Eich T 900....high pass filter??

[ebenezer]

Many class d bass amps have an hpf built in!...does that include the t900?

 

[fretmeister]

It's not just Class D.

 

Most bass amps do. Stops inaudible frequencies reaching the speakers, wasting energy and causing excessive wear on the speakers.

It's normal and a sensible part of bass amp design.

[pete.young]

Why not email Eich and ask them? They're usually able to reply to questions in a couple of days.

[Rodders]

I use a TecAmp Puma 900 which is the same amp just branded differently, I still use a HPF (in an analog preamp) in front of it and find it helpful. 

[Acebassmusic]

I've been looking at amp / speaker / hpf specs etc and have come up with a bit of a "theory" on this. I used to own a Puma 900 and it was a great amp and from what I can see the Eich is a slighly improved / re-badged version so I'll bass (😉) my thoughts on this.

 

As we know, the idea of a high pass filter (HPF) is to reduce the low frequency part of the signal so that the sound is cleared up, speakers are not pushed too far and amp power is not wasted on inaudible and/or unreproducable frequencies. This allows all the energy to be used to push the relevant frequencies, resulting in greater punch and clarity.

 

A quick look at quality bass speaker designs (Barefaced, Vanderkley, Bergantino etc) shows that their operating range starts from 40hz and heads upwards. Trying to put frequencies lower than 40hz at high volumes through them will probably end in tears. This is where a HPF comes in and one of the popular and highly reccomended ones is the micro-Thumpinator which filters out frequencies below 25Hz.

 

If you look at the EQ frequency centres for the Eich amp and think of the Lo and Lo-Mid in a slighly different way you in effect have a built in adjustable HPF! The Lo control cuts and boosts around 30Hz so if you use it to cut the signal it acts like a micro-Thumpinator. You then can use the Lo-Mid @250Hz to help shape the low end ouf your sound.

 

It seems a bit counterintuitive turning the bass knob down to sound more like a bass but I've tried this out live with a number of different amps cutting the lows and boosting the low-mids and find it cleans up the sound and gives it more punch....YMMV. Maybe Magan Trainor should have sung "It's All About The Bass (Knob)" 🤣