Millett "Starving Student" hybrid amp - Page 45

It may also just be the PS. Tube amps can be mode quiet enough that you can't tell they are on, but the PS filtering here is pretty minimal which will likely lead to a little bit of hiss. Probably not worth worrying about for this project.

Another small hint is that tubes pins are numbered in the opposite direction from transistors.



The transformer reduces Zout which is not necessary here. Also, I think the 2W rating might be a little generous there.

Actually, while it is never going to be loud or thumping, that seems fine to me for making a little noise on a desktop. I doubt the speakers go below 120Hz on their own anyway. I think it is worth the try, and it is doubtful that anything will be damaged by the experiment. At worst, it sounds too quiet and distorted. Also, you may eek out a tiny bit more volume by putting a small capacitor (100uF/16V is plenty big) across R5 and R11.

Unless you really want to drive small speakers, I'd recommend against this from first hand experience. The gain is 4x, and my smallest setting you can hear from across the room on my Senns, at least on the channel(s) that works.

The other channel(s) is loud static - scortched Mosfet? I'll look more tonight, but it is amazing how many joints I missed on p2p initially. Didn't test to see if the static got louder with the pot, as it was either my HD600 or 650 to test on... and, of course, I used the 650.

Vixr, beautiful work. Seriously. Very, very nice.

Since the gain is so high (4X x 15 = 60?) or so, at least that is how loud it sounds (and, no, it was not for extended periods), is there a way to tame the balanced gain? I'm using 50k stepped pots, and 470uF everywhere except c1 @ 150uF.

It may be the PS, but my amp is built with about as non-ideal an layout as can be done and has no hum or buzz. It also sits on my desktop in about as noisy a place as can be found (computers, monitors, fluorescent lights, etc.) and the only noise is a slight hiss at max volume. Her amp may be fine, but buzzing makes me think it's not.

I'm just trying to through a little caution in here before the inevitable "can this thing power my floorstander" questions start in once one person reads that it was used with any speaker. Bottom line if all you need is an 1/8th of a watt or so then yes, you can probably run some very small, efficient speakers with it if you size the output coupling cap properly. But I wouldn't expect great things out of it even when modified as much as possible. There are other ways to build cheap speaker amps that won't cost a lot more and will put out 1000x more power (gainclone).

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Caution and DIY shouldn't mix The whole point is to experiment and learn something.

The amount of power that people need is generally overestimated. I have been living with 8W amps in my main system (with fairly inefficient speakers) for years, and I never use even a fraction of that. If you are pushing 100W amps to their max, your hearing is most likely damaged from it.

Anyway, I have some little computer speakers that my neighbor threw out when he moved. I hooked them up, and this amp could make them much louder than I'd ever want for background music. For a desktop, I think this would work fine.



These reached volumes I would define as "loud" long before any audible clipping set in. Sound quality was crappy, and bass was non-existent, but for background, it was fine.

Fair enough, in the future I shall revise my stock answer to be "please ask dsavitsk".

I agree, wholeheartedly.

All depends on your desktop. Mine uses a pair of Ascend Acoustics CBM-170s which probably won't perform as well as your speakers did and I don't think I'd try it either.

Surely such a statement should never be uttered in an 'audiophile' forum?

BTW - my choice on the caps was purposeful.

I am much more of a treble and mids person, I like only a little bass and not the traditional thump that comes with tubes.

My preference in the past has been for SS amps that are on the lean side. I most certainly will play around with even more caps and parts and such, but it sounds really good now.

I do agree that anyone expecting to power something beyond small speakers or very efficient bookshelves will be disappointed.

However, if you are looking to have an all-in-one system for the office or desktop.... I think that putting a switched jack with speaker posts wouldn't be a bad idea or even just a mini jack (like what many computer speakers use).

If you want to make this as purely a speaker amp, look elsewhere, but if you just need a simple solution..What is wrong with this one?

How so? I'm going assume for a second that you mean the value, not the brand or sonic signature of the cap.

You know, the more you post the more confused I get. From what I read your can of choice is the AKG K400 which have a nominal impedance of 120ohms. Given your purposeful choice of 220uF caps your -3db point was 6Hz. What, exactly, do you think you were intentionally filtering out of the signal? And I don't even know what to say about the "traditional thump" comment. You might as well have said that you chose the gold enclosure hoping for a bright sounding amp. I know I chose a black chassis hoping for a blacker background.


Woot! I think you just said what I said about 30 posts ago when you were telling me that this would perform as good as the Bottlehead...


:timewarp:

@ holland, it is a steel case with some sort of plastic paint on it, inside and out. LOL at Nate...I thought a light colored case would use less power? All my black Hammond cases run down batteries like crazy...

That's kind of surreal. I have no idea what that is supposed to mean.

Don't concern yourself. It wasn't addressed to you.

There is a lot of hate in this DIY thread and its not just directed at me. Where is the love?

BTW - I would not expect the S.E.X. to work well powering big speakers either. I am sure that there are people doing it....and I am sure that it plays them at listen-able levels. I have seen some small horns in large casings where this works fine. I have been able to power speaker to loud levels even on my Headsix and it sounded pretty decent!

If you are on this forum I can almost guarantee that you are not coming here to learn how to make a speaker amp.

Nate....

It might be unreasonable to say that because it sounds good with headphones that it wouldn't with speakers. After all, headphones are just tiny speakers that have a specific purpose.


The capacitors were a purposely chosen VALUE, not brand specifically.

I have heard a fair amount of tube amps with headphones and all of them have had very thumpy low bass which was easily heard. That is not my style and that is the whole purpose of DIY, to get exactly what you want out of it.

Look what came in my mail today!


The rest of the parts should be here by monday. I gotta admit, I've only been reading up on headphone amps for a week, but I had to do something about the noise problem on my current setup. What really got me motivated to build this amp is the fact that tubedepot.com is about 15 minutes from my house. Can't wait to get this thing built so I can hear what I've been missing!

If I'm not mistaken, it's actually a vinyl covering over steel. The endplates can be aluminum like a Hammond, while the bottom is a thick piece of extruded aluminum. There are plastic bezels on both ends like the Hammond. At least, that's how the one is made that I used for the MiniMAX.

They have other models that don't use the vinyl-covered steel, but I kind've like it.