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Bobo_Grimmer

Ampeg SVT CL valve's

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Hey guys, This ampeg is my first valve amp and i have a couple of questions that you might be able to answer for me.

I bought the amp back in november, brand new, with a redundancy check. ^_^

I've gigged it ever since but last sunday after i'd set up at jam i couldn't bias one set of tubes. Looking inside i could see that one of the sovtek 6550 WE's was not working.

I don't want to sound silly but:

Does that mean that the valve has gone? or could it be another problem. ( i was going to swap it with another to see if the problem moves around with that valve)

Do i just purchase a replacement and then re bias the amp?

or Could i buy a different make of valve? (tonal variation may be...)

I have two weeks off gigging now so i have a little while to get it sorted. I did have to play a gig last night but it sounded fine. :)

Any help would be great. Thank you for reading. :)

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Not working like turned white, or lost its heater glow? Most of the time valves still glow when they are dud, its possible the valve is ok but not getting its heatier current, might be individually fused. Swapping about will tell you what you need to know. Is there just one bias control? Are the valves in there marked with an indicator of their matching? If it is written on them, you might be able to order a matching one. You could just sling one in, its one of those 'chances are you'll never notice' sort of things. Ideal is replace with a matched set, and the ones taken out as spares, or sell as a used quad and one spare.

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[quote name='Mr. Foxen' timestamp='1372343284' post='2124581']
Not working like turned white, or lost its heater glow? Most of the time valves still glow when they are dud, its possible the valve is ok but not getting its heatier current, might be individually fused. Swapping about will tell you what you need to know. Is there just one bias control? Are the valves in there marked with an indicator of their matching? If it is written on them, you might be able to order a matching one. You could just sling one in, its one of those 'chances are you'll never notice' sort of things. Ideal is replace with a matched set, and the ones taken out as spares, or sell as a used quad and one spare.
[/quote]

Thanks for the replay. :) It's not glowing anymore. I'm about to go swap the about to see what happens so i'll report back. There are 2 bias controls on the back and 6 6550's. As far as i know one control does a set of three and the other does the second set of three. They have 10 12 written on them is that a matching number?

brb

Edited by Bobo_Grimmer

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Ok i moved the non-glowing one with another and the problem has stayed with that valve. so it's not a fuse issue. Like i said i didn't hear any difference last night so maybe it is ok...

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Could be matching, what brand? See if you favoured valve supplier that stocks that brand can make anything of it. If there are two bias controls, only need to replace the 3 on that control.

Edit: now I see pics, the 10 12 isn't to do with the bias matching, that would be hand written or on a sticker.

Edited by Mr. Foxen

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[quote name='Mr. Foxen' timestamp='1372345486' post='2124625']
Could be matching, what brand? See if you favoured valve supplier that stocks that brand can make anything of it. If there are two bias controls, only need to replace the 3 on that control.

Edit: now I see pics, the 10 12 isn't to do with the bias matching, that would be hand written or on a sticker.
[/quote]

Good good. I'll look into picking one up.... replace 3? would that be if they were matching groups or do i need to replace the three anyway?

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replace 3 if you want it all properly matched. You can get away with not doing so most likely. If its off though, might contribute for faster death of other valves. I tend to favour replace all with valves I get at trade price, so I can test and sell the used good ones whilst they are still good, and not lose too much money that way.

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I don't see many heater failures, but I don't really deal with that sort of valve amp/valves. Ampeg use pretty low bidder stuff, so I wouldn't have high hopes of the valves lasting.

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Hum... ok. Might be an expensive thing to gig regularly with after all. I was wondering then if i could replace them with something a little more reliable? I see the 6550's aren't that expensive compared with some like the KT88's from the trace elliot V series amps. ([size=2]i may be mistaken as i'm still learning about these things[/size])

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KT88 are similar but more rugged, although many modern KT88 are 6550 in a different shaped bottle, or even just the same. I've not had that much to do with 6550, but Shuguang power valves have done well in a cheap and good sort of way.

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[quote name='Bobo_Grimmer' timestamp='1372348383' post='2124696']
Super. i'll look into it. May invest in something a little more rugged. :)
[/quote]

I recommend the gold lion or winged C varients, they seem to have the best life out of the valves I've used.

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[quote name='longtimefred' timestamp='1372367107' post='2125032']
I have been using tung sol 6550s in my v type V4 for years, I love em and are rock solid. Bet they would sound great in a CL
[/quote]

+1 one the Tung Sol RI 6550s.. They sound great in this too..

[URL=http://s778.photobucket.com/user/VTypeV4/media/BeavisChassis.jpg.html][IMG]http://i778.photobucket.com/albums/yy70/VTypeV4/BeavisChassis.jpg[/IMG][/URL]

I've had good experiences with both the Shuguang and the EHX KT88s also..

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Thanks for the advice guys. :) i had the valve tested and it is duff. Next thing is to find a replacement.

Thing is i guess valves are in matched pairs. Now the new svt cl has two bias controls. one for the left hand set and one for the right hand set. now if they are in pairs how does that work?

Does that mean i need to find out how they are paired and replace the pair or do i need to replace the three on the left? Can you get matched sets of three?

I'm confused as to how this works...

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[quote name='Bobo_Grimmer' timestamp='1372431244' post='2125709']
Thanks for the advice guys. :) i had the valve tested and it is duff. Next thing is to find a replacement.

Thing is i guess valves are in matched pairs. Now the new svt cl has two bias controls. one for the left hand set and one for the right hand set. now if they are in pairs how does that work?

Does that mean i need to find out how they are paired and replace the pair or do i need to replace the three on the left? Can you get matched sets of three?

I'm confused as to how this works...
[/quote]

You replace the three controlled by one bias control with matched ones, the control means you have control of the balance between them and their opposites on the other half, one half push, one half pull as it were. The matching is so the three sharing a control match each other rather than matching their opposites.

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[quote name='Bobo_Grimmer' timestamp='1372431244' post='2125709']
Thanks for the advice guys. :) i had the valve tested and it is duff. Next thing is to find a replacement.

Thing is i guess valves are in matched pairs. Now the new svt cl has two bias controls. one for the left hand set and one for the right hand set. now if they are in pairs how does that work?

Does that mean i need to find out how they are paired and replace the pair or do i need to replace the three on the left? Can you get matched sets of three?

I'm confused as to how this works...
[/quote]
I know the stores selling tubes advertise selling them in pairs for the SVT,and I find that confusing too.I don't know why for instance TAD
does that.Especially as they are the best store I know when it comes to recomending the right tube for you,and keeping good quality,tested tubes.
So,like Mr. Foxen said replace all three,is probarbly the easiest way to get them matched.You can ask the dealer about what info he needs.Or maybe you can even send the three tubes to be replaced.

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I emailed Ampeg to ask just to see what they might say and got this response.

Tubes are a great way to “customize” your SVT. Every brand has its own sound and flavor of tone. As long as you use the correct type of tubes in their respective sockets, feel free try out different brands of tubes. If you are happy with the sound of the stock tubes, the brand is Sovtek.

If you are replacing tubes in an SVT CL it will have power tubes which are 6550 type (the big ones), and must be replaced at the same time with a matched set (6 tubes). It is recommended that you replace the 12AX7 tube located in the back of the amp whenever changing the power tubes. This is the Phase Inverter which is one of the hardest working tubes in your amp. It is not recommended to use KT88 type tubes as there will be inadequate cooling for tubes that size.

For instructions on biasing please refer to page 9 of the manual here [url="http://www.ampeg.com/pdf/svtcl_om.pdf"]http://www.ampeg.com/pdf/svtcl_om.pdf[/url]

Some common names for 12AX7 tubes are – ECC83, ECC83S, ECC803S, 7025, 7025S, B759, 12AX7-A, 12AX7-B, 12AX7C, 12AX7WA, 12AX7LPS.

Some common names for 12AU7 tubes – ECC82, ECC802S, ECC82EH, 12AU7A, 5814A, B749, 6189, 7316, E82CC, E182CC.


[b]Technical Support Team[/b]
[b]MACKIE | AMPEG | CRATE | BLACKHEART[/b]
[b]LOUD Technologies Inc.[/b]

This is kind of a generic answer from them and an expensive option IMO.

I ended up getting 6 new 6550's and replaced the three on the left so now i have three spares. I also picked up a new gold lion 12AX7. :) £180 delivered from [url="http://www.hotroxuk.com/"]http://www.hotroxuk.com[/url].

I've let it warm up and biased the valves. everything seems great except one thing. While the amp is on and not on standby you can hear what sounds like some static from the cabs. I haven't heard this before. It doesn't get any louder or quieter with volume change on the amp and is there without anything other than the cabs plugged into the amp.

Does anyone have or have heard this kind of noise? is it normal?

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Frying eggs sort of sound? How old is the amp, more than about 15 years? Bad capacitors do that, they die over time, and Ampeg run then really close to tolerance so they die pretty easy.

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Sounds like bad caps, but without the excuse. Ding the valves with a chopstick and see if any are microphonic, they can be from new, and makes funny noises sometimes.

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