Feeler: Classic Solo

[ding]

front panel idea. still wondering if I should do a 6 or 12 step input attenuator instead of a dual pot but I got the pot for now so thats what I'll stick with for the moment.

I would be tempted to move the four toggles closer to the mic input XLR.

Cheers

Ian

I'll give that a try.

Here see if thats better.

 

[ding]

I think I'm just going to build out the extra HT. it's not like it's going to break the bank. Probably just use one 48v supply though.

That would simplify things a lot. It avoids possible ground loop problems. With two HT supplies you just wire the AGND of each one direct to the chassis bolt. One word of warning.  If you are sharing AC heaters, which it seems sensible to do, you could end up with two heater elevation circuits fighting each other.It should not really be a problem but just to be on the safe side you should fit the heater elevation components only to one of the HT supplies. On the other hand, if you manage to get hold of a mains transformer with two separate  AC heater windings, and there are plenty of them about, you can  build both HT supplies as normal and just wire AC heater windings,the PCB to separate windings.

Cheers

Ian

I was going on this that you said on page 3 reply #47. It seems you suggested that it would be fine building out 2 power supplies as long as I had 2 heater windings so maybe I misunderstood . Can you comment on the above quote?

Thanks

 

[ding]

This is what I thought you meant in that post.

 

[ruffrecords]

This is what I thought you meant in that post.

I can see where the confusion has arisen. I think I failed to pick up on it because in post #48 you said "That crazy big PTX I got looks like it has 2-250v at 0.2A and 2-6.3v at 3A so I will just run the heaters for each board @6.3V with no problem. " so I thought you had separate HT windings.

So, bottom line is, if you have two HT secondaries you can build separate HT supplies. You can use separate a heater windings with them or you can daisy chain the heaters from a single winding as long as you remove one of the heater elevation circuit.

If you have a single HT winding you have to build a single (meatier) HT supply with altered component values and feed HT from it to the other board.

You might get away with connecting a single HT winding to two separate HT supplies but I would be concerned about the effect on the two bridge rectifiers if connect the two analogue 0Vs together. Worst case might be smoke, good chance it would hum like crazy and if we are lucky it would work just fine. I need to draw it out to get my head around it and/or simulate it.

Cheers

Ian

 

[ruffrecords]

front panel idea. still wondering if I should do a 6 or 12 step input attenuator instead of a dual pot but I got the pot for now so thats what I'll stick with for the moment.

I would be tempted to move the four toggles closer to the mic input XLR.

Cheers

Ian

I'll give that a try.

Here see if thats better.

Yes, that's better.

Cheers

Ian

 

[ruffrecords]

You might get away with connecting a single HT winding to two separate HT supplies but I would be concerned about the effect on the two bridge rectifiers if connect the two analogue 0Vs together. Worst case might be smoke, good chance it would hum like crazy and if we are lucky it would work just fine. I need to draw it out to get my head around it and/or simulate it.

Cheers

Ian

I just finished simulating it with the 0Vs tied together. Seems to work fine. I suggest you give it a go.

Cheers

ian

 

[Deepdark]

In another hand, drawing a rc filter psu on a turret board wouldn't be that hard too. Once we know the piwer consumption, we can draw out the resistors and caps values, right?

 

[Deepdark]

We can take a look at this transformer too. http://www.antekinc.com/as-1t200-100va-200v-transformer/#PhotoSwipe1455536275235

There is 2x 200v coil and 2x 6,3v coil

 

[ding]

You might get away with connecting a single HT winding to two separate HT supplies but I would be concerned about the effect on the two bridge rectifiers if connect the two analogue 0Vs together. Worst case might be smoke, good chance it would hum like crazy and if we are lucky it would work just fine. I need to draw it out to get my head around it and/or simulate it.

Cheers

Ian

I just finished simulating it with the 0Vs tied together. Seems to work fine. I suggest you give it a go.

Cheers

ian

Yes you are right. My original idea was to use a 250-250 / 6.3-6.3 transformer I had laying around. But just looking at it all I could hear was paranoia about hum from the transformers. Maybe it's unfounded. So I decided a new smaller toroid from antek being $28 might not be a bad idea seeing as I'm going to also need a second one for phantom. I know you designed this thing to be a perfect and individual package and I'm stretching it beyond its original design but you always seem to design things with multiple uses in mind, which I really enjoy. Even though spice says so I will take your initial gut reaction and opt against doing it that way. So it's either go back to my huge transformer or modify the power supply. Thanks for all your help. I'm so excited to record some killer music with this!

 

[Deepdark]

Why not seing it as 2 single pre Inside the same box? I mean, Antek Have transformers with dual ht coil and dual filament coil. From there, simply separate the coils to each board and send each ground to the main bolt. I don't see why it would be a trouble. Each board are wired from a separate coil, juts like if we had 2 toroid,

 

[Deepdark]

http://www.antekinc.com/as-1t250/

Overkill, but would work and is not that expensive

 

[ding]

http://www.antekinc.com/as-1t250/

Overkill, but would work and is not that expensive

That's the one I have except it's the an-1t250 which is the older version without the added magnetic shield. I will probably just use it. I was a little afraid of getting hum with it but I will just get a 350mm deep case and put the toroid as far away as possible. I think that should take care of any hum issues. Hopefully?

 

[Deepdark]

I don't see why we would get hum. You could install the toroid vertically on the side pannel, at the extreme of the boards and  put a metal box, bolted on the chassis to cover it (and maybe cover the phantom transfoemr too) that way, you completly isolate the power tranny from the rest of the circuit. Install the output transformer as far as possible, maybe on the other side panel and wire it with shielded cable. Connect the shield to the chassis, instead of using the shield as your analgog ground connection. Input transformer is already shielded, mount the board on aluminium standoff, maybe something like 3/8 or 1/2 inches high. Use shielded wire for input and output xlr. And, maybe a full aluminium case. Maybe it would help. Par metal has a model with front and back panel aluminium and the rest is steel. So, you could install the power transformer on the back panel which is aluminium. I don't know, maybe it's just overkill, too

 

[Deepdark]

Another thing, I think Par-metal can add separation metal plate for about 25$ so you would be able to instal the plate between the main boards and the power transformer. If you go with a 2U case, you'll not be able to mount the transformer on the side panel. The transformer is to big, you will have to mount it on the bottom panel, as we usualy do.

 

[ruffrecords]

I had some hum troubles whilst building the prototypes but they all came down to the relative orientation of the mains transformer and the input and output transformers. I built two versions and in both the least hum was obtained with the mains toroid vertical. Attached is a photo of the first prototype I built. You can see the mains toroid mounted vertically on the rear panel. Notice how the output transformer is mounted on the right hand side wall. originally it was mounted on the base of the enclosure and it picked up some hum from the mains toroid.

Cheers

Ian

 

[ruffrecords]

And here is a photo of the second prototype I built. This had a narrow enclosure so there was not enough room to mount the toroid on the rear panel so I mounted it on the right side wall. This will induce hum in the output transformer if the output transformer is also mounted on the side wall so I mounted it on the base instead.  You cannot mount the toroid on the base of the enclosure as it then interferes with the mic input transformer.

As long as you use this scheme or the one in the previous post you will be OK.

Cheers

 

[Deepdark]

Ian, what is the power consumption? about what, 20ma or so?

 

[Deepdark]

Oh and if we install the toroid on the side wall and the output transformer on the opposite side walls is that ok? In case we used a rackmount type of chassis of course

 

[ding]

According to some experiments by DaveP somewhere in this forum I think as long as I mount the output transformer at 90 degrees from the power transformer I should be ok. That power transformer is a little over 4 inches wide so mounting it on the back or sides is out on a 2U enclosure. I will probably mount it on the bottom back corner and mount the output transformers on the opposite side wall. I think that should work. I think Ian was a little restricted with space with that enclosure. My guess is that a full 19" rack would probably help. If things get a little ugly I will just enclose the transformer in a metal transformer case.

 

[ruffrecords]

Ian, what is the power consumption? about what, 20ma or so?

The HT current consumption is 20mA or so.

Cheers

Ian