Is Doc a Saint or .... ??

[ALL212]

Ok...I'm in.  Been pondering the Mainline for some time and the sale has pushed me over the edge.

I know it doesn't come with BH upgrades but I'm sure there are those of you who have built this thing and have some good ideas.  I have yet to build a kit and keep it stock. I have no intention of changing that with this kit.

I'm in no hurry, would like to ponder upon this and get it right.

What say you?

[Deluk]

I normally get BH notifications but not this Mainline one. As Doc's "check you mail" post doesn't have "Reply" box I couldn't comment there. 

[Doc B.]

Sometimes it takes a while for the mail to be distributed. Here is the content of the email:

It's Mainline March! From now through March 31st you can order our premium Mainline headphone amp kit and get a whopping $200 discount by using the coupon code published below.

mainlinemarch

To sweeten the deal we found another batch of the rare and exceptionally effective IERC tube shields, and we will include a pair with every Mainline kit order until they run out. The awesome sounding 6C45pi tube used in the Mainline is a hot little sucker and these shields should extend their useful lifetime by 10-15%.

Use the coupon code mainlinemarch when you check out to get this special discount. Time to manufacture and ship will be our standard 4 or so weeks. Kits are shipped in the order that orders are received - order sooner, get it sooner.

Join us April 30th at Bottleheadquarters on beautiful Bainbridge Island for another great Seattle Head Fi user group meet. These meets are a fantastic way to sample lots of cool headphones and headphone amps, and meet like minded headphone lovers. Everyone is encouraged to bring their favorite headphone rig if you have one, or just bring hungry ears if you don't!

Also in April we will be releasing a super quiet DC filament supply for the Stereomour II, along with our superb sounding stepped attenuator upgrade as used in our premium BeePre preamp kit. Watch for those to come out in a couple of weeks.

[Strikkflypilot]

I love my Mainline, now fed by a Shiit Gungnir Multibit.
All I did was swap in some Auricap XOs in place of the stock parafeed caps
My build here: http://bottlehead.com/smf/index.php?topic=7463.0

[ALL212]

Some thoughts - not necessarily unique to me.

Replace the .1 and 10 uf film caps.

Put a choke in place of the 230 ohm resistor.

If I can find room use a full film cap in place of the 100uf PS cap.

Tip the other PS caps with small films.

I like 6SN7's - any good reason to use one in place of the 12AU7?  Will the circuit support this?  I know I have to modify the hole and wiring.

Any other things you folks have done to this beast?

[Rocketman248]

I'm trying to resist this one.  I already have a S.E.X. and a Crack-A-Two-A.  And I just bought an Eros and a new TT.  But I did just do my taxes, and have a nice refund coming.....

[Rhok]

I plan on buying a Mainline this year, and this is a smoking deal - it just unfortunately is not the right time for me to be able to buy it.

When I read the email it depressed me the entire day haha.

[Rocketman248]

Who am I kidding?  I have no willpower.  Plus, I did well enough on my taxes to buy two Mainlines, and I only bought one.  So I'm saving money!   

[Doc B.]

Thanks so much to everyone who is taking advantage of this deal. I happen to be particularly proud of this amp and it's nice to see so many people ordering one.

[Paul Birkeland]

Replace the .1 and 10 uf film caps.

Yes, though I wouldn't spend much on the 0.1uF caps.

Put a choke in place of the 230 ohm resistor.

Not a great idea.  The shunt regulated power supplies make a power supply choke pretty pointless.  Also, these need to be mounted on a different axis than the power transformer and output transformers, which I have yet to see done successfully.

If I can find room use a full film cap in place of the 100uf PS cap.

The hybrid shunt regulated power supply places great impedance between the power supply and the signal path, so replacing these capacitors with film capacitors is not a great expenditure of effort, and not all that easy since the power supply is PC board mounted.

I like 6SN7's - any good reason to use one in place of the 12AU7?  Will the circuit support this?  I know I have to modify the hole and wiring.

The 6SN7 draws twice the heater current of the 12AU7, which will place additional thermal load on the low voltage regulator.  PJ would have a better record of the thermal overhead available with this particular power supply, but I don't believe it's advisable. 

[ALL212]

Thanks PB!  I had some evil ideas that I think I can just put aside now.  Really looking forward to this kit.  And... probably a classic rabbit hole.  I'm thinking sometime in the future a pair of HD-800's now to go with this.   

[Paul Joppa]

PB is right. The Mainline uses the power transformer originally designed for the Eros, so the transformer is pretty much operating at its limits with the stock tube complement.

The 12AU7 is used as the hybrid shunt regulator. The regulator performance is dominated by the 431 chip, so using different tubes should have little or no audible effect.

[Doc B.]

"I know it doesn't come with upgrades"

It's our top line headphone amp kit. The whole circuit as it stands is an upgrade. My suggestion is spend the effort making it look however you think it should look to satisfy your taste rather than modifying the circuit. It's been pretty carefully thought out.

[NightFlight]

You will  get more out of swapping to a high grade balanced HP cable than changing the shunt regulator tube. Hell, the interconnect qualities are easily revealed by this amp.

IMHO, its just fine. The only thing left to do is to pick your colouration of choice. Changes are likely to be minute but with a high expense. Those changes may be  thought to be towards improvement, but the reality is they are small enough generally you could con yourself in into endless circles.

[Rocketman248]

Woohoo!!  Got the shipping notification today.  Unfortunately, I'll be on deployment until October, but at least I've got something to look forward to.  Thanks for the sale, Doc!