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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
atmasphere's avatar
atmasphere
11,874 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
9,868 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?
simna OP
165 posts
 

When comparing these two tube amplifiers everything else is the same except for the amplifiers. I have just switched between the amplifiers. I have tried both the 8 ohms tap and the 4 ohms tap.

I’m grateful for your posts but I wonder how I will know when the "damping factor" of a tube amp is problematic and how do I know what the "damping factor" of this amplifier is?

roberjerman wrote:

"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!"
This may be right, but how do I, an ordinary music lover, not a technician, know what to look for? What should I look for in specs for the tube amp and the speakers?

The LM34IA has 40W and my old EL84 amp (without boomines) has 35W so it can’t be due to lack of power. Speaker sensitivity is 89dB (Tannoy Eaton Legacy).

I have heard another possible explanation why I get this boomines. The LM34IA is slow and the capacitors should be replaced with "ultrafast capacitors". This maybe why I don’t have boomy sound from my old EL84 amp (Tube Technology Unisis Signature) which has "ultrafast capacitors".

So as I see it there are only two things that can cause this problem; the tubes (solution: try another brand with tighter bass) and/or the capacitors (solution: replace the capacitor to faster).
Maybe also this "damping factor" that I don’t understand what to do/look for to exclude.

Or am I totally lost in my conclusions?

lowrider57's avatar
lowrider57
5,417 posts
 
I’m not an EE, but I’ve never heard of a case where troubleshooting starts with changing out the caps.
If a tube amp/speaker sounds slow and boomy it could be the rectification of the amp.

I would not worry about damping factor.
It could be as simple as the tubes. Maybe you are hearing bass bloat.
What power tubes are installed?

https://www.line-magnetic.eu/en/products-line-magnetic-en/integrated-tube-amplifier-line-magnetic-en...

The Tannoy Eaton Legacy seems like an easy load to drive, but room placement is important and will affect results.

http://www.audiodrom.net/en/component/element/detail/29-stand-mount-monitors/576-tannoy-legacy-eaton



simna OP
165 posts
 

@lowrider57 

Yes, I'm gonna change the tubes, but I really wanna know the brand of the stock tubes before I do that. They are just labeled "Line Magnetic". If this dosen't do the trick I will have the capacitors replaced.

Yes, the speakers are easy to drive, and as I wrote, with my old EL84 amp there's no problem with boomines. Or, to be honest, there's a faint hint of boomines. And yes, I know there's a problem somewhere around 46-50Hz.

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