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"The Wire" Official Boards for All Projects Available Here! BAL-BAL, SE-SE, LPUHP

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B

barrows

Member
Joined 2010
tech ? on NTD1 v.3

Hi Owen,

I am ready to try adding some analog filtering to my NTD1 v.3. I see from an earlier schematic that the filter cap can be added at the input to the MOSFETS. My build has the 400 Ohm resistors: is 400 Ohms the correct value for figuring the corner frequency of the RC? Or is figuring the R for the filter circuit more complex than my (perhaps simpleton) understanding.
I am not going to add a strong filter, probably a corner around 200 KHz.

Thanks!
 
T

tER299

Member
Joined 2012
Tolik said:
DC offset with open input I measured is below 0.5-1.4mV
Switching transients are negligible on Audeze LCD3. The amp is DC coupled, so there is no caps to produce on/off transients.
Click to expand...

Ah, nice to know.

I've got two more questions though. What is the performance reduction I get when I run the Bal-Bal into a single ended output? And why are the measured THD to Volt performances for the Se-Se and Bal-Bal (as linked on this page The Wire - All Boards and Kits Explained Here!) the same picture?
 
B

barrows

Member
Joined 2010
no one...

barrows said:
Hi Owen,

I am ready to try adding some analog filtering to my NTD1 v.3. I see from an earlier schematic that the filter cap can be added at the input to the MOSFETS. My build has the 400 Ohm resistors: is 400 Ohms the correct value for figuring the corner frequency of the RC? Or is figuring the R for the filter circuit more complex than my (perhaps simpleton) understanding.
I am not going to add a strong filter, probably a corner around 200 KHz.

Thanks!
Click to expand...

Is no one willing to help with above question. All I need to know is if 400 Ohm is the correct value for R to use in the calculation of this filter circuit. Thanks!
 
S

Sabrosa

Member
Joined 2010
Paid Member
Anyone interested in going in on a buy of LME49610 chips?

It looks like I can get a minimum order of 135 for $5.09 each all-in (tax + freight). The only additional costs would be shipping from me and PayPal fees.

I need 22 for a BAL-BAL and pair of LPUHP, so that leaves 113 remaining to hit the minimum.

If there's enough interest I can start a thread in the group buy section.

Would love to grab a couple LME49870 as well, but I'm not too hopeful about being able to put together an order of 285.
 
agdr

agdr

Member
Joined 2010
agdraudio.com
L-Train said:
I'd be interested in 10 or so of the LME49610, or even the LME49600 since I just need them for headphone amps. I could also use 6 LME49870.

If anyone's looking to take charge on a group buy for LME49990 I'd be interested in 20 or so of those as well.
Click to expand...

FWIW, Newark & Farnell still have the LME49990 and LME49600 in stock right now (Farnell says the 49600 soon to be delivered) in single piece minimum quantities, although a group buy would likely drop the price a bit:

LME49600TS/NOPB - TEXAS INSTRUMENTS - Audio Power Amplifier, AB, 1, ± 2.25V to ± 18V, TO-263, 5 | Newark element14

LME49600TS/NOPB - TEXAS INSTRUMENTS - Audio Power Amplifier, AB, 1, ± 2.25V to ± 18V, TO-263, 5 | Farnell element14

lme49990 - Search Results | Newark element14

LME49990MA/NOPB - TEXAS INSTRUMENTS - OP AMP, 110MHZ, 22V/uS, SOIC-8 | element14 Singapore
 
mrsavage

mrsavage

Member
Joined 2011
I'm interested in a Texas Instruments audio chips

I'd be interested in 25 or so of the LME49610, or even the LME49600 since I just need them for headphone amps. I could also use 25 LME49870. And the LME49990 as well. Price determines how many. Maybe this group buy would change Texas Instruments plains to stop making these chips.:confused:
 
V

vincenti

Member
Joined 2007
maybe if someone wants to organize this make a excel table, managed received fund via paypal we can collect a large purchase for the opamps.

my suggestions is for each type (SE-SE, BAL ....) a fixed set of opamps must be purchased by members. we can reduce error and accelerate the calculation
 
F

FritzS

Member
Joined 2008
stockhammer.at/hifi/
Sabrosa said:
I also went ahead and purchased a small lot of the LME49870 since it seemed unlikely that we'd be able to put together a group buy for the minimum quantity. If you're interested in this chip you may add it to your order for the LME49610.
Click to expand...

What are the followers of LME49610?

Are LME49990MA a good substitute for LME49870?

I have some LME49600TS and LME49610TS in my stock too.
And some LME49990MA (single OPA, SOIC) too.
 
Last edited:
S

Sabrosa

Member
Joined 2010
Paid Member
From Owen's post above:

opc said:
The LME49610 does not have a replacement unfortunately. This has more of an impact on some of my other higher power amplifier projects, but not so much for the SE-SE, BAL-BAL, or LPUHP... all of which are fine with the BUF634 mentioned above. The added voltage headroom of the LME49610 allowed more power to be produced when run on parallel, and being limited to +/-18V does hurt power output on my larger amps (MPHUP and HPUHP).

As for the LME49990, that is also a pretty big loss, but there are alternatives here too. The LT1028 is a very good op-amp, and the LME49710 is also exceptional. The LME49870 is also one of the best if higher voltage output is required. I have used all three and been very happy with the results.
Click to expand...

The LME49990 maxes out at +/-18V, where as the LME49870 can go up to +/-22V. This extra voltage headroom is necessary for building the "overclocked" version of the LPUHP amp.
 
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