Bottlehead Amplifier Discussion / Comparison Thread: Crack, SEX & Mainline
Jun 1, 2014 at 6:35 PM Post #737 of 2,108
Thanks for the quick response. I expect I'll get hammered by the tax man.
 
Jun 1, 2014 at 8:35 PM Post #738 of 2,108
I saw already assembled one from uk in for sale forum.
Also for those in US i'm selling the Crack i recently got from Matt so if anyone interested PM me before i post it tomorrow morning. I know there are several there already but they just stock units while mine has several upgrades
 
Jun 2, 2014 at 3:39 AM Post #739 of 2,108
I'm sorely tempted to get myself a Crack, especially since I read it pairs very well with my HD650's. Has anyone shipped the kit to the UK? Does it travel well? I haven't used a soldering iron since school so is there a particular one I should be looking at?

I ended up paying £26.96 import for a crack plus speedball, which wasn't too bad (this was in the discount sale a few weeks ago so it was something like 5% off). 
 
It got here perfectly well, they package everything up very well. I used a cheap 40W soldering iron with no problems, though I have done quite a lot of soldering in the past. People seem to think a temperature controlled solder station is a good idea.
 
Jun 2, 2014 at 4:18 AM Post #740 of 2,108
£26 isn't too bad really. I would be happy with that. I need to check out the FS thread though if there's one in the UK for sale.

Thanks.
 
Jun 3, 2014 at 11:44 PM Post #741 of 2,108
Let me know if you want a pair of those RTI 10uF teflon caps. I bought some from a TC tubes that I wont be using (getting out of DIY & tube amps). Selling for $210. Send me a PM if you are interested.

Cheers

Nathan
 
Jun 4, 2014 at 1:44 AM Post #742 of 2,108
.  Recall that mainline is very similar in design to the ecp l-2, which sold for $2,500.  


Mainline was derived from our own $7500 6C45pi based 'big preamp/headphone amp' from 2003, designed quite a few years before the l-2 came about. And of course the spud concept goes back to the original WE417A based spud amp, built at a VALVE meeting in my basement around about 1994-5. Mainline is not a spud, as we use a hybrid shunt regulator that adds one more tube to the amp. I wasn't aware of the l-2. It is rather flattering to see others use a topology we have pioneered.


Sorry to reply to such an old post, but I thought I'd provide some context. Back in the day I saw Gary Dahl's Espressivo amp. I wanted one but could not afford the parts, so I decided to replicate it with cheap parts. Using the same basic topology, but under $100 in hardware, I made the Less-pressivo, which my wife cleverly re-spelled as the L'espressivo. I made a lot of modifications to the circuit over time (which are sadly offline right now due to a server crash -- maybe I'll find time to revive them) including making 71A based version using OPTs from Intact Audio. That is, I managed to make it really expensive again.

After a lot of experiments and some subtle circuit changes, I decided to make a few and sell them. I thought about calling the amp the L'espressivo, but I didn't want to step on Gary's toes, and I was unable to reach him to ask if he minded. So I called it the L-2 instead. I was aware of the Bottlehead amp which I assumed to be a parafeed spud (and that I think it is cool, and I think the Mainline is cool) but the L-2's direct progenitor is the above mentioned Espressivo. Maybe Doc can illuminate whether the Espressivo came from the 417 experiments.
 
Jun 4, 2014 at 2:44 PM Post #743 of 2,108

 
Hi Dave!
 
Gary and I live about five miles from each other. He did part of the build of his amp in my basement after I built the original proof of concept prototype for my big headphone amp, which was a 6C45pi spud with 6CK4 hybrid shunt regs. This looks to be a pic of the test fit of the layout of that POC amp, from maybe about 2001? The TL404 outputs used went into the big headphone amp I built after that. I try to purge the old project stash on a regular basis but I seem to recall that chassis is still kicking around in the old lab. On a side note that big amp from 2003 ended up being converted by us to use 437As a year or two ago, at the request of the client who purchased it.
 
Jun 6, 2014 at 1:44 AM Post #748 of 2,108
At first I thought he was using doorknobs...
cool.gif

 
Jun 6, 2014 at 2:57 AM Post #750 of 2,108
Thanks guys.

I bought these from a German eBay store, which I am having trouble tracking down atm.

Have two spare knobs that I was going to give to whoever buys my submissive.

Cheers!

Nathan
 

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