Tone,
There are a number of problems:
They cannot accept any DC, so push pull is essential.
There is barely enough inductance.
The interwinding capacitance is not controlled, so different makes with the same ratings will give different results.
I think 316a has done some work with them. Hopefully he'll reply.
Cheers,
There are a number of problems:
They cannot accept any DC, so push pull is essential.
There is barely enough inductance.
The interwinding capacitance is not controlled, so different makes with the same ratings will give different results.
I think 316a has done some work with them. Hopefully he'll reply.
Cheers,
I know some PP amps have been built with Talema toroids. There is a lot of variation in terms of primary inductance; some toroids are quite high.
If u use a parafeed type arrangement you can use toroids..I believe a 50va toroid with a 10:1 stepdown will work..so something like 230v-25volts...
The CCS can be something as simple as a resistor.
Just add a cap in one leg of the primary and voila!
But yes hopefully 316a can shed some more light on the subject.
The CCS can be something as simple as a resistor.
Just add a cap in one leg of the primary and voila!
But yes hopefully 316a can shed some more light on the subject.
Tone,
Then the primaries could be put in series.
Tiroth,
So desu ka?
I was just wondering whether the smaller ones would have enough inductance. He wouldn't want a 50VA thing in his preamp.😉
Ja mata.
Of course both ideas depend on the transformer being fed from a sufficiently low source impedance.
I wonder if it worth the trouble. How much does a run - of - the - mill audio stepdown transformer cost in that part of the world?
Kampai,
That's a good idea.🙂
Then the primaries could be put in series.
Tiroth,
So desu ka?
I was just wondering whether the smaller ones would have enough inductance. He wouldn't want a 50VA thing in his preamp.😉
Ja mata.
Of course both ideas depend on the transformer being fed from a sufficiently low source impedance.
I wonder if it worth the trouble. How much does a run - of - the - mill audio stepdown transformer cost in that part of the world?
Kampai,
dhaen,
Ee. As luck would have it I have a tiny 1.6VA 2:1 toroid (70000 series) and a larger 35VA 27:1 (62000 series) arriving Thursday. I'll measure the primary inductance and report back.
Ee. As luck would have it I have a tiny 1.6VA 2:1 toroid (70000 series) and a larger 35VA 27:1 (62000 series) arriving Thursday. I'll measure the primary inductance and report back.
Tone:
Major dumb question: what are you trying to accomplish? I've always found it useful to define a problem before trying to evaluate solutions.
Major dumb question: what are you trying to accomplish? I've always found it useful to define a problem before trying to evaluate solutions.
Toroids
Tone,
Toroids will work but the end result will very much depend on the quality of the core. So the final sound especially the highs is very much of a touch and go thing.
If you actually have the winding details(no of turns, layers etc), I know a guy in KL with Z11 grade core which will be adequate for OPTs and the price is very reasonable.
If you want to be sure, try Martin Electronics in Bencoolen Square in S'pore. He sells Lundahls at a price of about USD75 each.
Regards,
ckt
Tone,
Toroids will work but the end result will very much depend on the quality of the core. So the final sound especially the highs is very much of a touch and go thing.
If you actually have the winding details(no of turns, layers etc), I know a guy in KL with Z11 grade core which will be adequate for OPTs and the price is very reasonable.
If you want to be sure, try Martin Electronics in Bencoolen Square in S'pore. He sells Lundahls at a price of about USD75 each.
Regards,
ckt
toroids
nothing wrong with using toroids . Points to remember are to keep the DC well away from them and avoid saturation . I don't know about pre-amp usage but I've been using them as power amp outputs for the last year . Primary inductance is usually high but finding large enough sizes with the correct turns ratio can be tricky , this means that for power stages you need to drive with Low Ra valves . The main problem is the core size , when pushed hard the bass can fall apart but I doubt this should be a problem with pre-amp usage . Try them , they should work well for pre-amps . Best application to date for me is parallel feed , push pull is another possibility but you'll need to take into account balancing the output stage , keeping the HT low . Remember these things weren't designed to swing 400v p-p across them at 20Hz .
316a
nothing wrong with using toroids . Points to remember are to keep the DC well away from them and avoid saturation . I don't know about pre-amp usage but I've been using them as power amp outputs for the last year . Primary inductance is usually high but finding large enough sizes with the correct turns ratio can be tricky , this means that for power stages you need to drive with Low Ra valves . The main problem is the core size , when pushed hard the bass can fall apart but I doubt this should be a problem with pre-amp usage . Try them , they should work well for pre-amps . Best application to date for me is parallel feed , push pull is another possibility but you'll need to take into account balancing the output stage , keeping the HT low . Remember these things weren't designed to swing 400v p-p across them at 20Hz .
316a
As promised:
1.6VA as line input
==============
2:1
Primary inductance: 4.5H
Primary interwinding capacitance: 200pF
with 13k secondary load
-0.5dB at 20Hz
-0.3dB at 20kHz
The bad news is that distortion is on the order of 0.6% at 20Hz, -0.05% at 250Hz, 0.001% at 500Hz, and unmeasurable at higher frequencies. This would be excellant as line input for a tweeter amp, but the primary inductance just doesn't appear to be high enough for the low frequencies.
35VA as OPT
=========
27:1
Primary inductance: 146H
Primary leakage inductance: 10.5mH
Primary interwinding capacitance: 1.4nF
Not bad!
1.6VA as line input
==============
2:1
Primary inductance: 4.5H
Primary interwinding capacitance: 200pF
with 13k secondary load
-0.5dB at 20Hz
-0.3dB at 20kHz
The bad news is that distortion is on the order of 0.6% at 20Hz, -0.05% at 250Hz, 0.001% at 500Hz, and unmeasurable at higher frequencies. This would be excellant as line input for a tweeter amp, but the primary inductance just doesn't appear to be high enough for the low frequencies.
35VA as OPT
=========
27:1
Primary inductance: 146H
Primary leakage inductance: 10.5mH
Primary interwinding capacitance: 1.4nF
Not bad!
line doughnuts
with my very basic primary inductance testing I usually get 100H for a 50VA 230V:6-0,6-0 unit at 50Hz . This is more or less the largest size with the highest turns ratio . Sizes above that such as 230:9-0,9-0 etc require the output valves to be 6C41/6C33 type things . I am also tempted to unwind the secondary windings and use as a push pull anode choke . Anyone ever thought of doing this ?
316a
with my very basic primary inductance testing I usually get 100H for a 50VA 230V:6-0,6-0 unit at 50Hz . This is more or less the largest size with the highest turns ratio . Sizes above that such as 230:9-0,9-0 etc require the output valves to be 6C41/6C33 type things . I am also tempted to unwind the secondary windings and use as a push pull anode choke . Anyone ever thought of doing this ?
316a
316a,
How about using a CCS on one side, and then you can use the other side SE.😉
Nice for a driver anode choke?
You could even put a teeny amount of current feedback to the cathode from the 6v winding.
This is of course "pub talk"...
Cheers,
How about using a CCS on one side, and then you can use the other side SE.😉
Nice for a driver anode choke?
You could even put a teeny amount of current feedback to the cathode from the 6v winding.
This is of course "pub talk"...
Cheers,
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