Grateful Dead Music Forum

So I was rehearsing with a JGB band yesterday and had my Twin with Beyma Liberty speakers. I also had my 2x12 K-120 cab on hand. I was A-B testing and decided to go with the K's for the rehearsal. I had my vibrato-reverb pedal (the one that comes with the amp) plugged in. When I went to disconnect the Beyma's I unplugged the vibrato-reverb instead of the Beyma's. I then plugged in the K cab and played we started playing. In other words, I screwed up and had both the Beyma's and the K cab plugged in.

The entire first set I was surprised by this tone I was getting. It was clean, loud and flat out tasty. At the same time I kept saying “It seems like there is sound coming from both cabs". Finally after the first set I reached back to turn the amp of for a break and bang! I noticed both cabs were plugged in.

How close was I to blowing the amp? Is that even the case here?

You weren't going to blow the cab. The transformer in a tube amp will match the impedance of the load. If your total load impedance was too low, your risk would be to the transformer. Total impedance should be either 8 or 4 ohms, never below. I would have to know more about your configuration to tell you more.

I was more concerned that perhaps I could have blown the amp, tubes or anyhthing related to damaging my amp. My amp is a standard 65 re-issue twin. On the back it has three inputs.

1-Int. speakers
2-Ext. speakers
3- vibrato pedal

I unplugged input #3 when I meant to unplug # 1.

ugly rumor wrote:You weren't going to blow the cab. The transformer in a tube amp will match the impedance of the load. If your total load impedance was too low, your risk would be to the transformer. Total impedance should be either 8 or 4 ohms, never below. I would have to know more about your configuration to tell you more.

I do believe Twins have an OT at 4ohms and can "safely" handle 1 mismatch up or down so either 8 or 2.6.

Keir, you were running at 2. Basically your cabs were trying to suck more power than the amp could provide. I'd say lower volume, short period of time, no issue.

I played for about an hour and a half at high volume!
I am so grateful nothing bad happened!

keirweir wrote:I played for about an hour and a half at high volume!
I am so grateful nothing bad happened!

Keir,
I did the exact same thing at a gig! I left the internal speakers plugged in when I also plugged in my 2x12 e-120 cab. It sounded OK for a while and then after a bit of time at high volume it lost some oomph I was really scared I did tranny damage, but I had it looked over afterwards by a tech and it seemed ok.....the worst part of all this? I did this at a time when Scott Murawski sat in and used my Rig for a song and the rig just sounded crappy, it was very embarassing ... and I couldnt figure out why until I went to break down after the gig and noticed I had 4 speakers plugged in.

jeffm725 wrote:

keirweir wrote:I played for about an hour and a half at high volume!
I am so grateful nothing bad happened!

Keir,
I did the exact same thing at a gig! I left the internal speakers plugged in when I also plugged in my 2x12 e-120 cab. It sounded OK for a while and then after a bit of time at high volume it lost some oomph I was really scared I did tranny damage, but I had it looked over afterwards by a tech and it seemed ok.....the worst part of all this? I did this at a time when Scott Murawski sat in and used my Rig for a song and the rig just sounded crappy, it was very embarassing ... and I couldnt figure out why until I went to break down after the gig and noticed I had 4 speakers plugged in.

man o man

I have a recording of this rehearsal. This is the Simple Twist of fate.

This is my Twin running the K-120 Cab as well as the Beyma Liberty's in the Twin. Doh!

I am still trying to get away from my bright switch but its challenging (like giving up s'mores or somthing)... I would say the JGB project l I am in leans towards lets rip it up and see where it goes verse lets play it just like JGB.

http://www.mediafire.com/?bzp3kmhb9w40hc6