Crack;Bottlehead OTL

[ironbut]

I recently built this Bottlehead kit (actually, I had it at Chicago), and I have to admit, it's crossed my mind a few times to sell my beloved Zana Deux since I started listening to it.

The kit is about as easy as they come (more cutting/stripping wires than anything else) and I did it in about 4 hours.

Here's the killer part. The cost of the basic kit is just $220 and an upgrade kit with CCS boards for both the 12au7 and 6080 cathode follower is another $100.

The stock Crack has a strong tubey character but with killer bass and liquid mids and highs.

With the upgrade (called the Speedball), the sound becomes more transparent and fast. The frequency extension sounds better (particularly in the bass) and a quieter background reveals some of the best stage depth I've heard with dynamic headphones.

Speaking of which, the Crack is recommended for high impedance cans (120 ohm) but I've been using my 40 ohm AD2000's and it sounds killer with them.

It did however, run out of steam with a pair of K701's.

In Chicago I borrowed ASR's HD800's for a bit and suffice it to say, I'm looking to buy a pair of them as we speak.

So,.. if you've ever picked up a soldering iron or stripped a wire, this would be a great kit to get your feet wet and build an amp that you might just never need to upgrade from.

BTW, there's a Bottlehead forum where other guys and gals who've built this amp can help you along if you get stuck or better yet, let you know how to do further mods on this kit.

Crack OTL Headphone Amplifier Kit

[mrarroyo]

Good to see your post on the Crack here, was wondering when you would do so.

[ironbut]

Good to see your post on the Crack here, was wondering when you would do so.

Yeah, I've been neglecting my shilling duties lately but I think I'm on the comeback trail!

Ha,.. it took me a bit to find the VW in your avatar this time!

[Augsburger]

Great to read Steve, I have been waiting to see if the honeymoon effect on your new amp would take hold. Ever since you clued me in at CanJam I have been wondering how they would stack up against my Trafomatic. I feel the FORCE.....

[Voltron]

Nice to hear from you Steve, and glad you're liking the Crack so much, you old ho.

[ironbut]

Who you callin' old?

Yeah, I'm still lovin' the Crack. It's a real enjoyable listen while my ZD is like a magnifying glass for picking the sound apart.

[n_maher]

One of these days I'll get around to polishing and posting the schematic for the Menace-TC. The Crack probably looks a lot like it and coupling the output really helps when driving low impedance loads. I always found the HA-2 (and original Menace to a lesser degree) to be very hit or miss with low-ohm loads. I agree wholeheartedly though, for the price the Crack is great project.

[Beefy]

This might be a good next project for me. I was originally waiting for the parafeed jobbie, but this might be a better option to dip my toes into some basic P-P rather than another PCB. With the CCS upgrade plus a nicer attenuator it is still pretty cheap, I can play around with output caps, stain the wooden case......

*ponders*

[Currawong]

It has been in the back of my mind, since parting with the RKV, to pick up one of these or the Elekit amp as they tick all the right boxes for price and flexibility of use.

[Smeggy]

I've pondered it myself but the whole low imp cans thing was always a deterrent as mine are fairly consistently in the low range.

[Nebby]

The only thing I don't like about the amp is the top mounted jack, but I think it shouldn't be too difficult to mount it on the front wood panel (I think).

[Salt Peanuts]

I'm rather fond of the top mounted jacks, personally. I've also been fond of top-loading CDP's, too.

[Augsburger]

The only thing I don't like about the amp is the top mounted jack, but I think it shouldn't be too difficult to mount it on the front wood panel (I think).

I suspect it has been Doc's philosophy with these HP amps to make them as simple as possible to build, that is purpose for the top mounted jacks and IEC IMHO. No drilling holes into the side of the case and I believe all parts of the amp are attached to the top plate and the top just drops down onto the wooden base. Simplicity at it's best.

[Nebby]

It's very obvious that the amp was designed to be extremely easy to build and I realize that's the reasoning behind the jacks. I just prefer to have my jacks on the front panel

[guzziguy]

There's nothing stopping you from putting them there.

[Nebby]

That's what I said I was thinking of doing earlier.

[CarlSeibert]

Good to see your post on the Crack here, was wondering when you would do so.

Nice avatar.

[mrarroyo]

Thanks Carl, just wish it was my ... car!

[Torpedo]

^ mine too

[ironbut]

Hey Torpedo,

I see you like St Vincent too. Did you see um on "Austin City Limits" on PBS?

[Torpedo]

Nope, just got the albums to see how I like her. Need further listening to decide, rather good though

[crappyjones123]

can 6as7's be used without any changes to the amp? i think i have a few lying around from the singlepower extreme days. simple enough amp and good reviews with the 650s.

the website says that tuberolling can be done with 6080/6as7 variants. does that happen to include the 5998 tube by any chance? loved that tube on the extreme. dont know if it would sound the same in this amp but i figured i would ask instead of assuming one way or the other.

[ironbut]

can 6as7's be used without any changes to the amp? i think i have a few lying around from the singlepower extreme days. simple enough amp and good reviews with the 650s.

the website says that tuberolling can be done with 6080/6as7 variants. does that happen to include the 5998 tube by any chance? loved that tube on the extreme. dont know if it would sound the same in this amp but i figured i would ask instead of assuming one way or the other.

Yes,.. you can use all the 6080 subs as well as the gazillion 12au7 subs in the Crack. I've tried most of the the usual suspect and I'm currently running a Tung-sol 5998 and a CBS/Hytron 5814a in mine and lovin' every minute of it!

There's a good bit of info regarding all kinds of tube rolling/mods etc on the Bottlehead/Crack forum.

Bottlehead Forum - Index

[crappyjones123]

placed an order yesterday. ups tracking received today. amp should be here next thursday. headphones around the same time. its going to be a good weekend. any tips/pitfalls i should be aware of steve?

[ironbut]

All the bugs should be ironed out in the manual now so, just take your time.

If you don't have a nice wire stripper, you should buy one. A great deal of building this kit is cutting wires and stripping the ends. I put a strip of tape on my bench top and marked it with the most numerous measurements so I didn't have to pull out a ruler with every wire I cut (I think I marked it in 1/2 inch increments for 8 inches or so).

There's plenty of step by step pictures so double check your work against them.

There are several instructions that tell you to solder one end but not the other. Follow those closely since that usually means you need to connect at least one other lead to that junction and it always better if you only have to solder those junctions once.

Have fun!