Has anyone used Edcor interstage transformers? They sure are nicely priced for interstage transformers.
https://edcorusa.com/collections/interstage-matching-transformers
Three models
200:600, 17ma, 1:1.73, 5W
5k:20k, 20ma, 1:2, 4W
5k:5k, 30ma, 1:1, 4W
https://edcorusa.com/collections/interstage-matching-transformers
Three models
200:600, 17ma, 1:1.73, 5W
5k:20k, 20ma, 1:2, 4W
5k:5k, 30ma, 1:1, 4W
Bifilair (1:1) measures normally very good in the frequency domain.
For an interstage at high levels (a driver for output tubes) normal iron cores are good enough but i prefer c-cores anyway for that (just better cores)
If you like better quality amourphous cores or nanocrystaline cores are better options.
For line level or even lower level, iron cores are not the best choice.
For an interstage at high levels (a driver for output tubes) normal iron cores are good enough but i prefer c-cores anyway for that (just better cores)
If you like better quality amourphous cores or nanocrystaline cores are better options.
For line level or even lower level, iron cores are not the best choice.
This is an unusual application but worth mentioning. sorry if it is TL;DR
For driving high power class-AB2 or B stages, I've used Edcor amp-to-line transformers.
The 140V transformers have a center tap. It's possible to get a grid to grid peak voltage of 200V, so that high mu triodes like the 3-500Z can be easily driven. The low voltage side on them is 4 or 8 Ohms.
My setup uses a small power amp to drive the 4 ohm winding. The Edcor part is the WA-120. yes a 120W unit, but the actual drive power is only 25W peak at very most. At least to say the transformer's response and power handling is not in question. The driven tubes are the 3-500Z types in a modulator and output is about 900 Watts. The 140V center tapped transformers are made from 15 Watts to 400 Watts. Oversizing the transformer assures two things - lower frequencies handled better, and better drive regulation through the transformer, which is an issue in AB2 or B2 circuits as the grid impedance varies widely over the audio cycle.
Most people would use 'normal' power level driver/interstage transformers up to 15W, For that, the WA-15 has also the choice of a 4 or 8 Ohm low side and the 140V center tapped high voltage side.
Few tubes at moderate or low power require anything like 100 peak volts on the grid. It's just another option, for those including musicians who want to drive a tube type booster amp such as quads of 6550s or 6L6's in AB2 directly from a small practice or portable amp. The small amp's tone and volume controls take care of everything, and only a power switch is needed on the large power amp since it's driven at a few watts from the low power 'head'.
Be sure to calculate the turns ratio, since one side of the transformer is specified in Ohms and the other side is specified in Volts. For example:
The 15W unit would have a 1300 Ohm CT 140V winding can supply about 100mA grid current, and the pair of 6L6/GC needs only 0.35W of drive which is about 5mA, The transformer would have a very light load and good drive regulation indeed.
The 120W unit would give about a 160 Ohm CT 140V winding and supply a 860mA grid current which is more like what the big 3-500Z grids need on peaks. I ended up using the 400W model on that just to overkill it -that is, no chassis space issues since the big fat tube is anyway larger than the transformer, and there's absolutely no issue with grid circuit resistance or drive voltage regulation.
Further, running beam tubes like the 6L6GC or 6550 at full AB1 specification (e.g. 6550: 600V anode/300V screen), then driving into AB2, more power is possible, and of course the plate to plate load impedance is lowered because more current is available from the tubes, the limit is plate dissipation, and of course grid dissipation which isn't specified for the tubes but the saturation current may be reached before the grid overheats.
There are many more details to consider when doing this, but not enough space to begin.. since all tube types are quite different and this is considered experimental, even though it works well. YMMV
For driving high power class-AB2 or B stages, I've used Edcor amp-to-line transformers.
The 140V transformers have a center tap. It's possible to get a grid to grid peak voltage of 200V, so that high mu triodes like the 3-500Z can be easily driven. The low voltage side on them is 4 or 8 Ohms.
My setup uses a small power amp to drive the 4 ohm winding. The Edcor part is the WA-120. yes a 120W unit, but the actual drive power is only 25W peak at very most. At least to say the transformer's response and power handling is not in question. The driven tubes are the 3-500Z types in a modulator and output is about 900 Watts. The 140V center tapped transformers are made from 15 Watts to 400 Watts. Oversizing the transformer assures two things - lower frequencies handled better, and better drive regulation through the transformer, which is an issue in AB2 or B2 circuits as the grid impedance varies widely over the audio cycle.
Most people would use 'normal' power level driver/interstage transformers up to 15W, For that, the WA-15 has also the choice of a 4 or 8 Ohm low side and the 140V center tapped high voltage side.
Few tubes at moderate or low power require anything like 100 peak volts on the grid. It's just another option, for those including musicians who want to drive a tube type booster amp such as quads of 6550s or 6L6's in AB2 directly from a small practice or portable amp. The small amp's tone and volume controls take care of everything, and only a power switch is needed on the large power amp since it's driven at a few watts from the low power 'head'.
Be sure to calculate the turns ratio, since one side of the transformer is specified in Ohms and the other side is specified in Volts. For example:
The 15W unit would have a 1300 Ohm CT 140V winding can supply about 100mA grid current, and the pair of 6L6/GC needs only 0.35W of drive which is about 5mA, The transformer would have a very light load and good drive regulation indeed.
The 120W unit would give about a 160 Ohm CT 140V winding and supply a 860mA grid current which is more like what the big 3-500Z grids need on peaks. I ended up using the 400W model on that just to overkill it -that is, no chassis space issues since the big fat tube is anyway larger than the transformer, and there's absolutely no issue with grid circuit resistance or drive voltage regulation.
Further, running beam tubes like the 6L6GC or 6550 at full AB1 specification (e.g. 6550: 600V anode/300V screen), then driving into AB2, more power is possible, and of course the plate to plate load impedance is lowered because more current is available from the tubes, the limit is plate dissipation, and of course grid dissipation which isn't specified for the tubes but the saturation current may be reached before the grid overheats.
There are many more details to consider when doing this, but not enough space to begin.. since all tube types are quite different and this is considered experimental, even though it works well. YMMV
It depends on what you want. I've never tried Edcor but I've been happy with some of the Hammond models.
I use a 1:4 step-up on the input of my amp from their Broadcast range and this is solid, well-made and sounds excellent. Model 1140-LN-C.
Hammond are also very economically priced.
I use a 1:4 step-up on the input of my amp from their Broadcast range and this is solid, well-made and sounds excellent. Model 1140-LN-C.
Hammond are also very economically priced.
I am using a pair of Edcor PT in a pair of mono-blocks. Probably won't buy from them again. Long (15 week) wait time (yes, they told me it would take about 12 weeks) but Monolith supplied a pair of beautiful OT in ten days to the USA. They have a bit of residual mechanical hum that persists despite trying rigid mounting and isolating them with rubber washers. Not terrible but noticeable when close to the amps. They are also rigid in their customer service as I wanted to purchase a set of black end-bells and they refused. Just not a great experience. I'd rather spend the extra for an extraordinary product like Monolith!
I realize my comment doesn't directly apply to the OP's query but I thought the issues I encountered still have merit.
I realize my comment doesn't directly apply to the OP's query but I thought the issues I encountered still have merit.
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Thanks, I wasn't aware Monolith was still in business.
I have a stupid question though if anyone can answer... For the Monolith input transformers they spec all of them using the step-down ratio 4:1, 2:1 8:1 etc. I'm assuming this can be reversed to be step-up as well right?
The DC offset will all be the same stepping up or down? andyjevans experiments with input transformers, dht drivers, etc. is something I've been anxiously preparing to breadboard and hear, but with high end iron, I don't have any high end iron at the moment.