Something new is coming

After messing around with my Quickie sans OPT's, using larger (electrolytic) coupling caps and some high-impedance phones, I secretly hoped BH would someday come out with something OTL that would put out enough juice to power big headphones. Looks like my wish has been fulfilled! Count me in for this one.

I can't wait to hear what this sounds like with my Beyers - I love tubes, but am not a fan of transformers!
 
PS - please add a button for the BH badge in your new ordering system. I sent an extra $6 separately for a badge since I didn't see them on the new ordering page.....
 
Dr. Toobz said:
PS - please add a button for the BH badge in your new ordering system. I sent an extra $6 separately for a badge since I didn't see them on the new ordering page.....
Click to expand...

That would be a great idea for every product page.
 
I know I will regret asking, I am in danger of becoming an addict:

Has it been tried with low sensitivity AKG 240Monitor phones? The autoformer Quickie works with my 240M cans, but just barely.     

 
I haven't had a chance to try AKG240s, as my pair was donated to the studio several years ago. We have used 300 ohm Sennheisers and they can easily be driven way too loud. So Crack should work very nicely with 600 ohm AKGs. A high impedance headphone is the intended mate to this circuit, and my guess is you can probably deliver about 1/2W into them. The headphone mod concept for the Quickie was done simply to show how one can do some pretty unconventional stuff to a $99 kit. It works, but it's not the original intended usage of the kit. The output trans mod rather drastically reduces the relatively low gain and it's probably going to work best with low impedance headphones that are more sensitive.
 
Damn.  Just bartered my last nice pair of 12au7s, and sold the last of my 6as7s over a year ago (had bought them, ironically enough, to build a headphone amp :-). )

I'll be placing my order shortly!

-- Jim
 
Just ordered mine.  Happy birthday to me.  If I can get it by 3/17 that would be awesome.  Has anyone come up with a crossfeed circuit for it yet?
 
Wanderer said:
I know I will regret asking, I am in danger of becoming an addict:

Has it been tried with low sensitivity AKG 240Monitor phones? The autoformer Quickie works with my 240M cans, but just barely.     
Click to expand...
I managed to score some K240M's locally not too long ago.  I just plugged them into the first prototype, and you will certainly have more power than you can use.
 
I just ordered mine! I'm getting fond of headphone listening and the coolness factor of the Crack amp is something you just can't pass on.
 
If I can get it by 3/17 that would be awesome.
Click to expand...

It's probably going to be a week or two longer than that before we can ship. This new kit has a new chassis plate design and those typically take about three weeks to receive from the laser cutter.
 
vuntruong said:
Would it be wise to order 2 Crack and use them as a balance heaphones amp? 
Click to expand...

I have tried this before, and I wouldn't discourage such an attempt, but I would warn that the 6080/6AS7 is notorious for having pretty poorly matched sections. 

In a single ended circuit like the Crack, this is not particularly bothersome.  In a differential circuit, it will be far more pronounced. 
 
What would you recommend as the minimum impedance for a set of headphones to use with the kit?
Click to expand...

The output impedance of the 6080 cathode follower is around 100 ohms. So in theory the most ideal load will be 300 and 600 ohm headphones. You could push this down to 100 ohms and just expect somewhat increased distortion - in fact we tried it with 32 ohm phones and it sounded pretty darn good, but that is not the intended usage. The current wisdom seems to be that a S.E.X. amp with the 120 ohm resistors removed from the jack works best with low ( like 32 ohm)  impedance headphones. The curves of some 6080 relatives might give a little lower output impedance in the given circuit, but I have not pursued that yet. Remember, this kit is only about 10 days old.
 
You can also try increasing the output coupling capacitor value to get a little more mileage out of some borderline cans.

So Doc, where you expecting so many orders for a kit that is only 10 days old and has not had a lot of pre-release anticipation built up around it?  Pretty cool if you ask me.

-- Jim
 
Definitely cool. It's interesting to see more and more folks go for higher impedance cans these days. Since PB brought up this idea I been looking for precedents and in the process had noticed that there had been some attempts to revive a similar but different kind of 6080 based OTL headphone amp by some folks over on Head-fi that ultimately weren't able to happen for reasons of cost. The fact that we could use mostly parts that are already in stock (including an existing, great power trans design by PJ that we have made in quantity) allowed us to put together something for a really low price. Perhaps the word will get out over there that we are offering something for a very low price that is easily tweaked and could fill the bill.
 
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