Could it be source related if you had it with previous amps? I would try to run the Crack without any source connected and using a shorting plug (a RCA jack with an around 500 Ohms resistor connecting ground to center). If it's dead quiet with a shorting plug, then it's your source (without...

  The stock Crack is musical. It's warm but not laid back or "tubey". The HD 650 are also on the warm side of headphones. Don't get me wrong : that is nice, I can listen to them for hours without any fatigue (like I get with, say, grados). So IMHO, I think you can get a clinical or analytical...

ODAC... And spend the rest on a speedball!

  Yeah, you could lower the impedance of the output tubes by adding some transformers. But then, it wouldn't be a Output Transformer Less design anymore. S.E.X. has transformers and drives about any headphone you can throw at. Now you have to live with the output tube impedance and choose...

  You can replace the crack pot with 100 kOhms resistors. That would sure improve the sound. I think, you can just connect wires white to white, red to red, black to black and put a 100 kOhms resistor between the ground lugs and center of each RCA... It could be also interesting to reduce the...

  I'm not sure solid core is the best for a headphone cable since it's rigid and quite fragile if bent.

I had the experience two weeks ago. I forgot to bridge the two grounds on a new pot. My resistance went haywire, and I still decided I could start the Crack. Bad move. Even after shutdown and power cable removal, I got snapped when touching something inside. Something I never experienced before...

  +1 Don't forget to connect the two grounds when you rewire you new pot. If you don't, your Crack will go crazy and become potentially dangerous (some caps aren't discharging anymore at shutdown). half of the Crack's grounding is done through the small wire on Jamies's pot.

  Just to correct one thing. I think that all Bottlehead products never drift out of class A. Crack, S.E.X. and mainline are all Single Ended "Class A" designs, as opposed to other classes that use push pull design for higher output power. You have a maximum output voltage before clipping...

  You would receive better inputs if you posted your problems on the Bottlehead forum. Back there, you would be asked if your resistance checks and voltage checks were fine. Were they ? If the noise is only in one channel, then you have a cold solder joint in the signal path of this channel, or...

Use your Vali and save... for a Crack :)

It looks like the microphonics are often associated with the power tube. In my Crack, I tried three different 6AS7G (RCA, Svetlana and Rogers), all were noisy, even after some break in. I finally settle back to a rugged RCA 6080 with RCA or Telefunken 12AU7. I can dance next the crack (which...

Ringing sounds like Microphonics! It can be from the tubes (or sometimes caps). Doc said about it on the BH forum something like "It's a feature, not a fault!" Just don't tap the crack :) You can still test which tube is more prone to microphonics, try tapping them gently or around their base...

Nice review! I just don't get one thing. How can this thing be charged 2500$ in the US and like 3000 pounds in the UK, or in my case 3900 Swiss francs in Switzerland! This is like twice the US price.   Shame on importers, or on McIntosh if they fix the price.

I think it will work, but not bypass the preamp section of your integrated amp. With tape in, you still have volume control and gain from the preamp section, if there is some gain. Some integrated amps have a bypass, some RCAs that connect directly to the amp section. If you connect the quickie...