Hi
Think I need a buffer stage. According to different forums the low input impedance of the L25d by ljm means low bass levels when its driven by the minidsp 4x10.
A bufferstage seems to be the cure. The only buffers I can find on Ebay wich is where I do most of my shopping is tubebuffers.
If I dont want or feel I need tubes there is nothing for me. A stage like the cmoy headphone amp with its simplicety and low cost would be nice, anyone seen something like that?
Something easy to build at low cost with few parts...
Think I need a buffer stage. According to different forums the low input impedance of the L25d by ljm means low bass levels when its driven by the minidsp 4x10.
A bufferstage seems to be the cure. The only buffers I can find on Ebay wich is where I do most of my shopping is tubebuffers.
If I dont want or feel I need tubes there is nothing for me. A stage like the cmoy headphone amp with its simplicety and low cost would be nice, anyone seen something like that?
Something easy to build at low cost with few parts...
The input impedance of the L25d seems to be 3.3 Kohm. The 4x10 has an output impedance of 560 ohm, but the issue seems to be the 2.2 uF output capacitor - that implies a 21 Hz corner frequency with the 3.3 Kohm input impedance of the L25d. If that isn't low enough for you (does your speaker really go below 25 Hz), how about swapping the output capacitor of the minidsp?
If the output caps on the 4x10 is the problem, removing them will make the next cap the input caps in the l25d? Dont know if thats the solution
I have read in other forums bypassing the input caps on the l25d helps for some., but there will still be caps for the outputstages in the 4x10 to drive.
My speakers are diy open baffles who wont come near 25hz, 35-40hz maybe on a good day with lots of power 😉
I have read in other forums bypassing the input caps on the l25d helps for some., but there will still be caps for the outputstages in the 4x10 to drive.
My speakers are diy open baffles who wont come near 25hz, 35-40hz maybe on a good day with lots of power 😉
The input caps in the L25d are designed for the imput impedance of the L25d. They are not affected by the output impedance of the 4x10.
In that case I don' t think it will be an issue. My suggestion is "don't worry about silly speculation on online forums" 🙂
The thing is I bulit the speakers and the l25d amp at the same time using l25d for bass and a tube amp for a fullrange. I thought they played like they should and that I had made a mistake building open baffles, almost no bass and very dry(just like getting the phases wrong)
I blew the rectifiers on the l25d and had to use an old surround reciver for bass duty. Wohaa new speakers, this was fun, if only the surround reciver could make them play louder.
This is why I started searching for a solution and I belive the solution is a buffer.
If I'd only knew how to build one 🙂
I blew the rectifiers on the l25d and had to use an old surround reciver for bass duty. Wohaa new speakers, this was fun, if only the surround reciver could make them play louder.
This is why I started searching for a solution and I belive the solution is a buffer.
If I'd only knew how to build one 🙂
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And in what way would a buffer help? Maybe your old surround sound receiver just had more gain?
If the 4x10 can drive the surround reciver and not the l25d what will I need to make it do it then? A gain stage? Kind of thought it was the same thing...
What do I need? 🙂
What do I need? 🙂
The 4x10 can drive both, but one might have more gain than the other. A buffer is an interface to do impedance matching, a gain stage has gain. Isn't the gain of the i25d adjustable?
Dont know how to do it or if its possible.
I'm still googling for the solution, in minidsp 4x10 users manual rev3
jumpers for input sensivity and output gain are mentioned for new
boards.
Will check if my have the jumpers, then problem will be solved 🙂 I hope...
I'm still googling for the solution, in minidsp 4x10 users manual rev3
jumpers for input sensivity and output gain are mentioned for new
boards.
Will check if my have the jumpers, then problem will be solved 🙂 I hope...
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Maybe it is as easy as turning down your main channel a bit? What you need to look at is overall gain structure. What is the gain of your tube amp? How does it compare to the L25d? The L25d seems to have an input sensitivity of 1.6V, and the minidsp an output voltage of 0.9V (2V if balanced). The mismatch is less than 5 dB, so you could easily match that by turnin down the gain on the main channel a bit. No point in having an extra amp stage just for 5 dB.
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If it had been easy like that I wouldnt have the need to post here.
The tube is an integrated amp gain can be what i like it to be?
I might dont understand what gain is?
Do belive we are crosstalking, the words are the same, but we understand them diffrently 🙂
The tube is an integrated amp gain can be what i like it to be?
I might dont understand what gain is?
Do belive we are crosstalking, the words are the same, but we understand them diffrently 🙂
So what do you mean with the word gain? I use it in the pretty established meaning of amplifying factor, or ratio of output voltage to input voltage.
Instead of gain, it might be better to look at input sensitivity. What is the input sensitivity (input voltage required to produce full output) of your tube amp? You also need to look at the relative max power output of your amps, and the sensitivity of your speakers. Have you determined how many watts of power you need for the bass channel in relation to the main channel?
To simplify - what I am saying is that instead of trying to turn up the bass channel by 5 dB, why don't you turn down the main channel by 5 dB?
Offcourse i can and I have done that. The sound just wont get "right".
I have tried the l25d driven in both 4 and 8 ohm, even with heavy EQ it wont get right.
Thought the problem was the speakers until I changed the amp, the old surround reciver should in theory play worse with its 5x100 fantasy watts.
Now I belive its the minidsp who cant drive the l25d properly.
On a dutch forum I could see a resitorrs in series paralell configuration on the l25d input. Dont know the language, cant ask why or how...
I have tried the l25d driven in both 4 and 8 ohm, even with heavy EQ it wont get right.
Thought the problem was the speakers until I changed the amp, the old surround reciver should in theory play worse with its 5x100 fantasy watts.
Now I belive its the minidsp who cant drive the l25d properly.
On a dutch forum I could see a resitorrs in series paralell configuration on the l25d input. Dont know the language, cant ask why or how...
The surround receiver probably has a different gain than the l25d.
That should be easy to measure.
That would actually reduce the gain.
If you post a link to the discussion, I can have a look at it (no, I am not Dutch, but i have been living in Amsterdam for the last 17 years...).
Yes it will reduce the gain, but its not gain, but lack of bass wich is the problem.
The surround recivers gain is set by its volumecontrol right? I can put the volumecontrol of the reciver in almost any position and still adjust for that in the settings of the mini ds and the sound will be ok.
I will google and see if i can refind it, thx! 🙂
The surround recivers gain is set by its volumecontrol right? I can put the volumecontrol of the reciver in almost any position and still adjust for that in the settings of the mini ds and the sound will be ok.
I will google and see if i can refind it, thx! 🙂
But the lack of bass can only be because of lack of gain in the bass channel - we have already established that the impedance / output capacitor issues only show up below 25 Hz.
Yes.
But what you should do is turn down the volume, or turn down the main channel in the dsp, without turning down the bass channel, as the issue is that the bass channel is too quiet in proportion to the main one.
https://www.minidsp.com/forum/hardware-support/7597-re-minidsp-not-driving-new-amp-very-well?start=6
Think this is the same problem...
Think this is the same problem...
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