Tube Amp Archive

Thanks! Yes, pretty typical 5F1 (changed a few components to reduce flub/add treble), so good to know all is within spec.

Schematic if helpful:

Quick question: My 5F1 clone has 1.5k cathode bias resistors on V1A and V1B, for a 12AX7 (gain factor of 100). I've replaced it with a 12AY7 (gain factor of 45) and much prefer the tone, reduced gain, more clean headroom etc. Is the bias resistor still within an "acceptable range" for a 12AY7, or is...

OK I've been tinkering today, ran wires out from the Volume pot so I could easily swap out caps while playing. I tried 100 pF, 150, 220, 250 and 470. It seems 150 or 220 are the charm in this amp. It's amazing the difference (and improvement!) with the cap in or out. Sounds like it has a blanket ove...

Brilliant, thanks again, will have a go tomorrow and report back!

Thanks Martin. This is how the designer labels the pots, 3 2 1 left to right looking from the back of the pot. From the schematic it seems 1 is input, 2 is wiper, and 3 is ground, so I should put the bright cap between lugs 1 and 2, right?

I finally got a load of caps to try in my 5F1 based amp.

Quick question: Do I put the bright cap between lugs 1 and 2 of the Volume pot, or between lugs 2 and 3? I've seen it mentioned both ways. Or doesn't it matter?

Thanks for the suggestions. I'll give the 100pF cap on the amp volume control a go and report back when it's done. I'm basically looking for two things with my amp (an Amp Maker WF-55 kit): 1) Less volume. I've addressed this by changing the 12AX7 for a 12AY7 and it worked well, but I still rarely h...

This is all brilliant information, thank you so much. I'm coming from an audio engineering perspective (been a full time mastering engineer since 2011), so defining the correct terms is important to me. Electrical engineering, well I'm just a beginner, so thank you guys for helping me grok this stuf...

Quick question: Does a so called "Bright Cap" on a volume control (whether it be in the guitar, or the preamp input volume control on a simple amp like a 5F1) actually boost highs, or does it really act as a HPF and rip out lows, leaving the highs alone? I am guessing the latter, but I keep seeing i...

Thanks so much Martin! I knew I could rely on this place for some clear and experienced answers. So, it seems that most of my fears are ungrounded. I think the key penny that hadn't dropped for me was this: The signal voltage becomes relatively larger with respect to all of the other voltages, reduc...

Hi all, Something that I've been wondering about recently that I don't fully understand, but know I'll get a good answer here! The kit maker for my 5F1 clone sent me info on how to add a Wattage Reduction Switch to my amp, that goes from 4w (standard) to 2w or 0.4w. This apparently cuts the loudness...

Thank you for the in-depth answer Martin. It's a darkish sounding amp anyway, so I'd hate to lose any more high end. I'll try and hunt down the pull switched pot.

3) The online TSC shows that with the pot at minimum you have maximum attenuation of frequencies, and with the pot at maximum you essentially have it bypassed/zero attenuation. I'd like it to be the opposite way round. i.e. pot at minimum = no effect, pot at maximum = most effect. Is this possible, ...

2) Where exactly in the amp schematic would it be wisest to fit this pot? (See schematic in original post). Between the C1 coupling cap and the Volume control VR1, or directly after VR1? Or later in the circuit directly after the C2 coupling cap before the power stage?