Ampeg SVT 7 Pro Club

[baxter_x]

It's not too hard to believe since the 6 PRO is like this.

I think it's all the Ampeg line that is that way.

 

[rzero]

I think it's all the Ampeg line that is that way.

The is the only SVT I've owned, but the numbers vary by model:

It depends on the Ampeg. This is why they drive me crazy.

SVT 2 PRO:
ULTRA LOW: This switch, when engaged, provides emphasis to the low frequencies by boosting the low frequencies and selectively cutting the mid frequencies.
Ultra Low: +3dB @ 40Hz, -12dB @ 500Hz

SVT 200T:
Ultra Low Switch: 9dB Boost @40Hz

SVT 6 Pro:
ULTRA LO: This switch, when depressed,
greatly enhances the amount of low-end bass
tones.
ULTRA LOW SWITCH +2.5dB @ 50Hz
-12dB @ 560Hz
+1.5dB @ 5kHz

None are the same. IMHE the only one I found usable was the SVT200T. That knob should be glued out lol. But it useful to just punch it in if the room is too boomy.

The 7 PRO manual says +2dB at 40Hz and -10dB at 500Hz

 

[baxter_x]

It's getting complicated I agree......

 

[xI Jonathan Ix]

Do Ampeg SVT7 PRO users here find that they need to use preamp pedals to dial in their tones when they play live? I a, new to the whole thing, having been a guitarist all my adolescent and adult life, so I never learned those things.
Seems to me that front panel controls will the voice you are aiming for but preamp pedals are for tuning it to the band performing live within the specific space. Preamps are not really for ‘getting my tone’ (the amp should provide that in spades) but for making sure that tone doesn’t get swallowed up.

That just comes down to whether you and the people you play with are happy with your tone. You don’t *need* a preamp in front of the 7Pro. I found a preamp I like that allows me to go ampless when the opportunity presents itself. So it’s just easier to keep that on a board that goes with me to any gig.

 

[rzero]

Our drummer couldn't handle the crunchiness of the gain-knob controlled gain going DI into our recorder for band practice.

I was going to try just turning down the treble next practice for a poor man's speaker sim, but I decided to go with turning the gain down to about 10:30 so only the pre tube was clipping and cranking the MK.4.23 clean boost all the way up.

This is a much less crunchy/trebly tone. Works well even DI and even the drummer liked it.

It's actually amazing how thick the drive can get with the single 12AX7 if you hit it hard enough. When I first tried this years ago I wasn't thrilled and wished it sounded more like a multi-tube preamp, but now having gotten my clean tone dialed in better and having experimented with more overdrive pedals, I can say the single tube is a legit, respectable bass drive tone, even for higher drive sounds. It's just different than multi-tube. It decays into a cleaner tone quicker but retains tonal definition well. Maybe guitarists wouldn't like it for the former but it works quite well on bass.

I just saw that the MK.4.23 now has an option for 6dB more gain than my version. Creative Audio said via email it steps up the internal voltage to twice the regular model, which would come to 144V. Might have to check it out at some point...

Still using this setup. I've found if I have the onboard compressor at 10:30 or higher, the peak light stops flashing but the overdrive remains, and a subtle harshness drops out of the sound.

So it seems like you can't truly drive the 12ax7 "unimpeded" unless you hit the front end with a hot enough signal and dial in a certain amount of compression. But I've been using the compressor anyway lately, so this is fine.

 

[rzero]

Something I've noticed about the 7 PRO:

Even with nothing in the effects loop there is a definite tonal difference in DRY vs WET via the FX MIX knob. There is noticeably less high end on WET. With headphones or a tweetered cab it's pretty apparent. There is also a difference in feel to the extent I wonder if there is some type phase thing going on.

I've gone back and forth but lately I've preferred WET. For a while I was even blending the two at noon like a total psycho.

 

[rzero]

Latest in the saga of the 7 PRO effects loop:

It occurred to me there is also an option to bypass the effects loop via a footswitch. So I got naked TRS plug, which plugged into the footswitch jack mutes the amp and bypasses the effects loop, and connected the tip and sleeve tabs to defeat the muting.

This seems to give more of the clarity of the fully dry FX mix knob setting, but with a smoother high end, and more of the "feel" of the fully wet FX mix knob setting, which again makes me think there is a polarity thing involved. And again, this is without anything plugged into the effects loop itself.

If you're not using the effects loop on the 7 PRO, I would recommend trying this to see if you notice a different feel and smoother top end.

You could also get the footswitch. Looks like the AFP2 model has been replaced with the AFS2. $40 new.

 

[rickwebb]

And I'm BACK!
Long story VERY short- i found a used 7 Pro locally in immaculate condition.
Then i proceeded to order a new one from Sweetwater.
The new one arrived today... all Yamaha literature, etc. And it sounds brilliant.
I just might rack 'em both up and gig with them tomorrow night...

Well, after a year and five months, my pre-owned 7 Pro appears to have given up the ghost.
Hey, it paid itself off anyway. The new one i bought is still working, thankfully.
But i'm still not getting rid of my PB-800 or my B-4R anytime soon...

 

[pgpete]

For me the most simple signal chain. Bass, cable, amp, cab.
And I find the amp compressor very nice and useful. I set it at 10 o'clock and it's perfect for my needs.
I hate pedals, never found any useful.

I agree - if you favour mostly clean with a bit of hair when you dig in deep you can get that with the 7pro without pedals. and it sounds quite good.

 

[rzero]

After a few days of testing, I'm back with my new SVT 7 PRO.

I must say that I find it quite good, as already mentioned, the power is certainly not lacking, but I still have to find my favorite sound.

I noticed something that probably depends on the dynamics management of the class D amplifier.
I have found a noticeable increase in the volume of the harmonics on my bass, so much so that I sometimes have difficulty controlling them.
Is it just me or has anyone else experienced the same thing?

Yeah, I've fought this for a while myself, and the fact is that 12AX7 saturates quite a bit even with modest-output passives and creates a midrange hump that can enhance some obnoxious overtones.

The only way to dial it back on the 7-PRO is to use the -15dB pad or lower the signal going into the amp input somehow. If you use the pad with a passive bass plugged straight in, be aware that the pad lowers the amp input impedance and will "load" your pickups a certain amount and probably roll off some highs. I've tried buffers in front of the amp to counteract this but have found I still like the straight-in sound better.

Even with the pad on, my passive Jazz with 60s-style pickups can still get a "tubey" sound and I can still get a little breakup. It's quite apparent when I plug into my solid state practice combo how far from "pristine clean" even the padded sound is on the 7-PRO.

 

[rzero]

I was going to mention I replaced the fan in 7-PRO a few months ago with a quieter version and it is MUCH better for bedroom playing.

The one that comes with it is more of an industrial-type fan, which have little concern for noise in their design. If you dip down into the personal computer fans you can get about 60% of the rated airflow but with almost complete silence.

I had originally put in one with about 50% of the airflow. When summer rolled around, my amp started cutting out for a few seconds at a time after about an hour of very moderate volume playing. Worried it was the fan situation, I bought the slightly higher airflow fan before opening the amp up. The amp innards were actually BARELY warm after an hour of playing and it turned out the problem was pre tube finally going (replaced it with a standard EHX).

So I swapped in the second new fan while it was open anyway (you have to detach the main bottom circuit board and slide it towards the front of the amp to get the fan in and out). I also flipped the fan to blow into the case rather than outward, as the heatsink by the fan was slightly warmer than the one by the side vent, fwiw. The tube is closer to the side vent, but I don't remember the tube being very warm at all.

The fan is a Noctua NF-A6x25 FLX for $17. I also needed a short 3-pin to 2-pin adapter cable. On the first new fan, I had to pull the seat that the cable clips into on the circuit board and reverse it to swap + and - to get it to work, but I think I had to swap it back to the original orientation for the Noctua, if I remember correctly.

There were four little plastic spacers in the original fan that contact the heat sink that I took out and glued into the new fan, as they were a little loose and kept falling out when trying to slide the new fan into place.

I haven't used the amp in outdoor summer heat with the new fan yet, so I can't make any guarantees, but the original fan seems to be a bit more than is necessary, at least for certain uses, and you can get a LOT quieter by moving into the PC grade of fans.

 

[baxter_x]

I tend to consider the designers to know what they do better than anyone else, but if it works, that's fine.

 

[agedhorse]

Lower air flow on that amp in particular is a big problem that can end up with a costly repair.

Also, IIRC, there is a variable speed driver circuit that’s matched to the curves of the original fan. If the new fan doesn’t share the same curves, the control circuit won’t track well.

Reversing the connector will screw up any tech that has to deal with this amp at a future repair. That’s not something a tech would logically look for.

 

[rzero]

Lower air flow on that amp in particular is a big problem that can end up with a costly repair.

Also, IIRC, there is a variable speed driver circuit that’s matched to the curves of the original fan. If the new fan doesn’t share the same curves, the control circuit won’t track well.

Reversing the connector will screw up any tech that has to deal with this amp at a future repair. That’s not something a tech would logically look for.

My original fan was always one speed, and it was always dang loud. My guitar player would laugh every time I turned the amp on. I mean, maybe I got a particularly loud one, but it didn't sound weird or broken.

If memory serves, the reversed connector was an idiosyncrasy of only the previous new fan, and this one is the same as the original.

I'm going to risk it. I think the old fan was exacerbating my tinnitus. It seemed at least as loud as my solo practice volume. I'll let everyone know how it fares if I start using it in our hot warehouse jam space.

 

[baxter_x]

My original fan was always one speed, and it was always dang loud.

I think mine is also one speed. However, i don't consider it to be dang loud. I can hear it a bit but not what you describe.

 

[rzero]

I think mine is also one speed. However, i don't consider it to be dang loud. I can hear it a bit but not what you describe.

Interesting. I'll consider buying and trying another of the original fan if I plan to take it into the heat. As for at home practice, the concerns I had with these PC fans greatly diminished once I opened the amp right after playing and was shocked how cool everything was.

 

[agedhorse]

Interesting. I'll consider buying and trying another of the original fan if I plan to take it into the heat. As for at home practice, the concerns I had with these PC fans greatly diminished once I opened the amp right after playing and was shocked how cool everything was.

The overall impression of “coolness” is misleading, there are a number of specific components (different components in different designs) that are heat sensitive, which dictate the requirements for airflow (CFM, static pressure and direction).

When designing a (reliable) cooling system, thermal sensors are placed at multiple critical components to be sure they all track together.

Additionally, in some designs, there are also multiple sensors at key components that feed back temperature information to protection circuits. When these are used, it’s important that the cooling system doesn’t over or under-cool the sensors or protection circuits mistaking can occur (with disastrous results).

This is all part of a patent we were granted about 15 years ago relating to SMPS and class D cooling and duty cycle management.