My first build, a 5f6a

Hi all! My wife is sick of hearing about my 5f6a build, so I thought I could talk with you about it. I started with a Boot Hill Amps 5f6a kit. I changed some parts out--not because they weren't good quality, but I really just wanted to build it my way (OCD style:lol:).

I bought a Weber cab and finished in shellac and mixol. The cab has two alnico and two ceramic Weber Signature series speakers. I really like the sound, and they were very affordable.

I used ClassicTone output and power transformers, and all the voltages were perfect for me, 435V @45mA at the plate. I'm using JJ 6L6GC power tubes and EH pre-amp tubes, with a 12AY7 in V1. T think the rectifier is a Sovtek.

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I had to move the pilot light over to the ground-switch hole, so that I could fit my filter caps. I can't believe I thought that I could fit Solens in there:lol:
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I'm not happy with my sloppy heater wires, but it works!
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I felt like I was building a ship in a bottle. That chassis is tiny! I wanted to add B+ fusing, but I just couldn't make it fit safely. I have power and standby on one switch, although I might just replace with a normal power switch. I used Panasonic TS-ED caps for the reservoir (2x100uF) and screen filter caps (2x56uF). I hid the third stage filter (20uF) between the turret board and chassis and insulated the leads.

Once I swapped the OT primary leads, it worked! What a wonderful feeling!

So far, I really like the sound, but there's some noise at high volume. If I don't have a cable plugged in, I can turn up the volume to max, and I only hear some hiss, and turning up the presence seems to increase the hiss level. If I plug in a cable, then I hear 60hz hum at higher volumes. I guess the amp isn't the noise source, right? I guess it could be an input jack problem:confused:

Thanks for looking! It works fine, but I'd appreciate any suggestions for improvement.

If it works fine, button it up and enjoy it. Very tidy first build BTW.

Looks like big fun, congrats!

Nice work. You have demonstrated an amazing level of competence and know-how. I would guess that you have you built other reasonably complicated electronic devices before this one. And/or you did a lot of studious research for this project. Excellent work!

If you feel up to it, you might redo your heater wires. They should not pass between the rectifier wires. The twisting should be a bit tighter. And you could lay the wires down in the "front" edge/lip/corner as you redo them.

Not being critical per se, but with your level of expertise, it is easy enough to do and it will help reduce some of the noise.

FWIW, it wasn't long ago I did heater wires the way you did yours. Nobody's prefect.

Again, Awesome job!

Thanks for the tips on the heater wires, Dave! At some point, I'll redo them as you suggested,

have you tried different guitar cables and guitar. I had a bad cable that was causing some pickup. Have you also moved away from any significant electronic source such as flourescent lights. with a long/bad guitar cable you can have pickup.

internally heater wires good source to start with. just nudge them a bit out of way at diff points and see if it has effect. Next step you can run your heaters from a battery (pure clean source) and see if you still get noise. if you do then it is likely rectified (120hz noise).

thats enough for starters. great amp, I am jealous, I really want to build a Bassman. someday soon. Does it sound good playing blues?

Thanks, Cruisin Home! There is a lot of EM pollution in my music room.

I'm a bit confused about debugging the hum. If I have nothing plugged in and the jacks are shorted to ground, I don't get any hum. Does this mean that the heater wiring can't be the source of the hum, or would the preamp heater wiring noise only be heard with something plugged in?

Thanks!

yes, the jacks shorting do tend to make any V1 and beyond hum go through if the source was lets say heater noise coupling over to the input lead to V1. essentialy they are conncecting the input(s) to ground.

try those suggesstions I said and lets go from there.

OK, thanks! I'll try your suggestion tonight...and yes, blues sounds very sweet, but I can't get the volume past 3 without a loud knocking on the wall, from the next-door neighbors:)

So jealous.

So jealous.

No kidding.

I'm always in awe of the people here that can build their own amps. To have that much control over your sound. Count me as one of the jealous.

I'm always in awe of the people here that can build their own amps. To have that much control over your sound. Count me as one of the jealous.


If I can do it, then you can definitely do it too! I took my time, found a lot of great online information, and pestered the wise people of TDPRI and the Hoffman Amp forum:grin:

I think the buzz is external noise. I played with lead dress but couldn't get any reduction in hum,. When I replaced the back panel, the noise level went way down. Maybe shielded wiring is worthwhile from the jacks to V1?

For now I'll just enjoy it, and rework the wiring another time.

Thanks!
Rob