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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

KMTech Active Crossover + Burson SS V5 Discrete
KMTech Active Crossover + Burson SS V5 Discrete
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Old 4th December 2015, 02:45 PM   #1
Qwin is offline Qwin  United Kingdom
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Default KMTech Active Crossover + Burson SS V5 Discrete

I tried a pair of the KMTech Linkwitz Riley 3 way active crossover boards and their matching PSU board (all purchased ready built off the Bay). Just let them know your crossover frequencies when ordering and they build to suit and fully test before sending. These were used with my Yamaha NS-1000M speakers. The boards form a line level crossover that sits between your Pre Amp and 6 channels of Power Amp, which are required, to allow a separate channel to power each driver. Two boards are needed, one each for left and right speakers, I was really impressed with the improved performance they gave over the stock passive crossover.

KMTech Active Crossover + Burson SS V5 Discrete


Cap/Resistor upgrade
I decided this simple circuit was worth spending a bit of time and money on, so I bought some bare boards and decked them out with PRP PR9372 1% metal film resistors. There are a couple of Lytics and a handful of Ceramics on bypass duty, but the majority of caps are 5% Polyesters, x20/board with the signal passing through x12/board. I changed these for LCR 1% Polystyrenes, these improved lots of things, but most notably, the mid range, which had previously been slightly recessed.

Op Amp upgrade
The boards come with x5 OPA2134 fitted to each.
I found that with all five fitted, it sounded a little soft and lacked resolution, as the chips are all on dip8 sockets, I got into some Op Amp rolling.

The boards require dual channel unity gain stable devices, I tried the following in all kinds of combinations (Adaptors needed for SMD and/or single channel chips).

AD8066
AD825

Burson Supreme Sound V5 Discrete

LM 4562
LME49720 (NA)
LME49720 (HA Metal Can)
LME49723

LT1358

OPA1612
OPA1642
OPA2134


I got some major improvements with *AD825 for Bass and AD8066 for Treble* (Also worked for Bass), with LME49720HA and LM4562 doing well for Mid Range Band Pass and Input Buffer. OPA1612 worked well for Mid Range, as did LT1358, which could also do well in the Bass filter.

Burson Discrete Op Amps
The whole thing moved to a different level when I tried the new Burson SS V5 discrete modules (Launched 22 Sep 15). The more of these I fitted, the better it sounded, especially when used for the buffer and band pass filter for the Mid Range (+ op amps at *). With this arrangement it produced a Blacker background and deeper well defined Bass. I got a smooth top end and a very detailed and natural tone to voices and instruments. These new V5 modules are very compact and when soldered direct to my PCBs, which have 6mm mounting pillars, will fit in a 1U case with a few mms head room. Using the Burson modules has produced a seriously good sound with this circuit, which is now considerably better than the stock passive crossover, they gave a significant improvement over the other Op Amps tried.

KMTech Active Crossover + Burson SS V5 Discrete

Boards with Burson modules and new caps/resistors fitted.

KMTech also produce 2 way boards and versions with Balanced Input.
I suspect their boards wont work with every type of speaker, but they are cheap enough to try it and see. If you have complex crossovers with notch filters and zobel networks, there may not be a good match, as they offer no form of correction, simple crossovers offer a better chance of compatibility. These active boards work extremely well with the NS-1000M and the Burson SS V5 Discrete Op Amps get the very best out of them.

If you want to see my project in greater detail, find it here:

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Old 7th December 2015, 11:21 AM   #2
croweproductions is offline croweproductions  Canada
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Default KMTech Active Crossover + Burson SS V5 Discrete

Did you make that case or is it a stock Yamaha case?
Also is it digital or analogue in? If the digital, how do you find the conversion quality? Or is it all analogue?
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Old 7th December 2015, 12:10 PM   #3
merlin el mago is offline merlin el mago  Europe
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I guess is all analog.
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Old 7th December 2015, 03:13 PM   #4
Qwin is offline Qwin  United Kingdom
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Yes it's all analogue.

The input/output sockets are all RCA's at the moment.
They do however produce a version of the PCB for balanced input (Not output though).
When I do the final build and solder everything that is on sockets directly to the board, I will use the balanced boards as I think my next Pre Amp will have balanced outputs.

The case is a stock 19" x 1U x 255mm deep pro alloy case. I cut off the rack mounting lugs and painted it black and added the Yamaha Logo and other lettering myself, by screen printing it, using white non drip gloss paint.

KMTech Active Crossover + Burson SS V5 Discrete
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Old 7th December 2015, 03:17 PM   #5
croweproductions is offline croweproductions  Canada
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That's an awesome print screening job. Looks factory. You could sell those to other NS-1000 owners. Did Yamaha ever make such a thing?
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Old 7th December 2015, 04:42 PM   #6
Qwin is offline Qwin  United Kingdom
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Quote:
Originally Posted by croweproductions View Post
Did Yamaha ever make such a thing?
They made an active version of the NS-1000M for the Norwegian TV Broadcast Company. The crossover and Amps were all built in to a module that was fixed to the back of the speaker, so self contained.
AFAIK they never produced a stand alone Active Crossover for these speakers.

If you check out the fake rear labels I made for the binding post area I changed the wording to say "active" speaker system. I used the original type faces for lettering to make it all look authentic.
NS-1000A is somthing I made up.

I may as well post the pic:

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Last edited by Qwin; 7th December 2015 at 04:49 PM.
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Old 14th May 2016, 04:27 PM   #7
Jackcan is offline Jackcan
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I use those boards also. Using Sparko duals for the input buffers. WOW. Will be getting 8 more. Before doing so I built a real PSU for them. That was huge in all areas.
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