Amp under the weather? Check those tubes!

[Red_Label]

Yeah... I know... I'm preaching to the choir.

As some of you know - I've been thinking about selling the XTC lately. It just wasn't standing up to the new [to me] VHT Ultra Lead. This week it finally dawned on me that something wasn't right with the Bogner. It was sick. I was hearing ghost notes and just general mushiness.

So last night I checked the bias and she was pretty hot (like 33-34ma). So it'd drifted in the past several months. So I pulled it back to 29-30. Still wasn't thrilled with my tone though. So today I swapped the tubes around. I usually run it at half power, so I'm only running two tubes at a time. So I swapped the tubes I had been using with the pair in the sockets that weren't being used. Bingo! My sweet Bogner came back. She was even able to do some drop-C# tight metal type tones with my new EMG-loaded Eclipse. Maybe not like the VHT with KT88s can do, but still pretty decent.

I really didn't even consider swapping tubes before because these didn't have that many hours on them. But I guess that being a bit hot for maybe several months did them in. So I'll have to get another quad on the way. Been using =C= Svetlanas, but may be in the mood to try something else.

Also got a Marvel Mod kit on the way for it to see what I can do to kick her up a notch. Maybe I can get the Bogner to put the VHT back in its place!

So if you find yourself a bit "disenchanted" with an amp that used to do it for you, you might try new tubes if you haven't done so in a while. You'd think I'd know this since I've been gigging tube amps for aout 25 years now! DOH!!!

 

[FuseG4]

Re: Amp under the weather? Check those tubes!

bit hot for several months? That sounds about right.

I had a pair of NOS 6v6 in my tweaker for about 7 months. It's cathode biased. Anyways I always ran the master on full into an attenuator. It sounded great when I initially switched to NOS and then after a while I was wondering if "maybe the tweaker wasn't my thing anymore". When I stuck the stock tubes back in before selling it to fund the DRRI, my mind was blown, and a whole mess of punch and dynamics came back.

You can run down some tubes pretty quick.

 

[crguti]

Re: Amp under the weather? Check those tubes!

something very similar happened to my Boogie DC-5. I wasn't happy with the sound. it didn't seem a loud amp (running the master on 8) and I was hearing ugly harshness. I was blaming my guitars, then the cab, then the celestion V30. What I did? I touched all tubes with a screwdriver and I found that the tube #3 was a bit microphonic. I swapped the tube for the reverb tube... and bang!!! the tone came back and is the loudest amp ever. I couldn't believe it. All this time my amp was sick and only needed a preamp tube replacement.

 

[TwilightOdyssey]

Re: Amp under the weather? Check those tubes!

That reminds me ... my Bumbox is due for a valve check!

Thanks for the PSA!

 

[Chickenwings]

Re: Amp under the weather? Check those tubes!

if you want longevity from tubes then look at JJs.

 

[FuseG4]

Re: Amp under the weather? Check those tubes!

if you want longevity from tubes then look at JJs.

as a 6v6 guy I've been reluctant to try JJs, as a bunch of people describe them as having a more 6L6 character than other new production 6v6s. I'm not totally averse to trying them, but I always wonder if it would be something I would notice or not, and if I did notice, wether I would like them or not.
JJ EL84s and 12AX7s always sounded kinda dark and strong to me. Yeah you can beat the crap out of them and they'll take it, but I always went back to EH and Tungsol because I dig the brightness.

 

[Gearjoneser]

Re: Amp under the weather? Check those tubes!

The XTC is normally biased at 35mA. One thing you've got to do when running it on half power is make sure the amp's ohms is half that of the cab.
On half power, you switch the head to 8, while plugged into a 16ohm cab, or 4, when plugging into 8ohms.

 

[Red_Label]

Re: Amp under the weather? Check those tubes!

if you want longevity from tubes then look at JJs.

I've got a set of JJs laying around and have had several before. Like many here, I do find them to be pretty dark and I prefer the brightness of the Winged-C and EHX tubes that I've been using in a couple of amps.

 

[Red_Label]

Re: Amp under the weather? Check those tubes!

The XTC is normally biased at 35mA. One thing you've got to do when running it on half power is make sure the amp's ohms is half that of the cab.
On half power, you switch the head to 8, while plugged into a 16ohm cab, or 4, when plugging into 8ohms.

Hmmm... I'd swear that Charly told me it was around 32ma. But I might be confusing that with the Shiva I had. I've exchanged several emails with Bogner on both the Shiva and XTC.

When I ordered my quad of =C= EL34s, right after buying the XTC, I didn't even think to specify that they (the SRS web store I think) make sure that the quad fit in the XTCs range. So when I got them and biased the XTC, the highest tube tested at like 31.9ma. I remember being frustrated cause I wanted to be able to get it higher, but the bias pot was maxed-out. I contemplated soldering-in a different resistor, but never did. I did run the XTC for at least an hour, several different times and it seemed to stabilize at just under 32ma each time. But somehow it must've drifted between then and now.

The two tubes that are now in there and powered-up are showing like 30ma and 24ma. And I remember that spread being big when I first got them and tested all for. I picked the two middle ones, cause I wanted the closest pair. Now that I've got the pair with the biggest spread, the amp sounds its best. Go figure! LOL. Next time I'm gonna order from a different store I'm thinkin -- one that will guarantee a matched quad that's got a closer spread than that. Also, one that will guarantee getting me a set that's in the bias range of the XTC.

Yeah, my Uberkab and OS2X12 are both 16 ohms and I run the XTC at 8 ohms and half-power. Been doing that since day one.

 

[woemoejack]

Re: Amp under the weather? Check those tubes!

I thought tubes were my Shiva's problem for a bit until this past weekend...

Opened up my cab because I had not been in there for a while and realized it was wired for a 4 ohm load, and all the while I had been running it from the 16ohm tap on the Shiva... Wired it back to 16 ohm and it is pure bliss.

 

[Red_Label]

Re: Amp under the weather? Check those tubes!

I thought tubes were my Shiva's problem for a bit until this past weekend...

Opened up my cab because I had not been in there for a while and realized it was wired for a 4 ohm load, and all the while I had been running it from the 16ohm tap on the Shiva... Wired it back to 16 ohm and it is pure bliss.

Yikes! But it just goes to show you how tough these amps can be. Because I do a lot of A/B'ing and swapping speaker cables around back and forther between my heads, on several occasions I've found myself playing, but with no sound -- only to find that I hadn't plugged the amp into a cab. Always makes me want to kick myself hard, but as of yet doesn't seem to have damaged anything.

 

[Gearjoneser]

Re: Amp under the weather? Check those tubes!

Hmmm... I'd swear that Charly told me it was around 32ma. But I might be confusing that with the Shiva I had. I've exchanged several emails with Bogner on both the Shiva and XTC.

When I ordered my quad of =C= EL34s, right after buying the XTC, I didn't even think to specify that they (the SRS web store I think) make sure that the quad fit in the XTCs range. So when I got them and biased the XTC, the highest tube tested at like 31.9ma. I remember being frustrated cause I wanted to be able to get it higher, but the bias pot was maxed-out. I contemplated soldering-in a different resistor, but never did. I did run the XTC for at least an hour, several different times and it seemed to stabilize at just under 32ma each time. But somehow it must've drifted between then and now.

The two tubes that are now in there and powered-up are showing like 30ma and 24ma.

That seems kind of low, but it is frustrating to buy a quad of tubes only to find out that they fall out of range. I had the opposite problem with some old =C='s......they wouldn't go lower than 42mA.

Charlie actually biased my XTC at 35mA (JJ EL-34) and it sounds good, but I remember it sounding a little juicier at 38mA. 33-38 is supposedly the range spec for the XTC.

Here's what Eurotubes lists as mA range for a whole bunch of amps. I'm surprised at how high some of them are. I know I've preferred Fender 6L6 amps to be around 32mA.
http://www.eurotubes.com/euro-Generic-Bias.htm

 

[TheProphet]

Re: Amp under the weather? Check those tubes!

as a 6v6 guy I've been reluctant to try JJs, as a bunch of people describe them as having a more 6L6 character than other new production 6v6s. I'm not totally averse to trying them, but I always wonder if it would be something I would notice or not, and if I did notice, wether I would like them or not.
JJ EL84s and 12AX7s always sounded kinda dark and strong to me. Yeah you can beat the crap out of them and they'll take it, but I always went back to EH and Tungsol because I dig the brightness.

I've run the JJ's in a number of beasts (they actually make me want to try out a Laney AOR 30 again)

The JJ 6V6's don't have any real 6L6 character to my ears ... JJ 6V6's would be best described IMO as a hybrid of the 6V6 and EL34.

Very good tubes in the right amp. Turned my little Champ into a Mini Marshall in some ways.

EDIT: Tung-Sols and other brands sound pretty decent at low-medium volume. With the JJ's, I've found them to be mediocre at best at those volumes, but an absolute tone monster at higher volumes.

 

[Chickenwings]

Re: Amp under the weather? Check those tubes!

as a 6v6 guy I've been reluctant to try JJs, as a bunch of people describe them as having a more 6L6 character than other new production 6v6s. I'm not totally averse to trying them, but I always wonder if it would be something I would notice or not, and if I did notice, wether I would like them or not.
JJ EL84s and 12AX7s always sounded kinda dark and strong to me. Yeah you can beat the crap out of them and they'll take it, but I always went back to EH and Tungsol because I dig the brightness.

yeah man. I like tung sols too for 6v6, cos they sound like a 6v6! But i do have a set of jjs also, which are definitely more towards being 6l6 sounding in that they are bigger, more hifi, more headroom kind of sound. So yeah - i like 6v6s that sound like 6v6s too, but you know...some ppl want different things from their amps.
I was really juts making a pretty broad sweep about JJs in general, ive tried them instead of other brands 6l6, EL34, EL84 and 6v6.....and if its purely headroom and longevity a player is after then they are really heads and shoulders above the others.

edit: i think Mr Prophet is spot on in his assessment about jjs vs other brands at different volume levels too.

 

[Nightburst]

Re: Amp under the weather? Check those tubes!

Are you crazy man! :eyecrazy:

I've told you before and I will do it again. Just trade that Bogner classic in for a regular ecstasy 101b or 101a (because maybe you just like 6L6's more than EL34?)
Then put some higher gain tubes in the pre amp and behold in awe how monstrously heavy it can get. Perhaps the classic will take high gain tubes well also. But i doubt it because the classic is tailored in both the power and pre-amp to give the amp a more 'vintage' character. Which means not suitable for tight leads an chugga metal stuff. The classic IS more of a country/blues amp. The regular 101 is the amp that does it all. I have one so I know what I'm talking about.

Basically what you are about to do with the marvel mod is to turn a classic pre-amp into a regular modern 101b pre-amp. But the power amp remains 'vintage'. I have a feeling that this mod will only introduce unwanted fizz in a carefully thought out design. According to the Bogner website their amps have been given a factory gain upgrade from around 2003 because so many people wanted it. This is basically what the marvel mod is except that there is no fancy extra switch. I strongly urge you to think about this and read up on the bogner website, it's all there. The 101b is the amp you will love, it simply does everything as long as you set it up right. If you decide you don't like it, which is a good possibility in your case you won't have a decreased resale value because you have been tampering with the circuit.

I've been experimenting with a couple of tubes and also had a couple of matched set's I couldn't use because I have an old xtc just like Gearjoneser.
I've contacted the guys at Bogner about this and they told me that a simple mod to the bias resistor will address this issue. The original Ecstasies (the white chassis models like GJ and I have) were designed with Siemens tubes in mind in the 90's. Those tubes would today be called NOS and sell for the price of a small amp.
Right now I use a pair of 'cold' JJ E34L's. They are supposed to have some 6L6 traits. I dont know about that but they sure make my amp sound huge and fat. Better low end than EL34's, especially =C='s which are great tubes but wear out quickly. I've experienced this with 2 sets and read more people on the net having had this as well.
the only thing that is tricky with the E34L's is that they will bias at minimum of around 40mA which is a tad hot but the amp takes it for 3 years now and seems to be fine.
Next I think about using some normal EL 34 Mullards or Tung sol's.

 

[Red_Label]

Re: Amp under the weather? Check those tubes!

Yeah, I admit that I wouldn't mind trying a 101B. I'm just hesitant right now to sell/trade my Classic for fear of taking a loss on it. It's just HORRIBLE out there right now in the used market. I'd probably trade a guy straight across. But I'd want a metal grill or a black one like my Classic. I guess I could trade a guy just the amp guts and we could each keep our headshells.

Anyways... I may float that trade offer on a couple of the forums depending on what happens with the mod. It's totally reversable, but it's an easy thing for me to try. I gotta say though, I've been pretty happy with the Classic again since I swapped tubes around on Saturday. I was really loving the drop-C# tones I was getting last night with the 18v EMG setup in my new ESP. And I forgot that I've got a set of JJs that I might try in there tonight as well just to see how it sounds with them. They are not EL34Ls though. Just the regular ones.

 

[richard parker]

Re: Amp under the weather? Check those tubes!

I recently put Tung Sol EL34Bs in my Cornford and they are wonderful. Took a few hours playing in but now they are the best sound improvement I've ever heard from changing tubes. I re-tubed a 5 tube pre-amp in a 50w combo with JJs on the enthusiastic recommendation of the vendor and found them very uninspiring - dull and lifeless. The original no name Chinese pre-amp tubes were much better.

 

[misterwhizzy]

Re: Amp under the weather? Check those tubes!

I recently put Tung Sol EL34Bs in my Cornford and they are wonderful. Took a few hours playing in but now they are the best sound improvement I've ever heard from changing tubes. I re-tubed a 5 tube pre-amp in a 50w combo with JJs on the enthusiastic recommendation of the vendor and found them very uninspiring - dull and lifeless. The original no name Chinese pre-amp tubes were much better.

Does anyone really like JJ preamp tubes as tone generators? I've got one as my PI right now that I like a lot, but other than that, I just cannot get along with them. Ever.

 

[FuseG4]

Re: Amp under the weather? Check those tubes!

Does anyone really like JJ preamp tubes as tone generators? I've got one as my PI right now that I like a lot, but other than that, I just cannot get along with them. Ever.

I used them for a while in my DSL, I think. The DSL is bright and gainy, and the JJ helped to put a little girth in there.