Adcom GFP 555II Preamp Bass Lacking

"bypasses tone controls"

that is what the lab out does

Where are you getting the lab output, in the manual the bypass is stated to use minimal electronics including bypassing tone controls. There is no mention that I can remember of it being a lab output. The 565 has 3 sets if I remember right. What would be the the 3rd output be ?? 3rd leg output ??

I do agree though that using the "lab output" with 10 inch and above is a good choice. If I were using that setup @ 50 wpc I would mate it up with Cerwin Vega's which are way efficient, close to 100 db.

I changed my setup around. It's a budget system not too special:

ADS CD3 Cd player (Soon to be Adcom GCD 575)
Adcom GFA 555II Recapped with ELNA caps
Adcom GFA 5200 80 WPC into 4 ohms
a/d/s/ M-15 Speakers 4 ohms (1" Dome tweeter, 5.25" Cone mid, 2 10" bass drivers) in a single bedroom apartment.

Changing the speaker placement made all the difference. The Elna caps added greatly to the SQ of the preamp and gave the bass more punch.

The Lab output does in fact bypass as many filters as possible for the cleanest most "airy" sound.

I plan to run a 12" DIYMA subwoofer ported tuned to 29Hz as well.

I also want to upgrade my power amplifier to the matching Adcom GFA 555II. Good idea? I would expect it should sound better than the GFA 5200 Mosfet power amp but I have never compared them so I can't judge...

-Keith

Moviemakerkeith,
almost all of the adcom preamps use a tiny power transformer. it kills dynamics, and bass response. replace it with an outboard 400 watt toroid and you will be shocked at the sonic improvements in all areas. I have worked on a half dozen Adcom pres. they alll take a huge jump when the power supply is beefed up. best.