[amb]

I have not tested and determined the appropriate compensation cap values to use for gain of 3. While you could try and interpolate between the values for gain 2 and gain 5, I suggest staying with the tried and true gain settings. The difference between gain of 2 and 3 (or between 4 and 8 balanced) is only 3.5dB.

 

[NumLock]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif you need to think about some things like how many channels, what size trafos, (gain), and things like that too.

I am all new to this so I have no idea what I need or want. I was thinking of getting a LD MKVII. So something similar, balanced, xlr/rca inputs, ingle ended and balanced headphone jacks.

The 2 phones I plan to buy first are the Beyer DT8800 600ohm and HD600. Any suggestions on which way to go? I don't know how many channels I need or tarfos, gain, etc.

 

[amb]

NumLock, please read the β22 and σ22 websites, as well as the related discussions about them here and at headwize.com. It's a lot of information but that's the nature of this kind of project.

 

[NumLock]

Thanks AMB, I am reading it right now. Looks like I will need 4 channels/boards. I will do some more research and also build my own DAC first before attempting the B22. This is exciting but also depressing since I won't have a working amp anytime soon.
Thanks.

 

[linuxworks]

build a small amp, first. you can use that immediately. then build a small dac. you can use them both immediately

THEN work on the longer range projects.

 

[oneplustwo]

what linuxworks said! the B22 is a complex project that is certainly worth the effort but doing one (or two or three!) simpler projects first will serve you well. plus, it will give you an appreciation for how good the B22 really is as you'll have a frame of reference.

 

[Magsy]

I have HD650 (and I don't know how that compares to the HD800) but I had deep reservations in using a gain of 2x (4x overall).
However, now at over 100 hours I'm glad to say I haven't hit a single track when I don't have enough volume. I have been at full volume several times but usually around 2-3o clock. My source is 4v balanced.

When I ran a single ended passive I/V TDA1543 Dac (roughly 1.2v) in there was almost enough but occasionally it ran a little short. I do like it very loud tho and someobody else would be fine. (Using the balanced output but two boards input to gnd)

 

[IPodPJ]

Quote:

Originally Posted by amb /img/forum/go_quote.gif I have not tested and determined the appropriate compensation cap values to use for gain of 3. While you could try and interpolate between the values for gain 2 and gain 5, I suggest staying with the tried and true gain settings. The difference between gain of 2 and 3 (or between 4 and 8 balanced) is only 3.5dB.

Do you mean "(or between 4 and 6 balanced)" ?

 

[amb]

Yes, typo.

 

[pila405]

AMB - Is it possible to build B22 w/o ventilation holes on the top - only on the bottom/back?

Will the aluminium chassis do the work?

This is how it meant to be:

 

[nattonrice]

You will answer that your self if you went to his website store.
You can add it up your self.

 

[oneplustwo]

Ok... some of you may remember I toasted a B22 by making the mistake of not isolating the speaker jacks. Oops! Anyway, I fixed the boards and they all test fine as far as the initial setup goes. But when I hook everything up and power up, at first I get nothing and then a second later, a loud screech (this is through headphones... I disconnected the speaker outputs entirely.) When I move the stepped attenuator through it's range, the sound remains for the first 3 positions, then goes away for the next 6, and then comes back entirely at the last step. This happens with an input plugged in and without. Is it possible my stepped attenuator is toast as well? (The power supply tests fine as well BTW.)

 

[Rooford]

Hi,

I had a mishap with my 3 channel B22. The problem is with the ground channel. After hooking up probes to R9 and powering on, I saw a couple of sparks by the probe and powered down. Looking at the board I nipped/scrapped the board coating and probably shorted the left side of R9 to the ground plane. I should be more careful

I checked the diodes, it looks like CR7 is toast (nothing visible but fails the diode check on my multi-meter. Q25 measures differently to the other boards, I've been measuring between the base-emitter base-collector using the diode check on my multimeter. Q23 seems a little inconsistent measuring between the gate/drain/source when comparing to the other boards.

The other pnp/npn transistors seem OK, they pass the diode check when measuring between base-emitter, base collector.

Does anyone have any advice checking MOSFETS and JFETS?

The resistances between the gates/drain/sources are consistent with the other two boards. Other diodes on the ground channel board check out.

I've been listening with basic two channels, so I have two working boards to use as reference. Sounds great with just two channels by the way!

Before I order new parts I wanted to check if there are better ways of determining if the MOSFETS/JFETS are OK preferably in circuit. I've not powered up the ground channel since the mishap.

If the board will take too much re-work it might be worth starting over.

Thank in advance for any help anyone can provide.

James

 

[nattonrice]

I had the same thing happen multiple times (solder mask hole under R9 from a bubble) on the same board before I realized what was going on.
Replace D11 and Q25 and it should all be fine.

 

[oneplustwo]

Rooford - Like natto, I've done the same thing a few times. For me, it's been Q25 every time (or the corresponding one on the other side).

If you need to order them, I'd go ahead and get a few for spares (for both sides.)