JCM 2000 DSL 100 - Hiss normal?

[RamoneR]

I have a JCM 2000 DSL 100 and I am wondering if this is an acceptable level of hiss and hum it is producing? (video info below) As it sounds quite loud tbh.

I have just replaced all the valves with JJ valves and biased to 80mv. There was the same level of hiss before with older valves as there is with the new ones heard in the video. In the video the dsl100 is connected to a 1960A cab. I have tried different cables which seem to have no effect. The guitar is plugged straight into the amp and I have tried two different guitars.

I am not very experienced with this amp so not sure what normal is.

Due to posting restrictions as I am new here I cannot upload a video directly. But on youtube it is video 2uM1lfjmM94 which you can search for.

 

[junk notes]

Let me assist here.

 

[Kutt]

Does the amp sound make the same level of noise with no guitar and no instrument cable plugged in?

Also, do you have any more details on the preamp valves you installed? If they are rated for higher gain they could be contributing to the noise.

It's still somewhat difficult to tell by the video but I am leaning towards that level of noise being expected given the volume you are cranking it to. Others might disagree.

 

[Kutt]

Another thought- Almost every pre-owned JCM 2000 I've seen is missing the factory preamp tube shield from V1, next to the transformer. If yours is missing it's possible that it's picking up noise and amplifying it.

 

[RamoneR]

Thanks for your reply and for junk notes for embedding the video.

The valves are JJ 3 x ECC83, 1 x Balanced ECC83 and 4 x Matched EL34 bought from ampvalves in the uk and sold as a kit for the dsl.

The preamp tube shield for v1 is there. Although, going by your photo it is missing the rubber oring at the bottom.

I just tested again with no instrument cable or guitar plugged in and it was a bit odd. When turning standby on the hiss was totally gone, even at high vol and gain, on both on red and green channels. However, after about 30 second , it randomly started to hiss again loudly which happened as I was adjusting volume, the hiss sort of kicked in.

So I turned standby off and back on again a minute later. The hiss was gone again. Changing volume did not make it hiss again, until I then pressed the clean / crunch button, which then caused the hiss, and would only go when turning standby off and on again.

 

[PelliX]

The valves are JJ 3 x ECC83, 1 x Balanced ECC83 and 4 x Matched EL34 bought from ampvalves in the uk and sold as a kit for the dsl.

Especially for the V1 you want a low microphonics tested valve - those kits are generally a safe bet. If the hiss is no different to the old valves (and judging by the video), you're probably fine in that respect. The hiss in the video didn't strike me as very bad, but it's hard to judge of course. Rest assured that DSL's simply aren't dead quiet and especially with these high gain circuits a bit of noise is to be expected.

The preamp tube shield for v1 is there. Although, going by your photo it is missing the rubber oring at the bottom.

I wouldn't worry about that, myself. The rubber ring doesn't do much in my experience. If you want to slap one on, go ahead, but don't expect a world of difference. The shield is way more important.

I just tested again with no instrument cable or guitar plugged in and it was a bit odd. When turning standby on the hiss was totally gone, even at high vol and gain, on both on red and green channels. However, after about 30 second , it randomly started to hiss again loudly which happened as I was adjusting volume, the hiss sort of kicked in.

In standby there should be zero hiss or any other noise from the speaker - after all, the B+ is disconnected. If you get hiss while standby is engaged, it would lead me to assume that the switch might be dodgy/at fault. If I'm misunderstanding your statement, please correct me!

EDIT: Please don't take this the wrong way, but you are aware that valves need to warm up before operating correctly, so if you simply flick a (cold) amp on and take it off standby it can still take about 30 seconds or longer for it to produce sound?

 

[RamoneR]

In standby there should be zero hiss or any other noise from the speaker - after all, the B+ is disconnected. If you get hiss while standby is engaged, it would lead me to assume that the switch might be dodgy/at fault. If I'm misunderstanding your statement, please correct me!

EDIT: Please don't take this the wrong way, but you are aware that valves need to warm up before operating correctly, so if you simply flick a (cold) amp on and take it off standby it can still take about 30 seconds or longer for it to produce sound?

Yeah, before turning standby from off to on I leave the amp with just the power on for a good 2-3 minutes first. Then when switching off switch the standby from on to off , then the power to off.

When the amp is powered on but has standby set to off there is no hiss or noise apart from some very minor electrical noise.

With no instrument cable connected and flipping the standby from off to on there is no noise. Until randomly it seems to kick in after 30 seconds to 1 minute, and seems random as to what starts it off, it can be moving the volume, or changing from clean to crunch. When turning the standby from on to off and then back on it clears the hiss, until the above happens again. When having the instrument cable plugged in and turning standby from off to on the hiss starts right away.

 

[PelliX]

Right, thanks for clarifying. I think we might have our terms a little mixed up here; engaging or turning standby on means disabling or turning off the 'output'. Standby on = toilet break.

This sounds like one or more caps might be a dying, hence the delay in buildup before the noise becomes apparent. Providing it with more signal (like an instrument or even just the lead) is invoking that effect faster. Does the hiss alter or you do you hear any effect when giving the amp a slap on the top? I mean, don't take a hammer to it, but just giving it a bit of a bump.

How comfortable are you about poking the insides, performing measurements?

 

[RamoneR]

Right, thanks for clarifying. I think we might have our terms a little mixed up here; engaging or turning standby on means disabling or turning off the 'output'. Standby on = toilet break.

This sounds like one or more caps might be a dying, hence the delay in buildup before the noise becomes apparent. Providing it with more signal (like an instrument or even just the lead) is invoking that effect faster. Does the hiss alter or you do you hear any effect when giving the amp a slap on the top? I mean, don't take a hammer to it, but just giving it a bit of a bump.

How comfortable are you about poking the insides, performing measurements?

Okay so, with the standby set to 'on' and no instrument cable connected I gave it a slap and it produced instant hiss accompanied by a very loud 'thwhack' sound, the hiss remained after that.

So this could mean some caps need replacing? I am quite comfortable poking around inside and replacing parts or taking measurements etc

 

[PelliX]

Ah, no. If the slap did that you're probably just dealing with a bad connection somewhere. First clean the input (actually, all the) jack(s), re-seat the valves, give the pots a few good twists (though they sound fine) and flip all the switches a few times. Pipe cleaners are very handy for valve sockets and folding them can work for jacks, too. A shot of de-oxit or comparable is never a bad idea.

Presuming that doesn't resolve the issue, I would indeed start chopsticking the insides. It could be a bad solder joint or a loose wire somewhere.

Although I don't encourage slapping amplifiers, you could narrow the fault down by 'slapping' it with and without specific pre-amp valves inserted, channels selected, etc. You indicated that you're comfortable poking around, so I won't lecture you on safety hazards and how hard to whack it, etc. There's no shame in asking if you're unsure of something, though.

EDIT: While all the above is still good advice, do I understand you correctly in saying that it started hissing with standby on? In that case, your standby switch is not working correctly, fair and square. Check continuity on it in various positions and flick back and forth a bit. Also re-seat the output valves and check those sockets.

 

[RamoneR]

Ah, no. If the slap did that you're probably just dealing with a bad connection somewhere. First clean the input (actually, all the) jack(s), re-seat the valves, give the pots a few good twists (though they sound fine) and flip all the switches a few times. Pipe cleaners are very handy for valve sockets and folding them can work for jacks, too. A shot of de-oxit or comparable is never a bad idea.

Presuming that doesn't resolve the issue, I would indeed start chopsticking the insides. It could be a bad solder joint or a loose wire somewhere.

Although I don't encourage slapping amplifiers, you could narrow the fault down by 'slapping' it with and without specific pre-amp valves inserted, channels selected, etc. You indicated that you're comfortable poking around, so I won't lecture you on safety hazards and how hard to whack it, etc. There's no shame in asking if you're unsure of something, though.

EDIT: While all the above is still good advice, do I understand you correctly in saying that it started hissing with standby on? In that case, your standby switch is not working correctly, fair and square. Check continuity on it in various positions and flick back and forth a bit. Also re-seat the output valves and check those sockets.

I will give the PCB a good look over and do some cleaning. I will also try to identify like you say with specific pre-amp valves inserted etc. Safety wise im all good.

It started hissing when slapped with the standby switch set to the 'on' position and not when set to the 'off' position. I did actually notice a tiny blue spark from inside the switch when flipping the standby to the 'off' position.

 

[PelliX]

It started hissing when slapped with the standby switch set to the 'on' position and not when set to the 'off' position. I did actually notice a tiny blue spark from inside the switch when flipping the standby to the 'off' position.

Right, ok. The spark is normal if you are somehow looking straight into the switch.

Safety wise im all good.

Cool.

Could still just be a dirty valve socket - never rule out the simple stuff. Let us know how it works out!

 

[RamoneR]

Right, ok. The spark is normal if you are somehow looking straight into the switch.

Cool.

Could still just be a dirty valve socket - never rule out the simple stuff. Let us know how it works out!

I will do, will work it it some more tomorrow and update once i get somewhere.

Thanks for your help.

 

[Kutt]

As mentioned, next step is probably to do some basic cleaning.

Use an instrument cable plug and contact cleaner to clean all the jacks (sockets). Spray the cable's plug liberally with contact cleaner then promptly work it in and out of every jack/socket multiple times.

Take 1 preamp tube (valve) and spray its pins liberally and work it in and out of each preamp tube socket, respraying the pins for each socket. Do the same with a power tube (valve) in each power tube socket.

There is a chance a basic cleaning is all that is needed.

 

[Neil S]

That amp sounds pretty quiet to me, No louder than mine. The massive volume that would be produced at those settings where it is making a loud hiss would be in proportion.

 

[RamoneR]

So I have cleaned all the jack/ sockets, pots, valve pins and sockets etc with contact cleaner.

I did notice before, and after cleaning, one of the new power tubes/valves was glowing a fair bit brighter than the others internally in the section below the top insulating spacer (I think it's called). So I move it around with another valve/tube and it did the same in a different socket, so seemed to be the valve/tube. However, when putting the older tubes back in instead, the hiss remainded the same.

I have made a new recording showing the hiss, which remains after cleaning. As Neil Skene says above, maybe it is normal. However I am not sure. Hopefully the new recording will help.

Again, as I am new, for another day I cannot embed links. But if you search youtube for wiyfdcvacbQ you will find the video.

 

[PelliX]

There you go

It isn't the hiss that worries me, seems pretty much within spec, honestly. The crackling and the fact that it 'responds' to be slapped tells me there's a dodgy contact somewhere. You've pretty much ruled out the valves, which makes me wonder; did you find anything when chopsticking the board? Technically, slapping an amp should have no effect unless you have a reverb tank, etc.

 

[RamoneR]

There you go

It isn't the hiss that worries me, seems pretty much within spec, honestly. The crackling and the fact that it 'responds' to be slapped tells me there's a dodgy contact somewhere. You've pretty much ruled out the valves, which makes me wonder; did you find anything when chopsticking the board? Technically, slapping an amp should have no effect unless you have a reverb tank, etc.

Ah then that might explain the effect when slapped, as it is fitted with an Accutronics reverb tank N4BB3C1D.

Any idea why one of the new power valves/tubes was glowing more than the others? And didn't matter which socket it was in, still was glowing more than the others.

Good to know the hiss sounds within spec though, like I say I am not sure what normal is with this amp.

 

[PelliX]

Ah then that might explain the effect when slapped, as it is fitted with an Accutronics reverb tank N4BB3C1D.

Well, presuming you have the reverb turned up and slap the thing hard enough, sure, you'll hear the springs in the reverb tank do their thing - no crackling or hissing, though.

Any idea why one of the new power valves/tubes was glowing more than the others? And didn't matter which socket it was in, still was glowing more than the others.

Well, as it stayed with the valve (i.e. not the socket/position), it's obviously an inconsistency in that valve compared to the rest. I've had pairs of valves that I measured myself where one was noticeably brighter than the other, matched pairs in fact. It can be a sign that something is wrong, but it doesn't always indicate a problem. I wouldn't worry about it too much, provided it stays at that. Some valves are marked after testing, do these valves have a sticker on the base with numbers? Any big differences between them? Matching is a human process and people make mistakes, you know....

Good to know the hiss sounds within spec though, like I say I am not sure what normal is with this amp.

Forget the hiss, but that crackle/loose connection should be sorted out. Just my advice.

 

[RamoneR]

Well, as it stayed with the valve (i.e. not the socket/position), it's obviously an inconsistency in that valve compared to the rest. I've had pairs of valves that I measured myself where one was noticeably brighter than the other, matched pairs in fact. It can be a sign that something is wrong, but it doesn't always indicate a problem. I wouldn't worry about it too much, provided it stays at that. Some valves are marked after testing, do these valves have a sticker on the base with numbers? Any big differences between them? Matching is a human process and people make mistakes, you know....



Forget the hiss, but that crackle/loose connection should be sorted out. Just my advice.

The valve were all marked with a number 9.

I will go back through the board and try to find anything which is loose or such.

Thanks again for your help.