Considering a S.E.X kit but it seems impossible to find 6FJ7 tubes?

[Arnaud]

Hi All,

I'm new to the DIY scene and have been researching DIY tube Amp. The SEX kit seems to tick a lot of boxes:
- Ideally headphones (including low impedance) and speakers
- Point to point seems better than PCB based and I guess I will get more enjoyment and understanding from building it?

One thing that is stopping me for now is that 6FJ7 tubes seem impossible to source at the moment? Any alternative tubes that would work?

And maybe a strange question to be asking on here, but how does the SEX compares to the Starving Student II and the Elekit TU-8200R, even though I appreciate they both are slightly different price range

Thanks

[Paul Birkeland]

Before we released the new SEX kit, we bought up all the loose 6FJ7s floating around.  I would expect them to replenish and right now you can get some spares from vacuumtubesinc.com.

The Starving Student is really more of a simplified hybrid amp that looks a lot more like a Crack on paper but the FET source follower has boatloads of transconductance and the output impedance is super low consequently. 

The TU-8200R is similar conceptually but with smaller iron and a nicer box.  The specifications listed show 8W of power but do not indicate how low you can go at that power level, nor what the THD at those power measurements might be.  If a Lundahl transformer upgrade is available for that amp, that would be a good idea.

[Karl5150]

 I have built two SEX amps and the SSII.
I think the SSII is a very good sounding HP amp with a couple of cool features, but the SEX amp is the real deal.
I use a lightly modified SEX 2. amp as my daily-driver at work with speakers and a SEX 3. at home in a custom single channel speaker/stereo HP setup.
I was happy, well willing to gift the SSII to my son in law, knowing he will enjoy it.
I don't see ever parting with either of my SEX amps.
Karl
 

[Tubegopher]

Hi All,

I'm new to the DIY scene and have been researching DIY tube Amp. The SEX kit seems to tick a lot of boxes:
- Ideally headphones (including low impedance) and speakers
- Point to point seems better than PCB based and I guess I will get more enjoyment and understanding from building it?

One thing that is stopping me for now is that 6FJ7 tubes seem impossible to source at the moment? Any alternative tubes that would work?

And maybe a strange question to be asking on here, but how does the SEX compares to the Starving Student II and the Elekit TU-8200R, even though I appreciate they both are slightly different price range

Thanks

I just looked on ebay and there are quite a few 6FJ7 tubes for sale.

[mudvin]

how does the SEX compares to the Starving Student II and the Elekit TU-8200R

I have both a bottlehead sex and an Elekit 8200R with the Lundahl transformers.

I have to say that if you are driving regular speakers the Elekit is miles ahead of the SEX (the difference is staggering, I love the Elekit), both make great headphone amps (would say the sex is slightly better, the Elekit does not handle low impedance headphones). Plus combine the 8200 with the Elekit 8500 and you have even more power, more inputs and a Phono stage as well. Of course in fairness we are no longer talking similar costs, with the Elekit costing substantially more.

To be honest the bottlehead sex sound is not really my thing in general (Comparisons 2x bottlehead crack, elekit 8200, wd kel84, sansui 555a). However this is not about sound, the Elekit (with Lundahl) will power regular speakers well and sound full with great bass while the sex you will have to seek out high sensitivity speakers.

Negatives to the Elekit are that the Sex was a much better build, I actually feel like I accomplished something, whereas, the Elekit is more of a lego type thing. Mostly it all clips together.

[pingpongcomputer]

https://vacuumtubesinc.com/index.php/6fj7.html

I bought 3 pair here a few years ago, they were cheaper before the pandemic, but I got 2 pair with little to no noise out of the 3.

2 pair are likely to last the rest of my life. I really enjoy the sex 3.0 with c4s driving moderately efficient speakers for desktop use, and fostex th900's with a diy adapter to reduce the hp output.