Setting up my Aikido Octal All in One to use 12v tubes...

strider · « **on:** 31 Oct 2012, 06:11 pm »

I know there are a couple around here that have built the Aikido Octal All in One preamp from John Broskie; I need some clarification. What do I need to do in order to use 12V tubes in the input and output positions? It's currently set up to use 6V tubes, I have a seperate transformer for the heater circuit per Broskie's recommendation. It puts out 6.7V at 6A. The jumper changes make sense. What I can't figure out is if I need to change the transfmormer for the heater ciruit to one that puts out 12.6V, or can I use one of the voltage doubler options to double the voltage of the transformer I have?

I've tried to figure it out on my own, honestly. When I think I've figured it out, I start second guessing myself. Having two manuals for the same board, with information that doesn't seem to be applicable to the situation I see, makes it kinda confusing.

DaveC113 · « **Reply #1 on:** 31 Oct 2012, 06:16 pm »

I also made the mistake of buying a filiment trafo for 6V tubes, I thought it was 12V but I ordered wrong and used it anyway.... I think the best solution would be to replace the trafo with one for 12V tubes, then if you go back to 6V tubes you can change the jumpers to series instead of parallel.

What 12V tubes are you interested in running?

strider · « **Reply #2 on:** 31 Oct 2012, 06:35 pm »

Was interested in trying the 12SN7. Looks like they are about 1/2 the price of similar 6SN7 tubes on Ebay, but spec-wise they look pretty indentical to the 6SN7, except for needing 12.6V...

Any thoughts on the 12SN7?

DaveC113 · « **Reply #3 on:** 31 Oct 2012, 06:58 pm »

Quote from: strider on 31 Oct 2012, 06:35 pm

Was interested in trying the 12SN7. Looks like they are about 1/2 the price of similar 6SN7 tubes on Ebay, but spec-wise they look pretty indentical to the 6SN7, except for needing 12.6V...

Any thoughts on the 12SN7?

Actually, maybe the voltage doubler would be worth a try... you would have to remove and re-solder the 1st ps caps though (c13/14).

Seems like a good idea, I just went for the 6SN7, they are still very cheap unless you really want the rare ones, which are a poor value. I have a ton of 6SN7s I've accumulated now and most were under $10 each. I have a few more expensive ones and the only reason I'd keep them is as an investment, the basic Sylvania 6SN7 GTA/B are great tubes. Actually, all the 6SN7s are great tubes with some relatively minor variations in sound between brands, so I'd think the same would be true of the 12SN7...

strider · « **Reply #4 on:** 31 Oct 2012, 07:55 pm »

OK, the voltage doublers do refer to the heater circuit. Are those two manuals confusing to you as well, or am I confusing myself?

In your experience the pricier 6SN7 aren't worth trying? I have some newer Sylvanias, some 5692's, some mismatched RCA's. I thought I was missing something by not trying some of the hallowed NOS variants....

DaveC113 · « **Reply #5 on:** 31 Oct 2012, 08:29 pm »

Yes, I agree the Aikido manual can be very confusing. I did not get everything right the 1st time...

I have in my collection....

1. Sylvania 5692s, by far the most expensive I have at $80 for a pair

2. Metal base / black plate Russian 6H8C, got these for $25/pair, but they are going for well over $100/pair on ebay...

3. Normal Russian 6H8C, $2/each

3. Sylvania GTA chrome domes, both tall and short, price is about $50 for a quad for the talls, less for the shorts

4. Raytheon tall bottle GTBs, $7.50 each

5. GE coin base GTBs at about $8 each

#1 and 2 are very slightly better than the rest but I doubt I would be able to identify which tube was which blind. They are all very good in their own way. I was pleasantly surprised the GE coin base tubes are great too. So far my conclusions are the tubes are only making slight differences so I wouldn't spend big $ on the rarer tubes.

strider · « **Reply #6 on:** 1 Nov 2012, 01:09 pm »

Maybe I need to shop around some more. I don't have anything against the 6SN7, and there certainly are more choices in the 6 vs the 12SN7.

Do you believe in the virtue of having a seperate transformer for the heaters?

mboxler · « **Reply #7 on:** 1 Nov 2012, 03:53 pm »

Quote from: strider on 1 Nov 2012, 01:09 pm

Maybe I need to shop around some more. I don't have anything against the 6SN7, and there certainly are more choices in the 6 vs the 12SN7.

Do you believe in the virtue of having a seperate transformer for the heaters?

Hi strider...

Been looking at the same preamp, so interested in your project. Does the LDO voltage regulator for the heaters require a CT transformer? Also, can you post which transformers you bought for the project?

The reason I ask is that his LV Regulator kit can take a CT or non-CT transformer, and he recommends using a CT tranny.

Odd that his website mentions only one transformer, not two

Mike

DaveC113 · « **Reply #8 on:** 1 Nov 2012, 03:55 pm »

Yeah, I turn my heaters on to let the tubes warm up before applying high voltage... a 30 sec. time delay relay would be nice here. My amp has only one PT, but uses a rectifier tube so the hv is delayed a bit.

strider · « **Reply #9 on:** 1 Nov 2012, 05:13 pm »

Quote from: mboxler on 1 Nov 2012, 03:53 pm

Hi strider...

Been looking at the same preamp, so interested in your project. Does the LDO voltage regulator for the heaters require a CT transformer? Also, can you post which transformers you bought for the project?

The reason I ask is that his LV Regulator kit can take a CT or non-CT transformer, and he recommends using a CT tranny.

Odd that his website mentions only one transformer, not two

Mike

Going by memory, I don't think you need a center tapped transformer; there are a couple different options in terms of the way the power supply can be implemented. I am using an Edcor XPWR007 to supply the B+ and rectifier, I have a seperate transformer to supply the heaters. Not sure of the model on that one. The reason for the second transformer, as Dave's post eludes to, is to power up the heater circuit in the tubes so they can warm up before applying the other voltages. It's supposed to help the tubes last longer. Broskie sells a switch to turn the transformers on at two different times.

As far as the website, I find it confusing. Same with the manuals. For instance, with the Aikido Ocatal All in One kit I have a seperate manual for a Janus regulator board and one for an Aikido Octal board, which are two different boards that he offers. In other words, there is no manual specifically for the All in One board that I have. That's why Dave's advice is so helpful to me.

DaveC113 · « **Reply #10 on:** 1 Nov 2012, 06:14 pm »

strider, there is an all-in-one manual, I have it. But, it sucks just as much as the separate manuals, I ended up reading the manuals for everything related to power supplies and aikidos I could, including the 9-pin manual which is a bit better.

I think I have it figured out, my Aikido sounds amazing, so feel free to ask me any questions, I def. needed some help along the way...

mboxler · « **Reply #11 on:** 1 Nov 2012, 06:27 pm »

Sorry, guys, but is this the kit you are talking about??? There are SO many all in one's!

http://glass-ware.stores.yahoo.net/ocalcukit.html

Mike

DaveC113 · « **Reply #12 on:** 1 Nov 2012, 07:03 pm »

Mike, Yup, that's the one.

strider · « **Reply #13 on:** 2 Nov 2012, 11:47 am »

Quote from: DaveC113 on 1 Nov 2012, 06:14 pm

strider, there is an all-in-one manual, I have it. But, it sucks just as much as the separate manuals, I ended up reading the manuals for everything related to power supplies and aikidos I could, including the 9-pin manual which is a bit better.

I think I have it figured out, my Aikido sounds amazing, so feel free to ask me any questions, I def. needed some help along the way...

Ha! I do have a manual that's for the all-in-one. Talk about confusing...
I do feel bad for being so negative about the manuals. In all fairness I've never contacted Mr. Broskie for help or clarification on anything.

I'm still on the fence about changing the PS to use the same transfo with the voltage doubler circuit. The way it's written in the manual, it makes me feel as if the voltage doubler options are work arounds.

Could you elaborate on the how you implemented the relay for turning the heater power supply on early?

DaveC113 · « **Reply #14 on:** 2 Nov 2012, 04:09 pm »

Quote from: strider on 2 Nov 2012, 11:47 am

Could you elaborate on the how you implemented the relay for turning the heater power supply on early?

Sorry, I actually did not do this, but was considering it.... All you'd need is a 30 sec. delay relay and the power switch would immediately turn on the heaters and the relay would delay the power going to the HV trafo for that 30 seconds.

strider · « **Reply #15 on:** 2 Nov 2012, 04:59 pm »

Quote from: DaveC113 on 2 Nov 2012, 04:09 pm

Sorry, I actually did not do this, but was considering it.... All you'd need is a 30 sec. delay relay and the power switch would immediately turn on the heaters and the relay would delay the power going to the HV trafo for that 30 seconds.

Something like the relay at the top of this link?

http://www.surplussales.com/relays/retimed-2.html

DaveC113 · « **Reply #16 on:** 2 Nov 2012, 05:04 pm »

Yup, but you could look for a SPST (single pole single throw) but the DPDT will work fine too, just check out the wiring diagram on the unit and put it in between the power switch and HV trafo. The power from the switch will both activate the relay and provide power to the HV trafo, so the relay will only have 1 wire going through it, but connected to the relay in 3 places... then there is also a ground/neutral wire needed for the electromagnet.

mboxler · « **Reply #17 on:** 2 Nov 2012, 05:22 pm »

1 Mississippi, 2 Mississippi....20 Mississippi

http://tubedepot.com/p-dpst-3way.html

This will help with the wiring.

Ericus Rex · « **Reply #18 on:** 2 Nov 2012, 07:48 pm »

Quote from: DaveC113 on 2 Nov 2012, 05:04 pm

Yup, but you could look for a SPST (single pole single throw) but the DPDT will work fine too,

I looked all over for this switch. It appears to be a custom-made job. The link MBoxler gave is the only place I've found that exact switch. Of course you could use two SPST switches - I had room only for 1 switch that did both heater and B+ functions.

DaveC113 · « **Reply #19 on:** 2 Nov 2012, 07:57 pm »

Nice switch, lol!

If you do go with 2 switches, there are a couple options... 1. Wire in series so the HV cannot come on without the heaters. 2. Use DPDT (?) switches and wire HV in series and heaters in parallel. That way either switch will turn on the heaters, and HV won't come on unless both switches are on.

Another option is a rectifier that takes some time to warm up, I use a 5ar4 in my amp and it's been running for years with no time delay besides what the 5ar4 provides.

I don't mind waiting for the tubes to warm up but I'm starting to regret not putting the timed relay in, oh well, it can be done later....