Grid stopper resistors on tube socket

[rainywish]

I'm building a 5f2a using a mojotone kit. This kit has the standard eyelet board which has space for the 2 grid stopppers. But I was wondering if it wouldn't be better (noise-wise) to mount them directly on the tube socket and then use shielded wire from the input jacks? (grounded at the input jacks) Alternatively, could I mount them on the input jacks?

(I know the layout is made such they are in quite a good position, but from what I read from Aiken and others it might be a good idea to move them if you are a person who is sensitive to noise *raises hand*)

Thanks.

 

[tubeswell]

Yes, the best place for grid stoppers is right at the grid pins.

 

[clintj]

If you want quiet, swap out those 2 carbon comps for 1W metal film along with the 1M grid leak.

 

[rainywish]

If you want quiet, swap out those 2 carbon comps for 1W metal film along with the 1M grid leak.

Thanks for the response guys. I was wondering what the recommended wattage is for the 1M resistor. My local electronics store only has them available in metal film for a 0.4W rating. Would this be sufficient? (since there aren't any high voltages involved at this stage, as far as i can tell based on my limited knowledge)

Also, does someone have a picture of where the grid stoppers are soldered directly to the tube pins?

 

[clintj]

That power rating will be plenty. The 1W rating is not for the sake of overheating, it's to make the resistor quieter. All else being equal, higher power resistors are quieter.

 

[tubeswell]

I was wondering what the recommended wattage is for the 1M resistor. My local electronics store only has them available in metal film for a 0.4W rating. Would this be sufficient?

Yes 0.4W will be fine - the 1M provides the grid leak for the hi-gain input jack - hardly any current.

Also, does someone have a picture of where the grid stoppers are soldered directly to the tube pins?

You can mount the grid stopper between Pin 5 (control grid pin) and one of the spare/unused pins (Pin 1 or Pin 6) - with the lead from the 0.022uF coupling cap connecting to this other pin

 

[magic smoke]

Tubeswell is correct about the resistor placement hanging from an unused pin on an octal socket, I.e. your 6V6. I believe the op was asking about the 68k input resistors on V1. When I do this in my builds I use shielded cable and heat shrink tubing to make a cable with a resistor at one end. Make sure your shield is cut back and isolated from the signal. Even one little whisker can short your signal and give you a massive headache .

 

[magic smoke]

* This method is usually not necessary with fender layouts and builds, but can come in handy in a conversion or other situation where you have sub-optimal routing.

 

[clintj]

* This method is usually not necessary with fender layouts and builds, but can come in handy in a conversion or other situation where you have sub-optimal routing.

Or most lower gain builds. The tweeds and similar can be very quiet without resorting to measures like shielded cable. Ditch the input and V1 resistors for metal film, place heater wiring well (and elevate them if you like), and above all get the grounding right, and you'll have a respectably quiet amp with little extra effort.

I pull out all the stops on higher gain builds, because on those every little bit helps lower the noise floor.

 

[magic smoke]

I don’t have any photos of the process, but this is how I make my input cables lately. Talk about art, that’s one for the fridge [emoji51]

 

[rainywish]

Thanks for the answers and comments guys. This has clarified a lot for me.

 

[symbiotic]

A new standard has been set for hand-drawn diagrams.