[looser101]

Quote:

Originally Posted by rodentmacbeastie /img/forum/go_quote.gif To be certain, which output caps can I remove and which can be smaller? If you can tell me the C# from the schematic it would be very helpful. Again, I am new to this and want to be sure. Also, if I wired one board for the L/R- and B+ of -24V and the second board L/R+ and B+ of +24V, with seperate PS each would there be any possibilities here?

C4 is the output coupling cap. 470uF is good enough for low impedance headphones but some people prefer 1000uF. Not sure why Digger's amp lacks bass with a (too huge) 4700uF cap.

First of all to use these boards balanced, a balanced source is required. Otherwise it's a headache I would pass on. My preference would be to use one board per channel. Say Right channel side for + (w/coupling cap) and Left channel for - (without cap, just a jumper). Do the same with the second board, which would then be the + / - for the other channel (Right channel?). This allows you to use two power supplies, one per channel, if you so desire. No negative supplies should be used. Some amps can use bipolar supplies to get rid of the output caps but I don't think this is a good candidate, as currently designed.

 

[digger945]

Another possibility is the low pass filter from the tube output to the buffer input.
I tried the single 300 ohm resistor, per the schematic, and finally went back to the original 10K resistor followed by the 300pF cap to ground, forming the original low pass filter. Maybe I need to go back and reinsert the 300 ohm and try to find a different cap to make the new filter work correctly.
EDIT: I don't see why it would not work with just the resistor, per JB's schematic, passing all of the signal.
I'm warning up the soldering iron now.

 

[rodentmacbeastie]

Did Fierce put BG NX 1000uF 25V caps in C4 and C11? The manual calls for a 35V cap in C11 right?

And yes, I don't know why we would need a low pass filter unless your source is noisy. If the DAC is already low pass filtered, the only new HF noise should be from the Aikido's PS which is nullified in the circuit.

 

[digger945]

Yea, I own Fierces amp now, it came with BG NX 25V 1000uF in the C4 position, and that's all as BG NX does not get along too well with other stuff, even films. I can attest to this, I tried it, it sounds funky, but not real. Instrument get placed in wierd places, voice of artist behind you sometimes. Freeky when bypassed, not bad at all if used alone.
I guess if your gonna use a 48V PS then you will need at least 48 or 50V for C11, C12, C13, and, according to JB, C7,8,9 and 10 should be rated to the PS output in case a tube is yanked out with power on, or powered up witha tube missing from it's home.

The low pass filter is a part of the 24V aikido circuit, but when I upgraded to the DN2540 output tranny's the new schematic just called for a 300 ohm resistor in the R20/21 position, no mention of the cap to ground. I am listening to the 300 ohm now, definitely don't like it as much as the 10k in the R20/21 pos. and the 300pF cap to ground, forming the low pass filter. This low pass filter, according to JB, is just to strip away some of the high freq noise from the tubes anyways. I like the slam of just the 300 alone, but with the filter, it's like a machine gun shooting syrup coated jellybeans into my ears, yea it's good for sure.

 

[rodentmacbeastie]

Balanced Aikido


I see here that it looks all caps are present. The other article I mentioned he states that "carefully selected parts" would be needed.

 

[digger945]

A bit off topic...
You have heard it said that "misery loves company".
Well excitement loves company also, and I am excited.
What do you need to order, maybe I can help out?
EDIT: I clicked on the link you provided above, interesting, I had not read that yet.
Thanks.

 

[rodentmacbeastie]

OK, forget about the truly balanced circuit. I will simply build two normal 24V boards. I am wondering if the tubecad linear PS has enough juice for two boards or should I get a second? I am buying most parts from sonicraft. They have a 20% sale for a couple more days and 50% off Jupiter beeswax caps. I thought that I would mirror Fierce's recommendation, but I am open to suggestion. I also have to buy parts for a couple of balanced D1 I/V stages for my Buffaloso all the help is appreciated.

Here is Freak's BOM: http://www.lightmedark.com/aikido2.xls
Here is the D1 BOM: diyAudio Forums

-I am using all 1/2Watt PRP resistors
PRP 1/2 Watt Audio Resistors
-3uF/200V Sonicap Gen I for C1
-1uF/100V Mulitcap RTX for C12
-0.1uF/100V Multicap RTX for C13
-thinking about BG NX for C4 and C11 but this limits me to 24V, got FM 1000uF50V coming for now. Does C11 need to be higher than 50V if I use a 48V ps?
-C7,C8,C9,C10 get Panasonic FM 1000uF/50V
-C2 is a 220pF film cap
-C5,C6 .047 Wima
-for C3 it looks like Fierce used .47uF Muticap RTX and I could do that too.
-I was thinking that if there is no trade off for usinf the high voltage LM317 then I will use it even for 24V which leaves the door open for future expandability. Thank you for all the help.




I am using the same resistors for the D1 unless they are too big. The other parts I would love your help choosing. I am excited with parts arriving daily! I got my 10.2" touchscreen today as well as some SACDs and OCC wire for hook-up. Yesterday I got a Hakko soldering station and some 4% silver solder. The Aikido and D1 boards ready to populate.

 

[digger945]

Before I comment on the fierce aikido BOM, do you have the newer pcb's with the dual places for 317 reg or mosfets?..or the ones that have just the AOI silkscreen for regs only?
Yes I have some extra stuff you should order anyways but just wanted to get ^that^ out of the way first to make sure you get the right parts.
Also, is it safe to assume from here on out that your gonna need to order parts for 2 complete stereo boards?
The last line of the product description at glass-ware says " Each board holds two Aikido linestage/headphone amplifiers; so, one board for stereo unbalanced or one board for one channel of balanced amplification.", so 2 boards = balanced amp.


D1 I am unfamiliar with.

 

[rodentmacbeastie]

Quote:

Originally Posted by digger945 /img/forum/go_quote.gif Before I comment on the fierce aikido BOM, do you have the newer pcb's with the dual places for 317 reg or mosfets?..or the ones that have just the AOI silkscreen for regs only? Yes I have some extra stuff you should order anyways but just wanted to get ^that^ out of the way first to make sure you get the right parts. Also, is it safe to assume from here on out that your gonna need to order parts for 2 complete stereo boards? The last line of the product description at glass-ware says " Each board holds two Aikido linestage/headphone amplifiers; so, one board for stereo unbalanced or one board for one channel of balanced amplification.", so 2 boards = balanced amp. D1 I am unfamiliar with.

I have the new boards. I would live to hear suggestions for the parts, but soon as the sale is over at the end of November. I will need parts for two boards. I read the last line. This would describe a balanced amp if they were connected to nullify DC. So how are they balanced if they are simply two independant SE channels and not push-pull? There has to be a resistor or something to tie the two boards together. I know it can be done, just don't know how or if at all with this board? That said, I am all gung ho for two SE boards and I am sure it will sound great!

 

[digger945]

OK, one more ultra critical question,
Were you thinking of using this 24V aikido to do a 12SX7 amp in the future, or did you have plans for a totally new amp?..or did you just want to try the 6GM8 at 48V?

I just thought of it, the 6GM8 and the 12SX7 are completely different tubes, one in 9pin and one 8, they need completely different pcb's to work.
Just wondering Rod.

 

[looser101]

Quote:

Originally Posted by digger945 /img/forum/go_quote.gif I am still studying post #271 to understand how you can hook this up balanced to make it work. As I read the article at Tubecad in the link you posted above, I am beginning to understand what your talking about now.

The one linked is a dedicated linestage not a headphone amp.

The Basics.

 

[digger945]

I was just trying to get it in my head how the current is going to return to each half of the one board.
The source I understand, it's the aikido output I am confused about.

 

[looser101]

Pay close attention to the sinewave in the following drawing. It is equivalent to your music. When the + side of the driver is going positive, the - side is going negative (effectively twice the power, and not referenced to ground at the headphone). The balanced source takes care of the polarity of the signal for you.

* Image Courtesy of Headroom

 

[digger945]

I got that down, no problem.
I understand it with a direcly coupled solid state amp, but the output of the aikido, it's not the same. It's something I have never thought about before.

EDIT: Yes, I think I understand what you mean in post 271, just short one of the channels output cap on one board (the negative in this case for balanced). Coupling caps on the positive. OK, no ground. I got it.

 

[looser101]

The output of the Aikido like all single ended amps has an output that is (for sake of illustration) say B+/2, so 12Volts in the case of the 24V Aikido. In this case the headphone driver would see 12v on one side and ground (0volts) on the other (which would be bad since a current would flow across the driver when no music was playing). So what can be done about this problem? We use a coupling capacitor. In this case it will block DC in the output stage and pass AC (ie. music). The DC voltage at the output of the coupling cap is effectively 0 and since ground is also 0 then no current will flow. Hope that is what you are asking.