LC ZAPpulse Amplifier Q & A

[wytco0]

Following Lars suggestion in the UCD400 thread, this thread is suggested as a discussion place for the LC Audio ZAPpulse amps.

Although I have not used the LC Amps I have used their Predator power supply to power my UCD modules. I believe others have done the same.

We are extremely lucky to have the people involved in designing and building the LC and UCD modules in this forum and I for one would like to thanks them all for their assistance.

So first question about ZAPpulse, are there any new higher power versions planned?

[Lars Clausen]

Hi

At this point we have no plans to release our high-power version of ZAPpulse.

However you might have noticed that we have upgraded the power of the newest verion of ZAPpulse 2.2SE to 360 W in 8 Ohms and 720 W in 4 Ohms.

[Duck-Twacy]

Is that a newer version (or the same as the model sold a few months ago)? The cookbook and website still mention 286 watt@ 8 ohm at 69V DC.

[Lars Clausen]

Duck Twacy: Same as sold a few months ago, as long as it's the SE version you can run it up to 80 V rails and get the 360 W in 8 Ohms / 720 W in 4 Ohms.

The non-SE version however is limited by the 63V MKT caps.

LC

[mrsito]

For Lars:

I have just ordered 2 modules, and I see that you believe a modification to input resistors for LM6172 can change hiss coming from the Zappulse modules.

I would like to try this in my modules, if you can be more specific.

If you want to reply privately, please email at address

"mrsito AT yahoo.com"

Regards,
mrsito

[Henrik Juhl]

Hi Lars,

(Vi kunne snakke Dansk, men så går de andre glip af guldkornene..... )

Originally posted by Lars Clausen
The non-SE version however is limited by the 63V MKT caps.

Does this mean that one could replace the caps of the non SE version with caps of higher voltage rating and get the same power for the non SE modules - or are there any other limitations

The reason I'm asking is that I would like to use some toroids I allredy have rated at ±50 V AC (± 69 V rails) for subwoofer use - and me thinks not me needs the claimed extra quality of the mid and treble.

Possible ?

[bambadoo]

Yes You can, but bevare of soldering/desoldering issues on the Zappulse boards, because of the 4 layer pcb's.

[Lars Clausen]

Bambadoo: Thanks for answering that one for me. Exactly right ;-)

About the hiss issue, i have not had the time to test out the best way to do this yet, and also i have not had the time to make an instruction for you, so i am not going to expand on that particular issue just yet. Sorry

[bambadoo]

Thanks Lars.
I have after trying all of your comercial zappulse modules (from v1.0 to 2.2se) and become quite familiar with them. I have had my problems (with the v4p), but now they only play beautiful music. I have posted my system setup in several forums. The version that surprised me the most was infact the versjon zappulse 1.2, where I tried different mosfets. I ended up using the STP19nb20 and the music flowed with ease
Of course the 2.2se is better, but as an early design, the 1.2 impressed me.
Now I am using the 2.2se (with black gate) and some Elna cerafine psu caps. Diode bridges and 1 trannie /channel. In monoblock. Havent got any problems with hum or hiss.
One day I actually tried them with some 94db speakers I have in my basement. Audio Note AN/J (they are being upgraded), and the combination performed quite good actually. I heard some hiss from the
speakers, but it wasn't much. I am using an audio note dac, one ss preamp, and tried a Kora Eclipse valve pre, with good result. I have some problems with a ground loop or something with the valve pre, but the combination is very interesting. The Kora (upgraded with silver cable, mcap silver caps etc.) is like a pre with turbo. Very dynamic and the combination is extremely lifelike. The earlier zappulse modules didn't like the cable-spaggetti that was behind the amp, but the 2.2 is better here.
Btw. I am planning another pre. for my setup, however one of those I have in mind has got quite high output impedance. The zappulse modules have 17 k input impedance. Is there an easy way of making that input impedance higher?

Best Regards bambadoo
Greetings from Norway. It is snowing now, and it is almost weekend.

[Lars Clausen]

Bambadoo: Thanks for using all my products ;-)

The input of the 2.2SE goes to a virtual ground coupled op-amp, so the best way to increase the input impedance is simply add a resistor in series with the input, say 100k.

Of course your gain will drop from this also, but can be increased again by lowering the value of R4 to say 4k99.

Also here in Denmark it's snowing, it's beautiful, and it's also almost weekend ;-)