Bogner 20th XTC Tubes Make or Break the Tone

[DaveP]

I recent picked up another XTC 20th with 6L6's. I had one a couple of years ago and always missed it.
This one came loaded with JJ power tubes and JJ preamps throughout.

Well the sound was not as I remembered. This one sounded shrill and buzzy. The clean was OK but channel 2 and 3 sucked. Horrible tone.
I ordered a matched quad of Winged "C" 6L6's to replace the JJ's (which arrive tomorrow). In the meantime I replaced V1, V2, V3, V5 with some Electro-Harmonix 12AX7EH .
With just the preamp tube change the result was amazing. the shrill buzzing tone was gone and rich tone I remembered was there.

I can't wait to replace the power tubes and bias this as it should be. I think the previous owner just stuck these in without adjusting or checking the bias.


Bottom line. I think JJ's tubes suck in this amp (edited). IMO
This amp requires the proper tubes and bias (edited)

 

[mooncobra]

I have had JJ's that sounded good.

 

[SavageRiffer]

I recent picked up another XTC 20th with 6L6's. I had one a couple of years ago and always missed it.
This one came loaded with JJ power tubes and JJ preamps throughout.

Well the sound was not as I remembered. This one sounded shrill and buzzy. The clean was OK but channel 2 and 3 sucked. Horrible tone.
I ordered a matched quad of Winged "C" 6L6's to replace the JJ's (which arrive tomorrow). In the meantime I replaced V1, V2, V3, V5 with some Electro-Harmonix 12AX7EH .
With just the preamp tube change the result was amazing. the shrill buzzing tone was gone and rich tone I remembered was there.

I can't wait to replace the power tubes and bias this as it should be. I think the previous owner just stuck these in without adjusting or checking the bias.


Bottom line. I think JJ's tubes suck balls. IMO
This amp requires good tubes not shit tubes you put in an amp before selling it. This goes for all amps. The amp can be great but if you use crappy tubes it will never sound good.

Sorry to tell you man but JJ's don't suck. Tube can help shape your sound a bit, but they don't make it. JJ's are reliable, and all the builders who've been using them for years do so for a reason. There are cheaper tubes out there, but JJ's give them consistency. I call bullshit on anyone trying to make the tube debate. I've had a lot of amps and tubes and maybe have seen 1 bad JJ preamp tube and 1 bad JJ power tube. That's a pretty damned incredible track record for their brand.

As far as I know, and I've owned many Bogners, is Bogner uses Sino preamp tubes, not JJ. They use JJ power tubes, not preamp tubes. Moreover, I doubt you'd have such dramatic improvements from a preamp tube swap. Moreover, JJ's typically have lower noise than the EH preamp tubes and a little more clarity. I know that from experience.

 

[PBGas]

Ventura will have some good thoughts on this one....

 

[Ventura]

Ventura will have some good thoughts on this one....

Ha!!

What am I, the "tube savant" or something??!?!

Typically I would be able to chime in here, but unfortunately I'm not a 6L6 guy. That right there means I can't speak with any experience or authority on the matter. However, JJs are not always bad tubes - in fact - they're very robust and can take a lot of abuse and pV moreover a lot of competing brands. Of the tubes that are in there - are they biased hot enough? That can make a huge difference, and of course, making sure they're all working well as a quad. The other thing that should be carefully looked at and prodded at with an eraser tipped pencil is pinging each of the preamp tubes. If a preamp or two are dying, it'll run all the way through the signal chain and make it sound like shit.

A nice Genalex ECC83 in V1 is always a plus; and a solid performing PI valve like LPS or EiYugo (providing it's not microphonic, ahem) can do wonders to fatten up the tone.

That's all I have for you. Ping the preamps - check 'em for microphonics; swap out V1 to brighten, tighten, or level the overall tone; get a solid muscular PI slot valve in place to keep the 2 waves happy and smooth; then sure - check your power valves.

But in short - NO 20th Anniversary XTC should sound anything other than heavenly - period

(and I'm sorry I don't have more intel on 6L6 tubes, but if you connect with Jon at www.thetubestore.com he'll point you in the right direction guaranteed!!)

 

[DaveP]

Well I have never had luck up JJ's. I'm glad they worked for some. Very generic sounding to me. The EH were an improvement.
Thanks for the tips Ventrua once I bias the SED Winged "C"'s I'm sure it will be an improvement.

 

[steve_k]

If these are the factory JJ tubes, here's the deal....the 20th XTC has about 530 VDC plate voltage. Most likely, if you check the bias on it before you pull them, you will find the bias down around 15-20. This is very cold for these tubes, but with the excessive PV, its a safe bias. Also, Bogner amps have a lot of upward bias drift while playing. SED Winged C's are good tubes for handling the high PV but in my experience, don't match well with the XTC. If you want to get the most out of it, go with Gold Lion KT77's. They can handle the PV and deliver the goods.

That said, I have no problem with JJ's in most amps.

 

[Ventura]

If these are the factory JJ tubes, here's the deal....the 20th XTC has about 530 VDC plate voltage. Most likely, if you check the bias on it before you pull them, you will find the bias down around 15-20. This is very cold for these tubes, but with the excessive PV, its a safe bias. Also, Bogner amps have a lot of upward bias drift while playing. SED Winged C's are good tubes for handling the high PV but in my experience, don't match well with the XTC. If you want to get the most out of it, go with Gold Lion KT77's. They can handle the PV and deliver the goods.

That said, I have no problem with JJ's in most amps.

Was gonna offer this as an option but the Genalex (aka Gold Lion) don't make 6L6 tubesets.

Preferred Series 6L6 from www.thetubestore.com would be a safe bet - and I'd still recommend a preamp re-do as well.

 

[steve_k]

If these are the factory JJ tubes, here's the deal....the 20th XTC has about 530 VDC plate voltage. Most likely, if you check the bias on it before you pull them, you will find the bias down around 15-20. This is very cold for these tubes, but with the excessive PV, its a safe bias. Also, Bogner amps have a lot of upward bias drift while playing. SED Winged C's are good tubes for handling the high PV but in my experience, don't match well with the XTC. If you want to get the most out of it, go with Gold Lion KT77's. They can handle the PV and deliver the goods.

That said, I have no problem with JJ's in most amps.

Was gonna offer this as an option but the Genalex (aka Gold Lion) don't make 6L6 tubesets.

Preferred Series 6L6 from http://www.thetubestore.com would be a safe bet - and I'd still recommend a preamp re-do as well.

Was his 20th a 6L6? My bad. Still, same cold biasing from the factory to preserve tubes.

Substitute GL KT66 for 6L6 family.

 

[Ventura]

If these are the factory JJ tubes, here's the deal....the 20th XTC has about 530 VDC plate voltage. Most likely, if you check the bias on it before you pull them, you will find the bias down around 15-20. This is very cold for these tubes, but with the excessive PV, its a safe bias. Also, Bogner amps have a lot of upward bias drift while playing. SED Winged C's are good tubes for handling the high PV but in my experience, don't match well with the XTC. If you want to get the most out of it, go with Gold Lion KT77's. They can handle the PV and deliver the goods.

That said, I have no problem with JJ's in most amps.

Was gonna offer this as an option but the Genalex (aka Gold Lion) don't make 6L6 tubesets.

Preferred Series 6L6 from http://www.thetubestore.com would be a safe bet - and I'd still recommend a preamp re-do as well.

Was his 20th a 6L6? My bad. Still, same cold biasing from the factory to preserve tubes.

Substitute GL KT66 for 6L6 family.

 

[Loudness250]

JJ tubes are pretty good man. You just need to learn more which I'm sure you are from these dudes. Very knowledgable folks here. I know alot about tubes too but I would have given you the same advice these guys did.

 

[Ventura]

JJ tubes are pretty good man. You just need to learn more which I'm sure you are from these dudes. Very knowledgable folks here. I know alot about tubes too but I would have given you the same advice these guys did.

Kind words, Loudness250...!!

Let's bring RT back to where it once was!! The best gearhead forum on the net... Get involved, speak up, login, engage, and BRING IT!!!

Good to be back
Unkle Mo

 

[DaveP]

Thanks for all the advice. I appreciate it.

 

[DaveP]

Update:
Tested the JJ's and the bias was 13mA. So it was very cold.
I installed the new SED Winged "C" match quad and tested again. The bias read 34mA so I didn't have to pull the chassis to adjust. Bonus.
The sound is back. Now it sounds like it should.

Question: being the other tubes had a bias of 13 would the bias control even have the range to adjust correctly of would a resister be required to adjust the controls range?
For reference the plate voltage measured 525

 

[Ventura]

Update:
Tested the JJ's and the bias was 13mA. So it was very cold.
I installed the new SED Winged "C" match quad and tested again. The bias read 34mA so I didn't have to pull the chassis to adjust. Bonus.
The sound is back. Now it sounds like it should.

Question: being the other tubes had a bias of 13 would the bias control even have the range to adjust correctly of would a resister be required to adjust the controls range?
For reference the plate voltage measured 525

That's a very peculiar scenario

Just a tip, 34mA is a touch hot, but not bad...32mA is primo. But whatever, if you're not demanding full throttle from your amp, it'll sound warm and lush and low to moderate levels at 34mA.

Are you sure the bottles that were originally in there were 6L6s??!?!!? I can't believe how cold that is - that's nuts. I'd not worry about the why's so much as the "got it fixed now and life is good", but there's something not adding up with the glass being at 13mA per bottle with stock JJ 6L6 tubes - only to change to =C= and have them fall immediately within the range of "right". It's almost as though those 6L6 were accidental EL34s.

Trying to think outside the box,

But hey - NOW IT SOUNDS LIKE SEX SO GO HAVE SOME FUN!!!!

 

[DaveP]

They say JJ 6L6GC from The Tube Store. I tested all the tubes using a Mercury Tube Tester and they all tested good, no shorts or anything.
I was surprised at the reading of 13mA and by replacing them the bias fell into the acceptable range of 34mA

Bogner stated:
You can run the tubes at 40mA, but the tube life will be shorter.
Charlie recommended that you bias it a little lower, at around 32mA or thereabouts. So 34 should be OK,

As long as it's back to normal I'm good.