The Amp Garage

Thanks.

True, not that safe. But this amp never leaves my music room, and make sure our pets are outside when I play it.

A tiny guitar amp I made some time ago.

I had this small chassis lying around with the name tags "E80F" and "E81L" at the two openings for tube sockets, so that 'dictated' the tube choice.

A guitar amp I made some time ago, based on the clean channel of the Vox AC-15.

It could be caused by the 16 uF capacitor (just after the 22K Ohm resistor in the power supply rail) which over time lost some of its capacitance. You could check this by temporarily bridging it with a new/good capacitor of 16 uF (or higher).

Vox used to run a quad of EL84's at 50ohms (like on the drawing here selectable between 50 and 82.) The higher the resistance, the cooler they'll run, so why do you say a pair at 82 is going to do worse? Or is it more the implication that if it were a pair it should really be at 100 or 164 ohms at ...

I don't think a pair of EL84's at Vak = 300 V and Vg2k = about 310 V, and with a cathode bias resistor of only 82 Ohm, will survive very long. I think that's why Roberto suggest changing for a 150R resistor. Dunno for the rest. Exactly. OK, maybe you should have written it more clearly, like: "If y...

What you can try to do is: - pull out a pair of EL84s (one per side) - switch to 22 uF - switch to 82 Ohm (it's like having 41 Ohm on a quad) - switch to 8 Ohm and plug a 16 Ohm speaker (this will give you twice the Raa, so correct for a pair of EL84s) Tubes will run very hot, so the only mod you c...

Yes, you are supposed to double them if the graphs you are looking at are valid "per plate".

The EZ81 (= 6CA4) has way more (about 1.5 times) current capability than the 6BW4 and EZ80.

The EZ80 and the 6BW4 would run near their limits in an amplifier with 2 x EL84 pp at Vb = 300 V.

So I would choose the EZ81.

With the exception of the grounding of the secondary of the OPT, I never use the chassis for earth returns. I wire pretty much all earth returns to one central earthing point close to the instrument input(s). I connect the earth/ground lead from the AC inlet also to this point (and to nothing else)....

Thanks Colossal. The OPT is indeed oversized (30 Watt; intended for Hi-Fi). I fitted 2 x Jensen C12Q-8 in the cabinet (mono = 4 Ohm). It sounds very promissing but I did not play long and loud on it yet because of the neighbours. When completed it will move to our attic where I can play more freely ...

Hello all, New member, first posting. I have recently finished and tested the electronic part of a guitar amplifier. All that is left to be done, is making and installing the bottom plate (MDF with an aluminum cover on the amplifier side as a screen). The amplifier is loosely based on the clean chan...