Capacitor types and resistor values on the D'Lite

[RJ Guitars]

Hello All,

I am just getting started good on an ODS build - Generally following a D'Lite configuration and I have a few questions about capacitor types and values.

1) I see that a 1uf tantalum capacitor is called for across the presence pot. How critical is it to use a tantalum? Are there other good choices?

2) In a couple places - There are a couple Mallory GP series caps called for - 270pf and 470pf. I cannot find that exact type and value... will any another quality cap in silver mica work as well?

Overall, I'm curious how far off the exact values established on the D'Lite I can get by with without messing things up?

Thanks in advance,

rj

[Normster]

You can use a 1uF electrolytic for the presence pot. The tantalum is just more compact. Any type of 1KV ceramic cap will work for the snubbers, treble cap, etc. Most folks here will advise staying away from silver mica. As far as brand goes, we've had great luck with Panasonic.

[RJ Guitars]

Thanks Normster for the help...

Can you tell me about tube shields on the preamp tubes? I see they come with the D'Lite kits. Will I need these for my ODS clone?

thanks

rj

[nickt]

You can use a 1uF electrolytic for the presence pot. The tantalum is just more compact. Any type of 1KV ceramic cap will work for the snubbers, treble cap, etc. Most folks here will advise staying away from silver mica. As far as brand goes, we've had great luck with Panasonic.

Hi Normster - can you (or anyone else) characterise the difference between using silver mica's and ceramics? Thanks.

[Bob-I]

Hi Normster - can you (or anyone else) characterise the difference between using silver mica's and ceramics? Thanks.

To my ears Silver Mica is like the sound is held back, like it's trying to get out but can't. Ceramics let it out. Mica tends to have more highs and many people like that in Fender/Marshall type amps, but I like the grain and texture of Ceramic.

[Bob-I]

Thanks Normster for the help...

Can you tell me about tube shields on the preamp tubes? I see they come with the D'Lite kits. Will I need these for my ODS clone?

thanks

rj

Not really. I leave 'em off and if I really focus I can hear a slight difference. I leave 'em off only because it's easier to change tubes.

[BobW]

Here's a quote from DIYaudio forum:

All dielectrics suffer from dielectric absorption because polarisation is not an instanteaneous and perferctly linear function of the external electric field. Dielectrics in ascending order of dielectric loss are:
air, paper, polystyrene (KS), polypropylene (KP, MKP, FKP), polycarbonate, mylar (MKS, MKT), mica, NPO/COG, Z5U, X7R.

This means the ceramics have a higher absorption loss than micas. I interpret this to mean when you discharge the ceramic for a short amount of time, the energy stored in the dielectric will recharge the voltage potential across the cap, similar to how an electrolytic recharges itself. Some call it soakage memory.

Bob Pease, from National Semiconductor, has a great article on this subject. See Fig 7 and notice the amount of dielectric absorption error induced in the ceramic at the dischrge times shown. This approximates the largest amount of error between 10 Hz and 1kHz. Although in his article, he doesn't want a large error, since his application is not audio. I believe the larger absorption error results in more harmonics, since there is a larger amount of energy. I base this on the pics shown in figure 10. The pics before compensation clearly show a higher harmonic content then the pics after compensation. In our application, a high dielectric absorption is a good thing, and ceramics have a higher absorption than silver micas.


http://www.national.com/rap/Application ... 28,00.html

[TimS]

Here's a quote from DIYaudio forum:

All dielectrics suffer from dielectric absorption because polarisation is not an instanteaneous and perferctly linear function of the external electric field. Dielectrics in ascending order of dielectric loss are:
air, paper, polystyrene (KS), polypropylene (KP, MKP, FKP), polycarbonate, mylar (MKS, MKT), mica, NPO/COG, Z5U, X7R.

This means the ceramics have a higher absorption loss than micas. I interpret this to mean when you discharge the ceramic for a short amount of time, the energy stored in the dielectric will recharge the voltage potential across the cap, similar to how an electrolytic recharges itself. Some call it soakage memory.

Bob Pease, from National Semiconductor, has a great article on this subject. See Fig 7 and notice the amount of dielectric absorption error induced in the ceramic at the dischrge times shown. This approximates the largest amount of error between 10 Hz and 1kHz. Although in his article, he doesn't want a large error, since his application is not audio. I believe the larger absorption error results in more harmonics, since there is a larger amount of energy. I base this on the pics shown in figure 10. The pics before compensation clearly show a higher harmonic content then the pics after compensation. In our application, a high dielectric absorption is a good thing, and ceramics have a higher absorption than silver micas.


http://www.national.com/rap/Application ... 28,00.html

Good stuff. Thanks!