Tavda3172 wrote:It is ultimately the OT impedance that will limit the output power. ...The physical size of the transformer does not directly effect the output power but can/will effect the bandwidth, hence bigger iron usually sounds bigger.
Thanks for clarifying that. I'm certainly no transformer expert, but I'm trying to learn. The impedance mismatch is usually mitigated by switching taps (i.e. you're using an 8Ω speaker with 6L6s and you swap in 6V6s, then plug into the 4Ω tap to double the reflected impedance).
The size of the core certainly determines power handling capability.
From Aikenamps.com:
The two things that determine the power handling capability of the transformer are the core size and the gauge of wire used to wind the transformer. The core size is proportional to the power and the required low frequency -3dB point. A transformer rated for 50W at 80Hz is much smaller than one rated for 50W at 20Hz. The other factor in determining required core size is the number of turns that will fit on the bobbin. If you increase the power rating, you must increase the wire size, which means that less turns will fit on the same size bobbin, so you must increase the bobbin and core size to accommodate the extra turns.
So, if you push more power through an OT than it's designed for, once the core becomes saturated it would most likely cause some distortion, a loss of low end, and a loss of efficiency (power output). Sometimes that's a good thing (5E3 Deluxe), but not for a D-style design.
Tales from the Tone Lounge has an interesting discussion about transformers here.
6L's produce more current hence the need for the larger wire...if the wire cannot dissapate the energy being produced by the tubes it becomes saturated.. anomolies associated with an overly saturated transformer are decreased bandwidth.. (compressed) un-even order harmonics a much shorter tube life and the main enemy heat...More than the core can absorb breaking down the lamination on the wire causing the transformer to short..This to me is more critical than impedance matching and not to be confused with core saturation..
My D'Lite 44 came with a dual primary OT so you can run 6V6 or 6L6, EL34, etc.
I believe one is 4K and the other 8K.
At first I had the primaries on a switch.
I had a problem which I thought was related to that switch so I took it out.
Later I bought a 50 watt Prosonic OT.
I put the old OT in my 6V6 Hammond amp.
talbany wrote:6L's produce more current hence the need for the larger wire...if the wire cannot dissapate the energy being produced by the tubes it becomes saturated.. anomolies associated with an overly saturated transformer are decreased bandwidth.. (compressed) un-even order harmonics a much shorter tube life and the main enemy heat...More than the core can absorb breaking down the lamination on the wire causing the transformer to short..This to me is more critical than impedance matching and not to be confused with core saturation..
If wire cannot handle the current, it overheats and melts. That has nothing to do with "saturation". The critical issue of insulation is breakdown voltage beyond which one experiences arcing and subsequent shorting.
Maybe we're agreeing on that and the issue is one of nomenclature? I'm just a scientist with one of my degrees in physics and a couple decades working as an electrician. Forgive me if these niggling details grab my attention.
I believe Tony is talking about the electromagnetic Flux developed around the wire, in regards to saturation.
Of course if the wire is too small for the current and the insulation breaks down, it will fail eventually.
We know if the specs are exceeded the transformer will get hot, that is one of the things we can check.
I have however read conflicting reports on running an OT on the smaller side in regards to the resulting tone, from over saturation where some say it is a desirable feature while others say to stay away from such anomalies.
Perhaps it depends on the amp in question such as a Fender Deluxe might get some of it's characteristics from over driving the transformer as we know Leo exceeded a lot of specs on tubes and trannies in his early amps.
But on a more modern amp such as a 50 watt Plexi, you probably don't want that to happen or it wouldn't sound like a Marshall.
