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$110 Tube Hybrid Amp Group Buy - Page 19

post #271 of 280
If you say that the noise level is lower with the different transistors, I'll order a pair the next time I need something from Mouser or Digikey.

As for resolving power, detail/accuracy is the be-all and end-all for me. This is not the faux detail of HF emphasis I'm talking about. True detail with flat response is where it's at. All the other stuff (musicality, PRaT, space, involvement) derives from the information content. IMHO, with relatively low levels of accuracy (ie, lo-fi gear), you can get good results in these other areas with carefully engineered compensating inaccuracies. When I read headphone recommendations in these forums like, "you won't hear the potential of headphone X without a good amp like Y", I can't help but chuckle. It's the quality of X that reveals if Y is any good, not the other way around. If phone X is colored and muddy, the amp won't matter (drive issues aside).

My main purpose for persuing phones right now(*) is to have a reference that is uncolored by acoustics -- room acoustics, cabinet resonances, etc. Secondary is their ability to "draw me in". That can always be achieved by turning up the volume.

I listen while working to block outside noises and to audition new music in the background. When I listen to phones for pleasure late at night, the revelation of the music caused by lots of accurate detail is what works for me.

[edit] The dynahi boards are about 4" x 5". The space for the board in the HP100a is 4.25" x 12". So the two audio channels will fit. The boards are meant to slip under the heatsink ledge, so I'll have to cut off this supporting area. There are two sets of fat traces that will be cut off, going to each bank of power transistors that can be replaced with two copper busses. You have a dynahi case and you didn't even know it.

- Eric

(*) in spite of the fact that Frank got me into this mess by checking on the 110/220V issue
post #272 of 280
Thread Starter 
I can't say what is causing the lower noise. It could be the transistors, it could be just the way I wired the ground and the new plastic chassis. I can't tell you for sure.

I do value accuracy as well. That's why I love my PPA and my Etys, there's nothing else quite so accurate. But for me this new tube sound is something I've never quite experienced before while pursing only detail and accuracy through solid state amps and analytical phones. It is something that really complements the PPA sound very well. If I were to keep one, I would keep the PPA, but when my ears get tired from too much fine detail that needs to be actively digested, it's just that sometimes that "tubey sound" is very strangely satisfying when matched correctly.

And thanks for pointing out the dynahi dimensions. Mmm. Free dynahi casing...
post #273 of 280
I just looked at your mod posts.

You might have a problem with the 300R Dale resistors on the tube boards. One of them is on the grid, so it's fine. The other two are carrying 25mA each, dissipating 0.2 watts. Add the heat from the surrounding tubes and you're pushing their 1/4 watt rating.

[edit]If you really want "tube sound", check out the Consonance that Frank has. It's a completely different fish. The HP-100a is much more like the HeadRoom Max Home than it is like a "tube" amp. See my comments posted last week.

- Eric
post #274 of 280
Thread Starter 
Quote:
The other two are carrying 25mA each, dissipating 0.2 watts. Add the heat from the surrounding tubes and you're pushing their 1/4 watt rating.
Well they're rated at 1/4W, but that's a really modest rating, IMO... Those things from what I read can take much more than that so I'm not that worried. And plus I have the C variant which has lower thermal variation compared to the standard D variants.

I have another pure tube amp board that I will be populating soon, I'll have to see how tubey that sounds and if I'm really a tube person or SS person.
post #275 of 280
The 0.2W is just from the 25mA of DC. The amplified AC signal across these load resistors will add more heat.

Heat = noise, heat = resistance change = non-linearity. It's important to have very stable load resistors in the anode circuits. Maybe you have a "tube" sound because your mu stage might not be very linear with those hot puppies in it.

I used 5W Mills resistors. The tube section is dead quiet now: the amp's noise floor sounds exactly the same with or without the tubes. There's absolutely no noise from the tubes or hum from the filaments. The noise (when listening with Grados) is coming from the transistors, not the tubes. It can't be the modded power supply. I should get the scope out one day and verify this.

If you want really low noise tube circuits, use Caddocks for the loads.

- Eric
post #276 of 280
Thread Starter 
Hmm I'll have to check out the heat levels on the resistors sometime. Thanks for the tip, I'll report back with some results!
post #277 of 280

2nd round?

too bad I missed the 1st round buy. eager to know when will be the 2nd round? heard hp100a is out of stock, next round will be hp100b?
post #278 of 280
Time to bump a 3+ year old thread! W00t!

Anyway, knowing these have been discontinued, where the hell can I get one of these?

ARGH!
post #279 of 280
Quote:
Originally Posted by chinesekiwi View Post
Time to bump a 3+ year old thread! W00t!

Anyway, knowing these have been discontinued, where the hell can I get one of these?

ARGH!
http://www.head-fi.org/forums/f5/fee...8/#post1918494
post #280 of 280
Quote:
Originally Posted by FallenAngel View Post
I can use search too
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