Not all SV811 and SV572 are A2 tubes, SV811-3/10 and SV572-3/10 are good for A1 operation, please refer to the link:
SV811 and SV572 are A2 tubes
Regards
SV811 and SV572 are A2 tubes
Regards
Viva tubes are selling the Sv811-3 for 60 bucks per pc isn't it so much cheaper then many other Dht power tubes ? Sun Audio has a kit but in A2 running under 500v & produces 12 watts. Think you can easily do 12 to 15 watts A1 in pse so its like 2 tubes for the price of 1 modern 300B.
I bought a small 7K amorpous C-core transformer
, --> 4 and 8 ohm last year. I tested it with a signal generator with 6 ohm on the 4 ohm secondary, and the frequency -3 dB was 5 Hz to 85 kHz. 😀
The Chinese manufacturer specified it conservatively at 20Hz - 35 kHz 🙄.
Max core current 45 mA is so safe for the 25-30 mA of a 10 or 10Y.
So these modern OPT are great, cheap and small. [I also have a same build 5K:5K signal transformer, which when used as anode choke measures >> 100kHz].
My Lundahl LL2752 that "is specially designed for 300B". I use it in the 4 ohm mode, it gives a perfect square wave in 8 ohm dummy (slight disturbance at 135 kHz on rising edge) and gives a BW of 12 - 55 kHz on my 300B as long as I buffer the driver output with a SF. It runs 70 mA. Again, a very good result with a modern C-core.
I have used a toroid too for several years. BW > 200 kHz 😛 That had a warmer sound than the above C-cores.
In comparison to "vintage" tubes they are not as linear. I have seen there are 2 types too: the old one with cocke bottle (many found out it's not reliable) and the newer one with tubular bulb.
Regarding the SV811, I know nothing of the tubular but the old one was also rather inefficient.
Anyway they could be used if found at reasonable price....
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I bought a small 7K amorpous C-core transformer
I tested it with a signal generator with 6 ohm on the 4 ohm secondary, and the frequency -3 dB was 5 Hz to 85 kHz. 😀
The Chinese manufacturer specified it conservatively at 20Hz - 35 kHz 🙄.
Max core current 45 mA is so safe for the 25-30 mA of a 10 or 10Y.
So these modern OPT are great, cheap and small. [I also have a same build 5K:5K signal transformer, which when used as anode choke measures >> 100kHz].
My Lundahl LL2752 that "is specially designed for 300B". I use it in the 4 ohm mode, it gives a perfect square wave in 8 ohm dummy (slight disturbance at 135 kHz on rising edge) and gives a BW of 12 - 55 kHz on my 300B as long as I buffer the driver output with a SF. It runs 70 mA. Again, a very good result with a modern C-core.
I have used a toroid too for several years. BW > 200 kHz 😛 That had a warmer sound than the above C-cores.
May I have the link pls ?
Thank you
Yes, that's what I always say. The brand does not guarantee anything. A large scale production will almost inevitably result in better tubes and worse tubes. So when buying some selection is a must. Generic tubes with no kind of selection could be used for experiments but until people buy them for substantial money (which they think is reasonable only because they save some 20-30% in comparison to "first choice" tubes) it won't change....
However with the SV tubes the rate of failure was a bit too high....especially because they were and are not cheap.
Well that's the sad thing 45, when I purchase tube they're so called matched but who knows as Im not there to see it. Lol
Yes I've read of the reliability issues that you mention but most that I've read are about the Sv 572 series. In any case many thanks for sharing.
Cheers
Yes I've read of the reliability issues that you mention but most that I've read are about the Sv 572 series. In any case many thanks for sharing.
Cheers
I bought a small 7K amorpous C-core transformer
I tested it with a signal generator with 6 ohm on the 4 ohm secondary, and the frequency -3 dB was 5 Hz to 85 kHz. 😀
The Chinese manufacturer specified it conservatively at 20Hz - 35 kHz 🙄.
Max core current 45 mA is so safe for the 25-30 mA of a 10 or 10Y.
So these modern OPT are great, cheap and small. [I also have a same build 5K:5K signal transformer, which when used as anode choke measures >> 100kHz].
My Lundahl LL2752 that "is specially designed for 300B". I use it in the 4 ohm mode, it gives a perfect square wave in 8 ohm dummy (slight disturbance at 135 kHz on rising edge) and gives a BW of 12 - 55 kHz on my 300B as long as I buffer the driver output with a SF. It runs 70 mA. Again, a very good result with a modern C-core.
I have used a toroid too for several years. BW > 200 kHz 😛 That had a warmer sound than the above C-cores.
It's not hard to develop a high bandwidth OPT. But the sound of the OPT comes mostly from the materials and wire used and little to do with bandwidth.
The bigger core you use, the easiest it is to get high bandwidth. In clever transformer design, you just need to use clever math. Watch out for square dependencies, such as leakage inductance, and favor linear dependencies.
When it comes to selling and marketing, the hardest part is making a well performing OPT as compact as possible. Few people want back breaking wardrobe sized amps in their rooms. You need the most efficient shape, which is the cube, to fit the most material (core or wire) as possible.
Exotic methods in OPT development, such as exotic cores and shapes go more to a niche section.
These SV tubes are not made by Svetlana factory in St. Petersburg. They are made in Saratov. Svetlana name was stolen using legal shenanigans.
The bigger the core, the more chance for leakage L, and winding C. For a given interleave schedule, the smaller will have a larger bandwidth.
cheers,
Douglas
With a larger core lesser turns are needed and leakage L decreases in a square fashion, so less interleaving is needed for the same Ls, hence less capacitance. Core surface area also beneficially increases in a square fashion compared to MLT.
So you will always benefit from a larger core.
So you will always benefit from a larger core.
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I agree with Bandersnatch and disagree with 50AE.
Leakage inductance is inversely proportional to winding proximity, so smaller transformer has less LI than bigger one with the same interleaving.
Winding capacitance has two components: turn-to-turn and layer-to-layer. Turn-to-turn capacitance dominates. Generally, capacitance can be reduced by spreading out windings, whereas leakage inductance can be reduced by making windings more compact. So, reducing one, you increase the other.
Leakage inductance is inversely proportional to winding proximity, so smaller transformer has less LI than bigger one with the same interleaving.
Winding capacitance has two components: turn-to-turn and layer-to-layer. Turn-to-turn capacitance dominates. Generally, capacitance can be reduced by spreading out windings, whereas leakage inductance can be reduced by making windings more compact. So, reducing one, you increase the other.
I agree with 50AE.
He is a skilled transformer winder, not afraid to do prototyping and measuring (and listening).
Do you guys have the same experience? I guess not...
He is a skilled transformer winder, not afraid to do prototyping and measuring (and listening).
Do you guys have the same experience? I guess not...
Ls is
-inversely proportional to winding proximity (correct), but also
-increases linearly with the Mean Turn Length
-diminishes by the square of winding turns
-diminishes by the square of interleaving (nicely illustrated in RDH4 and Crowhurst pages)
Winding capacitance in OPTs:
-turn to turn - ridiculously negligible
-primary to primary layer (Cp)- almost negligible, can be sub hundred pF
-primary to secondary (Cs) - most contributing
-primary / secondary to core - can be contributing in some cases.
But a skilled designer and winder can distribute some Cs towards Cp. Capacitance also decreases in a non-linear impedance way with the decrease of voltage gradient ratios.
Patrick Turner has the simplest explanations on his pages of how to calculate OPT capacitances.
You can also, by clever interconnection of windings, bring overall capacitance a bit down without increasing Ls.
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A larger core permits the employment of less primary turns for the same flux density, hence power output.