u/KirkIsOurLemmy

Hello all, my Tiny Terror build has gone unexpectedly quick, its working and sounding great. So off to the next step:

This amp doesn't really have any EQ capabilities, only a basic treble cut control. So I thought it would be nice with an effects loop, I think an EQ pedal between the preamp and PI on this amp will really open up a lot of cool sounds.

So applying my newly acquired and very rudimentary knowledge I was thinking like this: the PT has enough filament current to heat one more 12AX7, what if I wire the first half as a cathode follower before the send jack, as a buffer and with a pot to dial down the signal level to not clip the pedals. And then the other half as a triode after the return jack, to restore the signal level, also with a gain pot.

So far so good, or have I gone off the rails already?

Because then I thought that a 12AX7 in triode circuit, that is a gain stage, like the gain stages in a modern high gain amp, that can add distortion. So I was thinking , can I configure the caps, resistors and pot for this stage to span the whole range from clean signal recovery to heavy clipping? So that say in the first half of the pot sweep it acts like a typical effect return level control, and for the second half it turns into an increasingly saturated distortion stage.

Does this make sense or am I completely off the rails now?

Thanks in advance :)

Hello all, my Tiny Terror build is working and sounding good, and I did some measurements on voltages. It is a 2xEL84 push/pull with 120 ohm cathode bias resistor shared by both tubes. The cathode voltage is 10.4 V. B+ is 319 V.

I have read that target bias voltage is 12 V, so am I running the tubes too hot? Should I change to a 150 ohm resistor?

Is this mainly about tube lifespan or can I expect some change in the sound if I increase bias voltage to 12 V?

Thanks in advance

Hello all, a question on how to wire the speaker out jack on a tube amp.

I am using a switched Cliff jack, there are two more lugs that are connected to tip and ring as long as the jack is unplugged, but get disconnected when you plug in your speakers.

I was thinking maybe I can do something clever to protect the output transformer. If the amp is started with no speaker connected, an open circuit, the OT will be damaged.

If I understand correctly its safe to put a higher resistance than the rated speaker impedance, you will just lower the power output, nothing will break.

So here is my idea, I have a left over 150 ohm, 5 watt resistor. What if i connect that between the two switched lugs? Then if the amp is started with no speaker connected the OT will see 150 ohm, very little power will be output but the OT will not be destroyed. The amp is 15 watt so quite small.

Would this work or am I missing something?

Hello all, I have only built guitar pedals so far but am about to start my first tube amp build, parts are in the mail :)

For fuzz and distortion pedals you typically get a more distorted and compressed sound if you run a 9 V power supply, and for pedals that can run for instance also on 18 V there is more headroom, cleaner sound. I guess lower supply voltage will mean clipping at lower signal voltages.

So my question, is it the same for tube amp circuits? I am building an Orange Tiny Terror, 2x12AX7 preamp and 2xEL84 power amp. Will supply voltage have any impact on the amount of distortion produced?

The reason I'm asking is that an original Tiny Terror has a power transformer with 238 V secondary voltage. I could not find one with that exact spec so I bought one with 250 V.

But then I had this thought, the secondary voltage is a product of input voltage, and ratio between primary and secondary winding in the transformer. The transformer I bought can be wired for a few different input voltages, among then 220, 230 and 240 V. Here in Sweden nominal voltage is 230 V, does that mean if I wire the transformer as for 240 V will I get a lower secondary voltage than 250 V then? If its simply applying the difference in ratio I would then get 239.6 V. Unless I messed up my numbers :)

Input, thoughts?

Thanks in advance