Crack Upgrade Path?
- Thread starter dumbo
- Start date
A stepped attenuator isn't a bad idea. You can also upgrade the 160uf caps at the output (voltage rating needs to be 150 or greater).
Better wire and RCA jacks are other decent options. I would go with continuous cast copper wire over silver, and maybe switch to cardas RCA jacks if you're comfortable drilling out the chassis holes a little.
Fortunately, the Crack performs well enough for these upgrades to be sensible.
Better wire and RCA jacks are other decent options. I would go with continuous cast copper wire over silver, and maybe switch to cardas RCA jacks if you're comfortable drilling out the chassis holes a little.
Fortunately, the Crack performs well enough for these upgrades to be sensible.
Just based on the decription and without having built it for the Crack, I would say install the BH Speedball upgrade kit above all else.
Next in terms of how much the sound of your Crack might change would be different tubes. You have lots of choice.
I am personally very much into "quiet" amps and I will try to reduce anything resembling hum and noise ... always.
I have changed out the RCA jacks, but mostly because I wanted more robust ones, not so much because I expect better sound.
I will probably cut more holes into the top plate in order to increase air flow. Any decrease in temperature inside the chassis will slow the ageing of parts and will keep your Crack sounding great longer.
Finally, how about better headphones?
Next in terms of how much the sound of your Crack might change would be different tubes. You have lots of choice.
I am personally very much into "quiet" amps and I will try to reduce anything resembling hum and noise ... always.
I have changed out the RCA jacks, but mostly because I wanted more robust ones, not so much because I expect better sound.
I will probably cut more holes into the top plate in order to increase air flow. Any decrease in temperature inside the chassis will slow the ageing of parts and will keep your Crack sounding great longer.
Finally, how about better headphones?
Got my kit today and looking forward to building it. My plan for upgrading is to build the kit as is, without any modifications. The 'upgrades' I have in mind include;
Actually, that is pretty much everything! The joys of DIY!!! Looking forward to first listening!
- Speedball
- Replace the headphone jack with a high quality locking Neutrik type
- Replace all resistors with Tantalums or non-inductive film types
- Replace all capacitors with film types, even on the PSU
- Replace sockets with teflon
- Replace volume control with DACT or Goldpt
- Replace IEC inlet with one that has both filter and fuse
- Replace RCA with a Neutrik XLR
- Replace cabling with solid silver or solid copper
Actually, that is pretty much everything! The joys of DIY!!! Looking forward to first listening!
Grainger49
New member
The threads in the Crack folder have a lot of improvements. My favorite is an improved signal path cap at the output. That is the capacitor you listen through. Bottlehead has selected the best capacitor they can afford to put in the kit at the price point they sell it for but it can be made better.
The stepped attenuator will also be in the signal path. PJ has appropriately pointed out that any amplifying device only modulates the power supply, therefore the power supply is in the signal path. Bottlehead is very careful about selecting the power supply for specific properties. Check here before modifying the power supply, but do that for sure.
The stepped attenuator will also be in the signal path. PJ has appropriately pointed out that any amplifying device only modulates the power supply, therefore the power supply is in the signal path. Bottlehead is very careful about selecting the power supply for specific properties. Check here before modifying the power supply, but do that for sure.
tdogzthmn,
I am not sure what you consider "reasonably priced" but here are two stepped attentuators (the websites list the dimensions) for around $150-$175:
Goldpoint (you can order from the website):
http://www.goldpt.com/compare.html
DACT CT2 (you can order from DIYCable.com http://www.diycable.com/main/product_info.php?cPath=31_71&products_id=274 ):
http://www.dact.com/html/attenuators.html
I am not sure what you consider "reasonably priced" but here are two stepped attentuators (the websites list the dimensions) for around $150-$175:
Goldpoint (you can order from the website):
http://www.goldpt.com/compare.html
DACT CT2 (you can order from DIYCable.com http://www.diycable.com/main/product_info.php?cPath=31_71&products_id=274 ):
http://www.dact.com/html/attenuators.html
I have used stepped attenuators from two auction site sellers located in the Far East: vintage_audio_lab and gigawork. They always have some items listed on the site and more in their stores.
Their prices are definitely reasonable and the units that I received worked just fine.
Their prices are definitely reasonable and the units that I received worked just fine.
tdogzthmn said:
In the power supply, fitting three 220uf film caps will be tough. Instead, run the stock first and second caps with the resistor between them, then use a Triad C7X and a 47-100uf cap after. This will impart 90 percent of the benefits of big film caps without the crazy space requirements. The C7X should knock the noise down enough to get away with this.
The Schurter 1A power entry module with line filter has approximately 30dB of attenuation at 50khHz for common modulation [and nearly 0dB for differential]. That's not bad. In addition to that it keeps all the RF crap out that might cause trouble.
The reason why I don't always use them is that they are really best at keeping noise from inside the device away from the line [the Crack isn't causing any as far as I can tell], plus there is a potential for ground loops when these filters live in more than one device, plus Doc's proposal to use some X2 caps etc is more flexible and effective.
Schurter filter graph attached, solid line is common, dotted is differential:
The reason why I don't always use them is that they are really best at keeping noise from inside the device away from the line [the Crack isn't causing any as far as I can tell], plus there is a potential for ground loops when these filters live in more than one device, plus Doc's proposal to use some X2 caps etc is more flexible and effective.
Schurter filter graph attached, solid line is common, dotted is differential:
Doc B. said:
Attachments
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.
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.
Attachments
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.
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
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
