33 replies to this topic

[logarhythm]

Evening Fellas,

I'm running my digital recorder / HD directly to my miniDSP's and the signal is too weak to get any decent volume out of it.

Can anyone recommend a good neutral pre-amp to boost the signal, either DIY kit or complete?

[Zaphod Beeblebrox]

Evening Fellas,

I'm running my digital recorder / HD directly to my miniDSP's and the signal is too weak to get any decent volume out of it.

Can anyone recommend a good neutral pre-amp to boost the signal, either DIY kit or complete?

Budget?

[gainphile]

An op-amp and two resistors should do well ?



I use this with my MiniDSP

[LogicprObe]

An op-amp and two resistors should do well ?



I use this with my MiniDSP

Waits for datafone..................

[gainphile]

This is how it's done (that small brown board)

Btw. which MiniDSP do you have? The newer version has sensitivity jumper. Mine are the old ones.

Edited by gainphile, 23 March 2012 - 08:18 PM.

[LogicprObe]

Just saw datafone come on line..........

[gainphile]

I assume he does not like op-amps

[LogicprObe]

I assume he does not like op-amps

Someone has it quoted in the tag!

As for op amps..............I agree with Rupert Neve.

[gainphile]

Interesting. Well MiniDSP uses op-amps anyway so one can't really get away with that.

I built discrete op-amps in the past. They sounded OK but I guess silicon wafer fabrications would have much tighter tolerances and lower distortions.

[LogicprObe]

As Rupert said.............as long as you bias them into class A, there is no problem.

[logarhythm]

Budget?

<$100 would be nice

Btw. which MiniDSP do you have? The newer version has sensitivity jumper. Mine are the old ones.

I have the newer ones but changing sensitivity modes doesn't seem to do much at all.

I run the DSP's on USB power, can the op-amp jobby still work that way?

[LogicprObe]

<$100 would be nice



I have the newer ones but changing sensitivity modes doesn't seem to do much at all.

I run the DSP's on USB power, can the op-amp jobby still work that way?

It can.........but I find there is not enough swing.
12V is better.

[logarhythm]

This one looks ok but as if I undertand correctly it's a passive pre-amp i.e no gain?

http://www.tnt-audio...t-preamp_e.html

[logarhythm]

It can.........but I find there is not enough swing.
12V is better.

USB is so convenient for me. I power the DSP's from the 2 Xbox USB ports.

Triamping leaves me starved of power points .

[gainphile]

I did not know MiniDSP could be powered from USB! That's awesome.

[gainphile]

I run the DSP's on USB power, can the op-amp jobby still work that way?

What about FET then?

http://lampizator.eu...tishizator.html

[LogicprObe]

Going on memory, 5v for a line level severely limits your dynamic range.

[logarhythm]

Going on memory, 5v for a line level severely limits your dynamic range.

So you think that USB power could be the culprit?

[logarhythm]

What about FET then?

http://lampizator.eu...tishizator.html

Kit I can do, but building from scratch....too hard basket

[Zaphod Beeblebrox]

<$100 would be nice

DIY is all you'll manage at that price.

[Arg]

I'm running my digital recorder / HD directly to my miniDSP's and the signal is too weak to get any decent volume out of it. Can anyone recommend a good neutral pre-amp to boost the signal, either DIY kit or complete?

I'm suspicious, something seems to be not hooked up or working correctly. What is the output of your source? What sensitivity is your miniDSP set at? It should make more of a difference than you say.

Also, what are you running the DSP outputs to? What is the sensitivity of the downstream component?

The other possibility is your miniDSP software is set to cut the output. There are several ways this can happen accidentally.

Edited by Arg, 24 March 2012 - 04:53 PM.

[hochopeper]

Going on memory, 5v for a line level severely limits your dynamic range.

The regulators supplying the op-amps in the balanced minidsp are 5V. I have no idea about the supplies in the unbalanced version since I don't have one so haven't looked into it.

This isn't to say this is a good thing but just as a reference for others. I'm actually looking to replace the opamps on the balanced minidsp but that's another story and I haven't looked into it too much detail just yet.

[LogicprObe]

Plus and minus 5 volts is actually 10 volts.
USB power is just +5V.

[logarhythm]

I'm suspicious, something seems to be not hooked up or working correctly. What is the output of your source? What sensitivity is your miniDSP set at? It should make more of a difference than you say.

Also, what are you running the DSP outputs to? What is the sensitivity of the downstream component?

The other possibility is your miniDSP software is set to cut the output. There are several ways this can happen accidentally.

Signal comes straight out of the hard drive in my digital TV recorder (aux out). It has a volume control.

HD (aux out) > MiniDSP (0.9v mode) > amps

Forgot to add that the amps volume levels (im using 2 yamaha integrated amps with a 3rd on the way, setting level between woofer and tweeter with volume control) are set to about half way. This is limiting output but should be louder than what im getting.

If I turn the amps volume to full I get ALOT of noise so not much I can do about it. Even now it's quite noisy, no idea why....

[hochopeper]

My guess would be that you want to look for problems on your interconnects or other noisy equipment they run near. Once you find the source of the noise then you'll be able to increase the gain on the amps again.

I had a similar problem, only identified it this week actually, was TV antenna lead between wall and TV that caused my problems. Disconnecting it from wall cleaned it up completely.

[logarhythm]

Interesting, I suppose I could have a fiddle with the cables. I never suspected that to be the cause of the noise but i'll give it a try tomorrow anyway.

[Arg]

What are the software settings?

[datafone]

What about FET then?

http://lampizator.eu...tishizator.html

Now were talking

[logarhythm]

What are the software settings?

I have just updated the firmware on the digital recorder box and the volume seems alot louder but will need to wait for the family to leave the house before I can do a serious test.

The minidsp runs 4 way xover plugin with gain set to max on all output channels.

[zog]

I used some inexpensive ebay preamp (ZoeTsang) modules, with some tweaks, to amplify the output of my miniDSP as it wasn't quite cutting it with it's levels going into my amp.

[andyr]

USB is so convenient for me. I power the DSP's from the 2 Xbox USB ports.

Triamping leaves me starved of power points .

Do you want convernience ... or do you want sound quality?

regards,

Andy

[logarhythm]

Do you want convernience ... or do you want sound quality?

regards,

Andy

Well i'd like to have my cake and eat it too

I can't say I have ever noticed degraded sound quality when using the USB powered DSP as an EQ. Other than the noise I find it to be fairly neutral.

But anyway, I do have a 12v regulated power supply which i'll try out tonight.

I used some inexpensive ebay preamp (ZoeTsang) modules, with some tweaks, to amplify the output of my miniDSP as it wasn't quite cutting it with it's levels going into my amp.

Thanks Zog, ill look them up. What tweaks did you perform on them?

[Batty]

How about a valve buffer ?

http://secure.oatley...017daaa247ac9db

I use one between DAc and T-Amp. Has a gain of 3x

[zog]

Thanks Zog, ill look them up. What tweaks did you perform on them?

It was a pair of these units:
http://www.ebay.com/...c-/190649688262
chosen as they do look like pretty much a basic K.I.S.S. generic opamp buffer.
almost excessively described here, and for a few posts afterwards:
http://www.stereo.ne...971#entry518971
but the key changes:
-> bypass input coupling cap (as miniDSP no DC on output)
-> use socketed opa2134
-> didn't use tiny onboard power, but fed DC from chunky power supply I used for the miniDSP as well.
-> stepped attenuator volume controls so I can precisely match the gain on the 2 units.

.. then again I havent been using my miniDSP much recently although it sounds a bit clearer than my passive crossovers......

Edited by zog, 27 April 2012 - 09:57 PM.