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Author Topic: Crack Upgrade Path?  (Read 62213 times)

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Offline Laudanum

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Re: Crack Upgrade Path?
« Reply #90 on: November 09, 2011, 04:50:06 AM »
Um...YES.  A definite improvement.  As other's have said, not night vs. day but noticeable.  Nicey nice.

I dont know about the pot but I like the Caps.  Not bad at all for affordable "basic" MKP's.
Desmond G.

Offline grausch

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Re: Crack Upgrade Path?
« Reply #91 on: November 03, 2014, 10:14:32 AM »
Reviving an old thread again, but this has some solid info in it and hoping to keep all of it in a relevant place.

I am planning on putting in the Belton tube sockets, and since this means some major rework, I plan on replacing some parts as I go along. I was just going to order resistors, but read the following and would just like to double-check before I order incorrect parts.

I am quoting DocB from the first page of this thread: "Careful here, you need to know what design parameters determined the composition of each of the original resistor. Resistors in the power supply must have an adequate voltage and power rating, resistors on the PC boards must in some cases be very precise metal film resistors, in other cases once again power and voltage ratings are critical. Grid stoppers may be best if left as carbon composition. Really other than that there aren't that many resistors in the circuit once speedball is in place."

I do not have Speedball installed, but will be replacing the metal film resistors and probably the power supply resistors. Resistance will stay the same, I plan on slightly increasing the wattage, but am not sure about the "voltage and power ratings" mentioned in the above quote. Would a 500V rating be sufficient? I also know that an increased wattage leads to a bigger resistor and potential mounting issues. Anything else I need to be aware of?
Gunter Rausch

Modded Bottlehead Crack
Modded Stereomour with Two-tone Orcas

Offline Paul Birkeland

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Re: Crack Upgrade Path?
« Reply #92 on: November 03, 2014, 12:55:52 PM »
The 270 Ohm resistors need to have long leads so that you can mount the one between the two 6 lug terminal strips on the power transformer.  Most 270 Ohm 5W resistors won't work here, so you'll probably need one 10W and one 5W part here.  These are not particularly audible in my experience.

I can't see any reason to change the 270K 1W resistor, but if you need a new one, any 270K 1W resistor will work fine.

The 22.1K resistors are chosen for good quality and adequate power dissipation.  You could spend a lot of money on nicer resistors, but they won't deliver the performance that the Speedball does.  (Same goes for the 3K cathode resistors)

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline grausch

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Re: Crack Upgrade Path?
« Reply #93 on: November 03, 2014, 10:53:18 PM »
Hi PB,

Thanks for the response. These changes are purely cosmetic in nature and I feel that I can do a better job now than I initially did. Plus, I really like working on the Crack. It is a really simple, yet elegant design that makes it very easy to experiment.

I will be replacing all the metal-film resistors with the mustard coloured Vishay / Dale ones on Mouser. Not very expensive and purely cosmetic.

Regarding the 270 ohm resistor, I was thinking of either using the Stereomour trick of using insulation from another wire to cover the exposed wire, or just make fly leads and solder the resistor to that. Again, purely a cosmetic change.

For the 270K resistor, still undecided. In any case, for both of the last 2, I will look up their specs and find something that can handle the 500V minimum.

Once all of these changes are implemented, I will have the base Crack built exactly like I want it, and can probably add Speedball at that point.
Gunter Rausch

Modded Bottlehead Crack
Modded Stereomour with Two-tone Orcas

Offline Paul Birkeland

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Re: Crack Upgrade Path?
« Reply #94 on: November 04, 2014, 08:27:14 AM »
I will be replacing all the metal-film resistors with the mustard coloured Vishay / Dale ones on Mouser. Not very expensive and purely cosmetic.
The two 22.1K resistors should carry at least a 1 Watt rating. 

Regarding the 270 ohm resistor, I was thinking of either using the Stereomour trick of using insulation from another wire to cover the exposed wire, or just make fly leads and solder the resistor to that. Again, purely a cosmetic change.
A 10W part will actually look better back there.

For the 270K resistor, still undecided. In any case, for both of the last 2, I will look up their specs and find something that can handle the 500V minimum.
Any old 270K 1W part should work, the 500V rating isn't necessary. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Colin

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Re: Crack Upgrade Path?
« Reply #95 on: September 24, 2015, 08:13:12 PM »
How is the sound quality changed if all the crack's stock cable changed with pure silver core cable? I'm a newbie in diy, very interest when hear the silver core cable interconect sound character. But a little fatigue in high tone, its get sibilance and 'overload' in treble. So is it possible to get the best sound when apply all the stock cable with it?

Offline bocosb

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Re: Crack Upgrade Path?
« Reply #96 on: March 17, 2016, 01:14:05 AM »
I just noticed that my bottlehead crack has reversed left-right channels (i bought it already built some time ago) - I would like to fix this and also upgrade the volume pot if i'm anyway taking it to an electrician.. any suggestions for a good value pot?

Offline borism

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Re: Crack Upgrade Path?
« Reply #97 on: March 17, 2016, 02:31:54 AM »
The Valab 100K ladder type attenuator has been used by a number of people here. It's only $33 on eBay.
Boris