https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/ Guitar Noise Discussion Board en-US Fri, 05 Jun 2026 09:41:23 +0000 wpForo 60 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/3/#post-184055 Sun, 18 Jun 2006 19:44:52 +0000 Live Sound Ricochet https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/3/#post-184055 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-184038 Sun, 18 Jun 2006 16:57:00 +0000
http://www.valvejunior.com/]]> Live Sound smokindog https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-184038 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182884 Mon, 12 Jun 2006 00:20:03 +0000
Tube amps are very tolerant of impedance mismatches. The impedance selected as optimum is arbitrary and based principally on the lowest distortion. You'll see considerable variation from amp to amp in the load applied to the tube, anyway. I'm speaking of pentode and beam tetrode output tubes, which most guitar amps have. With triodes the power level varies with the impedance, the most power being transferred when the load impedance (across the primary of the output transformer) equals the tube's plate resistance, but that's full of second harmonic distortion. Normally an impedance of about 2x the plate resistance is used, to give the maximum clean power output. Pentodes and beam power tubes have such high plate resistance that it's not practical to load them with such high impedance, so they have arbitrary plate loads. It seems there's a sweet spot for many of these tubes around what the ideal impedance would be if they were triode-connected. And when they're hooked up in an ultralinear circuit, they're operating as "partial triodes" with a lowered plate resistance, and that ends up being a pretty good impedance range for them. But even with triode tubes, you can run the impedance way up or down with impunity. It'll just sound different, and affect the power output.

What tube amps don't tolerate well is operation with NO load on the output (approaching infinite impedance.) Then the stored energy in the oscillating current in the transformer coils can produce damagingly high voltage spikes in excess of 10KV. Even loading the output with a resistor of ~20x the rated speaker impedance is enough to prevent damage from this, and it's often done. You don't lose enough power across that resistor in normal operation to notice it, but it'll save the output transformer, power tubes and sockets in case you forget to plug in or accidentally unplug the speaker.

Running a tube amp for a short while with the output shorted won't hurt a thing. It'll instantly fry a solid state amp, which doesn't mind if you forget the speaker but will fry if you plug in one of too low impedance.]]> Live Sound Ricochet https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182884 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182504 Fri, 09 Jun 2006 13:13:28 +0000 Live Sound greybeard https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182504 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182471 Fri, 09 Jun 2006 07:42:16 +0000 Ricochet sounds like my dad ( he was a electronics shop teacher back in the 60's) I remember him trying to explain to me back then how tubes work ...whoooosh..right over my head :lol: :lol: :lol: We were going to rebuild a old fender Princeton Reverb but unfortunately he passed away be for we found time to get together to do it ( this was about 10 years ago)
but I appreciate you guys helping me out on this :D --the dog]]> Live Sound smokindog https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182471 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182462 Fri, 09 Jun 2006 06:54:45 +0000
Then what advice would you give concerning mismatching impedence between speaker and amp?

I know that with solid state amps you are not supposed to use speakers rated lower resistance than the amp's minimum. For instance, you should not run two 4 ohms speakers in parallel (2 ohms) off an amp rated 4 ohms minimum. I know you know this, I wrote this for those who might not know this.

But what about what Smokindog wants to do? run a 16 ohm speaker from the 8 ohm Speaker Out on his Valve Junior?

You've got to write in simple, non-electronic language for most of us to understand.]]> Live Sound Wes Inman https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182462 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182453 Fri, 09 Jun 2006 05:25:21 +0000 Live Sound Ricochet https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182453 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182421 Fri, 09 Jun 2006 03:46:45 +0000 Live Sound Robbie https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182421 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182417 Fri, 09 Jun 2006 03:38:46 +0000
I am glad you reminded me, I had forgotten all about this. :D I did experiment with my PJ & B.

It is difficult to say what you would like, but this pedal has Mix which seems to give a fullness or depth to the effect. You can go from mild reverb to sounding like an echo coming out of a deep canyon. I myself like to turn Mix all the way up (clockwise). The middle knob is Speed. This controls how fast or slow your repeats are when using the pedal as a delay. This is probably the most important control if you want to use this pedal primarily for reverb. You simply turn it all the way down (counterclockwise). But I found you could turn it up to almost 12 o'clock position and this will sound like reverb as compared to delay or echo. The far right knob is Repeats. When using this pedal as a delay this will increase the number of repeats you hear after the original note.

This pedal also has long and short delay. When you step on the right footswitch the pedal will automatically turn on in long delay. Some complain about this. But I'm sure that some would complain if the pedal turned on in short delay as well. Anyway, it will turn on default at long delay and a green LED lights up. For short delay, step on the left footswitch. The green LED will turn red. To use this pedal as a reverb, you want to use short delay.

With short delay you can get plain reverb or a very good Country slapback tone. Great with a Telecaster.

Using long delay you can get U2 type multiple echos or delays. Good for rhythm or lead guitar.

So, I don't know what you will prefer. I liked Mix turned fully clockwise, Speed turned fully counterclockwise, and Repeats turned fully counterclockwise. This was a good deep reverb tone that I liked.

When your pedal comes in, write back and tell us what settings you like.]]> Live Sound Wes Inman https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182417 https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182416 Fri, 09 Jun 2006 03:34:03 +0000
I best be saving up for a tube screamer :wink:]]> Live Sound smokindog https://guitarnoise.forum/live-sound/epiphone-valve-jr-head/paged/2/#post-182416