New Member - First Build - Observations - Crack + Speedball

[audioguy]

Hello,

I'm a computer engineer who has been bitten by the audiophile monster.

I have a pair of HD6xx (HD650) and have been using it with a Topping D50s and a Drop THX AAA 789 amplifier. It's been nothing short of fantastic. I asked around for some tube recommendations and some awesome soul on Reddit suggested the Bottlehead Crack. Having a full electronics lab and experience in the field, naturally, I was sold.

I bought the crack back during the Cyber Monday sale and it arrived a month ago. I assembled it last week and I've been blown away by the difference in sound to my Drop THX AAA 789. It's such a colourful, original sound compared to an exacting SS amp! Obviously, some music such as classical and fast jazz is still better enjoyed on the 789, but for blues rock, and 80% of the music I listen to, I've been in love with the sound of the Bottlehead Crack.

A few days later, I assembled and added the Speedball upgrade. My first impression is that it really tightened up the crack and increased the dynamic range of the music. This should be good, right? Well, after a few days of comparing and contrasting against my 789, I found that the differences were very minimal between an exacting SS 789 amp and the upgraded Bottlehead Crack. I bought the Bottlehead crack for the very original "tubey" sound, and therefore, I decided to downgrade the small board of the Speedball back to the 22.1k 1/2W resistors. Once doing this, I got back the original sound of the "imperfect" amplifier, and it was the sound I was looking for. I left the large board on because I wanted full power transfer to headphones.

If I didn't have the 789, the full Speedball upgrade would have blown my socks off. But since I already have a great SS amp, I wanted something different.

Doc B, I wanted to thank you and everyone involved for a fantastic kit. I had so much fun building it and experimenting with the C4S Speedball and the effect it had on the stock Crack.

I wanted to fool around more with the pre-amp tube, but tubes are so stupidly priced right now. $149 for a CV4003 Mullard matched tube set? What?

Since I have a studio with great cameras and mics, I tossed around the idea of recording the entire build from start to finish but decided against it. If I do another build, I will certainly record the entire process with studio quality. Kinda wish I did at this point, though. But I'm not about to remove all the parts and start again, hah.

At this point, my 789 has taken a back seat and I only use it for Zoom calls, classical, fast jazz, and browsing the Internet. The Crack with the big board of the Speedball kit is really awesome, great job guys!!!!!!

Ryan

[Paul Birkeland]

You can get nice 12AU7s for a lot less than $150.  Here are some available right now:
https://www.ebay.com/itm/363720268200?hash=item54af6ad9a8%3Ag%3AUXwAAOSwRZJiAuB9&LH_ItemCondition=3000
https://www.ebay.com/itm/203830195576?hash=item2f7539f578%3Ag%3AocQAAOSwjHViB-F8&LH_ItemCondition=3000
https://www.ebay.com/itm/203830349807?hash=item2f753c4fef%3Ag%3AG98AAOSwTT5iCBVO&LH_ItemCondition=3000


A gamble? (one is a Mullard, none are tested)
https://www.ebay.com/itm/255315400340?hash=item3b71fbd694%3Ag%3A9CEAAOSwJ1Nh1epJ&LH_ItemCondition=3000

[audioguy]

Thank you for the prompt reply, PB.

Is the 12AU7 a direct drop-in for the Crack? I'm in Canada, so a lot of those ebay links may not ship to me, but I'll certainly look into sourcing a 12AU7.

Thanks!

[scblock]

There’s some good information on tubes for the Crack in the pinned tube rolling thread: https://forum.bottlehead.com/index.php?topic=663.0

[audioguy]

Update.

After several days of listening to my crack with only the big board in, and comparing and contrasting that to my Drop THX AAA 789, I decided that the bass was too loose on my Crack + Big Board, and the dynamic range had something to be desired now that my ears have adjusted.

I decided to add the small board of the speedball back in, and I'm very happy. I can now tell the differences between the Crack + Full Speedball and the Drop THX AAA 789. The gap between the two has lessened, but here are my impressions for what they are worth:

In my opinion, the Crack + full Speedball has these advantages over the Drop THX AAA 789:

- Much more open sounding than the 789. Larger soundstage? With the 789, while there is a nice soundstage, everything seems much more front and center than what the Crack + Speedball produces.
- Instruments seem a little bit less specific and slightly more fluid. Almost like they have a bit of reverb. I prefer it to the stale exacting sound of the 789 for Eric Clapton, blues, and most music.

In my opinion, the Drop THX AAA 789 has these advantages over the Crack + full Speedball:

- I think the bass is punchier and a tad deeper/tigher. This feels nice on fast songs, or music that requires exactness in the instruments to enjoy to the fullest.

Once again, thanks again for an awesome build and amp folks!

[Paul Birkeland]

That's great that you're going back and forth, there's often a lot to be learned from experiments that only cost time.

[audioguy]

Thanks, Paul.

Well, that's part of the hobby, right? To experiment, adjust, try new things until you find musical nirvana

One thing I can say though, is I'm addicted to crack and speed!