Ampeg SVT 3 pro, whats the deal?

shark561 · #1 04-10-2012, 11:24 PM

Hi, this is my first post, but I read the threads almost daily, great info on here.

Ok, so here is my issue. I have an Ampeg SVT 3Pro. It's the old version with the red/blue lettering. I got it about ten years ago, used. I had the tubes replaced then. I have never really bonded well with it. So its not really been used much until recently. I now play weekly at my church and want to use the 3pro. I really want to like it, but it seems really weak in volume and just lacks something. I have to crank it up just to get something half way decent.

I also have the Ampeg Micro VR, and I LOVE that tone. Its awesome! So last week I decided to bring that to rehearsal. I ran it through the same cabs I use with the SVT 3: ampeg 1510he, and ampeg 210av. Wow, what a difference! The sound was awesome, so warm and rich, and plenty of volume to keep up with two guitars, keys, and drums, and the volume was only on like 3 or 4. My band mates were like, "wow, what is that little thing" It totally kills your other amp!"

So what gives with the SVT 3? Why is the little 200 watt Micro VR, totally sounding louder and way better than the 450 watt SVT 3?

I read all the posts about the SVT 3 not being loud enough, and how I need to crank the gain, and push the EQ slider up. So I do that, but it's just plain weak! Why? What am I doing wrong? Should I have the tubes looked at again? Like I said, I really want to like the SVT, but my micro is so much better... I just want to toss the SVT out! Help!

mazdah · #2 04-10-2012, 11:32 PM

Either a bad tube (most probably in power amp section - 12au7/12ax7) or you forgot that you have to really CRANK the gain to get decent 3pro sound.

Also check the tubes models. If they are Sovtek 12AX7WA (those WA are important in this case!) you should change them to JJ or GT 12AX7C (again, C is important). The Sovteks WA are very low gain tubes and to me, they sound really weak in bass amp. The do the job great in overdriven guitar amps like Marshall.

Properly driven 3pro sounds VERY like SVT-CL - I sometimes can hear the difference between instrument cables but when we tested CL and 3PRO I'm pretty sure I wouldn't be able to distinct them only using ears.

There's also a "radical" way to drive 3pro - set the master at maximum level and use gain to adjust the volume. I wasn't a fan of this until I heard how close this sound is to all tube SVT.

TigerInATrance · #3 04-10-2012, 11:43 PM

Mine was like that too. I was unimpressed with the output and the almost mushy tone I was getting. It turned out to be the bias on the power section running at about 1.6mv when it should be around 25. I followed some one's instructional thread to try and bring it up to spec, but ended up going a little too far and caused overheating. I recommend taking it to a good tech and having it checked for correct bias. Or, if your handy with a multimeter check it yourself and then have a tech adjust it. Tubes shouldn't have that dramatic an effect on the sound, especially if they're relatively fresh.

So, I got my head back yesterday and it's loud and pretty punchy now. Very much feels like 450 watts to me.

vin*tone · #4 04-10-2012, 11:46 PM

There are a couple of tricks with the 3 Pro. Ignore the preamp limiting LED and get your gain level by ear. Don't use the bass boost switch, Also - make sure you crank the far right EQ slider.

shark561 · #5 04-11-2012, 12:00 AM

Thanks guys. I'll take a look at the tube type, also the bias. I had read about the bias issue and thought it could be that. I have no idea about how to check that so I'll for sure take it to a tech! Tigerinatrace, about how much did something like that cost you?

TigerInATrance · #6 04-11-2012, 12:06 AM

It cost me $200 because I toasted the MOSFETs trying to adjust. If I had let them do it it would have been a $45 bench fee.

shark561 · #7 04-11-2012, 12:08 AM

Ok yeah, I ain't touching it for sure then!

stiles72 · #8 04-11-2012, 10:58 AM

It's possible someone has the 12AU7 in the 12AX7 position, but my guess is that it just comes down to how you have the amp set. Even if the MOSFETS were out of wack, that really wouldn't affect the overall volume - just add some fuzz. At least on mine thats what happened. You allready have the master EQ slider bumped up - so play around witht he gain and master volume. Also dont be afraid to adjust the tube gain. All the way to the left should be a softer tubier sound, all the way tot he right should be more detaield and more volume like a solid state amp. And who knows - maybe tubes just aren't your thing. Maybe the VR is just voiced better for you. Nothing wrong with that either.

Primakurtz · #9 04-11-2012, 11:16 AM

I have to second the suggestion to have a tech check the bias. When I got mine, the volume was so low, it was almost silent. The voltages to the mosfets ranged from 0.0 to 4.2. Once I carefully nudged them up to an average of 24, the amp came to life - very loud, with excellent tones on tap.

shark561 · #10 04-11-2012, 02:11 PM

All great suggestions, thanks guys! I think I will give it one more try this week at rehearsal before I send it in and spend the $$. I do have the tube gain all the way to the left so maybe thats it. I have it there because I read thats the most tube like sound, so yeah maybe I just don't like the tube sound! HA!

Thanks!

TigerInATrance · #11 04-11-2012, 02:21 PM

Quote:

Originally Posted by shark561

All great suggestions, thanks guys! I think I will give it one more try this week at rehearsal before I send it in and spend the $$. I do have the tube gain all the way to the left so maybe thats it. I have it there because I read thats the most tube like sound, so yeah maybe I just don't like the tube sound! HA!

Thanks!

FWIW, I can't stand the sound with the tube gain all the way counterclockwise. In fact, I feel like there's better sounds with it set somewhere between 50% and 75%.

Oh and on the volume thing as it relates to bias... Once it was all fixed up and set right, it felt like the difference between a practice amp and a full on stage rig (which this amp should absolutely be...)

LarryO · #12 04-14-2012, 05:10 PM

settings on the svt3 vary greatly from cab to cab. I think it may like sealed cabs but im still playing with the eq. I do find its 450 watts (at 4 ohms) is not as loud as other amps but it's definitely more than enough with my 6x10. I can see if someone is using a 410 and/or an 8 ohm cab they may be less than impressed with output. But with a 4 ohm 6x10 its louder than I need it to be. Definitely a tricky eq though

Jerrold Tiers · #13 04-14-2012, 08:08 PM

Quote:

Originally Posted by LarryO

settings on the svt3 vary greatly from cab to cab. I think it may like sealed cabs but im still playing with the eq. I do find its 450 watts (at 4 ohms) is not as loud as other amps but it's definitely more than enough with my 6x10. I can see if someone is using a 410 and/or an 8 ohm cab they may be less than impressed with output. But with a 4 ohm 6x10 its louder than I need it to be. Definitely a tricky eq though

The 3PRO is definitely NOT going to have strong control of the speaker cones...... it's going to be more like a tube amp.

This is because it has essentially "zero feedback".... the mosfets just take what the 12AU7 gives them and "match it" to the speakers. There is no negative feedback to lower the output impedance, etc. (there is a circuit to balance the DC level on the output, but it does not respond at audio frequencies)

shark561 · #14 04-14-2012, 11:31 PM

I'm going to try it again tomorrow at rehearsal. Two cabs (15 & 2x10) so I'll get 4 ohms. I'll crank the tube gain all the way to the right and see how it responds. If it still is not cutting it I'll have the tubes and bias looked at.

shark561 · #15 04-15-2012, 06:55 PM

Well I must say, turning the tube gain all the way to the right really does help. This amp really needs a lot of tweaking to get a good sound, at least for me. I'll keep working with it. Thanks all.

JimmyM · #16 04-16-2012, 03:16 AM

The key to Ampegs is twisting knobs and turning up the gain with total disregard for what seems "right" to you. Also, the mid selecter switch is very powerful, and boosting and cutting the different frequencies you select will do nice things or very bad things. When you find the nice things it does, it's quite effective.

shark561 · #17 04-16-2012, 10:44 AM

As I said I have the Ampeg Micro VR and absolutely love it. Its simple and yet provides an outstanding sound. With the SVT 3 however, there are so many tonal possibilities that its hard to get it 'right'. You are correct Jimmy, this Ampeg (3 pro) requires tons of knob twisting! In my case it has only taken a few years of twisting to get a descent sound!

RSNG · #18 05-15-2012, 12:02 PM

Quote:

Originally Posted by shark561

All great suggestions, thanks guys! I think I will give it one more try this week at rehearsal before I send it in and spend the $$. I do have the tube gain all the way to the left so maybe thats it. I have it there because I read thats the most tube like sound, so yeah maybe I just don't like the tube sound! HA!

Thanks!

My owner's manual says that "the tube gain control varies the high voltage supply to the power amp tubes; at 10, the voltage is at maximum". This would lead me to believe that at 10, I'm getting maximum tube sound. Is this correct, or do I have it backwards?

Also, I've been leaving the master all the way up, and adjusting volume with the gain control. I've never really gotten the sound of my old tube SVT.

teemuk · #19 05-15-2012, 12:19 PM

Quote:

Originally Posted by RSNG

My owner's manual says that "the tube gain control varies the high voltage supply to the power amp tubes; at 10, the voltage is at maximum". This would lead me to believe that at 10, I'm getting maximum tube sound. Is this correct, or do I have it backwards?

Backwards. Less voltage => more clipping in the tube gain section and more "tube sound".

Note that the dial will also reduce the maximum (clean) output power the amp puts out. At the most "tubey" setting you have likely reduced the rated output power to about 40 watts / 8 ohms.

RSNG · #20 05-15-2012, 01:34 PM

Quote:

Originally Posted by teemuk

Backwards. Less voltage => more clipping in the tube gain section and more "tube sound".

Note that the dial will also reduce the maximum (clean) output power the amp puts out. At the most "tubey" setting you have likely reduced the rated output power to about 40 watts / 8 ohms.

Thanks for the info.

So, that's why it doesn't sound like my SVT. I'll try turning the tube gain a bit to the left, then. I sure don't want to cut the power too much. I'm using a 4x10 4 ohm cabinet, and it's adequate. But, I expected more from 450 watts.

I'm not used to having so many controls. I usually don't even use the eq. My old SVT always sounds good, with a minimum of adjustment. I can just plug in, turn up some volume, and maybe tweak the tone controls a little. I don't think there's any way to really make it sound bad.