Thinking of something to do with spare parts. Thought about a mono spud push-pull.
I have two Hammond 126B, can they be used in series to phase split? I was thinking of cathodyne to drivers, interstage coupled to the output tubes, then this crossed my mind for something simpler.
Might be a reason why I can't find threads on it but thought to ask anyway.
I have two Hammond 126B, can they be used in series to phase split? I was thinking of cathodyne to drivers, interstage coupled to the output tubes, then this crossed my mind for something simpler.
Might be a reason why I can't find threads on it but thought to ask anyway.
If the primary & secondary of the H126B are identical they could be connected as center tapped inductors. Then one of the H126Bs in a PP plate circuit cap coupled to a following CT H126B in a PP grid drive circuit.😀
The potential voltage swing is larger than is possible with ordinary RC coupling.
The potential voltage swing is larger than is possible with ordinary RC coupling.
Yes, you can connect series two primaries or parallel them. Always in reverse phase direction. Due to the fact they are located on separate magnetic cores, the signals won't be canceling and you will achieve perfect high frequency balance if the transformers are exactly the same.
This is a recipe for the perfect transformer phase splitter. It is important to match the transformers for the same primary inductance in order to have the best low frequency amplitude balance.
This is a recipe for the perfect transformer phase splitter. It is important to match the transformers for the same primary inductance in order to have the best low frequency amplitude balance.
In theory this will work but in reality since the 126B's are bifilar you will not get the results you expect. In order to split phase in this arrangement one secondary will need to be inverted in relation to the primary and an inverted secondary on a bifilar transformer means severe rolloff starting somewhere around 5-10kHz.
dave
dave
Thanks guys for the responses. I think I posted this in the wrong place. The mono amp I'm thinking about building is for a guitar amp. The frequency response shouldn't be an issue then I suppose.
as drawn the signals at the two grids will be in phase with each other. In order to get one signal with inverted phase either the primary or secondary winding needs to be reversed not both and this is a big problem with a bifilar transformer when it comes to high frequency behavior.
dave
That's true Dave. It won't work, sorry for misleading. Deleting the image to avoid confusion.
Then one must grasp the "flawed" single phase splitter transformer. Best to make it at the input level.
Then one must grasp the "flawed" single phase splitter transformer. Best to make it at the input level.
I checked the H126B spec sheet earlier, there was no mention of bifilar. Perhaps I missed that. Bifilar is expensive work & requires better insulated wire. I don't think the extra expense for what these transformers are meant for would justify the extra cost.
McIntosh has always done their bifilar transformers in house, all blended in to their production.🙂
McIntosh has always done their bifilar transformers in house, all blended in to their production.🙂
Even if they're not bifiliar, you need a specifical winding configuration for phase splitting transformers only. One secondary half is in antiphase to the primary due to the ground point needed to be picked up at the center and this leads to voltage potential incompatibility. You cannot interleave it with the primary or capacitance will jump tremendously.
there are two way to get compromised HF bandwidth from a bifilar transformer.
-invert the phase of the secondary at which point the large winding to winding capacitance shunts the HF to ground. I have actually done inverted bifilar designs using this effect to create a corner frequency at ~30kHz for dac usage. fwiw...the end user preferred the sound in the non-inverting position.
-load it down which causes a loss of amplitude in the magnetically coupled part of the circuit (low frequencies) and unity gain at high frequencies. This is essentially a shelf filter that typically happens in the 5-50Khz range depending on the actual circuit parameters. A high DCR winding resistance driven from a high Rp source into a large load can show upwards of a 3dB midband shelf.
Moral of the story is.... don't invert or load down bifilar transformers.... and gasp... they are capacitively coupled at high frequencies.
dave
-invert the phase of the secondary at which point the large winding to winding capacitance shunts the HF to ground. I have actually done inverted bifilar designs using this effect to create a corner frequency at ~30kHz for dac usage. fwiw...the end user preferred the sound in the non-inverting position.
-load it down which causes a loss of amplitude in the magnetically coupled part of the circuit (low frequencies) and unity gain at high frequencies. This is essentially a shelf filter that typically happens in the 5-50Khz range depending on the actual circuit parameters. A high DCR winding resistance driven from a high Rp source into a large load can show upwards of a 3dB midband shelf.
Moral of the story is.... don't invert or load down bifilar transformers.... and gasp... they are capacitively coupled at high frequencies.
dave
You are correct, a 2nd look at the spec sheet does indicate bibilar. I should have suspected something odd, this transformer line is HiPoted to only One KV. In all my experience with Hammond the HiPot has always been 1.5 KV or higher.
But it might be worthwhile checking in circuit anyway, would be interesting to know what the bandwidth would be as a CT choke while driven by triodes.
I never build an audio amp to respond to DC to Green Light!!😀
Now back to preparing for Winter here. Still much to do, no electronics these daze.🙂