Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

[RolanTHUNDER]

...I use the 16 ohm output of my Orange #4 tube head into the Marshall's right (when viewing the cab from the back) input which states "mono 8 ohm"). I was running this cab using one of the two 8 ohm outputs at the back of the Orange but found through experimentation yesterday that it sounded better with the 16 ohm output. I ran it in 7w.

Speakers are: Celestion V30 and T75. Both are 16 ohm. Its a stereo cab (left input [when viewed from behind] states "stereo 16 ohm") with auto switching I believe. Am I running my rig correctly or not?

 

[devastone]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

If I understand correctly, yes, if you are running into an 8 ohm cab, you should use the 8 ohm output not the 16 ohm.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

If I understand correctly, yes, if you are running into an 8 ohm cab, you should use the 8 ohm output not the 16 ohm.

Thanks for the reply. Not sure if I understand the cab correctly then. Its got two speakers of which each speaker is 16 ohms. I do not know if they're serial or parallel connected. It's a stereo cab which can accommodate two heads simultaneously. In that case both inputs will be occupied and each head will run each speaker separately. In my case I figured the mono input is the one to use since I'm only running one head at a time. Does this mean the cab is telling me I should use the 8 ohm output because in mono the speakers are actually placing an 8 ohm load on the head and not 16?

 

[devastone]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

They are parallel for the mono jack, so it is 8 ohms. If they were series it would be 32 ohms. So, if you are plugging into the mono jack, it is 8 ohms.

Unless someone has changed the speakers, which they may have since it had a V30 and a GT75, stock 1936 is 2C GT75s and stock 1936V is 2X V30s, so one of your speakers has probably been changed, but they should have matched the impedance.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

They are parallel for the mono jack, so it is 8 ohms. If they were series it would be 32 ohms. So, if you are plugging into the mono jack, it is 8 ohms.

Unless someone has changed the speakers, which they may have since it had a V30 and a GT75, stock 1936 is 2C GT75s and stock 1936V is 2X V30s, so one of your speakers has probably been changed, but they should have matched the impedance.

Thanks. The one speaker was definitely changed from the stock T75 to a V30. I'm very happy about this as I love the V30 and with the T75 its a great combo. Both speakers are 16 ohm.

 

[Darg1911]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

So, I'm assuming that this is the Marshall jack-plate that doesnt have the switch. Just two 1/4" input jacks, one says "Mono 8 ohms" (or something similar over the left input jack [which is on the right when looking at the jack]). Says "16 ohms" under each, individual jack. Is this the one? If so ... That cabinet, if it's all original, should have 2 x 16 ohm speakers.

If you plug into the "Mono 8 ohm" jack, both speakers are in parallel for an 8 ohm load. Both speakers will play. The amp selector should be set for 8 ohms.

The way that plate works is that the jack labeled as the right input jack (the one that doesnt say "mono") is a switched jack. When you plug into that jack, it effectively disconnects the two speakers from each other so you have two, separate 16 ohm speakers. When nothing is plugged into that jack, and you only plug into the jack that says "mono 8 ohms" above it, the two 16 ohm speakers are in parallel for an 8 ohm load.

You can plug into that "right input" jack if you only want to run that one speaker, but, it will be a 16 ohm load so the amp should be set to 16 ohm if you do that.

You can also plug a dummy plug into that "right input" jack and then plug the amp into the "left input" / "mono input 8 ohm" jack and again have a single speaker (the left speaker) running at 16 ohms. I only mention that in case there are two different speakers in the cabinet and you want to use one OR the other.

So, essentially, you can run either the left or right speaker (separately) at 16 ohms. Both speakers seperately, in stereo, for 16 ohms each side. Or, both speakers in parallel, mono, at 8 ohms. Just depends how/where you plug in.

Make sense?

 

[dave74]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Probably sounds better to you because it's making the amp work harder/hotter, but that's not good for the amp in the long run.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

So, I'm assuming that this is the Marshall jack-plate that doesnt have the switch. Just two 1/4" input jacks, one says "Mono 8 ohms" (or something similar over the left input jack [which is on the right when looking at the jack]). Says "16 ohms" under each, individual jack. Is this the one? If so ... That cabinet, if it's all original, should have 2 x 16 ohm speakers.

If you plug into the "Mono 8 ohm" jack, both speakers are in parallel for an 8 ohm load. Both speakers will play. The amp selector should be set for 8 ohms.

The way that plate works is that the jack labeled as the right input jack (the one that doesnt say "mono") is a switched jack. When you plug into that jack, it effectively disconnects the two speakers from each other so you have two, separate 16 ohm speakers. When nothing is plugged into that jack, and you only plug into the jack that says "mono 8 ohms" above it, the two 16 ohm speakers are in parallel for an 8 ohm load.

You can plug into that "right input" jack if you only want to run that one speaker, but, it will be a 16 ohm load so the amp should be set to 16 ohm if you do that.

You can also plug a dummy plug into that "right input" jack and then plug the amp into the "left input" / "mono input 8 ohm" jack and again have a single speaker (the left speaker) running at 16 ohms. I only mention that in case there are two different speakers in the cabinet and you want to use one OR the other.

So, essentially, you can run either the left or right speaker (separately) at 16 ohms. Both speakers seperately, in stereo, for 16 ohms each side. Or, both speakers in parallel, mono, at 8 ohms. Just depends how/where you plug in.

Make sense?

Correct about the non switching back plate. V30 in place of one of the T75's the cab came with. Both 16 ohm speakers.

Makes sense yeah.

Thing I'm most concerned with is this: is it OK for me to run the amp at 16 ohm into the right input (mono 8 ohm)? to me this sounded better than when I ran the amp at 8 ohm.

 

[dave74]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

No it's not good to do so. It forces the amp to work harder and it will run slightly hotter.
Hotter is better to a point for punchiness and brightness, but there's a point of diminishing returns when you go lower than an even-match on the speakers.

Impedance is resistance, kind-of like holding your thumb over the end of a garden hose.
Less thumb and the water flows easier and smoother, more thumb and the water gains pressure and punch, but clog it too much and you'll wear your pump out. (unless your on city water right? lol) The amp's transformer is like the pump.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

No it's not good to do so. It forces the amp to work harder and it will run slightly hotter.
Hotter is better to a point for punchiness and brightness, but there's a point of diminishing returns when you go lower than an even-match on the speakers.

Impedance is resistance, kind-of like holding your thumb over the end of a garden hose.
Less thumb and the water flows easier and smoother, more thumb and the water gains pressure and punch, but clog it too much and you'll wear your pump out. (unless your on city water right? lol) The amp's transformer is like the pump.

Light bulb moment. Thanks! I'll just go home and switch the output back to 8 ohm then. Actually I wanna run just one speaker to hear the tone difference so I'll use the 16 ohm output of either head thru the left (from back view) of the cab which is the stereo input and is 16 ohm. Your explanation above regarding that (and using a dummy jack or a jack not connected to anything...?) was clear too.

 

[Darg1911]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Light bulb moment. Thanks! I'll just go home and switch the output back to 8 ohm then. Actually I wanna run just one speaker to hear the tone difference so I'll use the 16 ohm output of either head thru the left (from back view) of the cab which is the stereo input and is 16 ohm. Your explanation above regarding that (and using a dummy jack or a jack not connected to anything...?) was clear too.

Agree with Dave, it's best to match amp and cabinet impedance. Old Fenders were reported to take the abuse of that type of mismatch pretty well, while old Marshalls were reported to not fare as well. It may be old wives tales more than anything seeing how Marshalls were probably more often run harder. At any rate, it's a safer bet to match the impedance.

Since you have two different speakers in the cabinet, may as well take advantage of the capability of the internally switching jack plate.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Agree with Dave, it's best to match amp and cabinet impedance. Old Fenders were reported to take the abuse of that type of mismatch pretty well, while old Marshalls were reported to not fare as well. It may be old wives tales more than anything seeing how Marshalls were probably more often run harder. At any rate, it's a safer bet to match the impedance.

Since you have two different speakers in the cabinet, may as well take advantage of the capability of the internally switching jack plate.

Good point. I have faith in my Orange and Marshall heads to take abuse On the flip side of the impedance equation: is it completely safe to run an 8 ohm amp into a 16 ohm cab?

I will play around with the auto switching like Dave suggested. This way I can isolate each speaker for different songs or parts and for cool mixing/overdubbing purposes. Come to think of it I can use the T75 alone for my future Iron Maiden tribute video

 

[Lake Placid Blues]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Measure it. Take a multimeter to the speaker cable. See if its a 8 ohm or 16 ohm. It won't measure exactly 8 or 16 ohms on the meter but a couple less because your measuring a static load. But then you know what it is, or if there's something wrong with the wiring, the jack, or one the speakers. These switching jack plates can go bad and be troublesome too. I like it hard wired either parallel or series. Ditch the switch.

 

[JamesPaul]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Look up the maximum power transfer theorem.

If you aren't matching the output impedance of your amplifier with the impedance of the speaker load, you will lose output power. That power isn't truly "lost", it has to dissipate somewhere. If the speaker impedance is lower than what the amp is set for the power dissipates in your tubes, which now work harder than designed for and will likely not last as long. If the speaker impedance is higher than what your amp is set for the power dissipates in the output transformer, which now works harder than designed for and could overheat.

Yes we are talking impedance, which is frequency dependent and not constant like resistance. So there is always some tolerance. But ultimately it will come down to how robust your tubes or transformer are.

Bottom line, don't mismatch impedance if you want optimal performance and longevity from your amplifier and tubes.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Measure it. Take a multimeter to the speaker cable. See if its a 8 ohm or 16 ohm. It won't measure exactly 8 or 16 ohms on the meter but a couple less because your measuring a static load. But then you know what it is, or if there's something wrong with the wiring, the jack, or one the speakers. These switching jack plates can go bad and be troublesome too. I like it hard wired either parallel or series. Ditch the switch.

I don't have a multimeter on hand now but I'm quite sure the cab and speakers check out well. I actually ran just the right speaker (T75) yesterday by plugging into the stereo input labelled 16 ohm while running the amp at 16 ohm. I could clearly hear the T75 running solo.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Look up the maximum power transfer theorem.

If you aren't matching the output impedance of your amplifier with the impedance of the speaker load, you will lose output power. That power isn't truly "lost", it has to dissipate somewhere. If the speaker impedance is lower than what the amp is set for the power dissipates in your tubes, which now work harder than designed for and will likely not last as long. If the speaker impedance is higher than what your amp is set for the power dissipates in the output transformer, which now works harder than designed for and could overheat.

Yes we are talking impedance, which is frequency dependent and not constant like resistance. So there is always some tolerance. But ultimately it will come down to how robust your tubes or transformer are.

Bottom line, don't mismatch impedance if you want optimal performance and longevity from your amplifier and tubes.

Solid info here. Thanks

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Guys I decided to stop running my amp in 16 ohm mode to the 8 ohm input of the cab. Yesterday I ran the 16 ohm output from the amp into the 16 ohm input of the cab which muted the V30 and drove the T75 solo. Instantly recognisable tone difference! Man that bottom end and softened high end are indeed different to the peaky-er V30 Love both speakers and this cab sounds really great! 1993 model so she aged well

By the way I consulted Orange online. Since my amp has 3 speaker outputs, 8-8-16 ohm, I can run a variety of cabs/chains. If I want to run two cabs or in this case my stereo cab in stereo I can use both the 8 ohm outputs into 16 ohm speakers or stand alone cabs and the amp will operate at 16 ohm. So since 16 ohm sounded "better" to me I can get another speaker cable, hook both cables up to the 8 ohm outputs of the amp and then plug them into both the inputs of the JCM 900. That would mean the cab is running in stereo and its speakers are operating at their peak of 16 ohm each AND the amp is operating at 16 ohm to match that load. Does this make sense?

 

[dave74]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Yes. It might well sound better like that than running from the 8ohm into the cab's 8ohm mono-mode.
"better" is subjective though, so really it just depends which way works better with your rig.

 

[RolanTHUNDER]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Yes. It might well sound better like that than running from the 8ohm into the cab's 8ohm mono-mode.
"better" is subjective though, so really it just depends which way works better with your rig.

Yes I think I'll run it this way in stereo then really determine whether it is "better" than 8 ohm mono mode. I also have the flexibility to run both heads at the same time into the JCM900. In that case it will be 16 ohm output from each amp into the inputs of the JCM.

 

[dave74]

Re: Marshall 1936 JCM900 212 16/8 ohm - Sounds Better When...

Yes I think I'll run it this way in stereo then really determine whether it is "better" than 8 ohm mono mode. I also have the flexibility to run both heads at the same time into the JCM900. In that case it will be 16 ohm output from each amp into the inputs of the JCM.

Yeah that's true stereo amping there.