Boothill amps 5F2? Anyone build one?

mikhett

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I'm thinking of taking the plunge to build one.Im an experienced NAVY ET but never built an amp B4. THANKS
 

mjcyates

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My first amp build was a Boothill 5F1. If you can solder, follow a layout/schematic, and pay close attention to details you can build one no problem.
 

Paul-T

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Yup, I built a Boothill 5f2a, first build. All straight from Dave except I sourced the tubes, and the PT as postage from US to UK is expensive. Couldn't be happier. It sounds absolutely fantastic with a 10 inch jensen alnico (if you're in the US you have lot of choice for speakers)

I built it pretty much straight; some time later I tidied up the wiring with solid core for the heaters, using #22 gauge for the preamp tube - it's easier to get it to stay in place... and, er, looks nicer. It's very quiet indeed.

Dave supplied the small 5W OT, 40-18115, Classitone, which sounds great to me. He still has it in stock. 4 ohm output only which could limit your speaker choice. I used the Hammond 290CAX for my PT - I wired it up with the 275V tap, influenced by jwhite, again it sounds amazing. I used rob robinette's mods for earthing, the diode rectifier backup and the virtual center tap for the heaters.

I have a feeling this is actually a 5F1 board, where you use three bigger power smoothing caps rather than 4 smaller ones. Loads of room in a 5F2a chassis!
 

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King Fan

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Boothill has a long-standing rep for solid kits at good prices, and the 5F2a is a good choice for a first build. Yeah, technically the 'a' matters. :)

Does Dave supply the transformers, or help you spec them? Getting the right ones, especially in today's supply economy, is a big deal.

Layout matters. I haven’t looked at Boothill's but with other kits out there I’d compare the power wiring and grounding to Rob's similar 5F1 and ask here when you see differences. Even in a simple amp like this you get several good choices and some less good ones.

Many kits supply wire I don’t love. You’re experienced, so likely know, and can likely source some nice 22ga wire, which is all you really need here. In a small amp like this the ability to take and hold shape (“lie down, boy, and roll over”) is key. Good solid core or pre-tinned wire really helps. Lots of threads here with good discussion. Here's one I recall discussing two local favorites.

https://www.tdpri.com/threads/valvestorm-or-mojotone-pushback.1062614/
 

D'tar

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Good price, great price... Whatever drives your motivation... Mojotone is pretty much one stop shopping on a complete kit. Shipping from multiple vendors adds up quick.

 

Paul-T

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I notice mojotone are out of Champ power transformers (I've been looking at a GA5 PtP) and maybe Output transformers so you're stuck with two suppliers either way - of course, if you need a cabinet, mojotone makes good sense.

I'm sure it's much of a muchness but Boothill do a good selection of metal film vs carbon resistors and pretty good capacitors.
 

Lowerleftcoast

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experienced NAVY ET
Nice first build. Since you have some experience, read through this: https://www.tdpri.com/threads/just-for-grins-a-draft-optimized-5f1.1088759/
and read through the Rob Robinette sites involving the Champ-ish amps. Also have a look at the 5E2 schematic. It has a choke that could be incorporated for additional power filtering. It is all food for thought. Then... make the sensible changes to the boothill instructions for a hopefully better finished product.

If you post pictures as you build, the shock brothers will kibitz. All will be well.
 

bermuda

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+1 on Boot Hill - I built 3 of Dave's amps -started with a 5E3, then 5F1, and a 5E7. All great amps from his layouts and posting photos on this forum for progress and quality checks.
 

Prophetsnake

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I bought a kit from Dave. Good quality stuff at the best price going. I've bought a few other odds and ends from him as well.
 

nolabjorn

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Boothill does provide good quality parts and he always answers emails and questions. His directions are not that complete, but we build to learn in the end.

Speaking of learning, I'm doing a Mojotone PR and the little silver mica caps are off value. There is a 10 PF that measures 74 in the Reverb Circuit (bright). And another one thats supposed to be 510 PF that measures 740 PF.

Any thoughts???
 

King Fan

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His directions are not that complete, but we build to learn in the end.

You’re right.I’m of the school that says super-perfect instructions aren’t really possible — or in fact desirable — so full points to Dave, some support and some leaning.

BTW in measuring small capacitance it can be fun to measure your probes / leads without anything in between, and see if you can figure out the meter's lower limit / precision.
 

nolabjorn

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I built a Champ from Boothill amps last year and after getting the ground bus more or less right, it fired up w/o any hum. I love the sound and love, love, the breakup when it starts to growl.

i'd love if anyone has other ideas on the 10PF cap measuring 74PF and the 500 silver mica measuring 740 PF.
 

jman72

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My son and I built a Champ from a Boothill kit a couple of years ago. For a kit, it was hard to beat price wise and for convenience. Awesome little amp.
 

D'tar

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i'd love if anyone has other ideas on the 10PF cap measuring 74PF and the 500 silver mica measuring 740 PF.

Hmmm. Odd. What are you measuring capacitance with as 74 and 740 are oddly similar for such different cap values.
 

King Fan

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Dang, I had the half-formed notion your meter only read in multiples of 10 x 7.4... :)

When I had to measure really small caps, I ordered in 5 or 10 (they're cheap) and measured 'em all. Gave a me a great sense of my meter's precision, bias (they may tend to read high in this range), and also (once I allowed for those factors)... which cap was best.

Now you made me curious. What does your meter say when you measure capacitance probe to probe? Do you have more than one set of probes to compare?
 

Lowerleftcoast

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Klein Tools MM700 Multimeter
Specs on this meter 40nF to 4000uF. So they claim it is accurate down to 40,000pF +/- 5%.

This meter is not accurate in the 10pF and 500pF range.

Carry on.

EDIT: you may try metering a .047uF in parallel with the pF value caps. The difference may be shown near the pF rating. (two caps in parallel add so, the .047uF and the 500pF cap may read ~47,500pF. Subtract the 47,000pF, leaves the 500pF reading.)
Also the probes are too long to provide accurate readings in the pF range.
 
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