Need Aguilar DB 751 Fan Noise Advice

[faulknersj]

I love the sound of this amp and it absolutely KILLS, but the fan noise is so loud that it might be a deal breaker for me. I can't understand how they could allow such loud fans on these amps. I reached out to Aguilar just in case this is an anomaly (I don't think it is unfortunately) so we shall see. The dual fans sound like they are continuously cycling and produce sounds like overtones that go Mwah Mwah Mwah. Even with the gain and master volume at 9 o'clock each, I can still here the fans.

This is likely a deal breaker for me if it can't be resolved.

Anyone else have experience with this?

 

[stockplus]

Might be apples to oranges here but I have a DB750 and it has some very loud fans that together also produce a cyclic oscillation effect. So I feel your pain. The loud DB750 fans are a know "issue" - but I was under the impression that that DB751's were somewhat quieter.

I looked into replacing my fans with something slightly less aggressive but was advised against it by the gurus here.

The DB750 noise is not too bad at coffee house acoustic gig levels, but it's a bit much for nighttime bedroom practice! These are heavy duty amps that shine at louder stage volumes.

Good luck!

 

[faulknersj]

“ a cyclic oscillation effect. “

That is the PERFECT way to describe it. It is definitely still happening on my DB 751. I’m pretty surprised by it actually. I don’t know that you could mic a cab in a studio environment without getting some of that bleed.

I am hoping I can just get used to it but I do t know if that is possible.

 

[agedhorse]

It's the sum-difference effect from the summing of the two noise sources, common with dual fan amps.

The amp requires a lot of cooling because of the output topology, and because a repair is going to be quite expensive, you may want to leave well enough alone.

 

[SharpCat]

For those living on the edge, could use THIS with a pair of 4 pin fans. (It can control 3 total.)

 

[faulknersj]

It's the sum-difference effect from the summing of the two noise sources, common with dual fan amps.

The amp requires a lot of cooling because of the output topology, and because a repair is going to be quite expensive, you may want to leave well enough alone.

Copy that. I am somewhat baffled that there wasn’t a design alternative embraced for these amps…

 

[StayLow]

I love the sound of this amp and it absolutely KILLS, but the fan noise is so loud that it might be a deal breaker for me. I can't understand how they could allow such loud fans on these amps. I reached out to Aguilar just in case this is an anomaly (I don't think it is unfortunately) so we shall see. The dual fans sound like they are continuously cycling and produce sounds like overtones that go Mwah Mwah Mwah. Even with the gain and master volume at 9 o'clock each, I can still here the fans.

This is likely a deal breaker for me if it can't be resolved.

Anyone else have experience with this?
View attachment 5303849

The aircraft-engine dual fan noise is normal for this amp, and one of the many reasons I’ve never sold an amp faster.

 

[Obese Chess]

Might be apples to oranges here but I have a DB750 and it has some very loud fans that together also produce a cyclic oscillation effect. So I feel your pain. The loud DB750 fans are a know "issue" - but I was under the impression that that DB751's were somewhat quieter.

I looked into replacing my fans with something slightly less aggressive but was advised against it by the gurus here.

The DB750 noise is not too bad at coffee house acoustic gig levels, but it's a bit much for nighttime bedroom practice! These are heavy duty amps that shine at louder stage volumes.

Good luck!

Yeah, the bolded points are key here - this is a massive, very loud amp, I don't get the impression it was designed with things like "coffee house acoustic gigs" or "nighttime bedroom practice" in mind, and as such I can't imagine fan noise was a consideration.

Boy do they sound good, though.

 

[agedhorse]

For those living on the edge, could use THIS with a pair of 4 pin fans. (It can control 3 total.)

No, totally inappropriate. There are multiple areas within the power amp that require constant airflow to remain within equilibrium, the original design considered this which is why there is always airflow through the unit. You wouldn't know what elements to sense because some increase and some decrease in temperature as the load changes. If you choose the wrong element, the amp could go into thermal runaway within the driver or predriver stages and fail catastrophically.

Copy that. I am somewhat baffled that there wasn’t a design alternative embraced for these amps…

See the above response.

Yeah, the bolded points are key here - this is a massive, very loud amp, I don't get the impression it was designed with things like "coffee house acoustic gigs" or "nighttime bedroom practice" in mind, and as such I can't imagine fan noise was a consideration.

Boy do they sound good, though.

Agreed, they were never intended to be a low volume amp.

 

[N4860]

“ a cyclic oscillation effect. “

That is the PERFECT way to describe it. It is definitely still happening on my DB 751. I’m pretty surprised by it actually. I don’t know that you could mic a cab in a studio environment without getting some of that bleed.

I am hoping I can just get used to it but I do t know if that is possible.

I've had some older amps like that one that have some loud amps but it has generally never been a problem for me. Amps like that are for playing loud at which case no one is going to hear the fans.

For recording, if you are going to mix the cab, just put the amp in a different room. I personally like to set up my amp and cab in a separate room so that I can sit there and track next to the amp with headphones on.

 

[Grinderman]

For what it's worth, none of the Ampeg SVTs I've owned, past or present, had fans that I found to be particularly objectionably loud in any sized room at any volume or situation.

If these things followed the same standards as high-end performance PC case fans I'd just suggest getting a better fan from Noctua.

 

[Wasnex]

I have seen several DB750s to go down...pretty much every DB750 I have come across. Some have required multiple repairs. Basically the amp turns on but fails the self-diagnostic required to transition fully to operate. Probably not a good idea to go screwing around with the amps' thermal management. It has enough problems with the proper fans .

No idea if the DB751 is more reliable....I hope it is because I own one . Not interested in trading out the fans. AFAIK the output devices for this amp are not longer made...so you really don't want to risk burning them up.

The variable sound my DB751's fans make is a bit unnerving, but apparently normal. My vintage SVTs have louder/more obnoxious fans, but the noise is constant. The Fan in my Marshall VBA 400 is similar to the SVTs...possibly even more obnoxious.

 

[logdrum]

Sorry to hear. But these and SVT CL and all them big amps are gigging amps and the noise is a non issue once the band starts playing. My advice is to get you some AI amps which do not have a fan for practice. I think you are okay. Unless you know what you are doing -- do not modify these fans. It's the price of using a big tube amp

 

[faulknersj]

No, totally inappropriate. There are multiple areas within the power amp that require constant airflow to remain within equilibrium, the original design considered this which is why there is always airflow through the unit. You wouldn't know what elements to sense because some increase and some decrease in temperature as the load changes. If you choose the wrong element, the amp could go into thermal runaway within the driver or predriver stages and fail catastrophically.



See the above response.



Agreed, they were never intended to be a low volume amp.

This is good to know! I have it my music room which is why it bugs me while i'm learning songs at lower volumes but I'm just going to crank this sucker up, enjoy it, and stop being a wuss lol!

FWIW, my Shuttlemax and Streamliner will still get most of the gigs with the exception of the big ones with lots of FOH support.

 

[faulknersj]

Sorry to hear. But these and SVT CL and all them big amps are gigging amps and the noise is a non issue once the band starts playing. My advice is to get you some AI amps which do not have a fan for practice. I think you are okay. Unless you know what you are doing -- do not modify these fans. It's the price of using a big tube amp

This is great advice! I just need to relegate the DB 751 to gig duties ha ha! I have like 4 other amps right now...probably need to thin the heard a bit!

 

[Grinderman]

I have seen several DB750s to go down...pretty much every DB750 I have come across. Some have required multiple repairs. Basically the amp turns on but fails the self-diagnostic required to transition fully to operate. Probably not a good idea to go screwing around with the amps' thermal management. It has enough problems with the proper fans .

No idea if the DB751 is more reliable....I hope it is because I own one . Not interested in trading out the fans. AFAIK the output devices for this amp are not longer made...so you really don't want to risk burning them up.

The variable sound my DB751's fans make is a bit unnerving, but apparently normal. My vintage SVTs have louder/more obnoxious fans, but the noise is constant. The Fan in my Marshall VBA 400 is similar to the SVTs...possibly even more obnoxious.

Sounds like Apple.

Maybe the consistency of the fan noise on SVTs is why they don't bother me.

 

[Grinderman]

Sorry to hear. But these and SVT CL and all them big amps are gigging amps and the noise is a non issue once the band starts playing. My advice is to get you some AI amps which do not have a fan for practice. I think you are okay. Unless you know what you are doing -- do not modify these fans. It's the price of using a big tube amp

An Ashdown Ant 200-watt pedal board amp looks attractive as a lightweight compact plan B.

 

[funkifiedsoul]

- but I was under the impression that that DB751's were somewhat quieter.

They are.
I once passed on a DB750 because of the fan, but with my DB751 it's a non issue. Reasonably quiet actually, and when I start to play my bass sounds so good I don't hear it at all. (even at home)

 

[David McIntire]

This is partly why I never got on with the big Aguilar amps. I cannot deal. I'm one who practices with the amps I gig with. My amps are on a lot. Noise fan noise drives me crazy.

My SWR Bass 350 has a fairly loud fan. But, it has a fan switch. I can defeat fan operation for recording or home practice. The Aguilar 750 and 751 were never created for home practice, but since folk wanna use em fer that, would a switch work as a solution? Probably not. But, a thot. I'm not terribly familiar with the 750(1) pieces an parts an such. And, from what I've read, the amps seem to be fragile and difficult to repair. My 350 generates far less heat at home vs on a stage. Maybe the Aguilars are the same?

And, tho they may not sound identical, I sure wish Aguilar would release a preamp version. They made stellar preamps! Using one with a great power amp should still be an option, in my opinion.

 

[SpiderBass1965]

I never had an issue with my Aguilar DB751. Fan noise goes with a high powered amp such as this. My Mesa 400, 400+, Ampeg SVT CL, VR, 2Pro all make some fan noise too. These are not bedroom amps and all have been used in a studio with no "fan noise" incurring in the mix. The DB751 is great tone monster and it will keep up with just about any "Live" performance situation.