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Problem related to Push-Pull or EL34?

Hej

I have compared my EL84 amp with an EL34 amp and what strikes me is that the EL34 amp is boomy. I know that my room has a problem in the bass region and it’s like the E34 amp makes this worse. So why is that? Both are Push-Pull, but my EL84 amp has got the original capacitors replaced to “ultrafast” capacitors. So this makes me wonder if there is any truth in what I've heard: 

  1. ...the Push-Pull design in itself increases the bass and makes the sound a little boomy.

  2. ...you can counteract this by replacing capacitors to “ultrafast” capacitors.

  3. ...EL34 tubes by design emphasis bass frequencies.

This makes me very frustrated because I really like this EL34 amp (LM EL34IA) except for this bass problem. The amp is in my budget range and I need the 40W it gives (which means Push-Pull).

Any thoughts?

simna
kalali's avatar
kalali
1,977 posts
 
In my limited experience, all things being equal, e.g., power rating, cables, speakers, etc., the tube amps with higher output impedance/low damping factor tend to have a more boomy bass response. You can try a different output tap, 4 ohm vs. 8 ohm, and see if that makes a positive difference.
lowrider57's avatar
lowrider57
5,417 posts
 
Good idea on trying a different output impedance. Also true about damping factor.
I expect some expects will weigh in about this.

roberjerman
4,319 posts
 
Tube amps with output impedances greater than 1 ohm will not have a flat response into a speaker's varying impedance. They will act as tone controls! So, choose your tube amp/speakers with this consideration in mind!
atmasphere's avatar
atmasphere
11,849 posts
 
Tube amps with output impedances greater than 1 ohm will not have a flat response into a speaker's varying impedance. They will act as tone controls! So, choose your tube amp/speakers with this consideration in mind!
While this is off topic, the actual situation is more complex than described above. This is because all amps make distortion, and the ear interprets distortion as tonality *unless the amp is clipping*. Apparently the brain has tipping points, where its processing of the sound changes from one portion of the brain to another- in the case of distortion, the brain can actually favor tonality caused by distortion over actual frequency response errors (or lack thereof). For this reason, an amplifier with a higher output impedance can often come off as more neutral than an amplifier with a lower output impedance, even though the latter is more 'flat'.
In the case of the OP, I think trying different taps is a good idea, and it may also be a good idea to try a different speaker cable. Tube amps have generally higher output impedances and so appear more sensitive to cables. For this reason its always a good idea to keep the speaker cables as short as possible. 
bdp24's avatar
bdp24
9,846 posts
 
The obvious question is, what speaker is the amp hooked up to? All amp/speaker combinations are "systems", the sound of each dependent on the other. Why is it assumed it is the amp that is boomy, rather than the result of the amp/speaker interaction?
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