Marshall 30th Anniversary Series thread (6100 / 6101)

[Jethro Rocker]

Hi all.

My 6100 has a big volume drop when switching to channel 3.
I've read in this same thread something along the line that the trim pots on the back can affect the overall volume of each channel when the loop is set in some particular way.
Did I get that right?
Or is it just normal this volume difference between chs 2 and 3?

Yes the trim pots affect it when using loop. Does it do this with nothing in loop? It should not.
If volume is same on channel 3 with gain up some, shoild be same volume. If not, potentially it us a weak preamp tube for channel 3.

 

[Eduberto Palitroke]

The loop is currently set to SERIES with a short cable as a jumper, so it's easier -at leat for me- to play at low volumes (which I'm finding out this amp can do pretty well).

If I set ch 2 to max volume and so I do with channel 3, there's a big difference.

I could set ch 2 to a lower volume but it sounds weaker that way so... do volume pots in each channel change tone or is it just that "louder is better" in my head?

Can this trim pots values affect channels separately? I guess not.

 

[Eduberto Palitroke]

I see the pots labeled as CH1 and CH2, so they do seem to affect someway, but there's the loop level switch, as well.

Too many buttons for my intelect...

 

[Thoma]

...
If I set ch 2 to max volume and so I do with channel 3, there's a big difference.
...

You should be able to reduce volume of ch2 by adjusting the respective pot on the back. Is the pot currently maxed out?
The pots are meant to adjust volume of ch1 and ch2 in respect to ch3, if one uses the effects loop.

 

[Eduberto Palitroke]

It's weird that without engaging the loop at all I got this volume drop and if I do jump it, either in series or paralell, the loop level button affects ch 3, as well as 2 and 1.

I'll bring 1 and 2 down to see whst happens but it shouldn't be that way, I guess.

And there's a lot of volume increase between modes A, B and C.

 

[Thoma]

It's weird that without engaging the loop at all I got this volume drop and if I do jump it, either in series or paralell, the loop level button affects ch 3, as well as 2 and 1.

I'll bring 1 and 2 down to see whst happens but it shouldn't be that way, I guess.

And there's a lot of volume increase between modes A, B and C.

All that seems fine.

 

[Mike_LA]

Um, well sort of.
If you are using the loop, set channel 3 as you want. Then balance channels 1 and 2 with the volume trim pots in the back.
Barring that, having no real electrical knowledge myself, if I had that issue I would try swapping preamp tubes around and hear if that makes a difference.

 

[Joesatch]

recently had one of these. very cool head it has a separate set of preamp tubes for each channel (lotta preamp tubes!). i needed to bias it for new power tubes and after getting a look at the guts i decided to sell the amp as servicing this would be quite a task should anything go wrong. Lots of IC's and components.

 

[Thoma]

servicing this would be quite a task should anything go wrong. Lots of IC's and components.

A short in a power tube with bad vacuum killed one of my amps, including the MIDI board. That's the one "with lots of ICs".

After a look at the schematics it didn't look too complicated to me.
So I tried it on my own.
I replaced some ICs, a FET, the voltage regulators and the PT Quartett.

It was my very first tube amp repair and I doubt that a defect in a 6100 amp gets much worse than this one.

A tube amp repair guy should be able to fix the amp, provided he knows how to read schematics.

 

[anitoli]

How is the gain level on channel 3? Is it full bore in your face gain with no volume, or lame wimpy lethargic gain with low volume?

 

[Eduberto Palitroke]

How is the gain level on channel 3? Is it full bore in your face gain with no volume, or lame wimpy lethargic gain with low volume?

Well the whole amp seems to be lacking some bite.
The tech said everything was ok -including preamp vslves- by I still feel something's missing.

 

[anitoli]

But you were saying that channel 3's volume was lower than 1 & 2. Channel 3 is the reference channel on these amps 1&2 have the trim pots to adjust the loop levels to match. And if not using the loop, (loop in parallel) the front panel volume controls should have enough swing to adequately level the channel volumes.

 

[Eduberto Palitroke]

But you were saying that channel 3's volume was lower than 1 & 2. Channel 3 is the reference channel on these amps 1&2 have the trim pots to adjust the loop levels to match. And if not using the loop, (loop in parallel) the front panel volume controls should have enough swing to adequately level the channel volumes.

Indeed.

If I don't use the loop in any way, ch 2 - mode B at, say, volume 10, is louder than ch 3 at volume 10. Mode C is more notorius.
I got to turn those trim pots down, as you guys adviced and it does work.
What I'm not getting is that loop level switch.
I'd asume it would engage and disangage the trim pots and affect just ch 2 and 1 -when using the loop-, but seems to work in some other way.

 

[anitoli]

The loop level switch is at two points in the loop, before the trim pots and part of the return op amp setup. It is only functional when using the loop / you have to have something plugged into it for them to work other wise it bypasses the loop with the parallel setup.

https://web.archive.org/web/20160430053930/http://home.myfairpoint.net/vze1u14s/sitebuildercontent/sitebuilderfiles/6100poweramp.pdf

 

[Thoma]

seems to work in some other way.

I try to put this kindly:
Sometimes an owners manual can help minimizing guesswork.

 

[Eduberto Palitroke]

I try to put this kindly:
Sometimes an owners manual can help minimizing guesswork.

It would've been kind if you didn't say you'd try to put it kindly

The manual says little about my concern, which might pretty irrelevant, I reckon.

 

[Jethro Rocker]

The loop is currently set to SERIES with a short cable as a jumper, so it's easier -at leat for me- to play at low volumes (which I'm finding out this amp can do pretty well).

If I set ch 2 to max volume and so I do with channel 3, there's a big difference.

I could set ch 2 to a lower volume but it sounds weaker that way so... do volume pots in each channel change tone or is it just that "louder is better" in my head?

Can this trim pots values affect channels separately? I guess not.

Likely louder better.

I see the pots labeled as CH1 and CH2, so they do seem to affect someway, but there's the loop level switch, as well.

Too many buttons for my intelect...

As mentioned above, loop level affects the device level in the loop which obviously affects all channels. Once level is set for ch 3 adjust separate loop levels on back so ch 1 and 2 match.
Then adjust relative volumes on the channel levels on control panel.
The manual does state it fairly plainly as I recall. Have a peek.

 

[anitoli]

The reason i asked if there was also a gain drop off is because TR101 on the control board can short and this creates a direct path for channel 3's signal to ground. The only reason you can still hear the sound is due to the channels intense gain.

 

[Anders Bak]

recently had one of these. very cool head it has a separate set of preamp tubes for each channel (lotta preamp tubes!). i needed to bias it for new power tubes and after getting a look at the guts i decided to sell the amp as servicing this would be quite a task should anything go wrong. Lots of IC's and components.

Yes, it is a crowded amp - but so good sounding!
Regarding the preamp tubes, the configuration is like this:
Number 1 (V1) is for channel 1
V2+6 Is for ch. 2 (and first half of V2 is also start of ch 3)
V3-4-5 is for ch 3
(V7 is the driver)
- so this really gives you the opportunity to make the channels sound as you like!!

 

[Interstelllla]

Hey heyyyyyy !!!

New member from France !!

Since yesterday I have the 6101 / Black One / EL34 / G12 Gold …. WONDERFUL

Just love the Clean and Crunch Channel

In few days I’ll receive the 1x12 6912 Closed Back in 200 watts

Can’t wait.

I had many marshalls : JCM 800 4010 / JVMs … several.
My First was Valvestate and now I still have a Modded Class 5

I Think this One Will be « One of the lasts » and will make me Forget the others