Crack Upgrade Path?

[grufti]

Three resistors and one capacitor will add about $1000 to your Crack on the street. Just kidding, we're not in the drug business here.

You can run this in PSUD II ahead of time to make sure that I am not pulling your leg.

Keep the three 220uf caps, keep the two 270 Ohm resistors in the B+ power supply, add a Panasonic TSED 470uf 250V cap as your fourth cap [one cap], parallel the two existing 270 Ohm 5W resistors with a 360 Ohm 2W resistor each [the combined value for the parallel resistors is something like 154.3 Ohm - this adds 2 resistors], and finally connect the new capacitor that you are adding with a new 150 Ohm 5W resistor [this is the third resistor].

I just finished that change and I'm blown away. Total expense way less than $10.

I measured THD+N before and after. The graphs are too large to attach. Shrinking has to wait until tomorrow. It's late. Try it anyway, this is the biggest gain I've had from any modification in 30+ years of building gear.

[eeyore]

Actually I have read, but not heard, that the Acoustic Dimension 41 step attenuator is king... But in the days of $1000+ headphones, a 41 step ladder attenuator for 200 Euro is not shocking... I was actually thinking of building a parallel crack, new chassis, etc, but keeping the power transformer. The original, and the upgraded, and compare the differences.

[Jim R.]

Grufty,

Thanks for the work on the PSU tweaks -- just may do that myself.

Here's another stepped attenuator from Poland:

http://www.khozmo.com/

They are 48 steps, priced about the same as goldpoints and shipping is free.  I hear they are rather large, but I can't access anything with the dimensional information.

If these would fit in the Crack and/or Stereomour, I may pick one up.

-- Jim

[dumbo]

A pic of the Goldpoint Mini-V compared to stock.  The chassis plate hole will need to be enlarged and the 1.1" knob just barely covers the small hole to the right of the pot hole.  Should have gone with the next size larger knob. 

[Doc B.]

Three resistors and one capacitor will add about $1000 to your Crack on the street. Just kidding, we're not in the drug business here.

You can run this in PSUD II ahead of time to make sure that I am not pulling your leg.

Keep the three 220uf caps, keep the two 270 Ohm resistors in the B+ power supply, add a Panasonic TSED 470uf 250V cap as your fourth cap [one cap], parallel the two existing 270 Ohm 5W resistors with a 360 Ohm 2W resistor each [the combined value for the parallel resistors is something like 154.3 Ohm - this adds 2 resistors], and finally connect the new capacitor that you are adding with a new 150 Ohm 5W resistor [this is the third resistor].

I just finished that change and I'm blown away. Total expense way less than $10.

I measured THD+N before and after. The graphs are too large to attach. Shrinking has to wait until tomorrow. It's late. Try it anyway, this is the biggest gain I've had from any modification in 30+ years of building gear.

For what it's worth, the installation of the Speedball upgrade may make this mod less noticeable, as it greatly improves PSRR. Not to say that the Crack isn't quiet in stock form too.

[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!

[Jim R.]

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).

[Jim R.]

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.