Y A A B - Yet Another Aikido Build

[Cappy]

Whereby I construct an Aikido output stage for various DIY DACs.

In this thread I will make vain attempts to build a good sounding non-resonant LCLC power supply, fumble around with grounding, experiment with different tubes and dissipations, clumsily interface with some Twisted Pear and PCM63 DACs in different ways, recklessly compare CREE diodes against tube rectification without the benefit of blind testing, and more.

Suggestions, corrections, ideas, or poignant personal Aikido experiences are encouraged.

I’ll be using Broskie’s fabu boards. Attached is a picture with composite teflon sockets installed. I wanted to use teflon and was able to find some nice PCB mount ones at DiyHifi Supply:

http://www.diyhifisupply.com/diyhs_sockets.htm

Note: Expect this project to move slowly while I gather parts.

 

[woodturner-fran]

I've built 2 now - both using his boards. One is a regular 24V aikido using 6GM8 tubes and the other is the newer version 24V one with the headphone amp built in.

Both are excellent performers. Top quality - don't think you'll be dissappointed.

Fran

 

[Cappy]

Fran,

Thanks for the encouragement.

Here is a question for you. I am looking at the Aikido manual now and there is a cap C3 on my mono board (C5 on stereo board) that is B+ to ground.

What is the purpose of this cap? Bypass of larger power supply final capacitor? Or does it serve another purpose?

 

[woodturner-fran]

God, right now I couldn't tell you - I remember something about it though - I think i used either 2.2 or 4.7uf wimas in there.

Fran

 

[JoshK]

What is the purpose of this cap? Bypass of larger power supply final capacitor?

Yes as I understand it, it is a PSU bypass cap.

 

[Cappy]

Josh,

Thanks.

******

I'm going to use DC on the heaters. I have very efficient horns and want as little noise as possible.

Parts are starting to arrive. Here is a picture of the Tentlabs IDHT Heater Supplies I'll be using:

 

[woodturner-fran]

What tubes are you going to use?

Fran

 

[Cappy]

I'm definitely going to try 5687s in the second position, as I like them and have a good variety of them.

I'll also try 6n6ps in the second position. I acquired 75 of them a few years ago in a Ukrainian drug deal gone wrong. I hope they sound good in the Aikido as they are a lot cheaper than Tung-Sol square getter 5687s. See the picture below. The weird tube/socket thingees are 6n6p to 5687 adapters I tried with my tube amp. I may not use the adapters with the Aikido as Broskie provides a lot of configurability and I can add jumpers to the board to switch the heater layout.

People seem to like the 6CG7 in the first position so I'll try a few of those. If anyone has a recommendation for a particular 6CG7 (or 6FQ7) I'd appreciate hearing it.

I've got some 6DJ8/6922/6n23ps so I'll try those in both positions.

My system doesn't need much gain in the DAC stage so 6n1ps probably won't work well. I'll try them anyway since I have some.

I don't know nothin' about the 12**7 valves.

I'm going to install jumpers on the boards so I can clip in different cathode resistors.

 

[Stixx]

tentlabs supply

Hi Cappy,

your heater current requirement with the tubes listed (6CG7 and 6N6P) will be in the vicinity of 2.8A... Is the Tentlabs module up to that or will you be using two of them?

I'm asking because I once had a look at the Tentlabs also...and the one listed on the Tentlabs site now is only capable of 1.5A max.


---O

 

[Cappy]

Stixx,

Good point to mention this, in case anyone else wants to use them.

I'll be using two, one for each mono board.

Bill

 

[Cappy]

I meant to say 5687 "D" Getter in my post above.

Later Tung Sols had a round getter.

There are 5687 Raytheon Square Getters of the same general period, 1955-59 or thereabouts, that also sound very good.

 

[kstagger]

I had a simple RC coupled 5687 linestage that I converted to use 6N6Ps. The 6N6Ps stayed - I liked the sound even more than the Tungsol 5687s (bronze or BP).

As usual, my speakers, my system ,etc

 

[Cappy]

Well that is good to hear.

What are your operating points?

 

[Steve Fay]

Choice of 6CG7's

I built the Aikidio several months ago now, and truely love it! When I first got it up and running I used electro-harmonix 6CG7's in both positions. Since I've tried RCA 6CG7s greyplates with the side getters much nicer and now I'm running RCAs black plates with the horseshoe getters. I don't think it gets much better than these tubes. WOW they are nice! They can easily bought on ebay fairly cheap. I'd really would be happy with either of the RCAs but the black plates are a little smoother sounding, tiny bit. Good luck with your build! You're going to love this preamp.

Steve

 

[Cappy]

Steve,

Thanks for the useful info. Just what I was looking for.

What B+ are you running at and what are the values of your cathode resistors?

 

[Karsten Sømand]

Hi Cappy

Great to hear about your Aikido. I am going to build an Aikido myself but it will take som time before it is finished.

Regarding tubes, please bear in mind that the EH 6CG7 actually is a 6FQ7 (a 6CG7 without shield between plates). I know that EH writes "6CG7" on the tube and the tube box, but it is a 6FQ7!

John Broskie recommends that you go for the "real" 6CG7 tubes. These are, however, only availabe as NOS tubes (at least to my knowledge).

I know that tubes are a matter of taste but according to Broskie you should go for the 6CG7 tubes from before 1965. And stay away from GE´s after 1970. Please note that I have no experience myself regarding these tubes - the words are from John Broskie.

I have read a lot of different opinions on the Internet about different types of 6CG7´s. It seems as the RCA clear tops and the RCA black plates are the best sounding tubes (and often, of course, the most expensive).

If you search on eBay for 6CG7 tubes please note that some sellers don´t know the difference between 6CG7 and 6FQ7 so please remember to ask them about this. According to Mr. Broskie this is rather "important" because the 6CG7 tube has the "shield between plates".

This shield i aka a screen between the two plates which minimizes cross-talk. Furthermore, it gives the tube a better mechanical stability. Both topics should be the reason for the superior sound compared to a 6FQ7.

Electrically the two mentioned tubes are the same so you will get no problems if you would like some tube rolling between these two types of tubes.

Good luck with your Aikido.

Karsten

 

[Steve Fay]

Hi Cappy,

I went looking for my build folder and can't find it, but I can tell you, I used the values out of the manual that comes with the boards from John Broskie. I know it gives two valus one for the input tubr and one for the output tube.

My B+ voltage is 297V which is very close to the 300V I was shooting for.

One lucky find I came arcoss was a remote controlled attenuator from Bent audio, (John Chapman at www.bentaudio.com call him that's the best) it not the one he displays on he site, which is a Gold Point attenuator with a motor on the rear of the unit and a remote to operate it, which is nice also, but this is the one he uses in the preamps he builds. Way nice! It's a little pricey but it's beautiful, controls attenuation, selects up to 6 inputs and has its own power supply and a diplay that mounts on the front of your preamp unit. He had it all setup and ready for installation , including the ribbon cables.

I wish I could find that folder! I think John calls it a PRM unit. He partnered with Gold Point to make the unit.

Give him a call if your interested.

Steve

 

[Cappy]

Steve,

Thanks. It was your B+ I was most interested in since I will be "resistor rolling" to hear the sound changes myself.

I agree, the Bent products are great. I have a TVC Kit I built from John using S&B Mk. III TX-102s.

My Aikido will be used as a DAC output stage feeding into my Bent Preamp. The output caps will be larger at 2.2 uF to accommodate the TVC.

I'll be using a Lundahl LL1683 Power Transformer which will give about 260vac out, given that my voltage is 120vac. With a choke loaded LCLC or LCRC (if the LCLC doesn't sound good) I can get a 210-215 vdc B+. With a CLC or CLCRC I can get 300 vdc B+. I'll probably try both. Does anyone have opinions on the sweet spot B+ for 6CG7 and 5687/6n6p? Steve, it sounds like you found success at 300vdc for 6CG7/6CG7.

Soon I will post my PSUD generated LCLC power supply ideas for a "design review" in this thread.

 

[Cappy]

Karsten,

Thanks, I'll look for 6CG7s with grounded screen.

 

[woodturner-fran]

Heres how my 24V aikido turned out:

This is the more recent board with the headphone output.

[IMGDEAD]http://img143.imageshack.us/img143/3451/dscn1746copyhj5.th.jpg[/IMGDEAD]

[IMGDEAD]http://img143.imageshack.us/img143/9487/dscn1747copypd5.th.jpg[/IMGDEAD]

[IMGDEAD]http://img85.imageshack.us/img85/5840/dscn1744copykg3.th.jpg[/IMGDEAD]


Fran