Community: Message List - DT25 Volume drop

Re: DT25 Volume drop

support@line6.com — Wed, 30 Jan 2013 14:25:18 GMT

If I recall suggestions say about a year for power tubes (and the recommendation to change the phase inverter while you're at it), but I think that's for 'daily' use, so you might be able to get a few years out of them.

Re: DT25 Volume drop

support@line6.com — Wed, 30 Jan 2013 13:32:24 GMT

That's true of any set of trace matched tubes by any company...Not just Mesa...Trace matching is nothing new...Mesa is using a very old and reliable approach for fixed bias amplifiers....Use fixed resistors...

The problem with skipping a bias check with these amps in thier stock form is that there is a bias pot...bias pots drift over time from gshock and degradation. Especially the crappy little blue pcb types...It's a good idea to check those...

If you really want to make your amp a true fixed bias, measure the value on the pot when it is adjuted proper and replace it with a fixed resistor...

Re: DT25 Volume drop

support@line6.com — Wed, 30 Jan 2013 13:02:34 GMT

Mesa may rebrand but they pair them with like biases so if you use a particular color you dont have to rebias on the next swap. The additional testing adds just a few dollars but it is worth not having to pull the amp out of the chassie to rebias.

Re: DT25 Volume drop

support@line6.com — Wed, 30 Jan 2013 10:51:29 GMT

Update on mine: Turns out it was a "worn out tubes" issue. I guess I didn't think they would go that fast....(but I did purchase a demo model, so who knows how many hours were on it prior to me getting it).

So I've had tube amps before but never had much experience needing to change tubes but any input on how often I should expect to change them in the future. Amp is played once or twice a week at band volume.

Todd

Re: DT25 Volume drop

support@line6.com — Tue, 29 Jan 2013 14:14:54 GMT

Seconded. I've can't remember the last time I read a post where every sentence made me shake my head.

Re: DT25 Volume drop

support@line6.com — Tue, 29 Jan 2013 02:55:25 GMT

".Remember EL84s' are designed to run at 100% dissipation."

That one made me throw up in my mouth...

Re: DT25 Volume drop

support@line6.com — Tue, 29 Jan 2013 01:43:59 GMT

Mesa tubes are just rebranded by Mesa and manufactured by JJ or Sovtek etc.. Go online and buy tubes from the tubestore or another online company. Always take out and save the stock tubes as spares. They are not good for anything else. Line 6 /Fender/Bogner/Egnater etc....are not going to give you good tubes with a mass produced amp. JJs' are good and very tough in these circuits.Remember EL84s' are designed to run at 100% dissipation.Larger octal based types (6L6-EL34-6550 etc...) run at around 70% when properly biased. EL84s' are designed to have a short life so keep several sets of spares if you are taking these amps out for any higher volume work. I am hoping to grab a used DT25/50 in the near future but when I do I will change the tubes before I use it. Good Luck and Have Fun!

Re: DT25 Volume drop

support@line6.com — Sat, 26 Jan 2013 19:53:06 GMT

I recently AB'd a JJ vs the SPAX7 and it sounded the same to my ear. I kept the JJ to replace the SPAX7 when it gets crunchy.

Re: DT25 Volume drop

support@line6.com — Sat, 26 Jan 2013 19:36:12 GMT

+1...However, an AX7 inverter tube runs at much higher current than it would as a preamp tube. Typically, it is a good approach to change your inverter at the same time you change your power tubes...

I am a long time Mesa tube fan..However, .a little while back I got several GTSAGAX7 balanced inverters...In comparing those directly to the SPAX7, can't tell much difference those two...But the price is a wash between those two...both are around $20...But I can tell you that I have SPAX7s in my ADA MP-1 that might be 20 years old and are still going strong...

Re: DT25 Volume drop

support@line6.com — Sat, 26 Jan 2013 19:23:03 GMT

I should note: The phase inverter is less important to the tone stack. Any quality 12AX7 will do (eg. GT, Mesa, or JJ). The SPAX7 is on the pricey side.