Getting rid of the rattle on a Vox VT40+

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VinylfanVinylfan Frets: 11
Hi
I have a Vox VT40+ that I bought a while back and don't use that often.  When I do use it, I notice what can only be described as a 'rattle' or some kind of hiss.  Seems to go down/lessen if I turn the treble down but then I don't have any treble control.

Any ideas as to whether it can be solved or reduced in some way?

The amp itself is great - plenty of options for me, plenty powerful enough for home etc. - just wish I could get rid of this annoying rattle.

Cheers
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  • ICBMICBM Frets: 32846
    Is it reduced if you turn down the power level control as far as possible and turn up the volume to give the same overall volume?

    It could be a microphonic or faulty preamp valve. My AD15VT is quite hissy on a couple of the settings, and it's related to using the valve in a particular mode. (Boutique Clean, AC15, AC30 and Boutique OD - I know the VT40 doesn't have quite the same settings.) 

    I can't remember having opened up a VT40, but if it's anything like the AD15 it will quite a pain to get into and change the valve...
    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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  • VinylfanVinylfan Frets: 11
    edited May 12
    ICBM said:
    Is it reduced if you turn down the power level control as far as possible and turn up the volume to give the same overall volume?

    It could be a microphonic or faulty preamp valve. My AD15VT is quite hissy on a couple of the settings, and it's related to using the valve in a particular mode. (Boutique Clean, AC15, AC30 and Boutique OD - I know the VT40 doesn't have quite the same settings.) 

    I can't remember having opened up a VT40, but if it's anything like the AD15 it will quite a pain to get into and change the valve...
    Hi

    Yes, I just played around with it a bit more.  By turning down the power value and turning up the volume the hiss reduces quite a lot (to nothing in some cases).  Turning the treble down reduces it even further.

    The amp settings where the hiss was really noticeable were - US Blues; AC£); UK Metal; US Highgain; BTQ Metal - this was before turning down the power and upping the volume.  This was with all other effects, reverb, delay etc off.  Gain was set to around 10 o'clock for all of them so it was only the power level and volume that I was changing.

    So is this normal or is the valve faulty in some way?  Any other tests I should do? Should it make a difference if I leave it for the valve to get warmer or doesn't it work like that?

    Cheers
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  • ICBMICBM Frets: 32846
    I think it might be normal. I tried two different valves in mine - other than the stock one - and they all did it to more or less the same amount. After that I got fed up of fiddling with it - it's quite a nuisance to change the valve :).

    The modelling circuit does actually change the valve bias and whether one or both halves of the valve are used, it's not just a token 'valve in the circuit'. It's slightly annoying because the noisiest setting on mine is the AC30, which is - possibly not by coincidence - the best sound in the amp. (And worse, the AD15 does not have a power control, being one of the smaller amps in the range - so I can't fix it like that.)

    The valve will be fully warmed up after only about thirty seconds to a minute, after that it won't make any difference.
    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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  • VinylfanVinylfan Frets: 11
    @ICBM thanks.  I'll leave it as it is then.
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  • FunkfingersFunkfingers Frets: 3327
    ICBM said:
    I can't remember having opened up a VT40, but if it's anything like the AD15 it will quite a pain to get into and change the valve.
    It is.

    A friend of mine simultaneously owned two ToneLab type amplifiers. Peering through their rear ventilation grilles, it was obvious that the valve in one of them lacked a healthy glow. Almost every screw on the outside of the amplifier needed undoing to access the valve. It was also necessary/advisable to disengage the block connector on a flying lead to avoid the possibility of damaging it.

    Fortunately, my friend has since sold both VOX amplifiers. If he had ever asked for my assistance a second time, I think that I would have resorted to something like this.


    "It's no wonder the Pacific Ocean is blue."
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  • VoxmanVoxman Frets: 2055

    A friend of mine simultaneously owned two ToneLab type amplifiers. Peering through their rear ventilation grilles, it was obvious that the valve in one of them lacked a healthy glow. 
    I assume you mean Valvetronix amps and as you could see the tubes through the rear grill these would be the later chrome amps.  The valves don't glow because unlike the original blue series valvetronix amps there's only low voltage going through them. Any glow you saw was from an led used for marketing effect only. The led had likely packed up in the one with no healthy glow.

    Changing the valves in these amps is actually relatively easy although it's rarely needed because they should last the life of the amp particularly as they only have low voltages going through them as I said. It's the blue series that are awkward because you can only see the valve tips sticking through the chassis and in the blues they do have much higher voltages going through the tubes. But duct tape wrapped around the tube end and gently wiggling it lets you get to these without having to undo the chassis.
    I started out with nothing..... but I've still got most of it left (Seasick Steve)
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  • ICBMICBM Frets: 32846
    edited May 14
    That’s not exactly true.

    The valves do glow in the VT series, and there is no LED. Although there is no high voltage applied to the *plates*, the filaments are operated normally.

    Getting to the valve requires taking the chassis out completely, and getting it out of its holder without taking the PCB out is possible but tricky - there isn’t enough room to reach it easily by hand, you need to use something like a flat screwdriver to lever it out, and a couple of bits of wood to grab it. Guiding the new one in and pressing it into the socket is a similar faff...

    This should show why!

    http://www.voxshowroom.com/ct/amp/uk/AD_series/ad15vt_tube.jpg

    http://www.voxshowroom.com/uk/amp/ad15_hood.html

    (The description at the bottom of how to change the valve is wrong, by the way - you need to remove, not loosen, the eight chassis mounting screws, and also disconnect the speaker to get the chassis out.)
    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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  • VinylfanVinylfan Frets: 11
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
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  • ICBMICBM Frets: 32846
    Vinylfan said:
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
    Trust me, I'm a professional amp repairer and it's enough of a hassle for me that I've left mine with the slightly noisier valve I put in to see if it cured the noise with the first replacement one but didn't :).

    I'm not 100% sure if the layout of the VT40+ is the same inside, but I think it's likely to be at least similar.
    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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  • VinylfanVinylfan Frets: 11
    @ICBM - thanks, that has reinforced my decision to leave well alone!  If you're a pro and find it a hassle then I'll undoubtedly just break it!  I'll put up with the noise and at least have learnt a few ways to lessen it via this thread.

    On a separate note, I've been thinking about a valve lunchbox head as I have a spare speaker.  Will start a new thread for that.
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  • BridgehouseBridgehouse Frets: 15721
    ICBM said:
    Vinylfan said:
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
    Trust me, I'm a professional amp repairer and it's enough of a hassle for me that I've left mine with the slightly noisier valve I put in to see if it cured the noise with the first replacement one but didn't :).

    I'm not 100% sure if the layout of the VT40+ is the same inside, but I think it's likely to be at least similar.
    Pah -- that's like a professional car mechanic running a crap old escort with noisy tappets cos they can't be arsed to replace them ;)
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  • VinylfanVinylfan Frets: 11
    ICBM said:
    Vinylfan said:
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
    Trust me, I'm a professional amp repairer and it's enough of a hassle for me that I've left mine with the slightly noisier valve I put in to see if it cured the noise with the first replacement one but didn't :).

    I'm not 100% sure if the layout of the VT40+ is the same inside, but I think it's likely to be at least similar.
    Pah -- that's like a professional car mechanic running a crap old escort with noisy tappets cos they can't be arsed to replace them ;)
    i'm not getting involved in this - you girls fight it out between yourselves!
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  • BridgehouseBridgehouse Frets: 15721
    Vinylfan said:
    ICBM said:
    Vinylfan said:
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
    Trust me, I'm a professional amp repairer and it's enough of a hassle for me that I've left mine with the slightly noisier valve I put in to see if it cured the noise with the first replacement one but didn't :).

    I'm not 100% sure if the layout of the VT40+ is the same inside, but I think it's likely to be at least similar.
    Pah -- that's like a professional car mechanic running a crap old escort with noisy tappets cos they can't be arsed to replace them ;)
    i'm not getting involved in this - you girls fight it out between yourselves!
    It's a play fight - don't worry.

    It's all part of the "try to prove @ICBM wrong on something for a change" challenge.

    It's a glorious feeling when you do. Apparently..
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  • VinylfanVinylfan Frets: 11
    Vinylfan said:
    ICBM said:
    Vinylfan said:
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
    Trust me, I'm a professional amp repairer and it's enough of a hassle for me that I've left mine with the slightly noisier valve I put in to see if it cured the noise with the first replacement one but didn't :).

    I'm not 100% sure if the layout of the VT40+ is the same inside, but I think it's likely to be at least similar.
    Pah -- that's like a professional car mechanic running a crap old escort with noisy tappets cos they can't be arsed to replace them ;)
    i'm not getting involved in this - you girls fight it out between yourselves!
    It's a play fight - don't worry.

    It's all part of the "try to prove @ICBM wrong on something for a change" challenge.

    It's a glorious feeling when you do. Apparently..
    Its ok, I figured that.  Still better to step aside when the grown-ups/big boys are fighting.
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  • BridgehouseBridgehouse Frets: 15721
    Vinylfan said:
    Vinylfan said:
    ICBM said:
    Vinylfan said:
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
    Trust me, I'm a professional amp repairer and it's enough of a hassle for me that I've left mine with the slightly noisier valve I put in to see if it cured the noise with the first replacement one but didn't :).

    I'm not 100% sure if the layout of the VT40+ is the same inside, but I think it's likely to be at least similar.
    Pah -- that's like a professional car mechanic running a crap old escort with noisy tappets cos they can't be arsed to replace them ;)
    i'm not getting involved in this - you girls fight it out between yourselves!
    It's a play fight - don't worry.

    It's all part of the "try to prove @ICBM wrong on something for a change" challenge.

    It's a glorious feeling when you do. Apparently..
    Its ok, I figured that.  Still better to step aside when the grown-ups/big boys are fighting.
    Er, am I grown up or a big boy? Cos I can assure you....
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  • VinylfanVinylfan Frets: 11
    Vinylfan said:
    Vinylfan said:
    ICBM said:
    Vinylfan said:
    Seems like a lot of hassle!  If it was a simple open, remove, refit job then I'd have considered it but I think I'll only end up causing more damage!
    Trust me, I'm a professional amp repairer and it's enough of a hassle for me that I've left mine with the slightly noisier valve I put in to see if it cured the noise with the first replacement one but didn't :).

    I'm not 100% sure if the layout of the VT40+ is the same inside, but I think it's likely to be at least similar.
    Pah -- that's like a professional car mechanic running a crap old escort with noisy tappets cos they can't be arsed to replace them ;)
    i'm not getting involved in this - you girls fight it out between yourselves!
    It's a play fight - don't worry.

    It's all part of the "try to prove @ICBM wrong on something for a change" challenge.

    It's a glorious feeling when you do. Apparently..
    Its ok, I figured that.  Still better to step aside when the grown-ups/big boys are fighting.
    Er, am I grown up or a big boy? Cos I can assure you....
    Well, I haven't been around here that long but I have heard tell of the legend of Bridgehouse and his bigness (sure I just made that up). So on that basis, I would go with big boy.  That suit you Sir?
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  • BridgehouseBridgehouse Frets: 15721
    @Vinylfan - any pictures that may have been PM’d to you are fakes.
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  • VinylfanVinylfan Frets: 11
    @ICBM - too late for that kind of backtracking now.
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  • VoxmanVoxman Frets: 2055
    edited May 15
    ICBM said:
    That’s not exactly true.

    The valves do glow in the VT series, and there is no LED. Although there is no high voltage applied to the *plates*, the filaments are operated normally.

    Getting to the valve requires taking the chassis out completely, and getting it out of its holder without taking the PCB out is possible but tricky - there isn’t enough room to reach it easily by hand, you need to use something like a flat screwdriver to lever it out, and a couple of bits of wood to grab it. Guiding the new one in and pressing it into the socket is a similar faff...

    This should show why!

    http://www.voxshowroom.com/ct/amp/uk/AD_series/ad15vt_tube.jpg

    http://www.voxshowroom.com/uk/amp/ad15_hood.html

    (The description at the bottom of how to change the valve is wrong, by the way - you need to remove, not loosen, the eight chassis mounting screws, and also disconnect the speaker to get the chassis out.)
    @ICBM ; it depends on which generation of Valvetronix. There is no led on the first generation ie AD15/30VT but the VT15/30 etc and the VT+ range do have led's, and the OP's amp is a VT40+ which has an led behind the tube. The valve glow in the VT and VT+ is very faint and you won't normally see it in daylight...hence the led. The valve change on the VT and VT+ is also easier I believe than the AD15/30VT models. 
    I started out with nothing..... but I've still got most of it left (Seasick Steve)
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  • ICBMICBM Frets: 32846
    Voxman said:

    @ICBM ;
    it d
    epends on which generation of Valvetronix. There is no led on the first generation ie AD15/30VT but the VT15/30 etc and the VT+ range do have led's, and the OP's amp is a VT40+ which has an led behind the tube. The valve glow in the VT and VT+ is very faint and you won't normally see it in daylight...hence the led. The valve change on the VT and VT+ is also easier I believe than the AD15/30VT models. 
    Ah, that would explain it. I thought the + range would be just 'tweaked' versions of the VTs with a different preamp. I know we've said this before, but why do they have to keep changing *everything* the whole time?! Surely it must cost them a fortune in R&D, and each time it seems like they make them worse...

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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  • VinylfanVinylfan Frets: 11
    Ok - it is a VT40+ so how difficult is it to change the valve?  But before we get to that, is it likely to be the valve based on the tests I've done so far?  Tests have mainly been around getting the hiss/rattle reduced by turning the power level down and upping the volume (and reducing it further by turning the treble down).  

    Also, how much is a valve likely to cost?

    Thanks
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  • ICBMICBM Frets: 32846
    The hiss does definitely come from the part of the circuit that contains the valve, although whether the valve itself is responsible, I don't know.

    I can't find any inside shots of the VT40+, but if it's more like the VT30 it will be easy...



    A valve is about £10, so if you fancy having a go it's worth a try.

    http://www.karltone.co.uk/ecc83-12ax7-53-c.asp

    Sovteks (especially the WB) tend to be darker-sounding than some of the others so I would probably start there.
    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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  • VinylfanVinylfan Frets: 11
    edited May 16
    @ICBM - thanks.  I think I'll try and take the case apart first and see if I can get to the valve easily/simply.  Is it likely to be a case of undoing the screws all round, disconnecting the speaker and then hopefully being able to get to the circuit and valve?

    Edit - just watched the video properly!  So ignore the question.
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  • ICBMICBM Frets: 32846
    Vinylfan said:
    @ICBM - thanks.  I think I'll try and take the case apart first and see if I can get to the valve easily/simply.  Is it likely to be a case of undoing the screws all round, disconnecting the speaker and then hopefully being able to get to the circuit and valve?
    It’s all in the video...

    The only things I would add are that the back panel is easier to get off and put back if you loosen the side chassis bolts slightly first, and tighten them last.

    And that I don’t know what the sock thing is all about :).
    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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  • VinylfanVinylfan Frets: 11
    ICBM said:
    Vinylfan said:
    @ICBM - thanks.  I think I'll try and take the case apart first and see if I can get to the valve easily/simply.  Is it likely to be a case of undoing the screws all round, disconnecting the speaker and then hopefully being able to get to the circuit and valve?
    It’s all in the video...

    The only things I would add are that the back panel is easier to get off and put back if you loosen the side chassis bolts slightly first, and tighten them last.

    And that I don’t know what the sock thing is all about :).
    The sock was my favourite part - I've just been to M&S and bought some long beige socks in readiness!
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  • VinylfanVinylfan Frets: 11
    edited May 16
    Quick update.
    I've opened it up - slightly different to the video, but the board with the valve comes away and out quite easily.  I sprayed a little contact cleaner on the speaker connectors for good measure and made sure all the other connectors were seated in firmly.

    Anyway, the valve inside is labelled 'Ruby 12AX7AC5' in red on the tube.  I don't recall seeing any leds near the valve so I'm sure any glow is from the valve.

    Not sure if this valve is original or if I should just try another valve entirely - and if I'd notice the difference.  Any pointers gratefully received.  They had an Electro Harmonix one on the site linked to earlier and quite a choice of others.
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  • ICBMICBM Frets: 32846
    The only way you'll know if it's the valve is to try another one. Rubys are Chinese-made and all Chinese 12AX7s are brighter-sounding in general. Avoid EH and Tung-Sol if brightness/hiss is a problem - they're also bright, which is odd because they come from the same factory as Sovteks, which are much darker. Sovtek WB would be my first choice, followed by Sovtek WA, and then JJ which tend to have a 'muddy/middy' character.

    At least, this is how they perform in standard high-voltage valve amp circuits. Whether that's true at the much lower voltages here - even if the filament is running at the normal voltage - I don't know.
    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone."
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