Fender Rumble Club

[Miles_ONeal]

You are right, checked schematics for that.

Either my ears decieving me or the components between the gain and master knobs make the two slightly different then.
As op amps should not lose highs turned down for sure.

I’ll have to play with mine and see. It could be a non-linear function of the circuit.

 

[g-mca]

During the recent Rumble 100 chaining chat, it was mentioned about the 4 ohms vs 8 ohms versions of the combo. I had a look into it as I didn't know what it was all about and it's taken me down the next rabbit hole! I'm not taking this to mean the speaker impedance. There was a link on the wiki page about speaker impedance, but not sure it was relating to my thoughts.

I need to add my disclaimer apology for dredging up something that will have come up over the years!

This is relating to the amp matching speaker resistance. The Fender website stated the following:

Rumble 40 > 40W @ 8 ohms with internal 8 ohm speaker
Rumble 100 > 100W @ 8 ohms with 4 ohm speaker
Rumble 200 > 140W @ 8 ohms with 8 ohm speaker (200W @ 4 ohms for external 4 ohm speaker??) UPDATED
etc....

I saw people were saying that the older Rumble 100 had 8 ohm speaker, but my question is, why is it now a mismatched internal speaker (8 ohm amp to 4 ohm speaker) when all the other rumbles seem to have the matching speakers (8 ohm amp to 8 ohm speaker)?

The article I was reading was saying that the resistance should match. Does this mismatch in the Rumble 100 have negative repercussions? Not sure if I'm misunderstanding something about all this....

Apologies if this was brought up in the recent chat and I missed it!

 

[toughluck]

Correct the Rumble 40 because it's obviously just 40 watts, not 400.

As for Rumble 200, it's 140 W at 8 Ω internal speaker, but if you connect an external speaker, it must be 8 Ω, and the total is 200 W at 4 Ω (8 Ω internal speaker+8 Ω external speaker). Do not connect a 4 Ω cab to that combo!

As for Rumble 100, there are two versions. One is 8 Ω, one is 4 Ω. Both are 100 W maximum power, there are two different power amps inside. Fender didn't just take a 4 Ω speaker and stick it in the combo, they changed the board as well.

 

[g-mca]

Correct the Rumble 40 because it's obviously just 40 watts, not 400.

As for Rumble 200, it's 140 W at 8 Ω internal speaker, but if you connect an external speaker, it must be 8 Ω, and the total is 200 W at 4 Ω (8 Ω internal speaker+8 Ω external speaker). Do not connect a 4 Ω cab to that combo!

Thanks, I've updated my typo, and put a strike through in the 200W part.

And thanks for the clarification on the 8 ohm + 8 ohm speakers. I see now how this relates to the wiki link...

• Impedance Guidelines for External Extension Speaker Cabinets

 

[toughluck]

I edited the comment to clarify the Rumble 100 combo versions. Fender didn't just stick a random 4 Ω speaker in place of the earlier 8 Ω, they also changed the board (the new board now has a pre/post setting for the DI out).
For whatever reason, when they redesigned the electronics, they decided to change the speaker to 4 Ω and design the new board for the 4 Ω. I'm not sure if it the reasons were ever clarified, but you shouldn't overlook any possible reason. One such reason could be that they wanted the new version to be a completely different product so they don't accidentally reuse old components in the new version (so they don't have to check which 8 Ω speaker goes in the box they are servicing for example).

 

[wooheehaa]

sorry for asking this if it answer is clear cut. . does it mean the rumble 100 with the 4Ω is louder than the earlier 8Ω version? if not, had a different sound?

 

[Miles_ONeal]

sorry for asking this if it answer is clear cut. . does it mean the rumble 100 with the 4Ω is louder than the earlier 8Ω version? if not, had a different sound?

There shouldn't be any difference in loudness. 100 watts into equivalent speakers produces equivalent volume, regardless of impedance. If all other parameters are the same (I've no idea if the speakers are otherwise equivalent but would hope so), the sound should be the same as well.

 

[g-mca]

I get the 7ender folk know what they're doing, but it's just strange to read about it and then see something that doesn't follow that rule that matching the resistance is the more efficient way? There will be some method behind mixing the 8ohm amp and the 4ohm speaker, but it just seems really confusing (especially given all the other models don't do this) and I'm just trying to see if I can find out what I'm missing.

This is the article I was initially reading (not bass amp specific):

Speaker Impedance: What Are Ohms in Speakers?

It mentions this water flow analogy....

...if you think of an audio signal coming from an amplifier like water pouring out of a spout, you can think of a speaker as a pipe. You can pump all the water you want into that pipe, but at a certain point, no more water can flow through that pipe.

Assuming that the amplifier and speaker are rated at the same resistance of eight ohms, everything works as it should. The amplifier isn't going to attempt to pump out more than the speaker can handle.

But what happens when you have a mismatch? Say you've got an eight-ohm amplifier but a four-ohm speaker. In this case, the amplifier can't provide enough current because the resistance is lower than its own. This is like pouring a one-liter bottle of water into a pipe capable of handling far more at a given time.

 

[dORSY]

I get the 7ender folk know what they're doing, but it's just strange to read about it and then see something that doesn't follow that rule that matching the resistance is the more efficient way? There will be some method behind mixing the 8ohm amp and the 4ohm speaker, but it just seems really confusing (especially given all the other models don't do this) and I'm just trying to see if I can find out what I'm missing.

This is the article I was initially reading (not bass amp specific):

Speaker Impedance: What Are Ohms in Speakers?

It mentions this water flow analogy....

...if you think of an audio signal coming from an amplifier like water pouring out of a spout, you can think of a speaker as a pipe. You can pump all the water you want into that pipe, but at a certain point, no more water can flow through that pipe.

Assuming that the amplifier and speaker are rated at the same resistance of eight ohms, everything works as it should. The amplifier isn't going to attempt to pump out more than the speaker can handle.

But what happens when you have a mismatch? Say you've got an eight-ohm amplifier but a four-ohm speaker. In this case, the amplifier can't provide enough current because the resistance is lower than its own. This is like pouring a one-liter bottle of water into a pipe capable of handling far more at a given time.

thats not how class D amps work. their Wattage is limited by their supply voltage and differ by the speaker impedance.

see: https://www.talkbass.com/threads/fender-rumble-club.1118826/page-2996#post-29194256

for a 4phm speaker, they need to change the poweramp section to match the speaker.

 

[RColie]

Some confusion here about the 4-ohm R100. There's no ohms mismatch or mystery about why Fender did what they did. Here's their technical note:

 

[dORSY]

original r100 8ohm power chip's datasheet explains this clearly, graphs included:

https://www.nxp.com/docs/en/data-sheet/TDA8950.pdf

ps: note that the amp does not use it's full power (almost never) but a fraction of it while playing. You can check this by hooking up a power meter between Your amp and the outlet.

 

[dORSY]

Some confusion here about the 4-ohm R100. There's no ohms mismatch or mystery about why Fender did what they did. Here's their technical note:

View attachment 7413854

yes. and i'm sure the change is also reflected in the correspondig official service manual. (i wish we had it)

 

[toughluck]

original r100 8ohm power chip's datasheet explains this clearly, graphs included:

https://www.nxp.com/docs/en/data-sheet/TDA8950.pdf

ps: note that the amp does not use it's full power (almost never) but a fraction of it while playing. You can check this by hooking up a power meter between Your amp and the outlet.

Rated power is RMS. For Hi-Fi gear, it's a 1 kHz sine wave. It could be a different frequency for bass amps, but I figure it probably isn't.

The way you can measure maximum power draw is this: With all tone knobs neutral and gain turned up to maximmum, input a 1 kHz sine wave and increase its amplitude right to the onset of clipping (a clipping indicator is very helpful here).
Once you set it correctly, increase master volume to the maximum and measure power draw.

The amp should be designed to handle this. Clipping will increase RMS power of the signal, so make sure there's no clipping.

 

[dORSY]

Rated power is RMS. For Hi-Fi gear, it's a 1 kHz sine wave. It could be a different frequency for bass amps, but I figure it probably isn't.

The way you can measure maximum power draw is this: With all tone knobs neutral and gain turned up to maximmum, input a 1 kHz sine wave and increase its amplitude right to the onset of clipping (a clipping indicator is very helpful here).
Once you set it correctly, increase master volume to the maximum and measure power draw.

The amp should be designed to handle this. Clipping will increase RMS power of the signal, so make sure there's no clipping.

See the graphs linked above. The original 8ohm r100's Class D chip is set to 100W by it's power supply Voltage that could also be read from it's circuit diagram.

 

[toughluck]

Absolutely. But I wanted to point out that power draw is going to be higher than 100 W (if that's what the amplifier provides). If the amp is 90% efficient and the power supply is 90% efficient, then power draw at maximum power will be 123 W.

 

[dORSY]

Absolutely. But I wanted to point out that power draw is going to be higher than 100 W (if that's what the amplifier provides). If the amp is 90% efficient and the power supply is 90% efficient, then power draw at maximum power will be 123 W.

Yes, the class D chip will draw whatever it needs to provide the output wattage set by limitations, input signal strenght and impedance. In reality my r100 draws 10-20Watts at a volume I would never use at home. Measured it once and posted here somewhere.

 

[G-Dog]

Posted July 30, 2021: Fun measurements time!
Did put a power meter b4 my r100c. (240V version)
From the wall
Idle it uses 10-11 Watts
Most of the time playing it at reasonable volumes it goes up to 15 Watt-ish
Playing uncomfortably loud, bit distorted on low notes 26 Watts peak

Note that I got no clue what's the polling rate of the power meter tough, so there could be higher spikes.

Absolutely. But I wanted to point out that power draw is going to be higher than 100 W (if that's what the amplifier provides). If the amp is 90% efficient and the power supply is 90% efficient, then power draw at maximum power will be 123 W.

Yes, the class D chip will draw whatever it needs to provide the output wattage set by limitations, input signal strength and impedance. In reality my r100 draws 10-20 Watts at a volume I would never use at home. Measured it once and posted here somewhere.

Is your 2021 post quoted above the one you're referring to, dORSY?

Hmmm, the back of the 240V Rumble 100 says it could draw up to 310 watts! If you're usually drawing just 15 Watts at reasonable volume and 26 Watts at uncomfortably loud volume, you must have very sensitive hearing. And if 2X volume requires 10X power, then your uncomfortably loud setting is just about half the volume you could get! Wow!

 

[John D Harris]

Rated power is RMS. For Hi-Fi gear, it's a 1 kHz sine wave. It could be a different frequency for bass amps, but I figure it probably isn't.

The way you can measure maximum power draw is this: With all tone knobs neutral and gain turned up to maximmum, input a 1 kHz sine wave and increase its amplitude right to the onset of clipping (a clipping indicator is very helpful here).
Once you set it correctly, increase master volume to the maximum and measure power draw.

The amp should be designed to handle this. Clipping will increase RMS power of the signal, so make sure there's no clipping.

Don't forget the Limiter for the power section - I'm not sure exactly what its impact will be, but there will probably be some impact.

I remember seeing some very impressive peak power ratings for the Rumble amps, which means since most music is not pure constant sine waves, the should sound somewhat louder than some amps with the same / similar ratings, that were not designed in the same way.

 

[SharpCat]

should sound somewhat louder than some amps with the same / similar ratings, that were not designed in the same way.

So, you're saying they Rumble?

 

[Yahboy]

I edited the comment to clarify the Rumble 100 combo versions. Fender didn't just stick a random 4 Ω speaker in place of the earlier 8 Ω, they also changed the board (the new board now has a pre/post setting for the DI out).
For whatever reason, when they redesigned the electronics, they decided to change the speaker to 4 Ω and design the new board for the 4 Ω. I'm not sure if it the reasons were ever clarified, but you shouldn't overlook any possible reason. One such reason could be that they wanted the new version to be a completely different product so they don't accidentally reuse old components in the new version (so they don't have to check which 8 Ω speaker goes in the box they are servicing for example).

Interesting. Does this change make lastest version R100 sound airly and less boxy ?