Aikido Tubes

[minhaj]

Dear Paul,

The seasoned DIYers know that tube choice either it is for input/output duty depends on personal taste and/or audio chain, before and after your pre. Try it for yourself. I strongly suggest you to start building your device ASAP and try tube combination in couse of builing process.

I tryied few AIKIDO designs (with gain without gain) with many tube combination but I like to restrain myself from telling you which combination I like best so that you do not get influenced from my statement.

Over last 10+ years I tried many a preamp SS and holostate and have come to conclusion that in audio the term 'best' is sin, it can be hardly 'better' sometimes for some instances.

TRY IT YOURSELF FIRST, THEN ONLY DISCUSS.

 

[2KW]

Thanks for the comments. I know that what sounds good is extremely subjective and that there are many combos that will work. Just want to get off on the right foot, and not start out with a complete Lemon.

I actually have some 12AX7's and 12AT7's in another preamp that sounds quite good to me, that I will swap around to see what the differences are, once this one is built.

My main objective with the resistor values is to get something that works, and doesn't damage the tubes, rather than obtain a specific gain / quiescent current.

Paul.

 

[minhaj]

Paul, you are in the right track, pls go ahead.

I am side tracking myself, excuse me for that but pls let me know if you use SE amp and horn loaded speakers. If yes then I tell you my story for your future project/development.

Thanks a lot. Regards

 

[Burnedfingers]

I actually have some 12AX7's and 12AT7's in another preamp that sounds quite good to me, that I will swap around to see what the differences are, once this one is built

I certainly would NOT use the 12AX7 or 12AT7 as input tubes because they will have way too much gain. You need a lower mu tube.

To be honest I would highly recommend that you listen to those that have built the Aikido before. You can gain a wealth of knowledge going over the problems that have been solved.

 

[2KW]

The speakers are Bass reflex. JBL2226 and a JBL horn. Not quite your high end HIFI setup but they were originally designed for high SPL. The amp is either a Peavey CS3000, or a Mosfet one I designed around BUZ901/906's.

I am using the 12AX7/AT7's in a line preamp that I just built from Fred Nachbar's cct.

I am always happy to listen to other peoples expierence / learn from their mistakes. Hence this post to find out what others have used.

Paul

 

[minhaj]

dear Burnedfingers,

Should I decide to drive 300B with 12B4/El86(triode mode)/6080/6C19P in a two stage SE config, I actully need 12ax7, 12AT7 in AIKIDO input.

For better built there is no alternative of practice building tube gear, basic electric/electronic knowledge, layout plan and design, good grounding scheme.

For instance I never had hum problem building my tube gears, I never had built any phono stage though.

We are team here - its really nice.

Regards

 

[tinitus]

How about 6AS7 as input tube ..... 6AS7-G/GA ????

Its a low-mu octal triode, and its on Broskie list and also listed as 6080/6082

 

[2KW]

How about 6AS7 as input tube ..... 6AS7-G/GA ????

Its a low-mu octal triode, and its on Broskie list and also listed as 6080/6082

I have the 9 pin board. It seems there are a few nice octal input tubes available though.

 

[tinitus]

In my younger days when tubes where not so common I was told that ECC82 was one of the better ones

With your JBL speakers it might be good with a "soft" tube ... I have experienced the ECC81 to be nice and soft with lots of clean power
I guess you should use it only as output

In other words .... 12AU7/12AT7

 

[2KW]

Thanks tinitus, The ECC81 may have too much gain, but the ECC82 looks suitable. I will get one when I get the ECC99's.

 

[tinitus]

You havent studied Broskies table, else you would know .... you can clearly see how much gain the tubes deliver if used as input tube or output tube .... there are one table at the blog site and another in the PCB userguide

In general it seems that none of the tubes have any gain in the output position, thus you benefit from the driver capabilities of the ECC81, without the high gain ... output impedanse 500 ohm ... and there are lots of them around, as is with the ECC82

ECC99, some highly respected people use it ... but I remember someone in here tried it in Aikido, and didnt like it ...so I guess it very much depends ... new tube only made by JJ, please correct me if wrong ... and its not listed on Broskies table either, I wonder why

Mind you, I am by no means no tube expert ... I have just been through the same thoughts and doubts as you have no, and thats what I ended up with at the time ... never build it though

 

[2KW]

Hi tinitus, now that you mention it..... your right ! All the tubes listed in the output have a gain of < 1. The ECC99 is not in the extensive list, though I do remember it being mentioned elsewhere in the manual.

Thanks for pointing that out.

Paul.

 

[tinitus]

I guess that ECC99 is best suited as driver tube in poweramps, not that I would know why

But I can guanrantee you that ECC81 is a very nice sounding tube, it can make violins sound like played by angels

 

[minhaj]

Dear Paul,

For tube rolling you can use !2AT7 no problem. But remember its not much linear beyond 4 ma current.

For AIKIDO I target 6 ma min. current for input tubes and 9/10 ma min. current for output tubes.

CURRENT IS YOUR FRIEMD HERE, MOSTLY.

Regards

 

[minhaj]

Dear Paul,

I thought I add up few more words for you. I am aware of your audio chain. AIKIDO should be the right gear for you.


PLS let us know the input impdance of your power amp. If it is 50K and above plus your interconnect cable is not too capacitive/too long any member of 12AU7 family is fine for input/output duty.

Paul, trust me your power supply, component layout and grounding scheme are more important that tube choice. Pay attention to these factors also. You can change tube anytime after you buld the pre its a matter of soldering 4 resistors only.

OR SHOULD YOU PLAN you will put your max effort into this design then it will be different ball game and your approach should be also different.

I am trying to help you not helping you much.

Regards

 

[2KW]

Hi Minhaj,
The impedence of the amp is around 10K. There is one question you may answer if you can. On the spec sheets for the ECC99, the linear region of the curves are from about 10mA up. I admit I don't really know what the curves relate to exactly, but wouldn't we want the quiescent current sitting in the linear region? say, at 15-20 mA.

http://www.jj-electronic.sk/pdf/ECC99.pdf

Thanks,

Paul.

 

[beau2317]

10mA will be OK. The curves are quite linear at that point. It's not going to change much (ie move up and down the curve much...it will pretty much stay at 10mA regardless of load).

But also 15mA would be OK.

 

[2KW]

Thanks, Would 15mA cause the tube to run hotter? Or decrease the life of the tube at all.

 

[SY]

No need to stress the tube. First, the linearity looks just about as good at 5mA (think constant current, not constant voltage; there's very little bunching at reasonable plate voltages). Second, the distortion is principally second order, which is canceled anyway in the Aikido gain stage. Third, with the lower dissipation and higher bias voltage to get the lower current, you've moved away from the region where you might get grid current distortion. Why not take advantage of all this and extend component life by running cooler?

 

[2KW]

No worries, that helps explain a lot. What would the ideal plate voltage be. I'm thinking between 200 - 300. Bearing in mind I plan on using a 6CG7 as the input tube. I have a 150 -0-150 xformer, and now need to decide how to configure the supply.

The man himself ( Mr. Broskie ) suggests closer to 300V to help reduce distortion. Would I be better to go for a full bridge, regualted supply at >300v, then split it into 2 seperate ( via passive filtering ). Or, use the centre tap to give myself 2 x 200V seperate supplies. This to seperate L&R channels.

In other words, Is L&R supply seperation more important than increased distortion from the lower plate voltage.

Thoughts?

Thanks.

Paul.