#1
I'm looking for some input on my Marshall 6100LM. It has a pentode/triode switch and a high low power switch. From what I understand, switching to triode does not require a change in speaker impedance. Switching from high to low power is a different matter since it is basically pulling two power tubes out of the equation. Marshall says that a change is not needed in impedance but a lot of people seem to disagree. I'm looking for some input on this before I screw up the amp. I'm running a single 4x12 cab with Celestion Vintage 30s. I'm running it in Stereo mode.
#2
I used to have the same amp. I set the impedance to match the cabinet. I never adjusted the impedance when changing the power settings. I had mine for years without any trouble.
Quote by fly135
Just because one has tone suck it doesn't mean one's tone sucks.
#3
Thanks for the input. I've been running it that way myself and never knew anything about the need to change the impedance in this situation. there is nothing in the manual about it. Some people express concern about red plating the tubes in this situation. I haven't played mine much at the low power settings but so far it seems to have done just fine. I should probably get a set of power tubes in case one pair burns out before the others though. I still have original Sovteks from back in the 90s in it.
#4
The low power setting cuts the HT off from two valves (at the cathode end) so you should switch the impedance switch down one notch for that. I don't think it will matter in triode mode.
Gilchrist custom
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#5
Quote by Cathbard
The low power setting cuts the HT off from two valves (at the cathode end) so you should switch the impedance switch down one notch for that. I don't think it will matter in triode mode.


Yep that's the heart of the debate. Everyone says it's fine to leave it when switching to Triode mode, but switching to low power mode is a different story. So I'm running 8 ohms in stereo at full power, which means I need to be running 4 ohms at half power? I wonder why Marshall says this is not necessary.
#6
What do you mean stereo mode? How have you got it connected up?
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#7
The head is connected to the cab via two speaker cables. Both head and cab are set to 8 ohm stereo mode. Basically each set of two speaker is run on a different stereo channel. It sounds better running in stereo up close to my ear, though I've heard people say it doesn't make any difference when you get away from the amp a little ways.

Connection is explained in the manual.
http://www.marshallamps.com/handbooks/pdf/30thanniv.pdf
Last edited by poppameth at Jan 10, 2012,
#8
The head isn't capable of running in stereo.

"Where two 8 ohm cabinets are employed the amp should be switched to
4 Ohms." By running your cab in stereo, are you not in principle running two 8 ohm cabs, therefore need to set your amp to 4 Ohms? So then switching to half power you need to select 2 Ohms?

Brain overload.
Quote by fly135
Just because one has tone suck it doesn't mean one's tone sucks.
Last edited by Dilberto at Jan 10, 2012,
#9
Well, the head has two speaker ourputs. They are both hooked into one 1960av cab which is switched to 8ohm Stereo mode (150 watt handling.) It may not be accurate to say the head is actually stereo. The effect is stereo in a sense. At least this is how it was explained to me when I bought this monster back in high school. It's always been set at 8 ohms on the head and 8 ohms stereo on the cab. Looking at the info in this thread and other places on the net it looks like this is probably an incorrect setup. I think I may be best just to switch both head and cab to 16 ohm mono. I believe you are right in saying that by running the cab in stereo it would be running two separate halves each as an 8 ohm cab, calling for a 4 ohm setting on the amp. From other info I've read, the higher the ohm rating on the amp the better it is for the amp. If that is true I'd hate to be running it at 4 ohms. I think I'm better off switching it to 16 ohm mono to preserve my amp. If I'm wrong about any of that please let me know. I have had this amp setting in the corner for almost 10 years without playing it, but I"m pretty sure I have always played it as 8 ohm / 8 ohm stereo with no issues but I don't know what kind of stress that could have been putting on the amp.
Last edited by poppameth at Jan 10, 2012,
#10
^ I have not read your post yet - I was typing.

Edit: Agreed. I'd just run at 16 mono.

Quote by Dilberto
The head isn't capable of running in stereo.

"Where two 8 ohm cabinets are employed the amp should be switched to
4 Ohms." By running your cab in stereo, are you not in principle running two 8 ohm cabs, therefore need to set your amp to 4 Ohms? So then switching to half power you need to select 2 Ohms?

Brain overload.



I agree.

I looked over the User Manual and I don't see any mention of stereo. I normally do not associate Marshall amps as even having that capability but I figured I'd better check with the 6100 since it has so much other crap. Why you would want to run in stereo with one cab I'm not totally sure anyway. Why you would want to run in stereo period I'm not totally sure.

On the back panel you have a choice of 16 or 8 ohms. You technically don't have a 4 ohm option without opening up the amp and doing something (according to this note).
"It should be noted that although the output transformer has 3 impedance connections, only two are switchable from outside the amplifier. These are 16 ohm and 8 Ohm on heads..."

If you run in half power (like I do) I can assure you that you cut the ohms in half.

Now - lets forget about the half power thing for a moment. I do believe that your cab has the ability to do stereo and that it is wired in Series/Parallel. I will just assume this for now. If each half of the cab wants an 8 ohm load and you are connecting to both speaker outs on amp (as I am assuming you are doing) then you may be mismatched here.

The 8 ohm speaker out is going to half of your cab at 8 ohms. check
The 16(4) ohm speaker out is going to the other half of the cab at 8 ohms. ??


Now introduce the half power business and you may not be running very efficiently.

My fear would be that when both speaker jacks are populated your amp automatically wants dumb down and run them in parallel so you would then be either at 4 ohms or some weird number like 6? Apply half power to that scenario and it gets worse.

Of course I hope I'm wrong about all of this and I've overlooked something and you're fine.

I would run mono from amp to cab at 16 and forget about stereo and half power (for now).

I think my brain hurts too


Quote by Cathbard
The low power setting cuts the HT off from two valves (at the cathode end) so you should switch the impedance switch down one notch for that. I don't think it will matter in triode mode.

+1 I think that is right too.
Last edited by 311ZOSOVHJH at Jan 11, 2012,
#11
I appreciate the input. When I first bought this over a decade ago, I listened to the salesman at Washington Music Center. I never really questioned the advice at the time. After a few years of playing with no issues, I put the amp away for about 10 years when other aspects of life took over. I've gotten back into playing in the last few years. I know a lot more now about working on guitars but I'm just getting started on working with amps. Only when I started looking at the benefits and drawbacks of half power mode did I come to realize something might be wrongs with my setup. I think you are correct and switching it all to 16 ohm mono would be for the best.
#12
No issue man it is always better to double check. This stuff like you were asking can get confusing. Which Slash cab do you have exactly and how do you like your Super Champ? And what is the significance of poppameth? It sounds like 'pop some methamphetamines'
#13
Yep. I had a feeling you were doing this. Those two outputs on the amp you are plugged into are simply parallel connections. So you are effectively running the cab at 4 ohms (two 8 ohm circuits in parallel = 4 ohm). What you should be doing is running a single cable to the 16 ohm input and set the amp to 16. When you go to low power, leave the cabling the same and switch the amp to 8 ohms.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Jan 11, 2012,
#15
The Slash cab is just a 1960A with a Slash plate on it and a snakeskin vinyl cover. The Super Champ is okay for practice but nothings special really. I don't think it really lives up to all the hype on it myself. Poppa Meth was a nickname for a character in a manga I was writing a long time ago. It was a little bit of a play on drugs to be honest, not that I or the character were into drugs. I just have a sick sense of humor.
Last edited by poppameth at Jan 11, 2012,
#16
Quote by kyle62
Glad to see another 30th Anniv owner. The half power switch absolutely does not require changing the impedance, it's purposely wired that way.

It may be able to cope but look at the schematic:
http://www.drtube.com/schematics/marshall/6100-63-04.pdf
All it does is cut off the cathode of two valves. There is no impedance compensation that I can see. Perhaps you see something I don't?
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#17
Thanks for clarifying Cath and I made a minor edit to my bolded part above. Should have stated 8 not 16.



poppa meth - ok ok. It has kind of a 'dealer' feel to it

I thought the SuperChamp was a cool little amp, but for what I like to play - it would just sit there.
#18

From "Spooged - Life's a Sticky Mess!"
The comic never made it past conception. Maybe one day I'll get back to it.

I bought the Super Champ on sale as a practice amp when I decided to start playing again. A couple of weeks ago I finally moved the room around where the Marshall was stored and made it more accessible. There is a huge difference in sound. The Super Champ just sounds cheap and over processed after playing on the Marshall again. I like Fender amps but you get what you pay for. The Super Champ is a nice practice amp, but little more than that.
#19
Champ > Super Champ
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#20
I miss my 6100!!
Quote by fly135
Just because one has tone suck it doesn't mean one's tone sucks.
#21
I actually thought about selling mine and getting a lower wattage combo since I just play for my own entertainment. But I can't do it! I'm keeping this thing until the day I die.
#25
Quote by 311ZOSOVHJH
You can find used Splawns starting at $900.

Can you post any pics of your amp or gut shots

Ever seen a gutshot from a 6100? It looks like part of HAL 9000's brain.

#27
The last Marshall that looked good on the inside was a 2203.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band