Fender Twin High Impedance Speakers

[The Dude]

There's a lot of truth in that. I will say this, though. More than once I've seen one of those "modeler kids" plug into their first real tube amp. The smile on their face says it all. They have no idea what they've been missing until they try the real thing.

[Justin Thomas]

Not just the kids, either...

Justin

[Chuck H]

I remember the first time I played a tube amp. It was a blonde Bassman head. The guy playing through it had an awful guitar he was blanging away on, but I could still hear "something" I always thought was missing from my game. I was probably nineteen years old! Remember that I mentioned that I came up as a musician in the 80's So I played through that amp, and though it wasn't just what I wanted it WAS doing things I always though an amp should do. Like some of that natural compression on the attack and an overall balanced EQ that some how corrected itself relative to playing style. Sort of more expressive and forgiving at the same time. Inside of a month I had a beat to $h!t Marshall head that I traded all my other gear for + some $$$. It was better than anything else I'd ever had before and it actually wasn't very good! And that's when I started modding. Trying to get that turd to sound "right". My next amp was another Marshall, but a better one. I played it for years with very little modification. Then I got the "what if" itch about stacking the channels and I started playing with THAT circuit. And now it's it's been that way ever since.

But it all started sort of late in my gear exposure circumstances with a blonde Bassman head.

[Justin Thomas]

My firstamp? Gorilla. 2nd? Crate GX30M. Huge step up. Next, a Marshall ValveState 8200 w. JCM900 2x12. Another huge step up. Then, it died. Then I got my first TUBE amp: a Fender Prosonic.

Game Over. I've never looked back.
Chuck, tubes and rawk will live at least as long as I do. Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers.

Justin

[Shawnobi]

I'd suspect that someone (slightly misguided) put in higher impedance speakers to lower the volume on purpose in the hope they could crank it into a 'sweet spot' without it being so loud. I've seen that advice given out to twin owners before on the web.

[Leo_Gnardo]

I'd suspect that someone (slightly misguided) put in higher impedance speakers to lower the volume on purpose in the hope they could crank it into a 'sweet spot' without it being so loud. I've seen that advice given out to twin owners before on the web.

Good observation. Also, the owner/user of this twin might have wanted to drive a heap of external cabs. Heck all he'd have to do is wire 8 ohm speakers in series instead of deal with oddball 32 ohm speakers. Those wacky musicians - where do they get their ideas???

[Justin Thomas]

I'd suspect that someone (slightly misguided) put in higher impedance speakers to lower the volume on purpose in the hope they could crank it into a 'sweet spot' without it being so loud. I've seen that advice given out to twin owners before on the web.

Too bad so many people confuse speaker impedance, speaker sensitivity, and power handling...

Justin

[Justin Thomas]

Good observation.... Those wacky musicians - where do they get their ideas???

...

Justin

[J M Fahey]

O=h, I always go for the simplest explanation, unless proven otherwise.

Rather than sophisticated "sweet spot tweaking" (which I don´t call impossible, just less likely) , I merely think somebody pulled a Rhodes cabinet out of a dumpster or similar "recycling operation" (or was about to junk one) , pulled the speakers and posted on EBay/CRaigslist "ORIGINAL, VINTAGE, Period Correct Fender 12" SPEAKERS !!!!!!" and Twin owner bought two, which he then hooked in parallel.
If asked (any/both of them) "do you know those are 32 ohm speakers?" I bet the answer would be "deer in the headlights" look, accompanied by "32 WHAT???"

[bobloblaws]

Back to the problem at hand, the amp is only putting out 50 watts into 4 ohms. I've verified the power tubes are good, B+ is fine and bias has been set for about 40 mA of idle current per tube. Is it possible that if the amp was used for some length of time with that mismatch that the OT became degraded?

[Enzo]

No. The transformer is just wire wrapped around iron.

[Chuck H]

This^^^^^^^^^^^^^^^^^^^^^^^^

You would almost certainly hear other symptoms if the OT were compromised. That doesn't mean it isn't, it's just not the first thing to suspect IME. Please give a description of your test method.

And have you scoped the signal through the amp to be sure there is no preamp clipping prior to the onset of power tube clipping? This would definitely be something to look for since the amp has already been well dicked with.

[bobloblaws]

This^^^^^^^^^^^^^^^^^^^^^^^^

You would almost certainly hear other symptoms if the OT were compromised. That doesn't mean it isn't, it's just not the first thing to suspect IME. Please give a description of your test method.

And have you scoped the signal through the amp to be sure there is no preamp clipping prior to the onset of power tube clipping? This would definitely be something to look for since the amp has already been well dicked with.

Good point. There is at least one existing pre-amp issue. Specifically, somebody who may or may not be the same somebody who swapped the speakers changed the 1 Meg channel volume pots for 100K. I'll measure the output power again after replacing those pots and checking for other possible problems in the pre-amp.

For the record, I'm connecting the speaker output to a 4 ohm dummy load and attaching my scope probe to the positive terminal on the speaker output jack. Then I take the peak voltage divided by 1.414, square the result and divide by the load impedance.

[Chuck H]

Good point. There is at least one existing pre-amp issue. Specifically, somebody who may or may not be the same somebody who swapped the speakers changed the 1 Meg channel volume pots for 100K. I'll measure the output power again after replacing those pots and checking for other possible problems in the pre-amp.

For the record, I'm connecting the speaker output to a 4 ohm dummy load and attaching my scope probe to the positive terminal on the speaker output jack. Then I take the peak voltage divided by 1.414, square the result and divide by the load impedance.

What is your input signal voltage/Hz? And what are the panel knob settings?

[bobloblaws]

What is your input signal voltage/Hz? And what are the panel knob settings?

All tone controls at 5 and verb and trem knobs at 1.

130mV sine wave. In this case I used a higher input signal than I normally would since the preamp gain was lower than normal and at a lower input signal I couldn't even get the output to clip.