#1
I have a Marshall 1987X that I run through an attenuator, so I usually have the volume on the amp turned up to get a nice distorted sound.

However, I've noticed recently that if I turn it down to volumes where it shouldn't break up, I can't get a clean sound from the amp. I could get clean sounds when the volume was turned down before.

I purchased the amp second hand, and I've never changed the tubes in it (I don't know whether or not the previous owner did), so I was wondering if this sounds like it could be fixed by changing the tubes, or if it's likely something else?
My Current Gear
Gibson Les Paul Standard Faded (Cherry Burst) || Gibson Les Paul Junior (Vintage Sunburst)
Marshall 1987X and 1960AX || Weber Mass 100
Fulltone OCD pedal || Ibanez TS-9 tube screamer || Big Muff Pi with Tone Wicker || Boss AC2
#2
if you're running it through an attenuator all the time it could well be the tubes. it's not harder on the tubes than regular use, but it is effectively like diming the thing the entire time, which is harder on them than running them at low volumes.
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#3
My .311 cents is that you want to experiment with some tube changes.

A 12AT7 (ECC801) or 12AU7 (ECC802) would be a lower gain 12AX7 (ECC803) preamp tube replacement that will have slightly less gain (90% and 70% respectively as a general rule of thumb) than what you have now.

A 5751 is also a drop in replacement for these tubes and also low noise. A NOS 5751 in the Phase Inverter slot (last preamp tube slot) would be the best thing for your amp.

I would put the order of importance at Phase Inverter, V1, V2, etc

If you have slightly crappy tubes in there now or even older tubes then consider replacing some of them. Depending on your budget will dictate what I would do and in what order of importance.

Also, running an attenuator can be hell on power tubes. It may not be affecting your power tubes with what you described but it could. Also, the power tubes may need to be rebiased - as they will drift and could drift into cross-over distortion over time - causing what you may experiencing.

I can help further with that too if you are interested as my Splawn is very similar (but with a lot more growl)
#4
Thanks guys - it looks like the amp has the following tubes:
Preamp: 2x ECC83
Power amp: 1x ECC83, 2x EL34

I love(d) the sound of the amp before, so ideally I'd like to get tubes that'd let me get back to the original sound. What do I need to know before I go and buy X-brand tubes and then install them? Looking online ECC83 just seems to be the British designation of 12AX7s, but just to be sure, are ECC83 tubes the same as 12AX7s?
My Current Gear
Gibson Les Paul Standard Faded (Cherry Burst) || Gibson Les Paul Junior (Vintage Sunburst)
Marshall 1987X and 1960AX || Weber Mass 100
Fulltone OCD pedal || Ibanez TS-9 tube screamer || Big Muff Pi with Tone Wicker || Boss AC2
Last edited by HenryB at Jul 16, 2015,
#5
are ECC83 tubes the same as 12AX7s?
Yep, exactly the same thing.

From what you've described I'm betting it's the power tubes. If you liked how it sounded before just get a matched pair in the same brand you have now.
Charvel DX-1 FR / DS-1 ST / DC-1 FR / Custom Strat / La Patrie Hybrid CW / Vypyr 30 / VK100 / 1960A
#6
Yes ECC83 is the same as 12AX7A. Some are even marked that way. And all of those are preamp tubes. Sounds like you have a 50 watt amp, the two EL34 tubes are the power amp tubes.

Tubes may be the problem, but attenuators are also rough on transformers. I fried the one in my Peavey MX running one a few years back, cost me $125 and that's installing it myself. It started sounding garbled, sent it to a tech to test (and he took my whole set of good 6L6 tubes, swapped them for two Fenders and two chinese garbage all weak as hell..) He found a bad power transformer.

If tubes don't do the trick, have a tech look at it, you may have overworked the power transformer.

I wanted to try out the attenuator, Tom Schultz Power Soak, and see how it would work since the MX is 130watts, gets kinda loud in a hurry. Clean as they get, but freakin loud...and the power soak took out the transformer, they are known for doing that. Been thinking about selling the thing...don't really need it, when I use the amp I just don't turn it up a lot, I use pedals for distortion anyway...And these days I use a Super Reverb, it's 2 ohms, the power soak only works for 4 or 8 ohm amps.
Hmmm...I wonder what this button does...
Last edited by Paleo Pete at Jul 16, 2015,
#7
I'll go ahead and change the power amp tubes first then - hopefully it's not the transformer!

I opened my amp and found that the two power amp tubes are the Marshall EL34s (42/02). However, I can't find the exact same tubes online - does anyone know which of the following would be the best replacement?
- 2x Electro Harmonix EL34EH
- 2x JJ EL34
- 2x JJ EL34L
- 2x Marshall EL34 Scetlana (though these are double the price of the others - worth it?)
My Current Gear
Gibson Les Paul Standard Faded (Cherry Burst) || Gibson Les Paul Junior (Vintage Sunburst)
Marshall 1987X and 1960AX || Weber Mass 100
Fulltone OCD pedal || Ibanez TS-9 tube screamer || Big Muff Pi with Tone Wicker || Boss AC2
#8
A lot of love for Svetlana EL34s in a Plexi but I can't imagine they're twice as good as JJs. Dunno about EH.

I think the "L" tubes offer more headroom than the standard ones. Double check that, but it's probably not what you want if you're using power break up and an attenuator.
Charvel DX-1 FR / DS-1 ST / DC-1 FR / Custom Strat / La Patrie Hybrid CW / Vypyr 30 / VK100 / 1960A
#9
JJ E34L tubes are awesome. Bigger, beefier tones than the EL34.
Put JJ ECC83S everywhere but V1.
Go to tctubes.com and find a nice NOS 12AX7 for V1. They normally have fairly cheap American tubes. RCA, Phillips, GE, all good.
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#10
Thanks for all of the help - much appreciated.

I ended up ordering a pair of these: https://www.watfordvalves.com/product_detail.asp?id=3206

Saw them recommended on a few forums, and they're not too expensive.
My Current Gear
Gibson Les Paul Standard Faded (Cherry Burst) || Gibson Les Paul Junior (Vintage Sunburst)
Marshall 1987X and 1960AX || Weber Mass 100
Fulltone OCD pedal || Ibanez TS-9 tube screamer || Big Muff Pi with Tone Wicker || Boss AC2