[Ferrari]

Quote:

Originally Posted by m0b1liz3 /img/forum/go_quote.gif What does the term 3 channel refer to with a headphone amp? I am used to this term being used for car amps (ie. L,R and sub). Oops, just realized that it must mean 3 possible simultaneous listeners?

A 3-channel active ground amp has 3 output buffers of the same design topology for left, right and ground channel. The ground channel is thus actively driven by 1 output buffer. In a conventional 2-channel amp, the ground is passive!

To answer our earlier question:
Yes, but shipment cost included… after negotiation. The new owner realized very well that I was the only one who used MKP//Teflon caps at the output.

Btw, wiring 3 JISBOS buffers into the SOHA can be a headache, but once all the cumbersome work is done, I’m pretty sure you will enjoy it.

 

[Ferrari]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Ferrari, I have thought about it, but on the first round of the SOHA II I decided to make an amp that is also really easy to case. The SOHA II is designed to fit into a Hammond 1455T2201 enclosure with enough room at the back of the box to hold the toroid needed to power the amp. Liike the SOHA, only one transformer is needed. If the amp is successful we can consider doing a 3 channel version.

Fully understand your thoughts. Thanks for the information.

 

[runeight]

In this case, three channel means using an active ground channel.

In a normal two channel amp, the output current flows through the headphones to ground and eventually back to the ground circuit of the supply. There are various reasons why some don't like this mode of operation, including noise and other signals on the ground circuit due to the currents flowing around the ground circuit.

A three channel amp uses one full amplifier channel as an active ground. This channel doesn't do any amplification, but its output is substituted for the ground of the main amplifier channels. Thus, the ground current from the amp channels doesn't flow through the ground circuit, instead if flows through the amp circuit of the active ground channel. The active ground amp pulls its "ground" current from the supply rails minimizing or eliminating current flows in the ground circuit of the amp keeping the ground "clean".

One limitation of this design is that the active ground channel amp should be able to source and sink twice the current that each channel can produce. This has to be considered when designing the amp, even though music signals won't, on average, cause the draw to be this large.

 

[Casca]

Just got through ordering all the parts for a millet build.........hopefully. I had to use three different sites and pay three different shipping cost to get everything. Mouser was out of stock for one .18 cent part and I wanted exactly what the list called for since I just don't know enough to be mixing and matching, so digikey has a $.50 order from me lol. I wasn't too clear on some parts from the BOM and probably ordered twice what I needed for transistors, but the parts aren't too expensive and I like having spares anyway. From the looks of it, I don't think it will be too difficult to build, even though I have zero experience building anything like this. Really, I think the hardest part is probably getting the parts. If I had known about Glassjar audio before, I would have ordered a kit from them instead of only the Alien DAC I just put on order and hopefully can incorparate into the millet.

 

[tomb]

Quote:

Originally Posted by Casca /img/forum/go_quote.gif Just got through ordering all the parts for a millet build.........hopefully. I had to use three different sites and pay three different shipping cost to get everything. Mouser was out of stock for one .18 cent part and I wanted exactly what the list called for since I just don't know enough to be mixing and matching, so digikey has a $.50 order from me lol. I wasn't too clear on some parts from the BOM and probably ordered twice what I needed for transistors, but the parts aren't too expensive and I like having spares anyway. From the looks of it, I don't think it will be too difficult to build, even though I have zero experience building anything like this. Really, I think the hardest part is probably getting the parts. If I had known about Glassjar audio before, I would have ordered a kit from them instead of only the Alien DAC I just put on order and hopefully can incorparate into the millet.

A couple of things -

1. This is too late now, I know, but - if you ever find yourself wanting for that $0.18 part, please send me a note. I make orders all the time to keep things stocked at Beezar. So, adding a $0.50/$0.18 part to a Beezar order is not a big deal and something we can always work out. Shoot - I may very well have spares of what you need, anyway.

2. I've just recently asked Jeff Rossel to feature the Millett MAX on his main page at Glass Jar Audio. He had told Colin Toole and myself sometime after Christmas that he would do this. As people often say, he is a one-man operation and such changes don't happen automatically. One can only note the slipped dates on our MAX website updates and the MiniMAX to see that stuff happens.

Glad to see you make your purchase! I think you will have fun building the MAX! Be sure to post in the main Millett MAX thread here or somewhere on DIYForums.org if you run into any problems. Just make sure you don't get the parts mixed up - transistors, resistors, etc. If you're using Vishay-Dale resistors, be sure to install them so that the rating is turned up and is easy to see. That will help us all help you troubleshoot if something amiss occurs. Good luck!

 

[m0b1liz3]

Sounds good. I might try to do this later on at some point. I live in Australia and like most people outside the US shipping sucks...

 

[headphonejunkie]

I am looking to build the jisbos for my soha(its been sitting around and since I have everything) but where is the info for it?
Any help will be greatly appreciated.
 
Thanks in advance
Greg

 

[tomb]

  I am looking to build the jisbos for my soha(its been sitting around and since I have everything) but where is the info for it?
Any help will be greatly appreciated.
 
Thanks in advance
Greg

Send an e-mail or PM to AMB.  The Jisbos are his.  If he replies with some documentation (it looks like he has removed it from his site), please let me know.  I thought I had documented his webpages on the Jisbos, but I didn't.  I have several of those boards and would rather have some documentation for them, if I decide to build them in the future.
 
All that said, there are better options out there at this point - especially for Grados.

 

[FallenAngel]

JISBOS was a great little buffer and I've built a few. If you still have boards, I'll look for the documentation, might have it somewhere.

The SOHA amp with jisbos was pretty great when I had it so I'll say definitely implement it.

 

[MisterX]

What do you need?
I think I have the pictures here somewhere, if not there's a finished one in the closet I can take new pictures of. 

 

[FallenAngel]

Sorry, I don't have the docs around any more, just a few photos.
 
The best I could offer is this photo.

 

[headphonejunkie]

Thanks everyone. AMB gotta hold of me and told me it is the @20 on his site with a few extra resistors added. So. I found it.

 

[MisterX]

Cool because my SOHA + (1st prototype) JISBOS is a PITA to take apart.
 
 

 

[MisterX]

Still looks pretty good for being in the closet that long.

 
Remember to upgrade to TO-220 regulators with heat-sinks if your using a "pirated" SOHA PCB.

 

[headphonejunkie]

You guys are making me get anxious about building the jisbos boards.