Is a SVT Pro 7 supposed to hiss this much?

[Marcus Cornall]

Hello all,

I have taken the plunge on a rig upgrade (after consulting on Basschat at length)

 

I bought a used Barefaced Big Baby II gen 3 

And a used SVT 7 Pro.

They seemed a good pairing.

 

They both arrived today ,and ...

 

The BB is STUNNING ! Only at home volumes ,but to me,coming from years of an old nameless ported 1x15 with a 200w speaker..the difference is astonishing,and I am so glad I chose it

 

The SVT ... I love the sound.I love Ampeg.And even by the odd sneak up of the volume  so far,I can tell it delivers huge bass ,and coupled with the cab..seems a great match.

I have got used to the fan noise .a bit much at home but this was to be a gigging amp so OK with that.

 

BUT the problem is ,if I turn the volume up beyond ten o clock the amount of hiss becomes really noticeable .that's with the amp flat/all eq at 'noon'

The hiss  is there irrespective of gain. Turning the treble up makes it worse.  

Yes it goes away if I turn the treble right off ..but i surely shouldn't have to.

And yes,all the above was with the BB tweeter fully on,and yes ,the hiss goes away if I turn that nearly all the way off,but,,,same thing..what if want treble?

And some of the mid settings accentuate the hiss too.

But it's directly linked to how high the volume is.

And yes,it's a 'rev H ' ..I did my homework on that.

 

I play Reggae at the moment ,and would have the treble off anyway, but I  ought the amp with the equal intention of using it with my clattery Fender Jazz with roundwounds for rock too.

 

So questions are,, could it be the cab tweeter at fault?

 

Many learned forum people,and Alex the BF designer,say that a speaker cannot hiss,only an amp.

 

Could it be solved by a speakon? 

I dont have one  but am ordering.

 

OR is the tube going? Never had a tube so don't know,but the other thing is I can't make the input gain clip until it is more or less full.i would've thought it should break up before that?

 

OR is it this- I have spent 2 decades with a 1x15 and no tweeter! And have now gone to a fantastic tweeter (and cab) - is it just that the SVT 7 pro ,and other amps ,hiss as a normal thing but I have never noticed?!

 

I will also own that with the gain up at noon or beyond ,it is probably a lot louder than I am realising,because the sound is so pure,devoid of that low mid bulge of normal cabs.

I was warned of this in another thread. But I was expecting to be ..well I thought the amp would sound hugely loud,but some of that may be psychoacoutic stuff...so maybe you set the gain high and you only need the  volume up to 9 o clock,

although I would've thought a knob should remain usable through its entire travel,not just hideous if it goes beyond a quarter of it's rotation.

 

I also realise it won't matter once the playing starts..to me..

But it's noticeably irritating when not playing ,and thats at home . At rehearsal vlou e I imagine it would be really noticeable and off putting, if the volume was above halfway.

 

And given the amp evolution since the peavey firebass head I am replacing with the SVT! I had sort of expected silent treble at flat setting.

 I have a Phil Jones 120w combo and it is devoid of teble hiss. 

 

To give an idea how loud this hiss is.,,.

Going by how loud the fan is,since that's fixed and you reading will,if you e got a 7 pro,know how loud that is ..... at 12 noon (half ) volume  the hiss is louder than the fan. 

 

I tried a passive Cort B2 and an active HB Marquess 5 through it so far.

Same hiss issue with each,but then the hiss is there even if no bass or instrument cable is plugged in.

 

Any help appreciated, as I will only have a few days in which to declare to the seller that I think the amp is faulty.

[agedhorse]

Any electronics before the amp (pedals and active bass for instance) can contribute to a higher than ideal noise floor. 

 

If a speaker has a tweeter sensitivity that is significantly higher than the low frequency drivers, this can result in the perception of more hiss than you might otherwise expect. This is common with tweeters turned up to "bite your head off" level that happens with some cabinets. The brighter the tone, the more noise present.

[Marcus Cornall]

Thankyou agedhorse.I know from reading this and other forums how great your experience is,and why. Deepest respect for taking the time to respond.

 

I have nothing between the bass and the amp.

I did wonder if it was a matter of the tweeter being capable.ef 'unnatural' relative  amounts of treble. I presumed that to get a 'flat/balanced relative amount from the woofer and the tweeter; I would have to turn the tweeter fully up.

But from what you are saying it could be then that to get the relative balance I should turn the tweeter down some.

And someone with a similar issue on a forum was also told that treble frequencies don't take as much power to amplify and maybe that's also part of this. 

I haven't had an amp this powerful before either so maybe am not used to the relatively higher starting 'noise floor',if that's the right term.

 

[Marcus Cornall]

I should have added that I am hearing the hiss sitting a couple of feet in front of the speaker.Not where I would be for playing I know and it isn't as bad standing in front of it facing the right way.

Am going to plug my FB head in as soon as its decent to do so (7.30 am here right now!) 

I will probably find even bigger amounts of hiss from it that I didn't hear before for lack of tweeter! 

[yorks5stringer]

Are you playing Whitesnake riffs?

[Chienmortbb]

To be a bit more serious, this was/is a problem with the big guitar rigs of the past when an affulent father would buy a 100W Marshall Head with 2 4x12s for his son. Then would come the complaint that the amp was noisy compared to his Leak HiFi amp.

 

So, not to put too fine a point on it, the SVT range were desiggned to drive cabs that have a limited HF response (like your 15s and the Ampeg Fridges).

The SVT 7 Pro has an awful lot of 4580 op amps and the cumulatuve noise of those in addition to the design itself, could be the problem. Agedhorse would probably call me out on that and I woud bow to his superior knowledge.

 

I must say that I have used Ashdown, Bugera, GK amps with tweetered cabs over the years and never had a probelm with noise/hiss.

[DGBass]

I've heard it said many a time that hiss is better than hum when it comes to bass amps. Some amps though are noiser than others, even from new. I recently had a chance to play through an old Ampeg B2-RE 450 watt amp with  1x15 and 4x10 Hartke cabs, both with horns and both horns were on at the time. The Ampeg was so quiet at idle I thought at first it wasn't plugged in to the cabs. There was virtually no hiss at all even at decent volume levels and controls set flat. I also have a couple of GK amps and even with the volume up high, they barely hiss at all through tweeter cabs. Pre-amps with a tube in them can pick up a bit of noise, especially if the tube isn't at its best. If you have the option try several amp heads with your cab to compare. It might just be a particular combination of amp/cab and not anything really wrong with either. 

[agedhorse]

16 hours ago, Marcus Cornall said:

Thankyou agedhorse.I know from reading this and other forums how great your experience is,and why. Deepest respect for taking the time to respond.

 

I have nothing between the bass and the amp.

I did wonder if it was a matter of the tweeter being capable.ef 'unnatural' relative  amounts of treble. I presumed that to get a 'flat/balanced relative amount from the woofer and the tweeter; I would have to turn the tweeter fully up.

But from what you are saying it could be then that to get the relative balance I should turn the tweeter down some.

And someone with a similar issue on a forum was also told that treble frequencies don't take as much power to amplify and maybe that's also part of this. 

I haven't had an amp this powerful before either so maybe am not used to the relatively higher starting 'noise floor',if that's the right term.

 

A tweeter is typically about 10dB more sensitive than the low frequency section, so with the tweeter level control fully up (assuming that's the only attenuation), there will be a 10dB bump in the high end compared with the rest of the speaker's response.

[Downunderwonder]

BB =  BigBaby by Alex at Barefaced? Most likely a compression driver rather than a tweeter. There's a bit going on with his HF control that I still don't really understand. Something about a crossover frequency control rather than a level control?

[Beedster]

I hate hissy amps, I can live with it when it's a cheapo or old, but when allegedly high end gear by manufacturers such as Markbass or PJB hisses noticeably out of the box it goes straight back, I'm not going to use EQ to deal with a design or production flaw. 

 

18 hours ago, DGBass said:

I've heard it said many a time that hiss is better than hum when it comes to bass amps. 

 

Ha ha, nice point, but I think I prefer hum  

[Marcus Cornall]

Hi Downunder,

Yes  a Barefaced Big Baby.And yes, sorry it is termed a 'compression  driver ' .I dont know the difference.it mentions a crossover but I thought that's just a matter of choosing at what freq the compression drive takes over.

Form what I have gathered since ,it may be that I assumed turning the CD full up ='flat' but apparently it could actually be that the CD adds relatively MORE treble than 'flat'/equal strength to the woofer.if you see what I mean?

 

Anyway I am reliably informed that speakers can't hiss..only amps.

 

Beedster- I hate them too ! And I didn't expect it from an amp this new.

It is second hand.it was advertised as being "in full working order" 

I dont know if excessive hiss counts as NOT in full working order or not.

 

Anyway a speakon cable is due to arrive today (been using a 1/4 I  jack speaker cable) so fingers crossed that gets rid of it.....

 

.

[fretmeister]

One of the reasons for a control on the tweeter/compression driver is to be able to remove that ultra high frequency hiss without really affecting your tone. The cab cannot generate hiss, it can only let it through.

 

The Ampeg is a noisy beast. Use the control on the cab to tame it. There's nothing actually wrong with any of your kit. But as others have said, other amp designs will have less hiss but some will actually have more!

[Marcus Cornall]

Thanks for chiming in Fretmeister,

 

I didn't realise Ampegs were known to be noisy. Are they all like that? 

Since my old head is 30yrs old SS , thought the hiss sitatuionmwould have improved. Is it because it's a real tube? The master is what makes it hiss though and it's the same at low gain or high.well..last bit of the gain adds a bit more,but I would expect that 

 I put the treble down for Reggae anyway of course,and yes I would be turning the tweeter off too..that makes the hiss go away.

 

But I also play rock ,and use a clattery Geddy type sound from a rojndwoind jazz,

Ie a 'normal' bass sound full open with treble.And with this amp the hiss would become nasty.

Not an issue when playing, but let's put it this way- I wouldn't want to mic the cab.

 

I got  proper speakon lead too but it didn't help.

 

But since you've been good enough to help,maybe you can reassure me further  about the ampeg -? 

 

I tested my Peavey FB head ,and firstly,there is less hiss with the peavey,although I am gauging volumes by ear here,so it isn't technically accurate.

 

 Secondly,it seems as loud as the ampeg , yet is only 475w at 8 ohms. Again use me that's by ear.

 

Thirdly , when i  first plugged the ampeg in ,the pre gain was clipping at about ten o clock. But second plugging in and subsequent,same bass, I have to turn the gain up to nearly full to get it to clip.

 

Fourthly ,the amp was superbly packaged, but when I tilt it tiny things rattle about inside.

 

And then there's the relatively high noise floor. The mid control affects it too.seems to be frequencies in between high mid and treble controls.

[Beedster]

I would try another preamp tube given the above?

[Marcus Cornall]

Yeah? You think the tube? 

My first tube so I don't know them.

The seller said he would check the tube.

Thing is i may not have long enough to get one before my window for arguing a return runs out.

I'm just really trying to find out if it's in working order but it hisses and that's the way it is,or if there's something actually wrong with it,because if so...not sold as described,and return.

[Marcus Cornall]

On 30/03/2023 at 12:27, Chienmortbb said:

To be a bit more serious, this was/is a problem with the big guitar rigs of the past when an affulent father would buy a 100W Marshall Head with 2 4x12s for his son. Then would come the complaint that the amp was noisy compared to his Leak HiFi amp.

 

So, not to put too fine a point on it, the SVT range were desiggned to drive cabs that have a limited HF response (like your 15s and the Ampeg Fridges).

The SVT 7 Pro has an awful lot of 4580 op amps and the cumulatuve noise of those in addition to the design itself, could be the problem. Agedhorse would probably call me out on that and I woud bow to his superior knowledge.

 

I must say that I have used Ashdown, Bugera, GK amps with tweetered cabs over the years and never had a probelm with noise/hiss.

Thankyou and wish I had known about the amp structure causing noise.

I did t realise that essentially then the ampeg is limited to old sounds only in that way.Rock players still use them,including Billy Sheehan,so I would've expected to hear talk of hiss issues in online discussions,but have not.

 

This factor is never mentioned when discussing amps' performance.

 

Anyway,if it's just how they are and there's nothing wrong with it,the  I am stuck with it for now anyway.

I will have to buy another one in the future and get rid of this.you 

[Marcus Cornall]

Sorry ....continued... you have helped a lot with that knowledge even if that's after the fact,and I am grateful.

[Marcus Cornall]

Another thing has started happening today..when I switch the amp on,after 10 secs or so I get a 'pop' ,and sometimes  a further one.thats with nothing plugged in.

[BassmanPaul]

Some amps have a delayed turn on of the speaker jacks to reduce turn on thumps from getting to the speakers.

[Downunderwonder]

Rattling definitely not normal. Send it back.

[Bill Fitzmaurice]

9 hours ago, Marcus Cornall said:

Hi Downunder,

Yes  a Barefaced Big Baby.And yes, sorry it is termed a 'compression  driver '

 

A compression driver is a type of tweeter.

Quote

Since my old head is 30yrs old SS , thought the hiss sitatuion would have improved. Is it because it's a real tube?

Back in the early days of SS they were much noisier than tubes, but I'm talking 50 years ago. Tubes aren't inherently noisy.

Quote

I did t realise that essentially then the ampeg is limited to old sounds only in that way.

I wouldn't say Ampeg is limited at all.

Quote

I would've expected to hear talk of hiss issues in online discussions,but have not.

That's because it's not an issue.

Quote

One of the reasons for a control on the tweeter/compression driver is to be able to remove that ultra high frequency hiss without really affecting your tone. The cab cannot generate hiss, it can only let it through.

Quite right. Other steps for minimum noise is to turn down the gain, turn up the master, and turn off the ultra high switch.

[Marcus Cornall]

Thankyou Bill.i acknowledge your expertise and welcome your input.

The hiss is there when I turn the volume up,and it doesn't  matter where I set the gain,from off to virtually full (at which point some extra hiss but ok )

And no ultra high.

So if Ampegs aren't hissy, do I have a faulty one do you think?

[Bill Fitzmaurice]

Usually hiss is created early in the signal chain, so gain amplifies it, making it worse as the gain is increased. If it's there no matter where the gain is set then it's taking place further along the signal chain. That could indicate a fault in the amp, perhaps something as simple as a broken PC board trace or a cold solder joint on a component. That's something that could have occurred when it was shipped. I'd call around to see if a nearby store has one that you could compare yours to. That way you'd know if yours is within spec.

[Downunderwonder]

12 hours ago, Marcus Cornall said:

Fourthly ,the amp was superbly packaged, but when I tilt it tiny things rattle about inside.

Danger Will Robinson!!!

[Marcus Cornall]

7 hours ago, Bill Fitzmaurice said:

Usually hiss is created early in the signal chain, so gain amplifies it, making it worse as the gain is increased. If it's there no matter where the gain is set then it's taking place further along the signal chain. That could indicate a fault in the amp, perhaps something as simple as a broken PC board trace or a cold solder joint on a component. That's something that could have occurred when it was shipped. I'd call around to see if a nearby store has one that you could compare yours to. That way you'd know if yours is within spec.

Thankyou so much Bill. That's superbly helpful,and I'm most deeply grateful to  you.

 

It was very well packaged but things can still be jarred by impact inside packaging. I hadnt realised things like solder joints might be an issue but it makes sense.

The guy I got it from is being very  good about it.he is sending me a new tube (because some said it could be that. I didn't see how,since it was the vol and not gain, but I have no experience..he said he had used it with a tweeterless 1x15 and so wouldn't have heard the hiss.

 

And he has said he will have it back and refund me if I am still not happy.

There are no stores near me with one unfortunately, so I can't do a comparison.

 

I guess i will try the tube,since he's been good enough to send it, and if it still hisses I will send it back to him and then if he wants to claim for it being damaged in transit ,he can do that.

And I'll have to try another one.

Now wondering whether to get another 7 Pro used (probably a bit put off that !) ,spend double the money on a new one,or try a different amp altogether. I like the sound of it though.