RN65 vs CF

[mat]

I hear more top end clarity on the Y clip. I would be interested to know the precise value of each resistor. IMHO the value differences would have more effect on the sound than the type given that you only swapped 2 resistors. I lowered the value on my V1a plate resistor and noticed a similar effect on the sound as your clip - a little crisper. Thanks for the post!
whit

CF=118.1 178.5
MF=120.7 181.5

If the difference is due to the value difference then it is a really good place to tweak the sound I should of cource have been posted the resistor values earlier

[ampdork]

Long time listener, first time poster.
I hear that the x clips want to sing more.
Sounds to me that if you were to hold that one note longer the x clips would sing sweeter and sooner.

[Tonegeek]

I hear more top end clarity on the Y clip. I would be interested to know the precise value of each resistor. IMHO the value differences would have more effect on the sound than the type given that you only swapped 2 resistors. I lowered the value on my V1a plate resistor and noticed a similar effect on the sound as your clip - a little crisper. Thanks for the post!
whit

Come on Whit - make a guess...or are you saying it's Y?

Now that I know the values, I would say Y are the Metal Films. My reasoning: There should be a slight reduction in gain from the MF resistors which are both of slightly higher value than the CF ones. In this part of the circuit, that would translate to a slight reduction in clipping which would tend to clean things up a tad.

[groovtubin]

I hear more top end clarity on the Y clip. I would be interested to know the precise value of each resistor. IMHO the value differences would have more effect on the sound than the type given that you only swapped 2 resistors. I lowered the value on my V1a plate resistor and noticed a similar effect on the sound as your clip - a little crisper. Thanks for the post!
whit

Come on Whit - make a guess...or are you saying it's Y?

Now that I know the values, I would say Y are the Metal Films. My reasoning: There should be a slight reduction in gain from the MF resistors which are both of slightly higher value than the CF ones. In this part of the circuit, that would translate to a slight reduction in clipping which would tend to clean things up a tad.

higher plate values=less plate voltage=more gain and dirt..

[dogears]

In this case, the higher plates have the exact 66% rule cathode resistors. So, they are not so much higher plates. The lower plates have higher cathode resistors which cause higher plate voltage and more headroom.

As a rule, higher plates, biased to spec, have more headroom and more gain. Less clipping.

higher plate values=less plate voltage=more gain and dirt..

[llemtt]

Hi Mat

Are you replacing those little (1/4w?) CF we saw in your pics with RN65?

I'am not surprised they sound so differently, on OD plates resistor "shape" accounts even more than bare resistive material, have you tried some 2W CF?

Anyway my guess

X=RN65

Teo

[mat]

Hi Mat

Are you replacing those little (1/4w?) CF we saw in your pics with RN65?

I'am not surprised they sound so differently, on OD plates resistor "shape" accounts even more than bare resistive material, have you tried some 2W CF?

Anyway my guess

X=RN65

Teo

Hi Teo,

The blue little resistors were 0.6W MF's. After those I did put in 2W CF's that I recorded before the RN65's.

Sorry, what You mean by resistor 'shape' ?

[Tonegeek]

In this case, the higher plates have the exact 66% rule cathode resistors. So, they are not so much higher plates. The lower plates have higher cathode resistors which cause higher plate voltage and more headroom.

As a rule, higher plates, biased to spec, have more headroom and more gain. Less clipping.

higher plate values=less plate voltage=more gain and dirt..

Ok, after brushing up on some tube theory, it appears a larger plate R = more gain, although I don't understand why except in terms of less current draw across the resistor keeps the voltage higher, translating to more gain.

Jim's "more dirt" sounds like the opposite of Scott's "less clipping" so can somebody clear that up? "More dirt" could happen if the downstream components get overloaded by the higher voltage but more gain does not necessarily mean "more dirt". ALso, I always associated "more headroom" with less gain (and more current). Sorry if this is off the original topic, but I would like to understand these relationships better.

I am still going with Y as the MF. My new reason (completely contradicting my earlier post ) is this: Louder=more gain=higher plate R's=MF. The Y clip sounds a tad louder although it does appear to be in the upper register. Maybe the non-linear response of the human ear could explain some of that. Of course it could be the non-linear response of the resistor types which would completely disprove my theory on the value discrepancies. Just guessing at this point.

[Bob-I]

Ok, after brushing up on some tube theory, it appears a larger plate R = more gain, although I don't understand why except in terms of less current draw across the resistor keeps the voltage higher, translating to more gain.

Thinking....

The plate load (Rp) is the resistance that changes the AC voltage. When the tube conducts lots of current, the voltage dropped across Rp is high, when there's little current through the tube, there's little voltage drop across Rp. There's your voltage swing.

The cathode resistor (Ck) sets the bias point of the tube. Like Scott said, typically you'd have a 66% ratio Rp to Rk. 220k/3.3k, 180k/2.7k, 150k/2.2k, 1.8k/120k, 1.5k/100k. Screwing with this ratio causes trouble.

Jim's "more dirt" sounds like the opposite of Scott's "less clipping" so can somebody clear that up? "More dirt" could happen if the downstream components get overloaded by the higher voltage but more gain does not necessarily mean "more dirt". ALso, I always associated "more headroom" with less gain (and more current). Sorry if this is off the original topic, but I would like to understand these relationships better.

I really can't comment on these terms. "Dirt" as opposed to "gain" are not terms I relate to.

One of the things I love about the Dumble tone is that it's not "over the top gain" like a SLO or 5150. The gain structure is just to the point of clipping smoothly so touch is a big part. Lighten up your touch and the tone cleans up, hit it harder and you get the organic grainy OD.

I am still going with Y as the MF. My new reason (completely contradicting my earlier post

Again I can't comment, I'm on vacation with my laptop, no decent headphones or monitors in sight. Too bad, it could be a fun exercise in spite of the fact that it's not the same as hearing it live.

[BobW]

after listening to the clip on my cheap work headphones, I am guessing the y recordings are the RN65s. The y samples seem to have a wider bandwidth, and the top end has a little more gain, giving the top end a slightly clipped signal. ...but hey what do I know?

[dogears]

I think Jim and I are saying the same thing.

Just think of it this way.

Cathode resistor bigger equals more plate voltage and more headroom, lower gain.

Cathode resistor smaller equals less plate voltage and more clipping, more gain

[groovtubin]

In this case, the higher plates have the exact 66% rule cathode resistors. So, they are not so much higher plates. The lower plates have higher cathode resistors which cause higher plate voltage and more headroom.

As a rule, higher plates, biased to spec, have more headroom and more gain. Less clipping.

higher plate values=less plate voltage=more gain and dirt..

he didn`t say NUTHIN about the cathode resistors dude! You just like spankin don`t ya! lol!

[dogears]

Yea, but the reason things may have changed was that the relationship of the cathode resistors to the plates changed. Six of one, half dozen of another. In essence, the slightly low value CF plates caused the cathode resistors to be proportionally larger. If he resized the cathode resistors to the same bias as the tight tolerence RN65 then the results would be very similar.

In this case, the higher plates have the exact 66% rule cathode resistors. So, they are not so much higher plates. The lower plates have higher cathode resistors which cause higher plate voltage and more headroom.

As a rule, higher plates, biased to spec, have more headroom and more gain. Less clipping.

higher plate values=less plate voltage=more gain and dirt..

he didn`t say NUTHIN about the cathode resistors dude! You just like spankin don`t ya! lol!

[odourboy]

I guess all this careful tweaking is wasted on me. I dissected this clip with a wave editor and while I hear differences (there seems to be a few more 'chirps' in sample y) I can't hear any tonal differences that couldn't be easily accounted for by small variations in Mat's touch between takes.

Good experiment Mat. As far as I'm concerned, without a more controlled setting, these are too close to call and I certainly had no preference between x and y.

[Tonegeek]

Regardless of what the explaination is, this is a fun excercise and I for one am challenged to increase my knowledge of tube theory, if nothing else.