[mgalusha]

Given the number of enthusiastic posts lately about digital switching amplifiers, I became interested enough to give one a try. Since I enjoy building things I wanted to go the DIY route but designing and building a digital amp is way out of my league. The only option was to purchase some amplifier modules and connect them up. I chose the LCAudio ZAPpulse 2.1 SE modules. There were several reasons for this choice.

• Previous experience with LCAudio products. I have used their LClock and ZAPFilter modules with excellent results.
• The enthusiasm of Kevin Whilden of Solar Hi-Fi. After reading his posts and exchanging several PM's I really wanted to hear these for myself.
• I wanted to try something different than the TriPath modules.[/list:u]
  
  I ordered a pair of the ZAPpulse 2.1 SE modules from Kevin Haskins at DIY cable. He shipped them immediately and they arrived several days later. Unfortunately one of the modules was damaged in shipping. This was not due to improper packaging, rather it was due to rough handling by the USPS. I emailed Kevin and he responded within 5 minutes and said he would ship a replacement that day. It arrived in two days in perfect condition. Kudo's to Kevin for amazing service.
  
  I had a pair of Parasound HC-1201A mono amps gathering dust in the basement. I originally purchased these several years ago from Audio Advisor for a second system. Unlike some people's amps, my pair were trouble free and have been supplying music in my shop for a few years now. I decided to recycle the chassis and power supply and use these as a test bed for the ZAPpulse amps. It turned out very well. The power supply was 64-0-64 DC and the ZAPpulse requires anywhere from 35 to 72 volts and with a 64 volt power supply is right at 255 Watts into 8 ohms.
  
  I got them up and running this morning with no problems.
  
  
  
  
  
  At this point they are implemented as plainly as possible. No fancy power supply caps or diodes. Only 10,000 uF per rail. According to the cookbook for the modules this is plenty good unless one is driving a 2 ohm load and even then only 20,000 uF is recommended.
  
  Other options are a low pass filter to compensate for a spike in the frequency response at about 70kHz. I have not implemented this yet but plan on trying it.
  
  Internal wiring is 24ga silver plated copper in teflon. 8 strands were used for the speaker connections, resulting in about 15 gauge.
  
  The big question of course is how they sound. At the moment they've only been powered up for a few hours, so it's much to early to tell for sure. But the first impression is very good. I initially connected them up to my HT system as it's in the basement next to my shop and If something went wrong I'd rather kill those speakers than my mains.    I powered them up and was greeted by complete silence. This was expected as they didn't exhibit any output on the bench but it's always a little worrisome to power up a new amp on real speakers. I put on a compilation CD and gently raised the level. No problems and it was immediately apparent that these amps had no shortage of power.
  
  The HT system normally has a Outlaw 750 driving it and the ZAPpulse amps drove the speakers with ease and authority. Cymbals were exceptionally clear and defined. It was good enough that I just shut off the lights and let the disc play. I was quite surprised that they sounded as good as they did, being cold and brand new. Of course the power supplies were broken in but the modules certainly are not. LCAudio chose to use BlackGate caps on these modules, so it's almost a sure bet they will improve quite a bit over the next few weeks. I'm going to connect these up to the FryKleaner at night and this should speed up break in quite a bit.
  
  I brought the amps upstairs and connected them to the main system. Very much the same impressions as in the other system. Plenty of power and seemingly effortlessl control of the speakers. After the system had been playing for about an hour and everything was warmed up nicely I started cranking it up. Very nice. It just got louder with no sign of strain or congestion. Normally this system has a pair of Odyssey Extreme mono amps, which are very good but will sometimes become a little harsh at higher levels and the sound stage tends to collapse a bit. The ZAPpulse modules did not do this. I'm not sure why and I'm nearly certain the system is not running out of power. The Extreme's should be able to put out a bit more power than the ZAPpulse's but the ZAP's seem to run in a more effortless manner.
  
  Enough rambling for now. I'll post more after they have some additional time on them if anyone is interested. For now, I'm just grinning. Very good sound for a very low price. The modules are $189 each from diycable. Obviously a chassis and power supply are needed but even so, the cost could be very reasonable.
  
  Mike G.

[_scotty_]

Given the number of enthusiastic posts lately about digital switching amplifiers, I became interested enough to give one a try. Since I enjoy building things I wanted to go the DIY route but designing and building a digital amp is way out of my league. The only option was to purchase some amplifier modules and connect them up. I chose the LCAudio ZAPpulse 2.1 SE modules. There were several reasons for this choice.

• Previous experience with LCAudio products. I have used their LClock and ZAPFilter mo ...

If you like Blackgates you will love Jensen 4pole or 4 terminal caps
they have a lower impedence at 1mhz than standard Blackgates.

[JohnR]

Nice work Mike

What size are the transformers? Also, you've paralleled the secondaries to get a single supply rail?

[mgalusha]

If you like Blackgates you will love Jensen 4pole or 4 terminal caps
they have a lower impedence at 1mhz than standard Blackgates.

Scotty,

The BG's are factory installed on the modules and according to the LCAudio literature pretty much make the amps insensitve to the main power supply caps. That said, it's likely I will try the Jensen caps for the main PS as well. I have some in my SACD 1000 and they seem to work very well.

What size are the transformers? Also, you've paralleled the secondaries to get a single supply rail?

John,

I'm not 100% sure what the VA rating is on the transformers. According to Parasound's web site they are 280VA.  Not exactly a powerhouse but sufficient for a test mule. If I'm happy enough with them a dedicated chassis, some larger transformers and better caps are in order.

The secondary is center tapped and the voltage off of the transfomer is 47-47 and is +63.7/-63.7 after rectification. I used the power supply that was in the chassis unaltered since the voltage was right. I wanted to get an idea of the sound/performance of these without breaking the bank right away.

Mike

[penance]

HI

Ive been thinking of building 2 monoblocs with the LC SE modules.

How would you describe the sound. warm thin?
is the soundstage good?

sorry for the questions.

[mgalusha]

How would you describe the sound. warm thin?
is the soundstage good?

sorry for the questions.

Hi Penance,

Don't apologize for questions, that what this circle is for!

I'm trying to reserve judgement on the sound since I only fired them up yesterday. I know they will take some time to break in, especially considering the BlackGate's LCAudio uses on the SE.

So far the sound seems very detailed and airy without being too analytical and bright. At this point the sound isn't what I would describe as warm but it's not thin and "dry" either. The amp appears to be providing a pretty accurate reproduction of the source. Until these have some more time on them, I'm not going to analyze the sound in great detail.

As for the soundstage, at this point I would describe it as large. Yesterday I was playing Buckwheat Zydeco - Ils Sont Partis, a decidedly non audiophile record, and some of the guitar was well outside of the speakers. Instruments appear well delineated in space and center images are well centered.

I figure after a week or so on the break in box they should be pretty well broken in. Keep in mind that I have about the bare minimum for a power supply and have not tried any of the compensation configurations listed by LCAudio. With a better power supply and a low pass filter on the input they may improve quite a bit. If so, these could end up sounding very good. Time will tell.

Mike G.

[penance]

Hi mgalusha
Thanks, sounds good so far then
i may well invest in some LC modules

[_scotty_]

Hi mgalusha, This LC module looks similar to the Tripath EVAL board I based my amp on without having to fix the implementation of the circuit.
If I read and understood the website info it looks like they might have a 50ns deadband time which is 15ns shorter than my amp.It should have potentially better high frequency reproduction than my amp and maybe better liquidity. The least expensive entry level amp they sell looks like it uses Jensens on the board to start with. I would be interested in putting Blackgates right next to the output devices for local decoupling and some
high speed storage right at the point of use. This is what I did on my DIY amp and it seems to work very well. I couldn't tell what type of small value caps were on the circuit board. Do you know anything about their products that isn't mentioned on their website

[mgalusha]

Scotty,

Download the cookbook from their site (if you haven't already). It goes into quite a bit of detail and has some good close up images of the board. Other than that, I don't have any other info. Just what's on the web site.

The board is mostly surface mount components of course but it does have some through hole components. It has two BG 47uF/160v caps on the board. I'm not sure if they are on the power rails or the output. In addition, there are 4 RIFA caps on the bottom of the board. Again, not sure how they are wired. I could probably figure it out but that would require pulling the amps apart and that's not happening for a little while. In one of the images in the cookbook they have an amp using BHC Aerovox 4 pole T-Network caps. These are similar to the Jensen 4 pole caps.

At some point I may try an external clock. The modules normally run at about 490kHz but can run up to 1MHz. That may make things a bit smoother as well. I was reading the fixes and tips section of their site and am going to install the Zobel RC network across the speaker output as they recommend. I did some testing with a radio and the amps are currently broadcasting nicely. According to their site installing the Zobel eliminates much of the EMI as well as preventing high frequency oscillations.

Mike

[beat]

very cool mike!
So basically, If one had a beat up amp with a good transformer and heat sink, you could just gut the thing and drop the 2.1se right in and you are good to go? You made it sound so easy! Is it 189.00 for the pair?

[KevinW]

very cool mike!
So basically, If one had a beat up amp with a good transformer and heat sink, you could just gut the thing and drop the 2.1se right in and you are good to go? You made it sound so easy! Is it 189.00 for the pair?

It's $189 ea...  but still a great value with the resulting sound quality.

Regarding your amp, what matters is the DC voltage existing in the amp.  You need both positive and negative voltage rails, between 24V and 69V.  If your beat up amp has this, then you can be rocking without hardly any effort.  Just wire up the modules according to the official cookbook, screw them to the chassis or heatsink with a little thermal grease, and that's it.  Those amps barely get warm, so attaching them specifically to the heatsink is not that important... there's not that much heat to dissipate. Just about any metal surface will do.  Let me know if you have any more questions on how to DIY these modules.

[tmd]

Hey Mike,
I am interested in these kits also and was wondering if you could post your most recent experiences and impressions of the sound.
Thanks, Neil.

[PeteG]

Mike
I'm interested in what you think of the digital sound compared
to ss/tube amps, especially the bass.

[mgalusha]

Pete and Neil,

At this point the jury is still out on the sound. When first built I listened to them in my home theater system. The preamp in that system is a Denon AVP-8000 and is of course solid state. They were substantially better than the Outlaw 750 that normally runs that system. The Outlaw isn't a bad amp, but it's not exceptional (except for value) either. I was very happy with the sound and had great expectations for them in my 2 channel rig.

I moved them to the other system and was less than thrilled with the sound. While not bad, they weren't really good either. I left them in the system for a week, playing them every evening and leaving them on the FryKleaner at night and while I was at work. After a week I felt they should be pretty well run in and did a comparison with my other amps. Normally I have a pair of Odyssey Extreme mono's in the stereo rig and they sound very good in that system. Tyson was visiting and I enlisted his ears as well. All amps had been powered on and were thoroughly warm, so that wasn't a factor. I played a track with the ZAPpulse amps and it sounded OK but was nothing special. I then connected the Odyssey's up and put the same track on. It was immediately apparent that the Odyssey amps were in a different realm. Every portion of the spectrum was more natural sounding. Bass was much better with the Odyssey's. I was a bit surprised given the buzz about how good digital amps do with the low frequencies. Dynamics were also much better. Basically the ZAPpulse amps sounded thin and flat. Like there was a signal compressor in the system.

I was rather surprised. This was just the opposite of what I heard in my other system. They were very dynamic and full sounding with massive sound stage. In the two channel rig it was entirely different. I had tried to avoid critical listening all week, hoping that things would improve as the amps ran in, but I knew it wasn't sounding right. The direct comparison made it very clear just how much different things were.

I connected them up to the HT rig again and they sounded much better. Admittedly this is an entirely different system but they seemed to work very well in that system, especially in comparison to the 2 channel system.

Thinking about it, I am pretty certain that my 2 channel preamp does not like the load of the ZAPpulse modules. The modules have only a 2K ohm input impedance. This is very low, especially when driven by a tube preamp. My preamp has an output impedance of 300 to 600 ohms (depending on which spec you read - I've never measured it) and this is certainly not providing a 10:1 ratio as is commonly suggested. I have been pretty busy and haven't had much time to play with this yet. I should be able to try some tweaking this weekend to see if I can get a better match. I also have a email to Lars Clausen, the designer to see if he has a preferred method for raising the input impedance or otherwise matching things up. I *hope* that getting a better preamp <> amp impedance match will raise the performance level. I am fairly certain this will be the case. I may drag the Denon Pre up from the basement but I really don't want to have to rewire the HT afterwards.

I'll post more if I can get the impedance sorted out.

Mike G.

[tmd]

Thanks for the detailed reply Mike. I for one will be disappointed if they don't perform better. Please do report back if you find a better match and a better sound.
Regards, Neil.

[KevinW]

I *hope* that getting a better preamp <> amp impedance match will raise the performance level. I am fairly certain this will be the case....

Mike,
This will definitely make a large difference.  Getting the input circuit correct is one of the tricks for extracting the maximum performance of these modules.  Based on the reviews of my amp, there is no doubt incredible performance can be obtained by the DIY'er.

[PeteG]

Thanks here too, hopefully it's the impedance match. I had a sim audio SS amp matched with a melos tube preamp and the impedance was not good and it sounded terrible but match them with something else and they sounded fine.

[mgalusha]

This will definitely make a large difference.  Getting the input circuit correct is one of the tricks for extracting the maximum performance of these modules.  Based on the reviews of my amp, there is no doubt incredible performance can be obtained by the DIY'er.

Kevin, I have read the reviews of your amp based on these modules and I have no doubt they are capable of delivering much better sound than they did in my main system. As above, they sounded very good in my HT system driven by a SS preamp.

I do have a question for you if you're willing.... I know you can't share your input design as this is the IP (amongst other things I'm sure) that makes your implementation unique but I would like to know if you are running the RC (Zobel) filter across the outputs that LCAudio shows on their web site? It's supposed to stop the amp from going into oscillation when unloaded suddenly. The reason I ask is their site lists this on the 2.0 fixes & upgrades page.  I've sent email to Lars asking if this is needed for the 2.1 modules but thought I'd query you as well while awaiting his reply.

Thanks,

Mike G.

[_scotty_]

PeteG, you should email Lars and ask him how to set up your input
for about 20kohms to 40kohms. Your tube preamp would like to see this
sort of input impedance or higher. 2k as an amplifier input impedance is 1/10to 1/20 the industry standard. Also the Zap amp should be set for the industry standard 26db of gain if it isn't already. I don't think it should take to much for the Zap people to correct this oversight in their kit.

[PeteG]

Scotty
 I'm using a sim audio w5 amp (47.5kohms) and I sold the tube preamp,
problem solved. I'm using a different preamp now.