[MrMajestic2]

Just found out from Twisted Pear that the JT does take DC if its less than 35V. Although the heatsink will get very hot when running that high. They recommend 5-12V. I will probably go external transformer anyway though.

Quote:

Originally Posted by amb /img/forum/go_quote.gif Looks like Joshua Tree has its own onboard rectifers and voltage regulator, and wants a 9V-15VAC single secondary transformer, not a DC power supply. Tapping off the σ22 won't be feasible. The Joshua Tree's current consumption is (200mA + (n * 150mA)) where n is the number of relay boards used (2 for balanced), so it's 0.5A in your case. Giving some headroom says you should use at least a 10VA transformer. As in any power transformer, you should place it well away from the β22 boards and the Joshua Tree relay boards to minimize magnetic field interference.

 

[SoapSeller]

MrMajestic2, We are on the same road.
I'm ordering parts from JRossel and have the Jouhua Tree on the way.

You can get DRV134 based BLD boards from assemblycraft, I'm going to build it with some THAT1646 that I've got from ebay

For what do you need the E12 for?

 

[Alick]

I've decided to go with the 330mm wide HiFi2000 Galaxy Max case(s) for my 4 channel beta22. I just have to decide which one(s) of the following four options to go for:

1. Everything (including PSU and transformer) in a 280mm deep enclosure. (I'd screen the transformer in an interior metal box).

2. Amp in a 280mm deep Galaxy Max and the PSU in a 230mm Galaxy Max sitting on top (the shorter case avoiding covering the amp's rear ventilation slots).

3. Amp and PSU in a 280mm deep case with the transformer in a separate cheap 'n' cheerful box not on show (but perhaps awkward to switch on and off).

4. As 3. but transformer and psu in the separate 'out of sight' box.

I plan to locate the amp (and possibly PSU) in a glass fronted cabinet which has reasonable ventilation via wide cable slots at the rear. I'm wondering how warm the amp gets, how much ventilation is required and which of the four options makes most sense. Thoughts?

 

[luvdunhill]

Quote:

Originally Posted by amb /img/forum/go_quote.gif FWIW, β22 isn't much different than most other amps as far as compatibility with stepped attenuators is concerned. Again, if you don't have a pot or attenuator plugged in to the backplane, the amp board input traces on the backplane are essentially "floating", high impedance nodes, and could pick up crosstalk from adjacent traces. That is simply not a valid mode of operation.

amb:

what about putting a 1k resistor in series with a 680pF capacitor to ground after the attenuator to form a RF filter?

 

[luvdunhill]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Looks like Joshua Tree has its own onboard rectifers and voltage regulator, and wants a 9V-15VAC single secondary transformer, not a DC power supply. Tapping off the σ22 won't be feasible. The Joshua Tree's current consumption is (200mA + (n * 150mA)) where n is the number of relay boards used (2 for balanced), so it's 0.5A in your case. Giving some headroom says you should use at least a 10VA transformer. As in any power transformer, you should place it well away from the β22 boards and the Joshua Tree relay boards to minimize magnetic field interference.

according to TPA, for the Joshua Tree attenuator:

"Input impedance ranges from approximately 2.2K to 10K (pretty easy load for a source like the Opus).

The output impedance is 750R."

If using the Joshua Tree with an amplifier like a Dynamight or β22, would a buffer be required to deal with the high source impedance? What are the effects of changing the 1M resistor to say 100K to counteract this?

 

[MrMajestic2]

Quote:

Originally Posted by SoapSeller /img/forum/go_quote.gif MrMajestic2, We are on the same road. I'm ordering parts from JRossel and have the Jouhua Tree on the way. You can get DRV134 based BLD boards from assemblycraft, I'm going to build it with some THAT1646 that I've got from ebay For what do you need the E12 for?

Didnt you post the same reply already?
http://www.head-fi.org/forums/showpo...&postcount=305

But I will answer again:

Assemblycraft doesnt reply to my emails, so Im guessing there is no interest in selling boards.

The E12 board is for headphone protection. its available from Amb's site.

 

[amb]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif according to TPA, for the Joshua Tree attenuator: "Input impedance ranges from approximately 2.2K to 10K (pretty easy load for a source like the Opus). The output impedance is 750R." If using the Joshua Tree with an amplifier like a Dynamight or β22, would a buffer be required to deal with the high source impedance? What are the effects of changing the 1M resistor to say 100K to counteract this?

The JT's output impedance is not high, and no changes to the amp is necessary. However, an input impedance of 2.2K is fairly low and may be a problem with some sources. For example, if the source has an output impedance of 600 ohms (not unusual), then that 600 ohms will form a voltage divider with the 2.2K input impedance to cause a 2.1dB signal loss. If the source output impedance is not linear across the audio band, then the frequency response will be affected. For example, most sources have an output coupling capacitor, which causes its output impedance to rise at low frequencies. When driving a low-ish input impedance like the JT, the result is a low-pass filter. Whether the rolloff occurs within the audio band depends on the coupling capacitor's value. If the source's output coupling cap is 1uF, then the -3dB corner frequency would occur at 72Hz -- which would be very audible! Not to mention that phase shifts would affect the signal well into the lower midrange region.

 

[SoapSeller]

Opps, I've used the "quick reply" option when going to work, and when I've come back and seen it with my message still in post it again

He seems to have some malfunction with the mail in his site, you can reach him in: vcgft at yahoo.com.cn.
(I've told him about that, but seems that he didn't fixed it yet)


About the E12, I must say that I like my headphones, and I starting to think that it might be a good idea to is it in my build.

 

[koike]

i am listening to my b22 now.
its perfect sounding but i am getting about 60~100+mV dc offset in my left channel only. i dont think that is normal right?

 

[Ferrari]

Quote:

Originally Posted by koike /img/forum/go_quote.gif i am listening to my b22 now. its perfect sounding but i am getting about 60~100+mV dc offset in my left channel only. i dont think that is normal right?

Is this DC off-set number is measured under load (with your headphone connected)? And is the DC off-set is ~0 (zero) mV without load? If this is the case, it seems to be that your left channel is unstable under load, in one or other way. You might try a Zobel network on your backplane board.
Take a look at ε22 website, AMB has pointed out how to construct a Zobel network. Good luck !

 

[el_matt0]

hey guys, good to be back on headfi, ive had a bunch of questions!! so ive been looking at a pair of Onix Signature Rocket 750 loudspeakers, im sure you guys are familiar with them. im TOTALLY new to the speaker world (and the world of b22 as a speaker amp for that matter), and im wondering at all if my b22 would be capable of driving such speakers? would it be a "suitable" pairing of amp and speakers, or is the b22 as a speaker amp mainly intended for bookshelves? assuming it is very possible to run the onix speakers from my b22, what changes would i need to implement to my b22 other than the addition of 4 speaker outputs with zobel networks across them? there is no need for any output selector right, my quad pot would simply control all headphone and speakers connected simultaneously? is this going to be possible to run off just one s22 and trafo, or am i going to need to purch at least one more s22/trafo to be able to amply power such speakers? im currently using a 100VA trafo. thanks for bearing with me guys if any of these questions were painfully obvious to any of you

!
*added note, my front panel was shipped out to me today from FPE so hopefully i should have a schnazzy b22 all cased up within the next few weeks!

 

[n_maher]

Matt,

A ton of what you're asking about is covered on amb's site, don't make me start hammering you again...

And no, I have no idea what the speakers are or what type of design they are. Again, amb gives some guidelines on his site about what parameters to look for if you're thinking about using the beta as a speaker amp.

Long story short, RTFM man.

 

[el_matt0]

finally arriveD! just a few cruddy quality photos with my unsteady hand on a cell phone camera, proper photos to come once ive cased it up nicely! one question i have, on my first wiring of the b22 i used the same navships wire that fierce freak used in his b22. im however wondering, is there something that is a little more flexible that would be just as suitable to use for the internal wiring? my only "beef" with the navships wire is that it is so resilient to bending it is quite hard to do a "neat" job wiring without wires going all over the place. stranded copper would be perfectly suitable right? what would be a good brand (id hate to end up using something "cheapy" that might bring down my amp!)! thanks guys

 

[el_matt0]

guys, any suggestions on a good choice for some more flexible wiring for my internal hookup wire (excluding the PSU wiring as that needs to be higher gauge i realize)? i just find the navships wire to be too resilient to bending to it appears uber messy! would just some standard stranded copper from parts connexion be fully acceptable? recommendations on gauge that would be ideal?

 

[amb]

Standard 22-24 AWG stranded hookup wire is perfectly fine for most internal signal wiring. Keep input wiring as short as possible to minimize interference and capacitive crosstalk. If they must run more than a few inches, consider shielded cables.