spritzer

It is a cracking amplifier. Next time around I'll test one with the current production pentodes.

Fuck!!!!

Happy Birthday!!

Yeah, the 007 will not work well with them but the SR-X Mk3 Pro worked pretty well, same with Lambdas. You can confirm though that it is possible to build a small Stax transformer that fits into your hand and actually works?

It really depends on the inrush current of the transformer but a 3AT would be my pick for US use.

Happy Birthday Deepak!!!

The next ones will be silver as they are just waiting for transformers. After that there will be two black units...

I doubt the verto was damanged, the reviewer just didn't listen loudly enough to energize the bias supply. Even Eric has said there is no sound for the first two minutes which is not good for the health of the diaphragm. Those small boxes worked just fine off a Grado RA-1 (normal version) driven by an iphone.

Here is a good article on the awesomeness of the Verto: http://hifipig.com/audiovalve-verto-and-rkv-mk-3-headphone-amplifiers/ So it basically doesn't work and I can't say I'm surprised. I've seen a lot of takes on the self bias idea over the years but this one is by far the worst. As one would imagine, to get +580V bias off the music signal would require some step up to help matters when the audio signal is low. No such luck here, just a huge voltage multiplier with all the issues they have and a pile of parts needed for it to work... or not as it happens. I built these: ...and they worked perfectly off a portable headphone amplifier and fit into the palm of your hand. Me thinks the person responsible for the Verto hasn't got a clue how to do this properly... As for the subject of transformers, it's been well known since the dawn of electrostatics that they didn't match well with transformers. Look at the history of brands like Sound Lab and Acoustat who spent a lot of time to make the transformers less of a crippling weak link in the performance of the panels. So many different designs have been attempted over the years but none have truly worked and the inductive nature of transformers and electrostatics don't play well together. For speakers they are a necessity given the very high voltages (Soundlab are up to what now, 20kV bias) but for headphones we can run on +/-400V and overdrive the transducers so amplifiers are a no-brainer. A word about just how stupid eric65 really is. I mean this is epic shit and he just can't figure out how moronic this really is. His great mod is to bypass the shitty transformers of the Woo WEE as according to him the gain is too high. Granted 1:50 transformers are a bit too much today and the iron Woo is using is wholly unsuitable for the job so good riddance. What Eric does though is he drives the Stax directly off the TRS plug on the RKV... wait for it.... single ended that is. - stators are grounded so there is at least that but we are talking about distortion close to the 20% mark and at very low volume. The theoretical max voltage swing of the RKV is 200Vpp but in reality it will be lower and we all know how great amps are when running right on the limit.

I knew you'd like it. It's funny though that the 136$ SET kit I've been playing with has a better PSU design than this pile of fail. A good point is the "DC" supply for the 5751 heaters. That's not how you are supposed to do it...

I like the silver look. You could contact Modushop as they will sell you silver side panels.

Looking good!!! That SumR looks awfully small though...

Behold the glory...

Looks to be the same case but I just pulled them from my pile of boxes. A note though, the KGST boards from the group buy will not fit in this box. The ones I used were specially made to fit it and they just barely do so. Also it runs hot... too hot. Chassis is at 43°C above ambient so I'll have to fabricate new top panels for these amps. The fuse rating depends on the transformer used. The amp draws about 60W.

Happy Birthday!!!

Yes.

Here they are together. KGSSHV mini quite a bit smaller. As for the sound they are very similar. The ST is a bit warmer and more fluid but that's it. Just look at the Antek units as they are all oversized so the pro's are less heat, less noise from the transformer but the negative is more inrush current and more overhead for the PSU to deal with as heat. Yup, it uses the chassis as a heatsink but this is a special version of the PSU.

For any filament or heater supply you have to regulate the DC which DNA doesn't do. A simple LT1083 supply would be great for heaters (a 7805 with a diode on the ground terminal also works just fine) but for DHT filaments you need a high frequency switcher to get optimal tube life. These tubes were never supposed to use AC for the heaters as a tube like the 300B was supposed to use batteries for the filament. It's what they had at the time and explains the low voltage.

That is a lot of cinnamon....

This one was just fired up. To say it was a tight squeeze into that box would be putting it mildly... Utterly oversized transformer courtesy of my Chinese supplier.

This has nothing to do with liking how something sounds. Plenty of people like Hifi-man and Ultrasone headphones even though they are dreadful. Just flip over the Stratus and look inside, the cheapest possible iron which everybody agrees makes or breaks an amp. Lousy circuit design and a "DC" filament supply which will burn up the tubes. What's not to like....?

DNA Stratus? It's firmly on the the "what idiot threw this together" scale....

Yeah, clueless people usually do.

Most of the work done on the mini in the last few months has been to monitor the temp and seeing how it behaves in warmer climates. It runs at about 20-25°C over ambient and is a bit warmer inside. Not too bad.

Ohh please enlighten me about these magical "inductors" and their properties. We were all so hopelessly lost until you came along...