Aikido octal all-in-one

strider · « **Reply #20 on:** 13 Jul 2010, 12:42 pm »

I received my kit the other day. Don't know that I've ever come across a PCB so thick. The kit looks to be fairly complete, looks like I may have gotten extra coupling caps in with mine.

The manuals lean towards the technical side of things, with lots of formulas and schematics as well as background info on transformer and capacitor types, etc. Still trying to figure out a couple of things before I start soldering, but that's what makes it interesting.

sts9fan · « **Reply #21 on:** 13 Jul 2010, 12:52 pm »

I know my Octal kit came with two sets of caps, Polypro and PIO I think. He wants you to pick the flavor you like. The board I have you can add a switch to toggle the caps. Could this change my mind on caps? Only time will tell.

Kris

JohnR · « **Reply #22 on:** 13 Jul 2010, 01:30 pm »

I picked mine up from the post office today. For some reason they had had it for a week but I only got a notice today. Never mind!!! The only way this kit could not be the absolute best value of any kit I've ever seen would be if it just didn't work - and that of course is highly improbable. More later

HAL · « **Reply #23 on:** 13 Jul 2010, 01:58 pm »

Quote from: sts9fan on 21 Jun 2010, 12:54 pm

Its a relay volume control and source selector. Some guy from China sells them over on DIYaudio. It has a remote and the small board has a digital display.

Any link to the attenuator? I looked a bit but could not find it.

sts9fan · « **Reply #24 on:** 13 Jul 2010, 02:56 pm »

This is the guy. He has offered a bunch of different versions. Mine was only ~$75
http://www.diyaudio.com/forums/vendors-bazaar/169737-promotion-hi-end-volume-control-module-ultimate-attenuator-audio.html

HiGHFLYiN9 · « **Reply #25 on:** 25 Aug 2010, 08:54 pm »

How are the builds going gents? Looks like there hasn't been a peep for a month or so

I recently picked up this kit and took the time to populate most of it over the weekend in the standard 6SN7 / 6SN7 line-stage config. Can anyone recommend a good single transformer for the build?

I'm also a bit confused regarding the Fullwave-Voltage-Doubler Rectification versus the Fullwave-Bridge Rectification. I've read through the post on the TubeCad journal and the Janus Rev A book, but I'm still a little nebulous as far as why it would be desirable.

I got those big hulking Dayton caps but it seems like the voltage is too low for line-stage config from the spec sheet in the manual

JohnR · « **Reply #26 on:** 2 Sep 2010, 09:30 am »

Hi - sorry, I missed your post. (Had The Lab in my ignore list for some reason...) My build is proceeding well albeit at a leisurely pace, at present I am waiting on some shaft extenders for the selector switch and attenuator, as my chassis layout ended up needing it. Once I get those I'll do the chassis work and update with some photos.

Quote from: HiGHFLYiN9 on 25 Aug 2010, 08:54 pm

Can anyone recommend a good single transformer for the build?

I'm still waiting on the transformer from diyhifisupply (long story, shipping error but they were very responsive in making it right). This one will need a dropping resistor for the rectifier filament.

http://www.diyhifisupply.com/node/638

If you're in the US the Edcor XPWR007 that was mentioned above should work well.

Quote

I'm also a bit confused regarding the Fullwave-Voltage-Doubler Rectification versus the Fullwave-Bridge Rectification. I've read through the post on the TubeCad journal and the Janus Rev A book, but I'm still a little nebulous as far as why it would be desirable.

This is just a matter of choosing the right circuit for your power transformer. If it has a 6.3V winding, then you will need to use the voltage doubler. If it has a 12.6V winding then you would use the full-wave bridge.

Quote

I got those big hulking Dayton caps but it seems like the voltage is too low for line-stage config from the spec sheet in the manual

If you mean the 30 uF caps, those are intended for use in the headphone amplifier configuration, which would typically be set to run at a lower B+ voltage than a line stage. However the 250V rating of the caps should be fine as (unless I'm missing something...) the voltage across them will be about half of B+. There may be an issue at turn-on time though... nonetheless there are plenty of sources of alternative caps, 1 uF should be plenty for a linestage. Also, the manual only makes a suggestion about typical values, see the chart on page 12 for a wider range of operating points. You can run the linestage fine off a B+ of 250V - mine will be in fact.

Hope that helps, let us know how it's going

HiGHFLYiN9 · « **Reply #27 on:** 2 Sep 2010, 08:58 pm »

Thanks very much for all the details John. I'm learning as much as I can as quickly as I can, but when someone takes the time to pass along what they know it helps immensely

I ordered some Obbligatos to use instead of those PartsExpress Dayton caps.

I'll likely be going with the Edcor, I've used them in the past and their prices are reasonable. unfortunately those blue bells never match with my projects though ;P

I had another quick question for you John. The kit included (4) 4.7 microfarad 400V MKP Audiophiler film caps in the PSU as bypass caps for 450v electrolytics, and the manual even calls for 630v handling for the film caps. Will the 400V be sufficient or should I get some higher power handling caps for the long run?

TIA.

JohnR · « **Reply #28 on:** 3 Sep 2010, 03:48 am »

I think they should be fine but I'll run a simulation in PSUD later.

More thoughts on the transformer coming, for now a couple of links

http://www.edcorusa.com/Products/ShowProduct.aspx?ID=512
http://www.hammondmfg.com/167.htm

JohnR · « **Reply #29 on:** 3 Sep 2010, 09:30 am »

OK, I just need to write down the transformer thing to get it clear for myself and for future reference.

Re filament power: as sts9fan pointed out above, Broskie recommends a rating of 4.5A at 6.3V in his blog here: http://www.tubecad.com/2008/09/blog0149.htm. However, if you look at the photos of his octal headphone amp - http://www.tubecad.com/2010/02/13/Octal%20All-in-One%20sideview.jpg - he uses an Allied 6K56VG, which is rated at 3.5A: http://www.alliedelec.com/search/productdetail.aspx?SKU=2270081

I'm assuming that this can be OK because the high voltage winding is not heavily loaded. Perhaps it "just depends" on the transformer. At any rate I don't think I personally would lose any sleep over using a transformer rated at 4A. You could set the regulator to 12V instead of 12.6V to reduce current a little.

Alternatively a separate 12.6V filament transformer rated 2.5A or higher could be used, such as the Hammond 167L12 or Edcor PWRC12.6V3A-1 (both linked above). A 14V toroid could also be used provided that regulator heatsinking is adequate - I like that option because my wall voltage sags below spec as much as 10% sometimes. In that case though I would up-rate C15 and C16 to 25V.

On the B+, with a 275-0-275V transformer with 8% regulation and a 5Y3 rectifier and 30mA load, the voltage across the first filter capacitor settles around 340V, according to PSUD. However during startup it peaks around 410V. if you were to swap in say a 5AR4 then you would have that voltage peak around 420V during startup and settle around 380V. Now this is just a simulation with a lot of assumptions built into it so I don't think I'd worry about it without measuring and finding an actual problem. But then again, I don't think a high B+ is really needed here anyway, so I would be inclined to use a transformer with a lower output in the first place, more around 225-0-225 to 250-0-250V.

So, on paper, here are some possible solutions. For a single transformer:

Edcor XPWR093. 500V(250-0-250)@300mA, 6.3V(3.15-0-3.15)@7A & 5V@5A. This is a total overkill solution for a preamp, but all the ratings are easily met with a single transformer.
Edcor XPWR074. 490V(245-0-245)@150mA, 6.3V@4A & 5V@3A. As above, slightly under-rated on the 6V winding.
Hammond 370JX. 500V C.T. @ 161ma, 5V C.T. @ 3A, 6.3V C.T. @ 6A. Another overkill (power amp) solution.
diyhifisupply TXsp. 220-0-220v/150ma, 14v/2.5A. 8V/2.5A - as mentioned above, requires a dropping resistor for the rectifier.

Here are a couple of good solutions for the B+ and 5V windings - a separate 12.6V transformer will be needed:

Edcor XPWR001. 500V(250-0-250)@100mA, 6.3V(3.15-0-3.15)@1A & 5V@2A.
Hammond 370CAX. 500V C.T. @ 81ma, 5V C.T. @ 2A, 6.3V C.T. @ 2.5A
Hammond 270X or 370X. 480V C.T. @ 46ma, 5V C.T. @ 2A, 6.3V C.T. @ 1.5A. Will need to keep the plate currents under control as HV current rating is on the low side.

As mentioned, I will be using the one from diyhifisupply for this project.

strider · « **Reply #30 on:** 13 Sep 2010, 01:05 am »

Is there a rhyme or reason behind the impedance of the attenuator for the volume control? I'm looking at getting one of the DACT type stepped attenuators from Gigawork on ebay.

For transformers I went with the Edcor XPWR007 for the B+ and an Amveco for the heater power supply:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=TE62070-ND

I bought one of his AC switches that allows the 2 transformers to be turned on seperately.

wushuliu · « **Reply #31 on:** 11 Oct 2010, 05:21 am »

I just ordered the Aikido LV. Seems pretty easy. It'll be my first tube pre...

JohnR · « **Reply #32 on:** 11 Oct 2010, 05:28 am »

Cool.

Mine got a bit stalled, still waiting for the power transformer from diyhifisupply...

strider · « **Reply #33 on:** 12 Oct 2010, 02:40 am »

In a star ground scheme, does every ground point on every input/output jack, volume pot, selector switch and capacitor switch have a seperate wire attaching it to the ground lug on the PCB?

So far I've got the input and output jacks wired up for a total of 10 lug terminated wires attached to a single bolt soldered to the ground lug. That leaves 16 more ground points to wire and attach to the inch long bolt in the middle of the PCB. It's starting to get pretty messy, should I continue doing what I'm doing, or am I missing something?

wushuliu · « **Reply #34 on:** 12 Oct 2010, 05:39 am »

I am completely new to working w/ tubes so excuse if this is a dumb question, but I was going to get the Aikido all-in-one then passed on it for the LV, partly because from the Glassware website it looks like you can't really elevate the tubes out of an enclosure without making room for the heatsink (below). Then while doing some searching I saw a pic of what looked like an Aikido mounted with the board upside down, with the tubes mounted on the other side allowing them to be elevated through the enclosure. Is this right? Is this what's normally done?

strider · « **Reply #35 on:** 12 Oct 2010, 11:16 am »

On the All in One board you are able to mount the tube sockets on the top side of the board and all the other components on the bottom. You must be careful about the orientation of the polarised caps, and the regulator pins need to be twisted 180 degrees, but other then that it's pretty simple.

sts9fan · « **Reply #36 on:** 12 Oct 2010, 03:12 pm »

Strider

Does your amp or source have the signal gnd connected to earth? If so I would not worry about attaching all the gnds to that point. Also these boards are layed out well so it MAY not be as much an issue imho. Anyway you can always add a switch to float the signal gnd from earth through the standoff.

wushuliu · « **Reply #37 on:** 12 Oct 2010, 04:18 pm »

Quote from: strider on 12 Oct 2010, 11:16 am

On the All in One board you are able to mount the tube sockets on the top side of the board and all the other components on the bottom. You must be careful about the orientation of the polarised caps, and the regulator pins need to be twisted 180 degrees, but other then that it's pretty simple.

Thanks strider.

JohnR · « **Reply #38 on:** 12 Oct 2010, 04:48 pm »

Quote from: strider on 12 Oct 2010, 02:40 am

In a star ground scheme, does every ground point on every input/output jack, volume pot, selector switch and capacitor switch have a seperate wire attaching it to the ground lug on the PCB?

I don't know about the capacitor switch, but yes for the others. Treat the signal as a pair of connections, not one.

strider · « **Reply #39 on:** 13 Oct 2010, 11:15 pm »

Thanks for the responses, guys.

I'm listening to it right now, only has a couple of hours on it but so far so good. It's housed in the chassis of an ancient Hewlett Packard oscilloscope that I cut down for a better fit. There are some cosmetic things that need to be addressed, but that'll have to wait.

Ben