[amb]

If you're using a source that is "too hot", then you might want to add an input attenuator at the amp. Here is a schematic of a switchable attenuator. It is drawn for an unbalanced (2 or 3 channel) amp, for a 4-channel balanced amp you'll need to double everything for the negative signal, and use either a 4PDT switch, or two DPDT switches.

If you use the same value for all the resistors, then the attenuator will drop the effective gain of the amp by one half (-6dB). A good value to use is anywhere from 10K to 47K.

 

[johnwmclean]

AMB, since on the subject of gain I have a question.
I'm building a dac that outputs 4Vp-p in balanced, my Beta 22 is set to 2 total 4 in balanced, driving 650's.
Do you think I'll have an issue with these gain settings?

 

[amb]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif AMB, since on the subject of gain I have a question. I'm building a dac that outputs 4Vp-p in balanced, my Beta 22 is set to 2 total 4 in balanced, driving 650's. Do you think I have an issue with these gain settings?

4Vp-p is only 1.4Vrms and should not be excessive with the HD650 on a low gain amp.

EDIT: I hope you really mean 4Vp-p, and not 4Vrms. If the latter, then the gain might be on the high side. Only way to know is to try it, I guess.

 

[johnwmclean]

Thanks AMB, for the quick reply. 4p-p is correct..

 

[askforwhy]

Hello guys,
I am planning to build 6-channel Beta22 combining balanced and SE amp. I would use balanced K701 and maybe balanced HD600 in the future. With a 23-step attenuator, will the default 8x gain(which would be 16x balanced) be too loud or not so flexible?

 

[johnwmclean]

There is no clear answer as it depends on your source output, and all sources vary to a degree. Gain 8 in balanced configuration is generally way too high with the 600’s from what I’ve heard and read. Maybe for this type of build you might want to try the gain positions socketed. Could be tricky with a 6 board build to get right first time round.

 

[askforwhy]

thanks johnwmclean,
I'll go for 5X first then.

 

[TimmyMac]

5x drives my sony SA5000 to uncomfortable levels at around one oclock, and still has plenty of juice to drive my 8-ohm speakers. Seems to be a good balance.

 

[alwayshungry]

Thanks for the input everyone. I'm using HD650s btw. Apparently the DLIII puts out 5.5 Vmax on it's balanced outputs. I was under the impression that 2.5-3.5V was normal. I contemplated replacing the resistors on my JT boards but it looks like the input attenuator is a better way to go. Thanks amb.

 

[El_Doug]

I just discovered that it is possible to stuff 4 B22 boards in a single day

 

[johnwmclean]

I averaged 10 hrs a board, 1 hr testing each. 40 hrs total.
Betcha the debuggings going to average out with my 40hrs

 

[aloksatoor]

i averaged 2 hours per board with around an hour to debug each

 

[askforwhy]

Sorry for my stupid questions again

But may I substitute the MLCC C1-C5 with silver mica caps?
I've purchased some cheap MLCC but I don't really trust their quality.

 

[amb]

Yes, you can use silver mica in those positions, as long as the fit is good and the cap can be mounted tightly against the board without extra lead-length.

 

[askforwhy]

Thanks, Ti