[Jaytor]

We could have used your VTV board and popped a tube on there. oooh la la

I forgot to comment on this. So far, I'm not that happy with the VTV tube buffers. I used these for more than a month so I think they got plenty of break-in.  They just never opened up - just sounded a little too subdued for my taste. I picked up a pair of Pass XA60.8 monoblocks about a month ago and have been listening to them since, so the Purifi amps have been sitting on the sidelines.

I'm planning to design my own input stage for the Purifis as my next experiment with these but I've got a few other projects I want to get done first and have been very busy with work as of late so it's been slow going.

[poseidonsvoice]

Thanks for the update Jaytor. Good to hear.

RonP...Pinnocchio is a good buddy of mine and his builds are superb, reliable and safe. 

I've started my Pass experiments and we'll see where it goes. Interesting fun so to speak. There are about 1-2 dozen amplifiers I can build into this platform.

I don't want to inundate this thread with my pics and verbage so if interested, link is above.

Best,
Anand.

[RonP]

I forgot to comment on this. So far, I'm not that happy with the VTV tube buffers. I used these for more than a month so I think they got plenty of break-in.  They just never opened up -

wow how disappointing. thanks for the update

[AKLegal]

I wonder if you can get away with not using an input cap on the Folsom if you put the Neurochrome buffer board before the input. Just short the input cap section.

[Jaytor]

wow how disappointing. thanks for the update

Well, it could be that they just weren't a good match to the rest of my system and my listening tastes. But, yes, I was disappointed, particularly since they weren't cheap.  I may try them in a different system to see if they sound any better to me.

I wonder if you can get away with not using an input cap on the Folsom if you put the Neurochrome buffer board before the input. Just short the input cap section.

As far as I know, the Neurochrome buffer is DC coupled so any DC offset will still be passed through (and amplified if you've got any gain in the buffer). Also, I think the Folsom design may require a cap or transformer to prevent adding it's own DC offset from input currents.

[mkane]

Aleph J here.

[mkrawcz]

I picked up a pair of Pass XA60.8 monoblocks about a month ago and have been listening to them since

So how do you like those compared to your JC5?

[AKLegal]

I forgot to comment on this. So far, I'm not that happy with the VTV tube buffers. I used these for more than a month so I think they got plenty of break-in.  They just never opened up - just sounded a little too subdued for my taste. I picked up a pair of Pass XA60.8 monoblocks about a month ago and have been listening to them since, so the Purifi amps have been sitting on the sidelines.

That is too bad. I've read alot of mixed reviews on VTV as far as build quality control but not much on sound quality. You have about seven pairs of mono blocks now right?

[Jaytor]

So how do you like those compared to your JC5?

Both are excellent amps, but the XA60.8s have the edge as they should given the price disparity. The Pass amps have a deeper, more layered sound stage and a gorgeous midrange - particularly vocals. I've sold the JC5 so I didn't get a lot of time to directly compare them. It's possible the JC5 has a bit more bass slam, but since the bottom 2 octaves come from the servo subs in my system, it's a bit difficult to say definitively.

This is definitely a keeper (at least for a while  ). It gives me a good target to shoot for with my DIY builds. But there are definite downsides. They are big and heavy (each amp is as big and heavy as the stereo JC5), and they use a lot of juice (400 watts each at idle) and therefore generate a lot of heat. But I certainly have no complaints about the sound quality.

I like having monoblocks in my system because I have a set of french doors on the front wall that I like to be able to get to without worrying about tripping over cables, and it's easy to hide the interconnects under cable protectors. Not so easy with speaker cables and power cable.

That is too bad. I've read alot of mixed reviews on VTV as far as build quality control but not much on sound quality. You have about seven pairs of mono blocks now right?

Hah. Only four pairs of monoblocks, plus a couple of older AB stereo amps (Bryston 4B-ST and Krell KAV-250a) . That's not including the 7 channel amp I have in my home theater or the 6 channel amp I have driving my whole-house audio system.

I'm working on another DIY Purifi stereo amp for the bedroom. I want something compact that will drive the NX-Studios I have on order. 

The build quality on the VTV tube buffers is excellent. ENIG plated PCB with mostly surface mount components and good quality parts. It's a well designed board that is nicely laid out. I just think it is not a good match for my system and taste. If you were looking for an amp with a mellower, more laid back presentation, or to tame a too-bright system, it would probably work well.

[Jaytor]

I wanted a small amp for the bedroom that will be used with a pair of NX-Studios. I built a stereo Purifi amp using the Neurochrome input buffers and a Hypex 3000w SMPS in a Galaxy 2U 230mm x 280mm case. I used the 3KW supply mostly because the 1200W suppliers were out of stock, but it does have the advantage of having multiple power connections.

In order to fit two channels in this case, I had to mount one above the other, and used a 10mm slab of aluminum for the upper case. It's a very tight fit and I have to remove the connectors on the Neurochrome board and hard wire the power connections.

Since the 3KW power supply is not designed for half-bridge amplifiers like the Purifi board, I wired the second channel in reverse phase (both inputs and outputs), to balance the load on the supply so I don't have to worry about large reverse currents at low frequencies (although I'll probably never play the speakers loud enough that this will be an issue anyway).

[DigIndig]

Figured I'd share my progress on my own amp builds as I work on my NX-Oticas as well. Last fall, I started a pair of Folsom EC7293 monoblocks, and back in January I bought a Elekit TU-8600S to assemble at some point since I had so much fun building a TU-8800.

Last weekend, I finally had time to start the 8600 build, and I did it over three evenings: the soldering split over two and the transformers and case the third night. It came alive immediately with no issues, and I can already tell it sounds amazing with just the Gold Lion 300Bs in it - I'll try a few other 300B tubes at some point, but for now this will do. The kit came with all the upgrades, and I added VCaps as well.




After that experience, I really wanted to finish my EC7293 builds, which had been mostly done minus final assembly and waiting on a few parts which had since come in. Like others, I decided to include the Neurochrome slow start boards, and also have a set of the speaker protection boards that I might integrate in later. For now, each amp will look like this:






I saw "will" because it was a bit of a mixed bag. The first one fired up just fine, and I initially tweaked it to have a 8mv DC offset. A little later I went back and was able to get it down to as close to 0 as I could (my meter will flash 1mv every 30 seconds or so).

I was not so lucky with the second unit. First, it had a .4v offset at the output jacks, and the photocells were only reading 2v with the light module. They read a full 8v with my LED flashlight, and the offset remained even if I used the flashlight on the PV cells. I also saw a .3v potential across the input with nothing attached, which seemed odd. As part of an experiment, I plugged a cable (with no signal) into the RCA jack to see what would happen and -poof- I had a smoking 7293 and a blown fuse! (Sorry, no pictures.)  Upon disassembly I discovered that one transistor leg had popped off the solder pad and was hovering less than 1mm above the pad - impossible to see with the board installed against the heatsink. Probably happened somewhere between the drive from my workshop and back, or in the months it's been sitting waiting to be assembled.

I've already fixed both the transistor and replaced the LED module, but of course the EC7293s are on backorder now, so in the meantime I have a really nice sounding monoblock. I still need to drill out a hole on the faceplate for the power switch, which I installed on a long enough wiring harness to fit wherever I finally decide to put it.

[Jaytor]

@DigIndig - Sorry to hear about your mishap. I bought the parts to build a pair of Folsom amps last year, but haven't gotten around to building them and have a couple other projects in the works, so these parts won't be used for a while.

I can send you a 7293 if you can replace it once the parts are available. If you are interested, send me a PM with your address.

- Jay

[mkane]

Pass Aleph J here.

[mkrawcz]

Just built this Pass ACP+ “naked” preamp. I wanted it for my computer desk to go with a pair of GR desktop minis. Now I have it hooked up to my Folsom and NX Studios and I’m not sure I want to take it out! This thing is really impressive.
 

[Jaytor]

Just built this Pass ACP+ “naked” preamp. I wanted it for my computer desk to go with a pair of GR desktop minis. Now I have it hooked up to my Folsom and NX Studios and I’m not sure I want to take it out! This thing is really impressive.

That looks sweet!  I'm tempted to put one together to give it a try but I think I already have too many projects in the works. Maybe next year if the kits are still available.

[Danny Richie]

I am about to release an ideal amplifier for the NX-Otica's. Stay tuned.

[poseidonsvoice]

That looks sweet!  I'm tempted to put one together to give it a try but I think I already have too many projects in the works. Maybe next year if the kits are still available.

I've thought about building it just for kicks and a plexiglass enclosure.

But too many projects...so nah...

Best,
Anand.

[corndog71]

I am about to release an ideal amplifier for the NX-Otica's. Stay tuned.

I’ve been waiting for this! 

….

still waiting.

[tortoiseman2542]

I am about to release an ideal amplifier for the NX-Otica's. Stay tuned.

Such an amp tease!! 

Robert

[cjsailer]

I am about to release an ideal amplifier for the NX-Otica's. Stay tuned.

Oh alright, was going to pull the trigger on one of PS Audio's amps.  But would this be in kit form though?  SS or tube?  Just a few breadcrumbs please.