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HE-500, LCD2, D5000, DT770, SR80, on a speaker amp (Emotiva mini-X A-100) Project - Page 201

post #3001 of 3639
I need one on an hp extension cable then I guess.
post #3002 of 3639

Yup, that should work fine.

post #3003 of 3639
Did your mini have background noise on the he4? Mine doesnt. My mags and 840s obviously do, but the 4 is straight black.
post #3004 of 3639
Quote:
Originally Posted by Thujone View Post
 

The best part, is that we all are using koiloco's jack :p

 

Installed 150ohm resistors to mine today. Bye bye noise floor.

 

So, you went for attenuation but no speaker load matching. What headphones are you using and did it knock out the noise?

 

I have what sounds like a 60 cps hum with the volume pot at 1/3 or higher, with no music playing. Is what I refer to as "hum" the same as others call "hiss?" If so, maybe the 2-resistor network would work best for me: R2 = 5 watt, 6 ohm...R3 = 3 watt, 2 ohm

post #3005 of 3639
The HE-4 had a minimal noise floor on the right channel, more prominent on the T50RP. Yeah, I basically looked around for 200ohm resistors and could only find 150. I wasn't looking to be real scientific or anything, I just couldn't listen to this amp in stock form.
post #3006 of 3639

FWIW, here's what I did based on koiloco's idea. 

 

I have a hum from my Mini a-100 that sounds like a ground loop or 60 cycles per second hum. I'm going to add resistors and see if they knock it out. The Emotiva Mini a-100 performs very well, for me, and sounds good. For the price, you can't go wrong. 

 

If you get a Mini a-100 and choose to modify it like koiloco with a headphone jack off the speaker terminals, you have to measure VERY Carefully because you only get on shot at it. There is limited space behind the face plate and I just barely got it "right."

 

You need to:

remove the knob - it pulls straight off. Not easy, but it's only friction mounted

remove the case cover and face plate (Put screws in a medicine bottle and use a foam pad in case you drop them)

move the heat sink to the side, actually towards the front just enough to reach the nuts on the speaker taps

and remove the volume pot board from the back of the face plate. Make sure you don't lose the little white, plastic washer between the volume pot stem and face plate's clear "window."

 

Measure the width of the front side aluminum accent and mark its position from top to bottom of the Rear side of the face plate. Measure and mark your "pilot" hole for your TRS jack. Draw a 1/4" hole centered over your pilot mark.

 

Digital calipers are essential for accurate measurements which is important when tolerances are so small. Make sure your 1/4" circle around the pilot mark does not impinge upon the edge of the volume pot board And its wire assembly.

 

If only installing a Single End TRS jack, put it on the front-left side of the face plate because there is more room to work, there. Note, I added a mini xlr because it looked too difficult to use a standard XLR without drilling into the volume pot circuit board and the front side aluminum accent.

 

Drill a pilot hole with a 1/16th inch drill bit from the back side of the face plate. Increase the bit size or use a step drill bit to reach 1/4" in diameter.

 

AppleMark

Blue and Clear wires are for + and - TRS/mini xlr jacks to speaker terminals.

 

 

AppleMark

Large black Mogami cable under  and around Toroidal power supply with splitter at the top of the volume pot circuit board going to TRS at top right side and xlr at the bottom right side.

 

 

Splitter on right side goes to TRS on right and xlr on left side of circuit board.

 

 

Circuit board for volume pot with jacks on either side.

 

 

TRS jack right next to harness plug.

 

 

XLR next to other harness assembly.

 

 

 

 

AppleMark

 

 

 

 

 


Edited by bluemonkeyflyer - 1/12/14 at 8:08am
post #3007 of 3639
I just took the faceplate off, didn't remove the pot or knob.
post #3008 of 3639
I noticed in those pics that the transformer is black on the outside. Mine is covered in some kind silvery foil. Does anyone know what this difference means -- newer vs older version perhaps?
post #3009 of 3639
Quote:
Originally Posted by robrob View Post
 

Use the right side of the graphic. 110 ohm resistors on the two + headphone wires will give you 12dB of attenuation which is about the minimum I'd recommend anyone start with, so 100 to 200 ohm 3 watt resistors is my recommendation. One resistor attenuation like this is usually fine for solid state amps but for any tube amp I'd recommend you go with the left side of the graphic's two resistor network to match the amp's expected speaker load.

 Would a 100 ohm, 10 watt, 10% resistor work? 

 

If using only R2 what does 142+ ohms speaker load do to a solid state amp?

 

Thanks for all the help!

post #3010 of 3639

I would recommend 1% resistors to minimize the risk of channel imbalance. Solid state amps shouldn't care what the speaker load is. 

Sonic Craft has a good selection of 1% resistors. 

post #3011 of 3639
You'd want wire wound 1% 1+ W resistor I suppose.
post #3012 of 3639
Quote:
Originally Posted by manbear View Post
 

I would recommend 1% resistors to minimize the risk of channel imbalance. Solid state amps shouldn't care what the speaker load is. 

Sonic Craft has a good selection of 1% resistors. 

Yes, that's what I figured with the cheap Radio Shack stuff they had on hand.

 

What about the watts=10?

 

BTW, I ordered the 5 watt/6 ohm and 3 watt/2 ohm 1% Resistors by Vishay, from Mouser.

post #3013 of 3639

I'm using 5 watt series resistors, and that's plenty. For the two-resistor network, I'm not sure what the wattage should be. 

post #3014 of 3639
Quote:
Originally Posted by manbear View Post
 

I would recommend 1% resistors to minimize the risk of channel imbalance. Solid state amps shouldn't care what the speaker load is. 

Sonic Craft has a good selection of 1% resistors. 

 

^This. 100 ohm 5 watt 1% wirewound Vishay or Vishay-Dale is what you want. 

 

For the two resistor network 6 ohm 5 watt and 2 ohm 3 watt 1% V-D wirewound is my choice.

post #3015 of 3639

I have a very basic electrical / engineering knowledge, so will be grateful if anyone can help me with the following. I plan to try my HE 500's from the 8 ohm speaker taps of the Cayin audio AT70 Tube integrated amp. I will use the Hifiman HE adapter & balanced HP cable. The links for all are as below :

 

 

http://www.cayinusa.com/Product_Name.asp?Category=26:56:40&types=1

 

http://head-direct.com/Products/?act=detail&id=104

 

http://head-direct.com/Products/?act=detail&id=146

 

Will there be any issues that i should watch out for or things should go fine ?

 

Thanks

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