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Forget it, the F2a is now one of those tubes that has been hoarded by speculators. They are available only at high prices, with an uncertain future availability. I would not recommend anybody to design and build around this tube unless they have a lifetime stock (one spare at least). So I’d suggest build so that you can convert to KT88.
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I live in a place that Online shopping is not easy and often not possible. I learned to build all transformers.
I collected the tubes just to make the amplifiers that I didn't sell
. I think ken shindo is the result of the japan audio tube diy population . He started his work when the tube had not turned on like today.Shindo had a lot of skill, which is rarely seen in the West today. Maybe Altec engineers in America used to do this. It seems that Shindo followed Altec, the type of assembly, even the Altec circuit and the color of the box.
I collected the tubes just to make the amplifiers that I didn't sell
. I think ken shindo is the result of the japan audio tube diy population . He started his work when the tube had not turned on like today.Shindo had a lot of skill, which is rarely seen in the West today. Maybe Altec engineers in America used to do this. It seems that Shindo followed Altec, the type of assembly, even the Altec circuit and the color of the box.
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Joined 2009
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What I like about the 300B is that they’ll be around after I’ve gone, so build with these tubes without worry. Build well, your amps may outlive you. The 300B has lower gain than the F2a so the Cortese uses a mu follower driver to ensure enough gain. Nice approach.
Nevertheless, two pairs of F2a means you have all you need for your personal enjoyment 👍
@Bigun What I like about F2a is that it is only made by Siemens and was good enough for military and post. I thought that if I buld with 300b, it must be a NOS Western Electric. For the price of a genuin WE300b I bought many lifetime F2a-s. Even a JJ300b costs the same these days. By the way I do not want to clone Cortese, but Klangfilm with EF804S driver. Those german engineers knew their tubes.
Is the tube like a car tire? Is it enough to match the size of the previous tire? mullard xf2 -xf3 and xf4....el34 one of the examples of great tubes in the sound. who knows something similar ? Unfortunately, they may not be available in the future... Shindo definitely did not follow the discussion of tbes circuits on the Internet. He has his own style in tbe amp.
A car tire has many parameters, not only size. See the tests and price difference. I stick to Continental. For me the best, like F2a.
When I saw this posts, I started to make a single f2a se .The image shows this amplifier.The assembly is point by point and No noise can be heard in the sensitive speaker.
Of course, the box is also effective.
There was no schematic for shindo f2a. In the catalog, Siemens shows a single circuit with 250 volts. .... I guess Shindo used a votage close to 350 volts., there is fix bias in the Shindo version.
Of course, the box is also effective.
There was no schematic for shindo f2a. In the catalog, Siemens shows a single circuit with 250 volts. .... I guess Shindo used a votage close to 350 volts., there is fix bias in the Shindo version.
When a low-power amplifier is made, half a watt more..... is mportant.
If reach 26 p-p in 8 ohm lode ......( blow 30 watt power dissipation in f2a tube) ..., it can said that you were successful with f2a. (10watt)
Some people believe thats is easy. But it is not so easy. The best drive tubes is 6aw8 . Shindo use only janphilips 6aw8...... Be careful, there are many defective tubes in jan philips , Sylvania forgot the quality check in production.
If reach 26 p-p in 8 ohm lode ......( blow 30 watt power dissipation in f2a tube) ..., it can said that you were successful with f2a. (10watt)
Some people believe thats is easy. But it is not so easy. The best drive tubes is 6aw8 . Shindo use only janphilips 6aw8...... Be careful, there are many defective tubes in jan philips , Sylvania forgot the quality check in production.
It is finished and the best amplifier that can be made.
I made opt and power transformer myself. I test the frequency response . from 20 hz and up to 30khz...10khs squre wave.you can use lundahll opt.
I made opt and power transformer myself. I test the frequency response . from 20 hz and up to 30khz...10khs squre wave.you can use lundahll opt.
I'm not worried at all. I will not make an exact copy. I will experiment with Plate to Grid, Plate to driver Cathode feedback. All what is fix now the driver tube (EF804S) and the transformers (Tribute). I want to taste vintage. I have and will have other amplifiers with high(er) bandwidth: 300B DRD, 300B Legacy, E84L PP, Zeus, The End Millenium, Sony V-FET, Tokin V-FET. (Maybe a Hiraga, if I have time 🤣 )
I gave this amp to my son who is going to Canada to continue his studies.
The left side is the old version and the right side is the new version