Crack Upgrade Path?

[grufti]

I ran a few quick and dirty measurement of my very nearly stock Crack build to have a baseline before any changes/upgrades. The graphs that I am attaching here are THD+N measurements at 1V rms at the output of the Crack. In each graph the blue line is the measurement of the Crack channel under test and the red line is a self-measurement of the test device to make sure that everything is in order.

This one here is the measurement with the stock PSU. I'll post only the measurements of the left channel. The right channel measures almost exactly the same.

Please let me know, if you would prefer not to have any measurements posted here. These look pretty nice, so I figured: why not?

 

[grufti]

This one is after the PSU modification that I described in an earlier post.

All PSU frequencies and their harmonics are way down, 120Hz is more than 20dB lower. THD is also slightly lower, not that it matters much. Most of it is very benign 2nd harmonic which the ECC82 family leans towards.

Now I'm really looking forward to the Speedball upgrade, especially after reading Doc's comment that it greatly improves PSRR.

 

[Doc B]

Posting measurements is fine as long as the reference voltages etc. are included as you did, and posting comparative measurements like this a great idea. Thanks for doing so. It will be interesting to see what you get with the Speedball.

I might suggest trying different 12AU7s too, as that might influence the 120Hz level at the output.

 

[Paul Birkeland]

Man, I am impressed, posting measurements is great, especially when you are comparing mods!  PM me your mailing address and I'll send you a choke to try in the power supply.

 

[ironbut]

Early impressions of the Speedball upgrade would tend to suggest to me that any big money upgrades should be done after you've installed it. That's kinda what I was figuring from Doc's impressions. Of course, there's nothing wrong with experimenting with the stock unit but I usually upgrade with some kind of sonic improvement in mind (I'm cheap and lazy so I try not to waste time or money).

Whew! I have to say that I love the way the upgrade makes vocals sound! I'm listening to "Raising Sand" (Robert Plant/Allison Krauss).
Outstanding!

 

[jrebman]

Steve,

If you haven't heard the HDTracks 24/96 version of "Raising Sand", you should try it.  The CD is good, the high-res version is fanastic.

-- Jim

 

[ironbut]

That's the one I'm listening to Jim. Not too shabby for digital (especially Tattered Rose).

 

[jrebman]

Steve,

Yes, not bad at all.  Looking forward to your impressions of the Crack with some other cans, and als what others will have to say about both versions of Crck.

-- Jim

 

[levlhed]

I got to do a comparison yesterday @ CanJam.  Really, for the $99 + your time you can't go wrong with the upgrade.  It should be the FIRST thing you upgrade IMO.  Install Speedball!
The difference is very significant.

 

[Dr. Toobz]

I got to do a comparison yesterday @ CanJam.  Really, for the $99 + your time you can't go wrong with the upgrade.  It should be the FIRST thing you upgrade IMO.  Install Speedball!
The difference is very significant.

What was the thing you noticed most between the two builds? I've been a little squeamish about adding a CCS to the Crack, as it seems like the results on my S.E.X. amp and Quickie have resulted in a quicker, but less warm and more pentode-like sound than the resistor (or choke) load.

 

[levlhed]

I suppose the result is similar, but I'm not sure it was necessarily less warm.  I should have spent more time going back and forth, but once I went to the upgraded one I never went back and listened to the stock one!  And I was back in there three or four times hooking my modded Nano up to it to steal another listen.
I think ironbut can help characterize it better as he has probably spent more time comparing the two.

 

[tdogzthmn]

I am thinking of wiring my amp with cotton insulated copper wire.  If the wire is unshielded will that cause problems and noise during use?   

 

[Paul Birkeland]

The stock wire is not shielded, just insulated.  If you do buy cotton covered wire, be sure to get solid core.  I've seen a few builds go really badly because stranded wire was employed. 

My preferred cloth covered solid core wire can be found here:
http://www.tubedepot.com/wire.html

Just be sure to pay attention carefully, as stranded and solid wire types are listed side by side.  I especially like this wire because the cotton is bonded to the PVC underneath, so you can strip this as though it is normal PVC coated wire.  Another nice aspect is that a little bit of overheating will make the PVC shrink away a bit, but the cotton will remain. 

 

[tdogzthmn]

I found the wire on hifi collective.  Its solid core copper AWG 28, 6N cotton insulated.  Its all white so I would have to label each strand during wiring so I dont loose track of the connections. 

 

[Paul Birkeland]

That should work OK for everything but the heater connections, where it will be pretty thin to get the job done IMO.

 

[grufti]

Wow! Speedball!

 

[nsorens]

Yes, WOW Speedball.
I used to feel that my Enhanced Sex/Hammer Dynamics speaker setup was a more involving listening experience, but now with the speedball upgrade the Crack /DT770(600 ohm) combo comes much closer to being in the "listening room".

 

[Doc B]

Thanks guys! The cathode follower setup on the 6080 is a really neat way to get the output impedance down to where it can run a pretty broad range of high impedance headphones, but the CF is kind of an imperfect beast in terms of distortion with an ordinary resistive load. Remembering the dramatic improvements we heard when we added a C4S load to the CF in the Foreplay preamp oh, so many years ago made it a certainty that I would try one on the 6080 in a Crack just about as soon as the solder was cool on the prototype. PB found a nice beefy transistor for the job in the form of the TIP50, and the project was a go. Gotta admit in this case the end result exceeded my expectations, and I've been using the C4S circuit for something like 15 years.

 

[mrarroyo]

nsorens were those huge caps part of the kit or an upgrade you installed? Thanks.

 

[nsorens]

Those are definitely non-stock....  They are the AXON True Cap 100uF / 250VDC caps that JREBMAN found at PartsConnexion, thanks JREBMAN! 
I built Crack stock at first and listened to the electrolytics that came with the kit. The stock parts are very good and the AXON's only make a subtle improvement. 
The Speedball upgrade is NOT subtle, it is huge improvement as everyone is reporting.