Best DIY tube headphone amp or DAC? - Page 2

in that case, it has no balanced input because it's not a balanced amplifier. 

 

It's a single-ended amplifier with transformers bolted on. 

 

You could get se-to-balanced transformers and plug them into any single-ended amplifier for the same effect. 

well, it's more or less true. You could get some 1:1 coupling transformers and hook them up to any SE amp and just neglect to connect the secondaries to each other and achieve the same effect. 

 

So what you have to ask yourself is whether that matters to you. 

 

 

Why dont you search and read up on the O2 (Objective2). It was designed to be able to power basically everything on the market.

I will most likely end up biulding one myself as its only 52 bucks for all the parts.

I am also looking at the Bijou and the Millet Max and mosfet Max. I kind of want a nice large gigantic amp for my desktop that looks flat out intimidating, but I dont want to take a teeny tiny circuit board and shove it into a huge box. I cant figure out the difference between the millet Max and mosfet Max apart from the mosfets in the mosfet version. I dont even understand what that is supposed to do (I think higher current output).

Also I have no idea what situation sthe EHHA and SOHA and Bijou are designed for.

 

When used outside of a feedback loop Mosfets and BJTs sound different. 

A digression from the rest of the thread, I know ... but the essential difference is that the Millett Hybrid MiniMAX is made to fit in the custom-machined Beezar/Lansing case.  It uses BJT's because those typically don't have to be biased with as much current and can use 1" high heat sinks that fit into the custom-machined case.

 

The MOSFET-MAX is based on the original, larger Millett Hybrid MAX.  It can use BJT's or MOSFETs, but has no performance advantage over the MiniMAX if BJT's are used.  However, the MOSFETs will provide much more current capability - suitable for Orthos and flea speakers, for instance.

 

All of the Millett Hybrids use voltages no more than 24-27V, so are quite safe when building.  Even the wall power comes from an off-the-shelf walwart.  (You can still burn them up, but they're not going to electrocute you.)
 

 

I'm assuming the mosfet max uses the mosfets and the minimax and hybrid max both use BJT's? Also, by feedback loop I'm assuming you mean that either the input or output is also connected to the gate (my teacher calls it the gate). We havent really gone over BJT's and none of us really understand the point of a transistor yet as we've only been covering theory but MisterX linked me to a wonderful ebook and I'll be thoroughly reading as much of that as I can. Theres like 9 volumes.

Not REALLY a digression, we are still talking about tube amps. If OP has a problem with this conversation though we can stop, but I think OP will benefit from this as much as anyone else.

So from my understanding, there are 3 versions of the millet "MAX". There is a "regular" Hybrid MAX, a MOSFET-Max version, and a Hybrid Mini version. The Millet Hybrid came first and used BJT's. The MOSFET Max is based off of the Hybrid but can use MOSFETS and provide higher current. The MiniMax was built for a custom case and uses BJT's.

So I guess the only question I still have is, what about the difference between the Millet Hybrid MAX and the Millet Mosfet MAX? I recall that one of them had room for a daughterboard DAC like skeleton or grub.

EDIT: OP, if you havent seen it yet, theres the ST-70 and a bunch of others from TriodeElectronics. I'm not sure as to the fidelity of these designs but they have all kinds of different power outputs. One guy used his to power a pair of DIY Dayton cabinets and there are tubes galore on this thing. Personally, I dont like the fact that it uses output transformers, but maybe give that site a once-over. Theres also a bunch from tubecad http://glass-ware.stores.yahoo.net/newhardware.html
The MOSFET-max will have more current output than the minimax if you use mosfets (because bjt's dont output as much current I guess) but other than that there will be no difference.
Edited by shrimants - 2/23/12 at 7:57am

Going back a few posts, there are very few fully balanced DIY tube headphone amps for dynamic headphones. Its not hard to tweak preamp designs to make one, but as far as I know there is no kit you can buy off the shelf. 

 

I'd check out Lynn Olson's site nutshell HiFi. His articles about THD are pretty good. 

His pre-amp "the raven" makes a nice headphone amp.

K&K audio sells PCB's for the raven, but you may find it easier to point-to-point the thing than work with them.

 

I would buy the Morgan Jones book "valve amplifiers" It is quite nice for starting to design Tube amps.

 

Why dont you like output transformers?

I mostly dont like them because of FUD and what I keep reading about them. I am still in the middle of research but from what it looks like, for high power you can either use output transformers or output capacitors. The transformers will cost a motherload and the capacitor route will just have gargantuan boxes/enclosures necessary. Again, this is just from some quick research. I also found that transformers are fine for audio as long as they are designed and engineered properly but that since guitar amps used to use any old transformer due to not needing a wide frequency response range, audio buffs got "scared" of them.

I still have to figure out what constitutes a good transformer for audio purposes and what, in terms of design, makes it behave that way.

EDIT: I just wanted to add, I'm not afraid of being wrong on the internet but I am afraid that someone will think that I'm insisting that I'm right. Such is not the case.
Edited by shrimants - 2/23/12 at 8:31am

 

Edited by tomb - 2/23/12 at 5:11pm

I too am interested in the differences between the Bijou, EHHA, and Soha. However, I would like to point out that it is kind of rude to ask which one is the "best" between all of them. First of all, each has their own strengths and weaknesses. Secondly, and more importantly, each is a DIY project by a hobbyist who spent their time, effort, and money to develop the model. Think of it like using various pieces of free software. Someone sat there to code through everything, and to belittle their project because someone else happened to do something better is not a very tactful thing to do. So please refrain from asking which one is BETTER, rather just understand the intricacies and beauty that went into the research, design, and development of each.