v. So, I swapped down to the 275v secondary and biased 340v B+ with a 5u4. That's the money. I honestly couldn't tell much difference on tone - I didn't give it a full workout - but the firm piano bass, the low end clean is definitely from the rectifier and filtering, not just the voltage. The 5u4 at 340v B+ whips the snot out of 380v with a 5y3. Both biased the same. Funny enough with a 22k resistor on the 10k pot, they were almost identical settings.

    Anyway, the 5u4 is the piece of the puzzle I e been looking for. And between the Ragin Cajun, 1058, Cannabis Rex, and C10Q, the Jensen was pretty sweet today. I've liked it in the past, but it was 100% the liveliest of the bunch. It's very full range, and I think modern speakers can end up cutting the wrong places when you have a single tone knob setup.
     
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  7. andrewRneumann

    andrewRneumann Tele-Holic

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    What was overdrive like between the 5Y3 and 5U4?
     
  8. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Much tighter and warmer. The firmer bass of the 5u4 really helps and actually kinda makes it sound dirtier. Just happier all around with it.

    The Jensen has some time on it, but not nearly enough to be called broken in. It sounds a lot harsher through the mic than in the room, but mic placement is everything when you're trying to capture the total sound of a speaker with something this size of a nickel in front of it. I'm not a sound engineer.

    But, it has a fantastic clean tone that I love. I'd like to hear a reverb pedal with it. It takes my Blues Driver really well. I was listening back to the recording, and I wanted to share this clip. One is the amp on 10, the other is the amp on 3 with the Blues Driver turned on. The distortion at the time made the pedal clip sound a lot louder than it was, but I had to really bring the level up on it to balance them out for this clip. See if you can tell the overdriven amp vs the clean amp and overdrive pedal.

     
  9. NTC

    NTC Tele-Holic

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    Really hard to tell. I think the first one is amp and the second has the BD.
     
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  10. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Yep. With headphones or good speakers you can hear the bass cut of the Blues Driver. But, considering an actual cranked amp vs one that is still comfortable to be in the room and gets the volume down for home playing, I was very impressed.
     
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  11. NTC

    NTC Tele-Holic

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    It wasn't the bass cut that clued me in
    It was the fact that the clean part was dirtier. I'll have to listen again to see if I hear reduced bass.
     
  12. jsnwhite619

    jsnwhite619 Friend of Leo's

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    So, after a few days of trying the lower voltage - and the "new sound" sinking in, I couldn't get over a little something that was missing. I never could sort it out with just the 5y3, the 5u4 is definitely what I was looking for, but the lower voltage just was missing something. I decided to go back to the 325v taps, and like every other time I've tried both options with other amps - except a 5f1/5f2 type - I just like the higher voltage in the end. More bite, bigger bass, etc., just more. I'm running 412v B+, but all I use is JJ's, so I'm rolling with it.

    However, back to the plate resistor experimenting, a little double-checking online confirmed my shared plate resistor is double-value in operation, so the initial 100k=200k, the 47k=94k, etc. That would explain the giant leap in gain initially with the 100k in place - and the low 89v plate voltage - and why the 47k cleaned it up so much. I played with a few and it has a 68k plate resistor right now, shared plate should = 136k. That's on the north side of 100k to keep the 12ax7 happy, and really smoothed out the overdrive. Overall gain took a hit from the 200k equivalent I had originally, but nothing that is missed or wasn't a bit too raspy and ragged.

    But, the overall experiment did make me think more about it. So many people wanting a cleaner and lower output 5e3, even with a 12ay7 in V1, I don't know that I've ever seen "lower the plate resistor" mentioned as an option. Anything down to 47k should be ok with a 12ay7, and it would lower the gain and increase the plate voltage/headroom. You see about people increasing the value to increase gain & overdrive all the time, but I don't think I've ever seen it talked about to decrease the value and clean up/reduce output. Probably because more gain & overdrive is what most people are trying to mod for on amps in general, but still.
     
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  13. NTC

    NTC Tele-Holic

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    Jsnwhite619, do you have a marked up schematic to show all of this? Your amp is different than, but in the ballpark of, the 5F11 based amp I spend most of my time with. With 6V6's and a 5Y3, it has 418V on the plates of some JAN Phillips tubes. I frequently run some 6L6'S in this amp with a 5AR4 (about 425 on the plates). The sound is clearer with the 6L6's. It has a 4K:4 BF Pro OT. It is VERY clean sounding. I have considered changing the second gain stage to be like the PR, but I decided not to...
     
  14. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Definitely in the ballpark - 5f10 based. I tried the parallel V1 because the lack of tremolo left half of the tube unused. I like the sound of it, but you don't have room on the 5f11.

    For the NFB, I straight copied a Princeton Reverb and increased the 2700 to 5600. There wasn't much OD difference in 5600 and 10k, just brighter, so I went back down. But, the 2nd gain stage & NFB is straight from the Princeton Reverb - 47R tail resistor to ground to allow for the bypass cap on V2 NFB circuit. It's all a balance. I have a 2uf on V1 because it got too muddy with a 25uf, but it's a different tone & feel in the end. Just more modern sounding I guess with the small bypass on V1, and the second stage on V2. Not a Mesa Boogie by any means, but it keeps that line between clean & dirty a lot better. It's like a clean boost vs a "cranked amp". All this is with a 12ay7, which was the goal. Adequate overdrive with a 12ay7 and cleaner sound. A 12ax7 rocks out as well, but is different on it's own as well, and the cleans aren't as sweet.

    What PT are you running for that kind of voltage with a 5y3? That kind of voltage and a 4k OT has got to be drawing some serious current with 6L6's. Are you running a 4R speaker or 8R? Is it one of the "not really a 5y3" versions? The JJ's really drop some serious voltage. I've never compared their 5y3 and GZ34 and got less than 35-40v difference at the minimum.
     
  15. NTC

    NTC Tele-Holic

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    PT is a Hammond 290BX. The 5Y3 is a Realistic gold plated pin tube, so probably 70's. GZ34 is Amperex, also old. The current with the 6V6's and 5Y3 is less than 50mA. With the 6L6'S and GZ34, it is about 100 to 105 ma - both at idle. The PT is probably a bit wimpy for full-bore 6L6 mayhem, but I don't push it. It usually has just an 8 ohm load (one driver). That really can't handle 6L6'S by itself either. The great thing is I can plug in either tube set and get these numbers (about 65 and 70 % dissipation) without rebiasing.

    Sorry, seems like I am hijacking this thread.
     
  16. jsnwhite619

    jsnwhite619 Friend of Leo's

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    All good - I always like new info. I've never run that PT in fixed bias, but I have it on my 5E3 clone, and I've used it on a couple other 5e3's I've built. JJ's across the board always hit around 370v B+ with a 270R bias resistor. If I'm thinking right, your 4k:4R OT should be 8k:8R with that setup. That's just wild that you're getting so much higher voltage with the same PT. I think it's rated for 138mA, so I guess you should be ok if you aren't going Neil Young all the time?
     
  17. 2L man

    2L man Tele-Holic

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    Hijacking continues ;)

    That is not whimpy transformer because I see it like this:

    Its output is 660V when current is 138mA and multiplying them the HV section power comes 91VA.

    When 330-0-330 is full wave rectified calculated peak voltage comes 465V without rectifier loss but max DC current comes 91VA:465V=195mA. This is because when CT tab rectifying is used there can flow current only half of the secondary coil at a time when they alternate and should not become too hot.

    If almost 200mA is used the output voltage does not come 465V, even when good efficiency silicon diodes are used, because peak current, which charge capacitors, will come double or triple because current can flow only when voltage after rectifier is higher than filter capacitor(s) and PT output voltage drop under 660V rating.

    However I don't recommend you try to take that high current long time but PT should be fine for 6L6GC about 40W PP amp.
     
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