Hi all,
Another basic question on which I would like some advice.
After looking at the general construction of output transformers with centertapped primary, I was wondering if one can hack together a crude ct system by connecting primaries in series and use the connection point as center tap.
The secondaries could then be connected in series or parallel as needed
The reason this might make sense is that standard untapped transformers are much more readily available.
Also this configuration could theoretically not have the problem of turn radii being uneven for two sides of a ct.
Folks, would this work ? If not, are there technical reasons for this?
Also, it would be great if the experienced and informed members could explain these concepts for the benefit of newer members
Another basic question on which I would like some advice.
After looking at the general construction of output transformers with centertapped primary, I was wondering if one can hack together a crude ct system by connecting primaries in series and use the connection point as center tap.
The secondaries could then be connected in series or parallel as needed
The reason this might make sense is that standard untapped transformers are much more readily available.
Also this configuration could theoretically not have the problem of turn radii being uneven for two sides of a ct.
Folks, would this work ? If not, are there technical reasons for this?
Also, it would be great if the experienced and informed members could explain these concepts for the benefit of newer members
They would not saturate if limited to the current allowed for an SE transformer with an air gap, but then you have the disadvantages of both worlds. For a given power output a PP OT will be smaller and cheaper than SE, so why use two SE where one PP will do?
The issue is not tapped vs. untapped, but PP vs. SE.
The issue is not tapped vs. untapped, but PP vs. SE.
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Yes true. For some reason I thought the OP was trying to use a pair of power transformers as an outoput transformer.
Do you really mean power transformers?
Power transformers will saturate. A power transformer is not the same thing as an SE output transformer.Heh I recognise how incredibly awful that might sound (literally) but in general se are easier to get ones hands on...
Df96: what exact advantages would pp have as opposed to this configuration? I mean in terms of how transformers work how would the physics differ?
Trobbins: you mean a series or parallel connection between equal secondaries right? Any reason why this will be class b only?
Merlinb: I agree. What I meant was that even se opts are easier to obtain from local manufacturers as compared to pp opts.
Trobbins: you mean a series or parallel connection between equal secondaries right? Any reason why this will be class b only?
Merlinb: I agree. What I meant was that even se opts are easier to obtain from local manufacturers as compared to pp opts.
PP OPT ensure good coupling between the two phases, so each output valve sees the same anode voltage swing (but in opposite directions). This helps balance. Two SE coupled via the secondaries will not be as good.darksideboy said:
SE OPT has air gap to stop saturation so for a given size and quality has less inductance so worse LF response.
The best type of mains transformer to use with a push pull amp is the type with two primaries that can be wired in parallel for 120V and series for 240V. Wire the windings in series and add the HT to the center tap that is not normally used when they are on mains.
The flux does cancel out when they are used like this and the quality will basic.
You need to choose the ratio to match the anode resistances to the speaker.
The flux does cancel out when they are used like this and the quality will basic.
You need to choose the ratio to match the anode resistances to the speaker.
It would produce sound, but that sound won't be that good. Not much high frequencies. Kinda like AM radio... Hifi audio transformers use different metal for the lams and have special winding configurations to avoid excessive self capacitance that would kill the highs.
There is a way.
That would be a "dual parafeed".
Which is two SE parafeeds with common drive in P-P and secondaries in series or parallel.
This consists of a choke in series with the plate, and the primary feed with a cap. This keeps the DC off the output iron. But it does not utilize a common center tap.
As noted before the common center tap will cause DC offsets and current offsets through the cores, which IF under what the SE iron can normally handle will be ok. If not, then core saturation will kill the low end, or else dramatically increase distortion on the LF, and perhaps on any signal that approaches the power rating of the transformer(s).
Hard to imagine that SE iron is cheaper or more available than PP... although I suppose "table radio" quality SE iron would be cheaper to make than good SE iron, since one would pretty much disregard all the careful steps required to make a good transformer and wind it mostly like a power transformer, but with a gapped core.
It's almost better to wind ur own using an existing set of cores... that's been done by Diyers...
_-_-
That would be a "dual parafeed".
Which is two SE parafeeds with common drive in P-P and secondaries in series or parallel.
This consists of a choke in series with the plate, and the primary feed with a cap. This keeps the DC off the output iron. But it does not utilize a common center tap.
As noted before the common center tap will cause DC offsets and current offsets through the cores, which IF under what the SE iron can normally handle will be ok. If not, then core saturation will kill the low end, or else dramatically increase distortion on the LF, and perhaps on any signal that approaches the power rating of the transformer(s).
Hard to imagine that SE iron is cheaper or more available than PP... although I suppose "table radio" quality SE iron would be cheaper to make than good SE iron, since one would pretty much disregard all the careful steps required to make a good transformer and wind it mostly like a power transformer, but with a gapped core.
It's almost better to wind ur own using an existing set of cores... that's been done by Diyers...
_-_-
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