Bottlehead Kits > Mainline

New top of the line headphone amp

(1/14) > >>

Doc B.:
Last year we retired the Smack headphone amp kit due to sluggish sales. There were a lot of really good aspects to that kit - adjustable output impedance to handle a wide range of headphones, both single ended and balanced headphone output, a single gain stage circuit with active loading and hybrid shunt regulation, and very good transformers. And very good sound - I thought it was clearly our best sounding headphone amp at the time. Unfortunately for Smack we revamped the S.E.X. kit and in doing so came up with an amp that pretty closely matched Smack sonically and offered enough power (2W!) to run tough cans like LCDs, HEs and K1Ks.

Smack's lower gain and 1/10 the power output was a compromise in the name of greater resolution and speed and more quiet operation. And we somewhat compromised the kit with a very functional but standard stereo volume pot to keep the price down. These things worked against the kit and our customers were buying S.E.X. instead for the same price.

So I decided to rethink the concept of a more premium headphone amp. I wanted to keep the positive aspect mentioned above, and I wanted a bit more gain and more power, and a better attenuator up front. We also had heard a lot of folks ask for extra inputs and express a dislike for our impedance switching setup that required turning the amp off and going inside to adjust output impedance and balanced/SE output.

And so here you see the prototype of Mainline, our new premium headphone amp. It uses 6C45pis as the power tubes and a 12AU7 as the two channel hybrid shunt voltage regulator. The 6C45s and the shunt reg are both loaded with C4S active loads. Zero global negative feedback as usual and parafeed transformer output using the same OT-3 we used in Smack. There is a switch which sets the output impedance for low or high impedance headphones, one that sets the output to single ended or balanced, and a source selector for two sets of single ended RCA inputs. Output jacks are both from Neutrik - that kinda obnoxious but very fancy locking TRS jack that tweakers seem to fancy for their Crack kit, and a four pin XLR wired in the standard AKG K1000 pinout for the balanced jack. The attenuator is the same as used in our Submissive 36 step attenuator with six coarse 9dB steps and six fine 1.5dB steps for a total of 56 dB attenuation. Output power is about 600mW. Input impedance is 25Kohms minimum.

I'm using it with HD800s with both balanced and single ended cables. It is clearly more resolving and much more quick and punchy than the very good sounding Smack amp that I kept for myself when we retired that kit. Bass is tighter and the top end is more open while the natural midrange is at least as good.

Kit pricing is expected to be around $1000 - just about what one would have paid for a Smack kit and a Submissive kit if they had coexisted, plus the step up to a 6C45pi configuration.

I'll be showing the prototype at the Seattle Head-Fi meet at the West Seattle public library this Saturday.

Spinifex:
You really seem to know how to get my hard earn cash. If this does sound better than the Smack, and if I can use it for my planars, I'll be one happy man with a $1000-lighter wallet.

tdogzthmn:
Very Cool!  Bottlehead has been releasing some great stuff so far this year.  I might need to track down another K1000 again to pair with this amp.

HF9:
Very nice, are these going to feature Bottlehead output transformers? Any thoughts on how it performs compared to a S.E.X. with stepper and Magnequest iron? That's definitely been my go-to amp for quite a while now.

Doc B.:
Yes, this uses the OT-3 output transformer that we used in the Smack. That is a transformer that has been tweaked for headphone use. I think the new amp will sound better than S.E.X., with higher resolution and a more dynamic and clean presentation partly because of the single gain stage and partly because of the shunt regulation and active loads. It costs more, and our philosophy is if it costs more it it should sound better. I have not tried it with K1000s. K1000s are ultra nearfield speakers more than headphones, they want speaker type power levels. I think they sound best with Paramounts and very good with S.E.X. I will try my K1Ks at some point - who knows? maybe I will be pleasantly surprised - and I should have a report on how well the amp works with LCD2s and HEs after Saturday's meet.

Navigation

[0] Message Index

[#] Next page