[dBel84]

Oh I agree, I never found the Bijou to be lacking in bass. I hope I never made such a comment or insinuated such..dB

 

[onform]

Lol thats what happens when you start thinking of other projects, (loudspeakers), you miss important updates. I posted a little while ago in the soha thread to ask whether it was worth waiting for the soha II, I cant beliave i missed this.

How close are we to a finished PCB/BOM??? I will purchase only from source. I was always wairy of the digi boards....

Does anyone else miss the single valve design???? It is part of what got me interested in the SOHA.

I cant wait to build it...tee hee

 

[dBel84]

Quote:

Originally Posted by onform /img/forum/go_quote.gif Does anyone else miss the single valve design????

I can't say that it was from lack of trying. See post # 93 , that blue thingamebob was the initial attempt at a self biasing design but the servo wouldn't settle and refelcted as mild variation at the output. I am still rather gobsmacked at how good it sounds, knowing that there is this dc bouncing about.

I reckon about a month for pcb's to be available..dB

 

[onform]

what sort of case dimensions are we looking at?? just so i can start thinking of an original design,, i have to do something to keep my mind off work until i can get the bits to build this amp..

 

[dBel84]

It has been designed to fit the Hammond 1455T2202 or 1455T1602, the former will take the transformer in the same chassis, the later will need an external wallwart for the transformer..dB

 

[m0b1liz3]

Has anyone tried it with a wallwart yet?
Any suggestions for acceptable supplies like this?

Any comparisons yet between the SOHA I and SOHA II sq-wise?

 

[runeight]

Hello gents. Been gone for a while, but I see that you guys have been talking.

Yes, SOHA originaly stood for Stoopid Opamp Headphone Amplifier because when Bill proposed the idea I thought it was stupid. But he and Mark persuaded me that it was worth a try to make a better low voltage tube amp. After a while I decided that I liked the idea of making a good low voltage hybrid.

SOHA II uses the acronym just to keep the lineage of low voltage hybrid. The amp is a natural successor to the SOHA. If the SOHA had tracked the way I wanted it to (and you can go look at my posts on the headwize threads) it would have had a discrete buffer very quickly. I also never liked the trimpot adjustment, but it was there in the interest of making things as simple as possible for guys who wanted a tube amp that wouldn't kill them.

The amp board is 160mm x 115mm and will fit the Hammond cases that dBel84 mentioned. It has a built-in PS, just like the SOHA, that provides the LV split supply, the B+ for the tube, and the heater supply all from a single 15-0-15/1A transformer. You can walwart it, but a normal walwart will not work because it doesn't have the CT supply. All of this has been discussed in the orignal SOHA threads and builders have bought walwart boxes to put the toroids into. You can do that here also while using the shorter Hammond box.

I've probably missed some things in this response.

 

[Beefy]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif and builders have bought walwart boxes to put the toroids into. You can do that here also while using the shorter Hammond box.

I've seen this idea before, and I really like it. I found that one of the really useful aspects of the Millett Max is that the transformer is so far from the amp, and that the casework is for just a small barrel plug instead of an IEC socket.

 

[m0b1liz3]

Does anyone have a link to one of these Wallwart boxes for transformers? Wouldn't they be bigger than a typical wallwart?

I am assuming that you meant there are empty wall wart type boxes that plug into the wall that will house a transformer. I can't seem to find such a product when I do a search though. Does anyone have a link for one?

 

[dBel84]

This is what you are looking for..dB

 

[m0b1liz3]

Now I just have to find a mains transformer with dual primaries so I can use it in Aus and NA...

 

[Beefy]

Quote:

Originally Posted by m0b1liz3 /img/forum/go_quote.gif Now I just have to find a mains transformer with dual primaries so I can use it in Aus and NA...

It took me 10 seconds to find this: RS Australia | * 91938-P2S2, Nuvotem, Toroidal transformer,15VA 2x0-15V o/p, 257-4913

If you had followed the links I posted in the specific thread where you were looking for toroids, you would have found it quite easily as well.

 

[m0b1liz3]

I asked about toroidal transformers for a different project. I like the idea of the mains transformer with the case dbel showed to make for a smaller profile case for the amp itself. (Planning to build a SOHA II later). A mains transformer should work almost as well and be much cheaper in theory. Since it would be so far away from the amp I would hope there would be no hum heard either. The dimensions on the one you put up a link for are pretty small though so it would work well too. I can worry about it later when the SOHA II pcbs are actually available.

Most high VA toroids wouldn't fit into a wallwart type ext case. I was asking about toroids for a gainclone. Thanks for the link btw, it will come in handy for that one. I suppose the same idea could work with an external case for a toroid but it wouldn't plug directly into the wall. It could be sort of like a laptop style PSU for the torroid if I really want to make the box for the amp as small as possible.

I have found a few examples here but the prices are much higher than NA even with shipping still. Might just have to bite the bullet and get it since I want to make things small.

 

[Beefy]

Quote:

Originally Posted by m0b1liz3 /img/forum/go_quote.gif Those are toroidal transformers. That is for a different project. I like the idea of the mains transformer with the case dbel showed to make for a smaller profile case for the amp itself. (Planning to build a SOHA II later).

One of us is confused, and I don't think it is me. The case that dbel posted is for a toroid like I linked.

Quote:

A mains transformer should work almost as well and be much cheaper in theory. Since it would be so far away from the amp I would hope there would be no hum heard either.

A mains transformer is essentially a toroid in a box anyway (sometimes with a very cheap rectifier setup for DC). But you don't nearly have the flexibility with an all-in-one product as you do compared to choosing your own toroid.

Quote:

I have found a few examples here but the prices are much higher than NA even with shipping still.

I would be very surprised if that was true, considering shipping weight. And if you give up the idea of having both 115V and 230V supply capability, then Altronics has some VERY competitive prices.

 

[m0b1liz3]

Well it is just a box with a plug in it and if the mains was small enough it would fit. No confusion, that is why I mentioned the mains thing.

In the end you are probably right beefy. I am trying to keep the cost of any of these projects low but the general consensus seems to be not compromise on power supplies. I don't plan on giving up flexibility either so will likely need to pay the $ to get what I want locally and not wait for the longer shipping times from overseas.