Load Mismatch Fender/Marshall

[jeff]

 I've read many times that a Fender is more tolerant of a speaker mismatch than a Marshall. Is this true? If so why? Does it have to do with the fact that most Fenders use 6L6s and most Marshalls use EL34s, and a 6L6 is more tolerant of a mismatch? Or are Fenders slightly mismatched to begin with? I could kinda see if an amp was set up to see a 6 ohm load using either a 4 ohm or an 8 ohm load wouldn't be as big a mismatch as using a 4 ohm speaker on an 8 ohm amp.

 Is this just a myth because Marshalls generally have an impedance selector and Fenders just have an ext. jack, therefore Fenders must be more tolerant?

[sluckey]

Is this just a myth because Marshalls generally have an impedance selector and Fenders just have an ext. jack, therefore Fenders must be more tolerant?

Maybe Fender was just more thrifty.

[jeff]

Maybe Fender was just more thrifty.

Thrifty, no doubt. But is there any truth to this?

[bigsbybender]

It seems that way.......

At least, I've worked on countless Fenders and far fewer Marshalls, however I've never had to replace a failed Fender OT, but I've replaced several Marshall OT's despite the fact that I see way more Fenders. The Fenders are usually just in for age-related repairs (Caps, noisy resistors, etc) Marshalls seemingly have a high rate of OT failure in comparison. I actually can't say that impedance mismatch is the cause, but it seems to be a best guess.

j.

[HotBluePlates]

Gerald Weber is the only person I've seen write this.

I have noticed that Marshall amps of some time periods have had more than average OT issues (the transformers most often cited in my limited experience have been Dagnall transformers). I think Marshall switched suppliers to correct their issues.

I can't think of a technical reason that Marshall amps should be any more sensitive to mismatching than Fender amps. You'd have to investigate the effects of varying loads on EL34's.

For the most part, old tube books cite lower output power and/or increased distortion as the effects resulting from higher or lower than optimum loads.

Pure guess: Maybe the fact that the oldest Marshalls were assembled from surplus parts from any supplier who could deliver the lowest price lead to some anecdotal evidence that they were finicky. Fender certainly used the least expensive thing they could find, but perhaps they were building on a big enough scale to get good pricing on quality parts.

[whittele]

When I worked as an amp tech at a music store in SC, the repair shop bread and butter was replacing Marshall OP XFMRS mostly due to the shorting pin style impedance selector "falling out" and opening up the secondary.  We always seemed to be ordering both parts every time.

[octal]

The other thing to consider is the type of playing likely to be done with each amp- I'm sure some people run Fenders dimed, but most folks looking for a traditional "Marshall" sound are pushing the output tubes into squarewave city, running into a power brake, etc, all of which is rougher on the OPT.
 

[HotBluePlates]

When I worked as an amp tech at a music store in SC, the repair shop bread and butter was replacing Marshall OP XFMRS mostly due to the shorting pin style impedance selector "falling out" and opening up the secondary.  We always seemed to be ordering both parts every time.

Duh! I forgot about the plug-in impedance selector. I think you won the prize with that observation!