NE-80100 low frequency cut-off ?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Script

Well-known member
Joined
Nov 27, 2008
Messages
2,263
Location
Japan
What's the low cutoff frequency of the NE-80100 DOAs? Do they attenuate down very low bass (below 50 or so Hz) by default?

I found two module cards in my junk pile and thought I should quickly test before ditch. Turns out they are working, no humming, no crackling. Haven't measured in detail but bass loss is clearly visible on LED metre, some -2dB or -3db on very-low kick drum from a drum machine that goes ridiculously low, so not necessarily a bad thing ; ) Overall 'louder' and 'rounder', like Mr Rumble gone. Other than than, the overall freq spectrum sounds fine. But was wondering whether this is a feature of the DAO or me feeding it wrong.

In quick test I fed from gear output driver with cap, wired directly to the module card input, where a volume pot sits shunted to ground before the actual NE-80100 summing AMP. So this might be creating a HPF ? Should feed low (near zero) impedance, I assume ?

Or is the loss in bass because I run the DOA underpowered? It needs +/+22V but that tranny only puts out a max. of 22/22 unloaded (PSU trimmed to +/-21.95V), so unhealthy and underspecc'ed for the test and DOA runs out of steam ?

Thanks for observations, insights and experiences with these DOAs.

---
Here's the schematics of the card module (see NA80169(MA)).
NE80100 in PM schematic.png


And the very quick-and-dirty test rig showing the actual modules. The second pot is an AUX amp feeding directly into the DOA summing node onboard, hence the toggle switch.
IMG_test rig.jpg
 
Had swapped out all caps before testing, except the 0.0047 (4n7). Didn't have, but should be fine, I think. Didn't swap 10uf BPs in AUX circuit though... ah...
 
Swapped BPs on aux too. No difference. DOA swallows ultra-low bass. I mean that drum machine, when straight into mixer and turned up in vol, causes speaker cones to almost 'earthquake'. Thru that DOA, the speaker cones calm down considerably. -- Good :)

PSU still too weak though. Minus when loaded with those two cards idles at -21.30V. Crapping out could be cause of bass loss ?
 
yes, if it's bass loss in the form of clipping/distortion, then weak PSU can have influence. But it has to be really weak to crap out on a simple line-level signal like we have here (you're not driving headphones or speakers directly from this, are you?)
 
(No, into op amp line mixer.)

Unlike shown in schematics, module had BP 100u on output already.

Got a PM with suggestion to use
- BP 47u btw. INV IN of op amp and 1K8 to GND
- as well as BP 100u or 220u on output. Stuck 470u, as I don't have 220u here right now.

Quick listen and that seems to have solved it. Now which one did it ? Still needs more testing, but oumph is back -- for better or worse.

Out of mere curiosity only I will later also try driving a transformer, don't intend to with this though. Yamaha themselves used the NE-80100 with BP 100u on output to drive some 500:600, which I don't have. And I think I remember having read on this forum that this DOA doesn't happily drive 600, IIRC.

NE-80100 into XFMR.jpg
 
Last edited:
It was the 10u and 1k8 forming a filter at 8.84Hz on inv. IN of op amp.

Stuck 100u in for now, which pushes the corner down to 0.884Hz -- all the lowest low bass mayhem is back. Not sure what I prefer. Might make it switchable or turn into selectable Low Cut, hmm

This module came from a Yamaha PM series mixer (consumer model), so I guess Yamaha put the 10u there on purpose.
 
Last edited:
Back
Top