Mesa/Boogie 750151F SPAX7 Preamp Tube Reviews

No noise gate needed with these in the gain stages of my TC-100. Channel 3 doesn't even need a noise gate.

Replaced all preamp tubes from the original Mesa 35 Mark 5 with SPAX7s. Not a massive difference because the original Mesa tubes are pretty high quality to begin with. But one noticeable difference is the ability to clean up the tone on the gain channel using the volume knob. You can go from Medium high gain to edge of breakup by rolling it down to 3 on the volume. I replaced them all but I bet you would get the same results by just replacing V1 and V2.

Hard to find decent tubes these days w questionable manufacturing/availability coming out of China and Russia. These 12AX7s must pass an array of tests before getting the SPA pick. Just a better tube quality with greater odds you won't have a failure. You can certainly pay more but I do not really think you are getting a "better" tube. I will buy a few of them whenever stock comes in just to have on hand. I run a large Synergy system so one can always use preamp tubes on hand.

I pulled out the stock JJ from my Orange Terror Stamp and replaced it with the Mesa STR tube. Before the Stamp was on the icepick side of tone, now it's much more warm sounding and makes the hybrid amp more suited to my style of playing. I'm very satisfied, the slightly higher cost is completely negligible in my book considering the warranty and results.

I replaced all the pre amps in my DSL40 SPAX7 in V1 12AX7 in V 2 and 3 and a AUT in V4. What a power house this amp is now. Can't go wrong with boogie tubes.

I replaced V1 and V2 of my JP2C with these, and heard a noticeable improvement in the clarity and sound of the amp. I can't be sure if replacing these with the "regular" preamp tubes would have yielded a similar effect, but... I'll stick to these.

Put in V1. Amp is much quieter. Everything sounds better...cleans, crunch, overdrive. Will replace other tubes with MESA tubes as I can afford to. Highly recommended. Sweetwater’s packaging is the best.

Note: Had to cut the shrink sleeve to get it to fit. Not a big deal.

Cleared out some GT 12AX7's and used this in the power section as I was told by a salesperson and Wow !! this in the V1 alone is incredible but I will be investing in more because my amp V1,V2,V3 are pre amp and I am think of the clarity and headroom I will have if I put 2 more of these in V2 and V3 because V1 with Mesa 12AX7-A in the others is just incredible especially in my Carvin Legacy VL100

Not a NOS tube. Wasn't expecting one.
But it delivers clean sound for modern production preamp tube. Much less noise and microphonics compared to the older used up tubes they replaced in the cathode follower and phase invertor and V1 positions.
My clean channel is more pristine.
First time trying these specifically. Great first impression.
Would buy them again. Also use one in a Vox Valvetronix Head. That is quite a positive change in that backup amp. I would put it up for a gig without a second thought. Before? Not a "go to" amp. Now it could be.
There is a difference between them and the Mesa 12AX7 tubes they replaced in the Vox and the Lee Jackson. SPAX7 is quiet and cleaner when compared in my setup.
Not a holy grail tone. Just "Does the Job" and sounds good.

I recently picked up a very used AD30VT and ordered a variety of 12AX7 to find what worked the best. The SPAX7 won, giving plenty of grunt along with great clean tones and with the lowest noise signature,

Usually a new set of tubes is a bunch of fun. These are next level and have my Triple Rec screaming. I am not sure I can ever go back now

Put one of these in the V1 of my Blues Jr and gold pin JJ"s in V2 and V3. Amazing sounds of bliss, no hum and warm articulation with plenty of volume and headroom. Great tubes!

Picked up a used Mark V combo and, like buying a new house you change the locks and toilet seats, I decided to replace all of the tubes. Got the tubes, loaded them up, all is well. The previous owner had a JJ 12ax7 in V1 (the input stage for all channels), which caused Channel 1 to break too early. Now it's as clean as can be. I actually used these tubes for all input positions. Every channel is articulate, punchy, and strong. Just like you'd expect a Boogie to be..

Even better, Mike Harris made sure that the tubes went out as fast as possible and I received them in record time. Ordered Wednesday, got them on Thursday, now ready for a festival gig on Saturday.

I have tried a few of these and they do make a world of difference.

I replaced all seven pre-amp tubes (12AX7) on my Mark Five with these SPAX7 tubes. Excellent performance!! Well worth the few extra dollars!!

Sweetwater is always a great place to get your gear!!

I have a Fender 2x12 HRD and can't be happier for going with these! Quiet when the volume is down, but a great response when turned up. So nice to turn the amp up and control volume with the guitar, getting Santana-like tone from the amp without any pedals. Clean is beautiful. Don't spend time deciding like the rest of us and just go with these... you will love them!

They are excellent tubes. They did not however fit inside my amp's tube shields so I had to remove the shields and leave the tubes unprotected.

Worth the extra price,improvement over most other 12AX7 tubes. I tested the SPAX7 against three others; a Mullard, a JJ, and a stock one from a Marshall 1watt tube amp, in everything I could find that uses a 12AX7 preamp tube. The Mesa/Boogie shined the brightest in my DSL1CB. It even changed a cheap, huge Behringer tube pedal into a great drive pedal for guitar,bass,vocals,synths. Subtle but just right for most uses.

I'm using it on a dual mic preamp, and it gave awesome results, nice round, warmth, clear sound. Totally recomendable!

I had a gig coming up and my Mesa Roadster was having some tube issues. Sweetwater was all sold out of the normal Mesa 12AX7 unfortunately so I figured I'd give these SPAX7s a shot since I needed some tubes asap. They're really great sounding tubes. Very quiet! I could barley tell my amp was even turned on when I wasn't playing! Even though they're supposed to be no different from the normal 12AX7, I still noticed a small difference in tone. Not a huge difference... but each channel's characteristics were slightly "tweaked" by the change.

Mesa recommends that you use this tube in the V1 position... I'll probably do that next time but use regular 12AX7s for the other positions.

This one is a consistent performer. Offered at a really decent price,definitely worth the dinero. We purchased our first one to add to an ART preamp that we use to warm up bass and vocal tracks. After a short break-in period, the change was obvious- livened things up nicely. Have since stocked up on a few, use them when appropriate. They are not the best option for every single 12AX7 tube socket; a random switch out across a handful of small tube amps showed mixed results. All the amps, in various degrees, sounded better than with the stock Chinese tubes,but wow...the SPAX7 we added to a Blackstar HT-1HR Mkii head, alongside a Genelec 12AU7, made the biggest difference off all. We've been recording with that head for a while now and it's been an ear-opener listening to the same tracks duplicated after the tube change. It was fun and cool experience..and a blast,like a break-in party for an old amp after a high $$ upgrade. Replacing the Genelec with a less expensive Tung-Sol, the amp still sounded great, with the shine to the tone obviously sourced from the SPAX7. Very satisfied with price,performance,and consistency, so we keep a few stocked up. Best source is Sweetwater, and the tubes always arrive in new, unbroken condition.

Sounds good - as expected.

I put one of these in my Hartke HA3500 and its not bad. The tube added a little bit of brightness to the tone. Give it a try.

I decided to upgrade some of my tubes in two of the Mesa/Boogie amps I have - a Mark V and a Express 5:50 Plus - to these ultra quiet pre-amp tubes.

The tubes arrived quickly and packed well. I own an Orange VT1000 Valve tester. I decided to test all of the new tubes prior to installation to verify their integrity and also determine their tested score. Three tubes tested fine, but the fourth was bad - never able to complete the full test procedure. I retested the bad tube numerous times, but the results were always the same. An inspection of the tube revealed a ghostly white residue inside the top portion of the tube - usually a sure visual indication the tube is bad.

I immediately notified my sales rep. He apologized for the inconvenience and stated failures, while rare, can occur. He told me a replacement would immediately be shipped to me and I could dispose of the faulty tube. I'm glad I held onto it. He turned my case over to Sweetwater tech support who requested I return the tube. I felt as though they questioned my determination the tube was defective, but if Sweetwater wanted to incur the additional return shipping charge to see the tube, I was happy to oblige them. I returned the tube and received a new one that passed the tests in my VT1000.

The tubes that tested fine received exceptional scores in my tester. I have two installed in my amps and they are performing fine.