5f4 Super and 5e7 Bandmaster questions and transformers

Discussion in 'Glowing Bottle Tube Amp Forum' started by theprofessor, Jan 8, 2019.

  1. theprofessor

    theprofessor Friend of Leo's

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    I've gotten a bug to build another tweed amp at some point this year, and I'm trying to take it slow (we'll see how that works out). I was initially attracted to the idea of a 5f4 tweed Super in 2x10, but I've recently begun to think about a 5e7 tweed Bandmaster with its 3x10 configuration. For reference, I've attached .pdfs of both schematics below in the second post of this thread.

    Some questions have come up that I'd like to have your input on. Since they require a lot of explanation, I've bolded the actual questions and also put them in red.

    First: In comparing the schematics, the 5f4 Super and the 5e7 Bandmaster are identical in every way, save one part: there is a 4.7M resistor ahead of the V2b grid (pin 2) that connects to the .1 uF coupling cap in the 5f4 Super. In the 5e7, that same resistor is 10M. And that's it. Every other part (including the voltages on the schematic) is the same.

    So:
    I've read some about the impressions of these two amps, and they seem to be fairly different narratives (I've never had the opportunity to hear either in person). It seems that the Super doesn't behave exactly like the Bandmaster and that the Super likes to stay clean longer as well. Perhaps this is wrong, but it does seem clear that a tweed Bandmaster is an über cool amp, whereas the tweed Super doesn't seem to have the same volume in its fan-club (aside from Leo himself, I suppose). I don't really understand why this would be the case. The discussion below and some preliminary questions set up the final question at the end of the post.

    So here are the questions:

    1. What difference does the 10M as opposed to the 4.7M resistor make in that spot on each amp?

    2. I believe the same PT, OT, and choke can be and (in some cases, at least) indeed was used in both the 5f4 and 5e7.

    PT: The Super lists the PT as 8087, the OT as 45216, and the choke as 14684. Given that everything is identical on the schematics, including the voltages, it seems evident that both used the Triad 8087, which seems to have a modern clone in the Classictone 40-18073 (http://www.classictone.net/40-18073.html), among others. I'm not exactly sure if that's the one I'd go with, but it seems applicable to both models. There is also the 40-18029, which could give you lower voltages with the lower tap, but it'll have a bunch of extra wires (not a fan of that).

    OT: There seem to be some different stories on the Bandmaster OT. The Super used a 4-ohm tap for its (2) 8-ohm speakers. The Bandmaster, of course, has (3) 8-ohm speakers. I believe at least some (all?) of them ran a 4-ohm tap as well, which was a mis-match to the speaker load ([3] 8-ohm speakers / 3 = 2.67R). It seems I've seen some folks suggest that there was actually a specially wound 2.67R OT tap, but I'm not sure. All that to say: at least some specimens of both the 5f4 and the 5e7 ran a 4-ohm OT. The difference was the speaker load, with the 5f4's (2) 10" speakers running at 4R each and the 5e7's (3) 10" speakers running at 2.67R each (assuming a 4-ohm OT). The OT on the Super schematic is listed as 45216. The Bandmaster schematic doesn't give a Triad number. I have read, however, that they both used Triad 1848. There are several current models that have the correct 6k primary impedance and multiple taps. The Classictone equivalent of 45216 on the 5f4 schematic is Classictone 40-18088, and it actually has 2.67R, 4R, and 8R taps: http://www.classictone.net/40-18088.html

    choke: It is well documented that a lot (if not all) the chokes that come in amp kits for the 5f4 and 5e7 (including Mojotone's) are woefully underspec'd for the current. Given that the schematic for both the Super and the Bandmaster puts the choke before the power tube plates instead of after them means that the choke would need to be spec'd for 200-250 mA (the Mojotone one that comes in the kit [MOJO 777] is spec'd at 3.5 Henries of inductance and 100R resistance, but only 100mA of current!). Again, Classictone makes a choke that looks like it would do a much better job with the current, though I don't know what difference the inductance and resistance specs make to the performance:

    Classictone 40-18058 is rated for 250 mA of current, 3H of inductance, and 125R resistance.

    Hammond 159S is rated for 225 mA of current, 4H of inductance, and a resistance of 65R.

    I'm sure there are others, and I'm planning to keep the choke before the plates rather than move it after the plates (at which point a smaller choke would be fine, though one would need more filtering of the B+ with the caps). What is the difference in inductance and resistance between these two filter chokes, and how do those specs compare with the choke or chokes used in the 5e7 and 5f4?

    3. So this is what I'm driving at:

    I love the sound of the Bandmaster, and it seems to be prized by others. I think I'd like the 5f4 Super, but I don't know. And it doesn't seem to be as well loved in terms of Fender tweeds as the 5e7 is (and the fact that the 5f4 was supposedly one of Leo's favorites suggests to me that its reputation for higher headroom, longer clean, and brightness is correct; that's what he liked).

    • Could I simply use a 2x10 configuration like the Super and get close to the Bandmaster tonality?
    • I know that the third 10" speaker will add a great deal to the sound of a Bandmaster, in comparison to a Super, but is the magic of the Bandmaster versus the Super really only (1) 10" speaker?
    • How important is the impedance mismatch in the Bandmaster sound? Though the Classictone OT listed above actually includes a 2.67R tap, it would seem advisable to stick with the 4R tap to me. Am I wrong?
    • Except the one resistor listed at the first of the post (4.7M versus 10M), it sure seems it would be easy to build a 5e7 using a 4-ohm OT that would run either (2)-10" speakers on a 4-ohm load each or (3)-10" speakers at 2.67 ohms each. But it sure seems to me that there must be more to the difference in sound between these two amps...
    • In the end, I'd rather have the portability of the 5f4 if I can get close to the sound of a 5e7. I'm wondering out loud how different the 5f4 and 5e7 really are.
    Either way, I'm planning on running a pair of vintage Tung-Sol 5881's and a 5U4 rectifier.

    Thanks for listening to my long-winded explanation and my questions!
     
    Last edited: Jan 8, 2019
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  2. theprofessor

    theprofessor Friend of Leo's

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    Here are the schematics for the two amps.
     

    Attached Files:

  3. Uncle Daddy

    Uncle Daddy Tele-Holic

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    I bought a clone based on the 3x10 Bandmaster and I found the tall cab a problem with regards to portability, so I fitted the chassis in a 2x10 Super cab and lost one of the speakers. I kept everything else the same, and didn't really notice a huge difference in tone or volume. I left the nfb resistor as it was and it sounds pretty clean with a later break up.

    I think Hammond now makes a Bandmaster O/T with the 2.5 ohm output. Weber makes the correct value choke, if I recall correctly. Mine has a 4ohm o/t into 2 8ohm P10Rs.

    The Super is a fine sounding amp, the 2x10 giving a swirly 3D sound. Both tone controls also affect the gain level, so you can go from a semi scooped mid tone to full on gnarly. I also use 5881s to try to keep the volume more manageable.
     
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  4. Wally

    Wally Telefied Ad Free Member

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    pprof, imho, there are four Fender amps from that period that belong in on classification...the 5E7 and 5F4 you mention and the 5E5A Pro as well as the 5E8A Twin. Pull one of those 5u4’s from the Twin and you have a very, very similar amp compared to the other three.
    Those resistors you mention are in a local feedback circuit. The larger resistor results in less cancellation. chck out the negative feedback circuits in the output section. The Twin has the least cancellation there.
    I have owned the Twin the Pro, and the Bandmaster...two of those at one time. I like the Bandmaster.....wonderfully smooth overdrive when pushed. The other two are great amps, as well. I have never played through a Super.
    If I were building, it would be the Bandmaster.....ommv.
    Side story. I sold the two ‘59 Bandmasters and the Twin to a fellow in Cali....long ago. One of the Bandmasters came to Me as only a chassis...circuit complete. I had to buy a retro cab and installed Emi Alnico speakers. It sounded just as good as the original 5E7. However, the buyer called me before shipment and said he did not need the cab and speakers for the non-original amp. Believe it or not, he had found a ‘59 cab and speakers for the chassis!!!
     
  5. King Fan

    King Fan Friend of Leo's

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    2x10? 3x10? One resistor different? I think the sword for your Gordian knot is called "5F6a." :)
     
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  6. Bob Arbogast

    Bob Arbogast Tele-Afflicted

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    I built a 5F4 in about 2003. A few years later, I mounted the chassis in a 5E7 cabinet. (I'm pretty sure I made the 4.7M/10M swap.) The new amp was bigger in every way. The only downside was portability. FWIW, I had a pair of Weber 10A125-30W speakers in the 5F4 and a trio of Weber Sig10AS speakers in the 5E7.

    (Down the road, I got rid of all my tweed amps in favor of my BF Vibrolux Reverb clone.)
     
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  7. John E

    John E Tele-Afflicted

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    I can't help you at all with the schematics... but I had to add here that the best clean sound I have ever heard or had in my posession was a 5e7 built by Mark Norwine into a burnt out Blues Deluxe amp. That amp was unbelievable. It sounded great with any guitar or pickup combo I ran through it. And it was LOUD (which is why I (STUPIDLY) sold it). I am sure the EV12L in there didn't help.... Heck just 4 on the Vol knob would cause animals in Africa to stampede... LOL.
     
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  8. Wally

    Wally Telefied Ad Free Member

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    I am suspecting that he built the 537 circuit but used the Blues Deluxe transformers???? The 5E7/5F4/5E5A amps are 26 watt amps, iirc. Neither of the Bandmaster I had were out of the ordinary loud and went into a very compressed, smooth overdrive. The Blues Deluxe PT would deliver different voltages and the OT would not do what the BD OT does.
     
  9. theprofessor

    theprofessor Friend of Leo's

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    Thanks so much for the responses, everyone!

    As for the choke: what difference do the specs on inductance and resistance make in terms of choice?

    @Bob Arbogast : I know you're something of a 10" speaker connoisseur. In a 2x10 configuration (5f4) in which one is looking for alnicos would you recommend the 10a125s (30W)? I do know I really like the sound of the Eminence 1028ks.
     
  10. Wally

    Wally Telefied Ad Free Member

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    Very, very different amp, ime.
     
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  11. John E

    John E Tele-Afflicted

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    Good question, I think so but I'm not positive. I know he said he tweaked it a bit but other than the cabinet and the chassis I'm not sure what else he was able to reuse. I know he threw the circuit board away and built the 5e7 circuit into the chassis so I am thinking you are correct in that he used the existing transformers. It was already built when I bought it. What a great amp... one of the ones I let get away that I still think about (and kick myself - HARD) often. It's the clean tone that I dream about when talking about ultimate clean. Between the cabinet and the speaker that amp was not only loud but it weighed like 75 lbs. I am also thinking that speaker was so clear and focused it probably made the amp seem much louder than it actually was. The beam from that speaker was like one of those infomercial flashlights cutting through a pitch black night! lol
     
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  12. King Fan

    King Fan Friend of Leo's

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    Just joking around. I didn't know what you've experienced and the Prof has researched, that the Bandmaster is better liked than the Super. I do know the Bassman is revered -- though no doubt for very different reasons.
     
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  13. Bob Arbogast

    Bob Arbogast Tele-Afflicted

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    The 1028 is one 10-inch speaker that I have no experience with. So I can't comment on it. (Maybe someone will donate a pair for me to try.:p

    FWIW, I did prefer the Sig10AS to the 10A125. My recollection is that It has a rawer voice.
     
  14. Wally

    Wally Telefied Ad Free Member

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    Bob, the Emi Alnico 10 ranks right up with the Weber clone of the P10R....some folks prefer it. IMHO, it is one of the best speakers I have ever used. I once loaded an 8x10 checkerboard Marshall cab with them to sit under a 1979 Md. 2203....wonderful combination.
     
  15. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

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    @theprofessor, thanks for putting this all in one place... a Super/Pro/Bandmaster is on my short list to build. And, I've read bits and pieces about the trannies and choke, but never had it all in one place to reference. But, your questions were the same as mine. I am just not close enough to build time to ask them outright.

    Hopefully someone can answer your question about the choke.
     
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  16. pedro58

    pedro58 TDPRI Member

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    I would, perhaps, think more in terms of application than in terms of one amp sounding better than the other. They're both so similar, the difference would be negligible. Maybe in a studio or private rehearsal space you could take advantage of whatever the Bandmaster's extra speaker has to offer. Maybe if you've got a really good attenuator, you could do the same. But in a band or gigging situation, the Super is a better choice, for many reasons, volume and portability being at the top.

    IMO, folks who prefer the BM are enamored of its rarity more than any tonal advantage it has over the Super. And how many people have played the two circuits in an A/B comparison? I haven't.

    I built a 5E5-A and ended up preferring it with a 2 speaker configuration. I never liked the 15" speakers I tried in it, and I tried about 4 or 5 different ones. I was about to convert it to a Super with a 2X10 baffle, but a friend of mine begged me not to do it, to just sell him the amp, so I did.

    I have since acquired and modded a 5D4 Super and it is fantastic. Two speakers is enough...
     
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  17. King Fan

    King Fan Friend of Leo's

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    Ok, I don’t know much about chokes, but I thought 4 Henries was the spec and that there were basically just a small and a large Fender choke, and the big one was for the pre-plate slot.

    And somewhere I heard good things about the 'NSC' stuff Doug Hoffman sells.

    [​IMG]


    Sent from my iPad using Tapatalk
     
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  18. theprofessor

    theprofessor Friend of Leo's

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    Thanks so much. This is kind of what I'm driving at. It just seems almost impossible to me that they would be night and day different. To be sure, the extra speaker and the bigger cabinet would make things bigger and more 3-dimensional, I would guess. But given that they're basically identical, save the 10M local feedback resistor in the Bandmaster as opposed to the 4.7M one in the Super, it's hard to believe they're not very close in tonality. It did occur to me, too, that the reason it is more prized might have to do more with rarity rather than tonality. Thanks!
     
  19. Wally

    Wally Telefied Ad Free Member

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    I cannot speak to an A/B comparison of the 5F4 and the 5E7. I can only say that there was something about the two 5E7 Bandmasters that I had that was different from any other tweed amp...or any other amp....that I have ever owned.
    Prof, no matter which speaker configuration you decide to build, I would suggest three things. First, get the voltage correct. Secondly, Get the OT correct for whichever speaker configuration you choose. I’ll try to remember to get whatever info I have on that. I know where I would go for trannies...especially the OT. Thirdly, I would suggest putting the local feedback resistance on a switch to go from the 5K to the 10K so that the difference can be experienced. I have a sneaking suspicion that that is what I liked about the Bandmaster circuit. At the time I owned those two...and the 5E8A as well, I had no idea what amp was more or less rare. I do know that I have owned two 5E7’s, and I have never had a 5F4 Super come anywhere close to me.
     
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  20. theprofessor

    theprofessor Friend of Leo's

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    Thanks, Wally. I agree on all points. To take them one-by-one:

    1. Voltages - The Classictone 40-18073 PT is 325-0-325 @ 200 mA, 5V@3A for the rectifier, and 6.3V@5A for the filaments. The Hammond 290DX is identical, but with 4A for the filaments. The Mojotone PT (MOJO752) for both the 5f4 and 5e7 is higher-voltage, at 355-0-355, with 5V@6A for the rectifier and 6.3V@6A for the filaments. Where the Classictone and Hammond are rated at 200mA of current, the Mojotone is rated at 300 mA.

    To go with the Classictone for a moment: the spec sheet gives voltages for a 5U4 rectifier, depending on the current: anywhere from 356V@200mA to 396V@100mA. The Fender schematic shows a B+1 of 410V. http://www.classictone.net/40-18073.pdf

    2. Output Transformer I'd love to get the OT just right. At the moment, my plan is to get an OT with an 8R and 4R tap and put them on a switch. I can play the chassis as a head with a single 12" speaker until I get the cabinet and multiple 10" speakers sorted out, and then I can switch to 4R for either 2 or 3 speakers, whether 5f4 or 5e7. Please do let me know what you'd recommend for an OT. I think I know, but I'd like to hear specifics.

    3. 4.7M versus 10M local feedback resistor. I also have a hunch that the 4.7M local feedback resistor has a lot to do with the extra headroom in the Super, and I'm planning on building it with the 10M resistor. I like the idea of a little earlier breakup like the Bandmaster. It's a great idea to put it on a switch to move between 5f4 and 5e7 circuits with the mere flip of a switch.
     
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