[djork]

Hi folks, I'm thinking of making a B22 amp to drive speakers and a K1000. I'm currently thinking of making a two board version (two betas and two sigmas), as I have no inclination to upgrade to a balanced setup anytime soon in the future.

Any good experiences to share or for me to take note of?

Thanks for looking.

 

[utilisateur]

I think you'd be better off with 4 beta and 4sigmas
Even if you ignore everything else, 2sigmas powering 2betas driving a K1000 or speaker would simply develop too much heat !

 

[djork]

Quote:

Originally Posted by utilisateur /img/forum/go_quote.gif I think you'd be better off with 4 beta and 4sigmas Even if you ignore everything else, 2sigmas powering 2betas driving a K1000 or speaker would simply develop too much heat !

Hi, by that does it mean that if you have double the boards the workload is split hence less heat?

 

[n_maher]

I don't think that two betas w/ two sigmas would have any issues with the K1000s. With the stock heatsinks the amp you're describing could easily be good for ~18WPC for 8ohm loads so the real question would be what speakers are you thinking about trying to drive?

 

[KT88]

a friend of mine has built a 4 board B22 with 2 sigmas (only one was connected at the moment) and there's much to be desired. It does a nice job of driving the K1000's, but not as good as some of the speaker amp I've tried.

As for speakers, I hope I'll have a chance to test it with both sigmas this weekend on my Morel-USA Perfect709 speakers. Obviously I'll try the K1000's with the 2 sigmas as well. Just to see what difference (if any) it has made. BTW, the amp had a gain of "2".

 

[amb]

Gain of 2 is way too low for the K1000. I tried a K1000 with the default gain of 8 on my 3-channel active ground β22 and it's barely enough. The volume knob has to be set very high to get adequate levels. Those K1000s are extraordinarily inefficient, but β22 does have enough voltage swing headroom to make them really sing if you set the gain high.

 

[n_maher]

I guess w/ my Wadia and it's 4V output it's less of an issue that others might have.

 

[SoapSeller]

I'm the friend KT88 talked about.

My β22 is balanced so the affective gain is 4.
And have been used with TPA Opus DAC which have 2V output IIRC.

To reach listenable volume levels, the knob has been set to about 75%(using TPA JT).
I agree that it's not optimal for the K1000.

Anyway, I really enjoying it with my K701, so I don't really care

 

[ericj]

I'm curious, where are people getting this wacky idea that less gain is better?

 

[n_maher]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif I'm curious, where are people getting this wacky idea that less gain is better?

In practice I think that you should use as low a gain as possible, what's the point of never turning the volume pot past 9 o'clock? Seriously, it's not like something bad starts to happen if it takes cranking the knob to 3'clock to reach reasonable listening levels.

I'd be curious to know what source Soap Seller is using.

 

[ericj]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif In practice I think that you should use as low a gain as possible, what's the point of never turning the volume pot past 9 o'clock? Seriously, it's not like something bad starts to happen if it takes cranking the knob to 3'clock to reach reasonable listening levels. I'd be curious to know what source Soap Seller is using.

I agree, but that's a matter of having As Much Gain As You Need, and maybe a Little More Just In Case.

Because what's the point of having an amp if it doesn't go loud enough?

Maybe I'm just severely biased because i own so many 600-ohm dynamics, and inefficient orthos. I need a gain of at least 8 to make most of my orthos really sing with a typical 1vrms source. My dad, on the other hand, with his 32-ohm DT231's and the relatively high-volt line output on his Wave Radio (what can i say, we don't pick our parents) could stand a gain of 3 or 4. I gave him 6 and he never went above 12:00.

 

[n_maher]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif I agree, but that's a matter of having As Much Gain As You Need, and maybe a Little More Just In Case. Because what's the point of having an amp if it doesn't go loud enough?

Agree, 100%. The other complicating factor is that enough people have complained about the lack of adjustment when using a 24-step attenuator with a high-gain amp that word has gotten around. Also, even on basic Cmoy's the standard gain of 11 can cause problems with poorly matched pots so there's another source of the "lower is better" mentality.

 

[utilisateur]

Imho i'd prefer having the lowest usable gain so i have full control over the volume with the equipment i use everyday instead ov having the volume at 1/4 turn or in the first few steps - i imagine gain of 8 would be too much to use the amp in balanced mode for example!?
Have parts for a balanced β22 at 2x gain on order personaly but maybe i'm missing something?

EDIT: WAY TO SLOW

 

[SoapSeller]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif I'd be curious to know what source Soap Seller is using.

Quote:

Originally Posted by SoapSeller /img/forum/go_quote.gif And have been used with TPA Opus DAC which have 2V output IIRC.

Usually it connected to a Squeezebox.

For my high-sensitivity 'phones(K701) gain of 4 seems good enough.
If I will ever acquire headphones that are harder to drive, I'll probably raise the gain(or build a new one

).

 

[n_maher]

Quote:

Originally Posted by SoapSeller /img/forum/go_quote.gif Usually it connected to a Squeezebox.

Ack, missed that the first time somehow. All I can say is that you must listen a lot louder than I do.