Replacement Tubes for Ampeg SVT CL

[JGbassman]

Hey all, it's looking like it's time to finally replace the tubes in my beloved Amgeg SVT CL, as the original tubes are a little older than ten years, and have lost that shimmer. They are still working ok, the sound is just dull compared to what it used to be.

Saying that, I'm looking for a set of matched tubes. I know there are many threads on this matter, but in this age tubes sources have been drying up, changing, and what was relevant a few years ago might not be today. I'm looking for anyone's experience with a certain vender or seller as of late, or a various brand.

I'm not a tube roller, nor do I even know that much about them. To be honest, I couldn't even tell you what brand of tubes are in my CL. As they are factory stock, I'd assume JJ tubes, but I don't know.

Speaking of JJ tubes, I've seen a few ads on eBay for JJ sets. Are there differences in these? I've noticed some are made in Europe, some in China. Are there other brands of tubes that are better quality? Like I said, I don't know much about tubes, so I thought I'd reach out here and see if one of you knowledged souls could direct me to the path of enlightenment.

Thanks in advance.

 

[beans-on-toast]

Changing a set of tubes in a CL is expensive. If cost is an issue, start with just the small signal tubes, what many call the pre-amp tubes They are located in the top chassis as well as the bottom one in your amp.

Sounding dull as you described is often down to a tube in the preamp or the power tube bias not being set properly.

As for the power tubes, if they can be biased with the LED's, they still have life in them.

Here is a pointer to know when to change tubes in the TalkBass Portaflex Wiki.

Tubes | TalkBass.com

The age of the tubes doesn't matter, it's how much they have been used and how hard they have been driven.

The most important consideration when buying tubes is to find a vendor that sells tubes that have been burned in, tested for noise and other issues, and matched with a high attention to detail. There is a lot of variation in the methods that are used by resellers. Some out and out lie and will sell bad tubes and poorly matched sets. So you have to be careful.

Pay attention to the warranty offered. Use the tubes to check them out when you receive them. Never just put them in storage for when they are needed, well after the warranty period.

There are many good vendors, I avoid ebay. I like these places, no particular order:

Their Apex matching system is good.
Tubes | TalkBass.com

Invalid Link Removed

Excellent testing and matching. Selection is limited relative to the others.
tctubes.com vintage vacuum tubes

 

[JGbassman]

Thanks beans,

Money isn't an issue, this amp is a money maker for me and will be gigged about 1-2 times a month for a high end tribute band, with shows 60-90 minutes. Sound and reliability are the two that matter the most.

I did tour with this amp, so it's seen thousands of miles and probably close to a thousand shows. I do run the master gain 80%+, and set volume with the pre gain for stage volume. Not sure if that would be considered pushing the tubes or not.

The power amp tubes still seem to bias fine according the the lights on the amp, it's just a little dull. I might try changing out the preamp tubes and see if that does the trick. That certainly is a cheaper route to go for sure.

I will definitely look into the sites you posted, and I value your input on this greatly, which I thank you for.

 

[beans-on-toast]

Thanks beans,

Money isn't an issue, this amp is a money maker for me and will be gigged about 1-2 times a month for a high end tribute band, with shows 60-90 minutes. Sound and reliability are the two that matter the most.

I did tour with this amp, so it's seen thousands of miles and probably close to a thousand shows. I do run the master gain 80%+, and set volume with the pre gain for stage volume. Not sure if that would be considered pushing the tubes or not.

The power amp tubes still seem to bias fine according the the lights on the amp, it's just a little dull. I might try changing out the preamp tubes and see if that does the trick. That certainly is a cheaper route to go for sure.

I will definitely look into the sites you posted, and I value your input on this greatly, which I thank you for.

Ten years out of the tubes in a gigging amp is pretty good.

If you change out your power tubes. Keep them as spares. Make sure you label them so that they can go back into the same sockets. That helps keep the set matched and the three on each push and pull side balanced.

The master volume in the CL is an attenuator. The lower it is set, the more it knocks down the preamp signal level. Running it around 80% makes no difference in how hard the tubes are pushed. Running the master set closer to zero and the gain set high will run down the preamp tubes faster. They are being driven hard into distortion at a low volume level. What pushes the power tubes hard is high gain and master settings. This sends a higher level signal to the power amp. Loud out the speakers is pushing the power tubes harder. But that's how the amp was meant to be used.

 

[JGbassman]

Ten years out of the tubes in a gigging amp is pretty good.

If you change out your power tubes. Keep them as spares. Make sure you label them so that they can go back into the same sockets. That helps keep the set matched and the three on each push and pull side balanced.

The master volume in the CL is an attenuator. The lower it is set, the more it knocks down the preamp signal level. Running it around 80% makes no difference in how hard the tubes are pushed. Running the master set closer to zero and the gain set high will run down the preamp tubes faster. They are being driven hard into distortion at a low volume level. What pushes the power tubes hard is high gain and master settings. This sends a higher level signal to the power amp. Loud out the speakers is pushing the power tubes harder. But that's how the amp was meant to be used.

Ok, sounds like I might have been doing something right at least, lol.

I'm not a distortion guy, I like my amp and speakers clean with just a little growl and tube compression when I dig in my strings. I generally set my master to about 12-4 o'clock, based on the gig. Preamp gain controlling volume, I never got past 12 o'clock, generally kept it around 9 o'clock. I let the PA do the heavy lifting. It is/was always transported in a heavy duty road case, and given time to acclimate to the stage before turning on. In the winter months, the road case would let the amp cool off slowly when placed back in the trailer.

One last question.

Upon further reading, I've decided on just replacing the entire tube set, and going to keep the original set as spares. Which ones run as sets? Looking from the rear, there are the three banks of power tubes. Do they run in line, front to back, (I'll assume this is the case) or matched running long ways (handle to handle, for a lack of better orientation description)

When I replace them, I'll want to mark the originals as sets, so I want to be sure.

I suppose I could find this information on the web, I should probably quit being so lazy..

Anyway, thanks again.

 

[beans-on-toast]

Ok, sounds like I might have been doing something right at least, lol.

I'm not a distortion guy, I like my amp and speakers clean with just a little growl and tube compression when I dig in my strings. I generally set my master to about 12-4 o'clock, based on the gig. Preamp gain controlling volume, I never got past 12 o'clock, generally kept it around 9 o'clock. I let the PA do the heavy lifting. It is/was always transported in a heavy duty road case, and given time to acclimate to the stage before turning on. In the winter months, the road case would let the amp cool off slowly when placed back in the trailer.

One last question.

Upon further reading, I've decided on just replacing the entire tube set, and going to keep the original set as spares. Which ones run as sets? Looking from the rear, there are the three banks of power tubes. Do they run in line, front to back, (I'll assume this is the case) or matched running long ways (handle to handle, for a lack of better orientation description)

When I replace them, I'll want to mark the originals as sets, so I want to be sure.

I suppose I could find this information on the web, I should probably quit being so lazy..

Anyway, thanks again.

The power tubes are grouped in two sets, the triangular three on the left and the triangular three on the right. I would draw a picture, assign a number to each socket on the drawing and mark each tube with the associated number. Just to have that record.

The preamp tubes are in the top chassis, some disassembly required to change them. The tubes in the bottom chassis ate easier to get at.

 

[JimmyM]

I'm totally happy with the JJ's in my HSVT-CL. Have tried a few different ones in the preamp, like a new Tung Sol and a handful of NOS tubes that I still have, but they're all too bright for my tastes while the JJ's make it sound like my 69 with all NOS tubes.

 

[JGbassman]

I'm totally happy with the JJ's in my HSVT-CL. Have tried a few different ones in the preamp, like a new Tung Sol and a handful of NOS tubes that I still have, but they're all too bright for my tastes while the JJ's make it sound like my 69 with all NOS tubes.

That's cool, I'm not trying to reinvent the sound, I'm happy with the way it sounds with the stock tubes, I'd just like it back to where it was. If those are the stock tubes then that's good enough for me.

The combination of Geezers and Pro Steel strings gives me the midrange growl I love, so I don't need a crazy bright set of tubes. I'm not even sure what comes stock in them, to be honest.

Ampeg spent a lot of research time developing a formula to make the amp sound good. Whatever they chose is good enough for me.

 

[JGbassman]

I also watched a video where they were matching the tubes in groups of three to get them as even as possible. I like how he had the numbers written on the tubes themselves. It that common practice to have the values written on the individual tubes so they can be grouped?

 

[JimmyM]

I also watched a video where they were matching the tubes in groups of three to get them as even as possible. I like how he had the numbers written on the tubes themselves. It that common practice to have the values written on the individual tubes so they can be grouped?

Yeah, it won't hurt them.

 

[JimmyM]

That's cool, I'm not trying to reinvent the sound, I'm happy with the way it sounds with the stock tubes, I'd just like it back to where it was. If those are the stock tubes then that's good enough for me.

The combination of Geezers and Pro Steel strings gives me the midrange growl I love, so I don't need a crazy bright set of tubes. I'm not even sure what comes stock in them, to be honest.

Ampeg spent a lot of research time developing a formula to make the amp sound good. Whatever they chose is good enough for me.

Well the regular CL comes with EHX and Sovtek tubes while the Heritages come with JJ's. And I've played plenty of CL's with the EHX/Sovteks and they always sound fine to me, too.

 

[JGbassman]

Well the regular CL comes with EHX and Sovtek tubes while the Heritages come with JJ's. And I've played plenty of CL's with the EHX/Sovteks and they always sound fine to me, too.

Ah, I didn't know that! Now you have my wheels turning. Sounds like the JJ's might be an upgrade in the eyes of Ampeg, as the Heritage is their flagship. Hmm.

 

[Wasnex]

I also watched a video where they were matching the tubes in groups of three to get them as even as possible. I like how he had the numbers written on the tubes themselves. It that common practice to have the values written on the individual tubes so they can be grouped?

Ideally you buy a matched sextet of 6550s. The tubes are matched for plate current (PC) and transconductance (TC), and the ratings are typically indicated on the base of the tubes. Next best would be to buy two matched trios that are relatively close. This works with an SVT because it has a bias control for each trio of output tubes. Some models of SVTs also have a PI balance control as well, although I believe this feature is missing on the CL.

Here's an image where you can see the ratings.Link Removed

FYI, Different vendors use different equipment and voltages to test and grade their tubes. The point is the matching process is not standardized, so you can't use the PC and TC ratings from different vendors to create a matched set. However, if you buy multiple sets of tubes with the same rating from the same vendor, the matching should be relatively good. Unless, of course, they change their matching process.

 

[JGbassman]

I'm planning on buying a matched set from one of the venders listed by beans, so that won't be an issue. By having the numbers, I can get the tube sets as closely matched as the purchase will allow. Seems I've learned quite a bit today. I definitely thank everyone for their input, and by all means if anyone else has anything to say I'm all ears.

 

[Wasnex]

I'm planning on buying a matched set from one of the venders listed by beans, so that won't be an issue. By having the numbers, I can get the tube sets as closely matched as the purchase will allow. Seems I've learned quite a bit today. I definitely thank everyone for their input, and by all means if anyone else has anything to say I'm all ears.

The numbers are essential if you have an amp that does not have variable bias, like a Mesa 400. The ratings will determine how much current the tubes pull on idle.

Since an SVT has variable bias, the specific ratings are not as important. You set the tube current with the bias controls.

However a vendor may ask if you want early or late breakup, which also relates to the ratings.

 

[coreyfyfe]

I'm planning on buying a matched set from one of the venders listed by beans, so that won't be an issue. By having the numbers, I can get the tube sets as closely matched as the purchase will allow. Seems I've learned quite a bit today. I definitely thank everyone for their input, and by all means if anyone else has anything to say I'm all ears.

I just put a set of tung sol reissue 6550s in my 74 SVT. Ordered them from TC tubes as linked above. They're good about their testing/matching process and if you mention they're for an SVT on the order form they'll do the testing at full amp voltage (usually test up to 500V if you don't provide the higher number).

A little pricier than other vendors, but I've not gotten a bad set of tubes from them.
tctubes.com vintage vacuum tubes

 

[Windowliquor]

I can vouch for eurotubes.com. I needed a set for a Traynor YBA300, ordered on a Saturday and had them midweek. Reasonably priced and have performed like champs for a year so far.

 

[JGbassman]

I can vouch for eurotubes.com. I needed a set for a Traynor YBA300, ordered on a Saturday and had them midweek. Reasonably priced and have performed like champs for a year so far.

Rob are you in the U.S. Or overseas? Just trying to get an idea on logistics.

 

[Wasnex]

Rob are you in the U.S. Or overseas? Just trying to get an idea on logistics.

Eurotubes is a US company that sells exclusively JJs.

Eurotubes - Vacuum Tubes by JJ Electronic - ECC83, 12AX7, 6L6. 6L6GC, EL84, EL34, KT77, KT66, KT88 - Eurotubes Inc.

 

[JGbassman]

Ok, I'm noticing there are KT-88 being offered as well as the 6550's for power tubes. It's saying the KT-88's are compatible, is there a difference? My amp is spec'd with 6550's, I don't want to mess it up.