Building a 5F6-A

[Bob M.]

It'll be my 2nd 5F6-A build, and my first build came out just great. Plus, I have two originals - it's one of my favorite amp designs and a great sounding amp.

I went thru the parts bins in my shop and I have almost everything I need, except for the transformers (power and output) and a choke.

I'd love to get some recommendations for these three components from the more informed forum members.
Techs in the know are aware that the post rectified B+ in the 5F6-A is about 432 Vdc for the power transformer as opposed to the way too high B+ voltage in the reissues of these classic amps. The output transformer should be a 2 ohm output. Not sure about choke but I'm assuming I could use the same/similar choke as other amps using 2x 5881 power tubes with a similar B+ voltage.

Thanks in adv for your recommendations,
Bob M.

[Chuck H]

Well I'm sorry I can't endorse any iron because I haven't built one of these. I'm just keying up to say...

Why not something different this time? I mean, you already have three 5f6a's. Two originals and one clone to take out so the originals can stay safe at home. Why not a reverb/trem amp? Or something with more hot rod gain?

No judgment here. You do you man. I'm only sharing my own perspective because the only times I've built the same amp more than once was because someone else wanted one.

Something I built for a customer but haven't for myself yet is a dedicated reverb amp. The one I made was a 1x10 15W tube combo but there are no rules. It filtches a little power from the host amp to drive a reverb tank. This allows you to keep the oginal amp tone untouched and also sounds better reverberating overdriven tones than a built in reverb. With a little thought it could be made to run effects too. Wouldn't that be a snazzy thing to have for your three Bassmans?

[mozz]

What about a 6G15 standalone reverb? I built 2 of those and there's nothing really like them before a old amp.

[Bob M.]

I already have one of those standalone Fender 6G15 reverb units, an early brown tolex 1961 version.
Bob M.

[Chuck H]

I already have one of those standalone Fender 6G15 reverb units, an early brown tolex 1961 version.
Bob M.

That's cool for sure. But that goes into the input of the amp. The circuit I'm talking about powers the tank from the WHOLE amplifier tone. ie:.. When you plug your 6g15 in and overdrive the amp you're overdriving the reverberated tone. With the circuit I'm talking about you are reverberating the overdriven tone. There's a big difference in clarity, effect, note separation. And the same goes for effects. When you distort a chorused tone you get mush. But when you chorus a distorted tone you get lush.

But like I said, you do you. Just defending my suggestion because your reply didn't actually represent what I was talking about and I wanted to clarify the difference and advantages. If you mostly play clean or get your distortion with pedals ahead of the 6g15 (and I don't so that may be a real difference) then the 6g15 is a truely iconic effect with great results and a signature. Since I play dirty and DI most of the time I do better with a different signal chain. Artist gonna be artists and however you make music is the right way for you.

EDIT: The original question still stands though. Why a fourth 5f6a? It's one of the best sounding circuits in the world to be sure. But just one of them. There are others.

[loudthud]

What is the B+ on the clone you built ? What transformers were used to build it ?

Just to make doubly sure you get the right OT, I'd be tempted to measure it's primary impedance.

[Bob M.]

Chuck H.,
I appreciate your comments and your logic is sound but everyone looks at these things slightly differently from one another. I agree that having four amps of the same design is basically the department of redundancy department. But in my world they would all be somewhat different from each other, feature-wise or speaker-wise or in a myriad of different ways, some complex and some not so complex.

As it happens, I'm cleaning out a storage locker and came upon a four by ten unloaded cab I forgot I had. I lucked into a 5F6-A empty chassis that a guy decided he didn't have the time to build and I was looking for a winter project to keep me busy during our snowed in times indoors. I have about everything I've ever wanted amplifier-wise (well, almost - I'd like to have an AC-50 head if they weren't so damn expensive these days). But that's another story. This way, I can experiment with various features that I wouldn't add to a real vintage amp and have some fun doing so. Besides, in my experience, no two amps are really ever the same.
Bob M.




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[Bob M.]

Chuck H.,
I think your project sounds great, perfect it, post it here for free for all to use or sell it online, as you prefer.

I redesigned the reverb circuit for the Peavey Nashville 400 amp (years ago) and that's become the preferred reverb circuit for that amp over time. I posted it on the Steel Guitar Forum, free for all to use.
Bob M.

[Bob M.]

Loudthud,
I have so many amplifiers I'd have to look up this information in my files. I'm sure I did the proper research at the time of building this amp about fifteen years ago. Plus, it sounds pretty damn good.

Yes, I'll carefully check out all parameters on any transformers I might buy. I'm kind of a 'measure twice, cut once' type when it comes to buying transformers. Bob M.

[Chuck H]

Chuck H.,
I think your project sounds great, perfect it, post it here for free for all to use or sell it online, as you prefer.

I redesigned the reverb circuit for the Peavey Nashville 400 amp (years ago) and that's become the preferred reverb circuit for that amp over time. I posted it on the Steel Guitar Forum, free for all to use.
Bob M.

I would post it but I no longer have the schem on a computer file because it was never backed up. I might have a paper schem somewhere. Maybe I did post it here but it would have been forever ago.?. Anyhow, since I did it several others, including MOJO, have come out with something similar for sale. The only real trick to it was the input. Which is just a voltage divider that feeds a reverb tank about 1W of power. I had a VU meter on the front so you could dial in the right amount of drive for the tank with amplifiers of any wattage and a protection circuit in case someone failed to adjust it correctly. Other than that it was just an amplifier. I may build one for myself some day but the truth is I hardly play anymore so,.. Priorities.

EDIT: And true that re: no two amps even of the same circuit sounding the same. And the 5f6a has been an example in my own life. I heard one at the 2009 Winter NAMM show that had the very best clean tone I've ever heard but no so much the overdrive. And I played through one at a "jam night" party that was one of the best overdrive tones I've ever had but not so much the clean. Same circuits. Same 4x10 configuration. Very different sounding amps. Hell, even a JTM45 is very close to a Bassman but sounds very different. So I digress.

[Mick Bailey]

When buying transformers for amp builds or replacements, my first choice is always Hammond. I've never once regretted this and they're predictably good, reliable and consistent.

[Chuck H]

When buying transformers for amp builds or replacements, my first choice is always Hammond. I've never once regretted this and they're predictably good, reliable and consistent.

+1 to this. But I've never built a 5f6a. So while I agree about the Hammond transformers I have no first hand experience with this model amp. I read in one of the Weber books that the original Triad 5f6a transformers were labor intensive being paper bobbin and seven interleaves. I think someone here debunked this once but it sticks in my head because I can't imagine Gerald pulled that out of his butt and printed it in a book. Hammond doesn't offer anything like this. Not even Mercury does. Pretty much all the Bassman transformers you'll find are just standard Fender transformers with a Bassman footprint. If the seven interleaves on a paper bobbin thing is true then this would be a boutique transformer made made for special customers that want something authentic. And pricey. Not knowing how far this project is intended to go I didn't suggest any transformers.

[Helmholtz]

I have an original 45249 OT (as used in the 5F6A) in my '61 Concert.
It measures essentially the same as an average BF SR OT (measured 3 of them) or a Fender '59BM RI OT.
Extra interleaving should show in lower leakage inductance, which I didn't find.