dubadub,
The output transformer is a single ended UL version. I bet it is made to have DC on the primary (air gapped core).
The two transformers are 13H and 18H, definitely not a parafeed output transformer.
So why not just use it in the traditional way?
That will eliminate the choke, and the coupling cap.
In addition, the low frequency phase of the UL connection will not include the phase shift of the cap (cap is gone when it is not parafeed).
Unless the UL tapped output transformer was specially made without an air gapped core, then there is No advantage to using it in parafeed mode.
The output transformer is a single ended UL version. I bet it is made to have DC on the primary (air gapped core).
The two transformers are 13H and 18H, definitely not a parafeed output transformer.
So why not just use it in the traditional way?
That will eliminate the choke, and the coupling cap.
In addition, the low frequency phase of the UL connection will not include the phase shift of the cap (cap is gone when it is not parafeed).
Unless the UL tapped output transformer was specially made without an air gapped core, then there is No advantage to using it in parafeed mode.
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Hey, I'm just sharing schematics 😁 I must admit, I don't understand the point of parafeed; if you must spend as much on a pair of high-quality chokes and save on cheaper OPTs, why not just get better OPTs?
I have Hasimoto HC-203U on my 6B4G amp, replacing 10w EDCOR 3.5K. Night and Day. 10/10 do recommend.
I have Hasimoto HC-203U on my 6B4G amp, replacing 10w EDCOR 3.5K. Night and Day. 10/10 do recommend.
The MPS standard series feed outputs work great too.
This is what I built in a couple of incarnations:
https://hifihaven.org/index.php?threads/sakuma-schade-6v6-amp.8961/
Initial schematic on page 2 post 23.
This is what I built in a couple of incarnations:
https://hifihaven.org/index.php?threads/sakuma-schade-6v6-amp.8961/
Initial schematic on page 2 post 23.
The point of parafeed is to optimize the output transformer for audio parameters and let the plate choke deal with the DC bias and provide a high impedance AC load for the output tube.
I suppose I meant the economic point. Yes, it makes one component bear the load instead of another, but how much money is saved?
E I'm cynical, curious, and an *******. So gimme it all. 😎
E I'm cynical, curious, and an *******. So gimme it all. 😎
Hard to say about the $ issue. Parafeed can give better bass response when the components are well chosen. The DC blocking cap can also be used to provide a resonant lift to the bass within the circuit. My 6V6 amp has lower measured 1kHz distortion with the parafeed setup compared to the series feed with the equivalent MPS transformer. A lower bass -3dB point as well. With a $50 output transformer, the overall cost compared to a good series feed transformer works out pretty well. Series feed SE outputs aren't really known for their great bass response.
Vacuum Tube Amplifiers that have an output transformer:
Some say that really great bass response and great bass sound starts with an output transformer with laminations that do not have air gaps.
Agreed.
But that sounds like . . .
Either a push pull output transformer
Or a Parafeed output transformer
They are both capable of having the same primary inductance.
But there are differences of a Push Pull amplifier, versus a Parafeed.
Here is one important difference: What the loudspeaker "sees" when looking back at the output transformer.
Push Pull has an Intrinsic Symmetrical damping factor.
Parafeed has an Intrinsic Non-Symmetrical damping factor.
If you want to "see" the difference, just put on some loud Bass music on and watch.
Push Pull . . . No "woofer walk"
Parafeed . . . "woofer walk"
Do not forget, parafeed plate Chokes have to pass the same DC current that a traditional SE output transformer has to pass.
The DC current requires the plate choke's laminations to have air gaps.
And the chokes have to have even more inductance than a traditional SE output transformer has to have.
(however high the parafeed output transformer's primary inductance is, it is in parallel with the plate choke's inductance).
All of my amplifiers are monoblocks, and they are balanced differential push pull (2); push pull (2), and a self inverting push pull (1).
The self inverting push pull is due to be converted to be like one of the other push pull amplifiers (to make a pair of matched mono blocks)
I have stopped designing and building traditional SE amplifiers, and parafeed SE amplifiers. I did enjoy listening to Single Ended;
but I am moving on to balanced differential, and push pull amplifiers.
Just my opinions and my Experience
Some say that really great bass response and great bass sound starts with an output transformer with laminations that do not have air gaps.
Agreed.
But that sounds like . . .
Either a push pull output transformer
Or a Parafeed output transformer
They are both capable of having the same primary inductance.
But there are differences of a Push Pull amplifier, versus a Parafeed.
Here is one important difference: What the loudspeaker "sees" when looking back at the output transformer.
Push Pull has an Intrinsic Symmetrical damping factor.
Parafeed has an Intrinsic Non-Symmetrical damping factor.
If you want to "see" the difference, just put on some loud Bass music on and watch.
Push Pull . . . No "woofer walk"
Parafeed . . . "woofer walk"
Do not forget, parafeed plate Chokes have to pass the same DC current that a traditional SE output transformer has to pass.
The DC current requires the plate choke's laminations to have air gaps.
And the chokes have to have even more inductance than a traditional SE output transformer has to have.
(however high the parafeed output transformer's primary inductance is, it is in parallel with the plate choke's inductance).
All of my amplifiers are monoblocks, and they are balanced differential push pull (2); push pull (2), and a self inverting push pull (1).
The self inverting push pull is due to be converted to be like one of the other push pull amplifiers (to make a pair of matched mono blocks)
I have stopped designing and building traditional SE amplifiers, and parafeed SE amplifiers. I did enjoy listening to Single Ended;
but I am moving on to balanced differential, and push pull amplifiers.
Just my opinions and my Experience
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Chinese yoke? 🙂
20H as anode choke, paralleled 10uF-18H primary: assessable transfer over 100Hz.
At 20Hz the resulting load of the tube is about 2k .... the trioded EL84 output impedance also 2k. :-(