Adcom GFP 555II Preamp Bass Lacking

I recently acquired an Adcom GFP 555II for 50 bucks. When I first tried it I noticed that it sounded very flat, had virtually no bass at all (lab output) and a slight amount of bass with the contour on. I replaced all the old capacitors with ELNA caps. It sounds much better now, however it still has a weak bass output. Any ideas on what could be wrong or is this what I should expect from Adcom? I'm running an Adcom GFA 5200 Mosfet power amp as well. Running four 10" bass drivers but the bass is just not there. Thanks for any help, -Keith
we really need to know everything about your setup including wire, room size, speaker placement, speakers used and source. Also what did you use for a pre amp previously?
Did you try using the bypass output ???
"Is this what I should expect from Adcom" It is.
Slikric, isn't the bypass the lab output?

the Adcom should have bass

try different wire for starters
The bypass is just that, uses minimal electronics, bypasses tone controls, has a much more fuller sound. I have had this model, close to 20 years ago.
Besides that, 4-10 inch drivers with a 50 wpc amp, cmon already. There is a Monster Cable, I forget which 1, I have several pairs at home that will add noticable bass, but I am in Denver right now 1200 miles away.
"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...

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.
Sounds like a great idea. I looked around but where would the best place be to order one and about how much can I get a good one for?