Partial Speedball?

[ejwt]

I've recently built the Crack, which I auditioned for a couple days before adding the Speedball upgrade.  I think I may prefer the Crack without the Speedball, not sure, since it is hard to A/B.  I've seen where others have mentioned it being more fatiguing, which is what I'm experiencing.  This was my initial reaction before searching if others had this same response, so I don't think there was any pre-conditioning going on.
See https://bottlehead.com/smf/index.php?topic=7395.msg71414#msg71414 [nofollow]
I had made a stepped attenuator mod from the very beginning, so I don't think the volume pot or increase in gain mentioned in that thread is the source of what I'm hearing.  I've also tried several tube combinations as well. 

I'm spending a bit of time listening with Speedball before I go back to listening without it.    I found a blog detailing a Crack build titled "Making Music Sing: The quest for a Hi-Fi headphone system" (seems dead to comments)  that mentions Speedball picking up RF interference, and that he "removed the constant current source" resulting in a partial Speedball.  I thought that's all there was to the Speedball is the constant current source.  Any idea what he is referring to?  Has anyone tried experimenting with adding the Speedball mod to only the 12AU7 or 6080?
   

[Doc B.]

My thought about this is you may need to look at your source component, as the Speedball is likely to be revealing more of its character. Speedball isn't likely to "pick up RF intereference" any more than the stock circuit. It will actually give better isolation from any noise that might come in from the power supply. It does increase the gain of the input stage, so any noise coming in from the ahead of the Crack will be louder at a given volume setting.

In terms of using one half or the other of the kit - if you know what you are doing it should be pretty easy to implement. If you don't know how to do it, you might be better off going with either no Speedball upgrade or the full upgrade.

[ejwt]

Thanks for the feedback Doc.  My source is fairly clean, I'm feeding un-compressed .wav from ripped CDs to a Chord Mojo.

What is the increase in gain with Speedball?  I believe both my Crack and Speedball Manuals are quoting 15 dB.
 

[Paul Birkeland]

The Crack w/Speedball pencils out to about 23dB and closer to 20dB without the Speedball with no loads in each situation (relatively unloaded). This is about 15x gain.