Valve amp on subwoofer

[Keith_W]

I am getting a new pair of subwoofers made. This is a custom job and will look like an extension of my entertainment cabinet:

... if you can imagine the cabinet extended either way sideways, that's what the sub will look like. You can also see that the valve amps are placed on either side of the TV. I need to create some space there because I will soon be upgrading to a larger TV, which means that the amps will have nowhere to go, except on top of my new subwoofers.

These subs are configured in an isobaric back to back configuration, which should reduce vibrations somewhat. However, the sub designer advises me that no matter how much internal bracing he designs in, vibrations can never be eliminated.

My question: will there be any harm in placing the valve amps on top of the subs? If I have no choice but to do it, can someone recommend an isolation platform that is PROVEN to reduce vibration and tuned to bass frequencies?

 

[audio.bill]

Keith - I realize this isn't what you want to hear, but tubes are microphonic by nature and as such the least desirable place to put them would be on subwoofers. Since you stated that you will have no alternative to positioning them there, I think the only type of isolation platforms that would be effective in such a situation would be an active isolation system like the Halcyonics or something similar. Unfortunately that type of platform is very costly so you might want to reconsider any alternatives. Would it be possible to setup a pair of amp stands on the floor next to each speaker?

 

[treitz3]

Bad, bad, bad idea IME Keith. What you are proposing is the worst case scenario for a solution.

Tom

 

[DaveyF]

Keith, generally the best solution is to have an audio system separate from the TV/Home theater system. Getting the TV out from between the speakers pays major dividends IME.
OTOH, if that is not possible, how about placing the amps on the floor either a) behind the speakers or if room allow, b) besides the speakers. I presume you will be doing away with the JL subs? Therefore, why not place the amps in the space where the JL's were residing?
Tube amps on top of a sub is a no/no. Tube amps in front of a sub is not much better, but at least you can more easily address the issue of amp isolation.

 

[Keith_W]

audio.bill and DaveyF ... I think you guys are right. I had major doubts about my plan anyway, and thought i'd ask the forum to see what the consensus was. I'll put the amps next to the speakers. They will be directly in front of the subs if I do that though. Maybe I need to dampen the valves with some valve rings. Thank you for your replies.

 

[FrantzM]

Hi Keith and welcome back

I do not have any intention of derailing your thread but to me the important question is why valve on a subwoofer? On a full range I could understand the logic but on a sub?

When it comes down to it .. Subwoofer must move air at low frequency thus the "vibrations" .. That is what they do and tubes microphonic tendencies will be exacebated at those (low) frequencies ... save from putting the amps in another well insulated room the solutions could quickly become very expensive and the gains not obvious to me ...

Again I apologise if that is not what you want to hear. Again, I sincerely would like to understand why it is valve you want on your subs.

 

[Ron Resnick]

I share the puzzlement about why you would want tubes on your subs. If it simply is to maintain tube purity across the frequency range I can totally understand that.

I am dogmatically 100% tubes in my electronics (not a single transistor anywhere in the signal path). But even I would consider, and even adopt, solid-state to power subwoofers. (I hold my nose at Class D amplification but, for subwoofer towers, I would even consider Class D solid-state to achieve very high amplifier power to control big cone drivers in subwoofer towers.)

 

[audio.bill]

I may be wrong here, but I don't think that Keith intended to run his subs with tube amps. With his title "Valve amp on subwoofer" I think he was only referring to his tube amps driving his main speakers being placed on his subwoofers, not being used to drive them. As you can see from his system photo above the speaker cables appear to be going from the tube amps to the main speakers. Am I correct, Keith?

 

[Keith_W]

Exactly right, Bill. My original intention was to place the valve amplifiers on top of the subwoofers. NOT use the valve amps to drive them. I'll be using a Class D amp to drive the subs.

 

[FrantzM]

Exactly right, Bill. My original intention was to place the valve amplifiers on top of the subwoofers. NOT use the valve amps to drive them. I'll be using a Class D amp to drive the subs.

Ok I understand now .. Simple answer don't place the valve amplifiers on top of the subs ... Put them (amps) as far away as possible from the subs ... Then do use some kind of vibration control.