My first tube amp build 5f2a

[spi]

Just wrapped this up. I took my time building it, also researched a lot both before and during. It has some mods, but nothing to change the tone much, mostly for safety:

• Added a RC filter stage of 22uf + 250R before my B+. This was to reduce noise and it also drops the B+ voltage by about 10V.
• Added a 250K bleeder resistor. This was really effective. I also bought a capacitor discharge tool, but turns out that I didn't need it as the bleeder worked wonderfully, but it's nice to have just in case.
• Used 24-16-8 uf filter stages instead of the standard 32-8-8. The 5f1 uses 16-8-8. I don't know how much this changes things since I can't compare it to anything else, but I figure it kind of splits the difference between the two.
• Added power tube grid stop (1K5) and screen resistors (470R) to the 6V6. I got this idea from the Hoffman schematics.
• Added rectifier backup diodes for protection. Got this idea from Robrob site.
• Changed feedback from 22K to 33K to account for 8ohm speaker.
• For the grounding I followed tdpri user King Fan's diagram.

I think that sums up the mods.

Despite going slow and careful I still made a few gaffes:

• I accidently wired the rectifier heater filaments to the pins where the rectifier plates should go. I was using a black-and-white printed wiring diagram and wasn't paying close enough attention to the colors. Luckily I trimmed them with enough length to reach far enough to where they needed to go. I realized it right after soldering.
• I also wired the power transformer to the fuse instead of the switch. This one I trimmed a bit too short, but since I hadn't wired the other end yet, that side could make it to the switch, and the short one was spliced to the power neutral. This too I realized right after soldering.
• After testing the sound on bench and hearing it work, I put the chassis into the cabinet, and tried it again to get no sound--quickly realized I forgot to plug in the speaker. I'm really happy I used a switching jack on the speaker to short it to ground or this could've been bad, but it seems like it came out unscathed.

I haven't played a 5f1 or 5f2a before, so the sound is new to me. So far I'm digging it.

 

[anevilspar7an]

How's the clean tone you are getting so far?

 

[gtt]

Any sound clips? I would love to hear it!

 

[spi]

How's the clean tone you are getting so far?

I'm not great at describing tone, but sounds really nice to me.

This is my first Fender-style amp. Although I've owned and built tons of pedals, I've only owned one tube amp before--it's Peavey Classic 30, and I've had it for almost 30 years now. So I don't have a lot of experience with different amp tones other than pedal-in-a-box replicas.

Any sound clips? I would love to hear it!

I may try to get a clip later.

 

[hamerfan]

One point: The feedback resistor influences the character of a tweed amp. A higher resistor gives you a more rawk tone, but on higher volumes you need more damping to have a workable tone. So i made a switchable feedback.

 

[HamishR]

It's a cool feeling to play through an amp you've built isn't it?

If you don't mind I have some tips to share - I've built a lot of amplifiers ad learnt a lot along the way! Fortunately not too many the hard way!

One thing is that you really want to keep filament wiring away from the rest of the circuit as much as possible. Where you have it leaving the lamp holder I would suggest it goes straight down to the power tube via the rear edge of the chassis - similar to where you have the filaments going to the preamp tube. Keep the green wires tucked into that chassis lip as far from the circuit as you can.

Invest in a big soldering iron so you can solder those ground connections to the chassis. It is a bad idea to connect the grounds to the transformer bolts. It's easier, I know - I have done it in the past! But with vibration etc those bolts can become loose and you REALLY don't want to lose those ground connections.

And fill the eyelets with solder. It's far less likely that any wires will come loose that way. You will never see an old Marshall or Fender without those eyelets filled. The fuse holder looks like a dry joint waiting to happen.

Other than that it looks really good, especially for a first build. I strongly recommend watching some of Psionic Audios videos of YouTube. I have learnt so much from him and my amps have never been better since using his tips.