Resistor recommendations for standard ST-70 driver board

[mugsy]

Hi!

I'm shortly to receive a new driver board from Dynakits, and I'm considering what resistor types to use.

Being a little green in this area, which resistors are directly in the signal path and would benefit from high quality carbon films like Kiwame or Rikens?

From the CAE Dynaco restoration board PDF they suggest the following:

3W metal oxide for 47k (x4) / 18k x2) / 270k (x2) / 330k (x2) / 1K (x2) types

Half watt (or higher) carbon FILM for: 270k (x4) / 18 k (x2) / 10k (x2)

Half watt (or higher) metal film for: 47 ohm (x2) / 620 ohm (x2) / 1M5 ohm (x2)

Would anyone care to add to this? I have read elsewhere (the Tube Dreams website store on Ebay) that for the two 1k resistors in the middle of the board is is best to make these quality carbon films if you can afford it. Are there anymore resistors in the signal path which would benefit from being upgraded? I would be interested in people's experiences here.

Many thanks

- John Yellow_Light_Colorz_PDT_06

[mesherm]

If you mean the two 1k grid stopper resistors, as far as I know they can be ordinary 5% or better carbon comp or film. Nothing really special about them.
The two 47k resistors on either side of 7199 triode section phase splitter however should be at least 1%. The closer the better. 1 watt 1% metal/carbon film should work fine. I usually use 1% metal films for just about everything 1 watt and below. Above 1 watt to 4 watts I use 2% or 5% metal oxides

[mugsy]

Thanks Mesherm! Yellow_Light_Colorz_PDT_12

Cheers,

- John

[erichayes]

Hi John,

I use metal film resistors, not for their tolerance (usually 1-2%), but for their thermal stability (±50 ppm/°C). Metal oxides are a good choice for anything 1 watt and above, and have almost as good a Ct as films-- ±350 ppm/°C.

Carbon films are okay for non critical applications, but should be avoided in phase inverters or differential amp applications because their Ct is so godawful it's not even spec'd.

For some reason, carbon compositions are the near-universal choice of designers for stopper resistors on output tube control grids. They just sound better than anything else.

[mugsy]

Hi Eric - thanks for your reply.

I have a bunch of 3w metal oxide types which I'll be using in my amp. I'll only use carbon types (Kiwame) for resistors directly in the signal path (which I believe is all the 1K types). The Kiwames actually have lower noise than metal films (or so the marketing says! Yellow_Light_Colorz_PDT_08 )

Cheers,

- John