Some not very happy experience with my used GFA-555 II AMP

Hardrock.ca

I finally got a USED GFA-555 II from AudioGon, In the hope to improve my Monitor 10B's sound quality, unfortunately it doesn't. Here is the story:

I hook it up with HK3490's preout

I find the sound from the GFA-555II lacks some clarity compare the sound directly from the HK3490 receiver's speaker out. It's not very easy to describe the difference. it likes a very mild noise in the high end. something like Sibilance, I have to listen to it carefully, then I can notice it.

In term of volume, the volume from GFA-555II even slightly smaller than the volume from the HK3490's speaker out. I expect GFA should and can produce bigger or much bigger volume.

Finally, when I turn off the power in GFA, it still sounds for a few seconds, first the left channel fade out, and then is the right, is this means anything wrong.(is this normal?)

I think I used a very good Monster cable, I also tried Luna 6 cable to connect the HK3490 preout and GFA , I got the same thing.

If listen this GFA-555II AMP alone, it seems it works fine, but just by comparing with the output from the HK3490 receiver. I feel this AMP does not fully work but I am not sure.

Please help me to sort out the situation,
Thanks a lot in advance!

Joe08867

I would get the Adcom looked at. I am thinking something might be going south in it.

heiney9

Something is wrong with it if you're not getting clarity or volume better than the receiver. As far as the fading and you may hear a farting type noise when you power down, that's normal and you should turn the pre/receiver off first if the noise bothers you. You won't hurt anything either way.

Either talk with the seller to get the situation rectified or have it checked out.

H9

sda2mike

yeah, the shutdown sounds normal...you may have some past-ripe caps in there or some other issues..good luck

michaeljhsda2

So if I am understanding you correctly...you are using the HK as a preamp? Perhaps that's the problem. I would suggest adding a source (MP3 player, computer sound card, etc.) with a volume control directly to the amp and see if there is an improvement.

just reread your post and you said it sounded better without the HK in the loop. I would try to find a better preamp IMHO.

heiney9

michaeljhsda2 wrote: »

just reread your post and you said it sounded better without the HK in the loop. I would try to find a better preamp IMHO.

Yes, I agree that should be step one before taking it in to have it looked at. Also communicate with the seller now so you aren't springing it on him at the last minute.

H9

AsSiMiLaTeD

I'll throw an alternative point of view in. The 3490 is a fantastic receiver, and has a great amp section built in. This is not your standard AVR, it's a 2 channel beast of a receiver. Perhaps you're just hearing how good the sound in the HK really is.

heiney9

AsSiMiLaTeD wrote: »

I'll throw an alternative point of view in. The 3490 is a fantastic receiver, and has a great amp section built in. This is not your standard AVR, it's a 2 channel beast of a receiver. Perhaps you're just hearing how good the sound in the HK really is.

Unlikely.

H9

DaveHo

Do you have a multi-meter? First thing I would do is check the DC output from the amp. With no source & no speakers connected, turn it on & let it sit for a bit to stabilize. 20 minutes should be enough. Set your meter to read DC voltage & measure the voltage between the + & - of each channel. Anything less than 50mV is considered OK. More than that, you should have it serviced.

-Dave

Hardrock.ca

Actually I only compare the sound from GFA-555II which uses HK3490 as preamp
and the sound directly from HK3490's speaker output. and I found the sound from GFA is not as good as the sound directly from the RECEIVER in terms of clarity and even volume!

I did not try hook it up with MP3 player yet. and I will try and thanks for the suggestions!

michaeljhsda2 wrote: »

So if I am understanding you correctly...you are using the HK as a preamp? Perhaps that's the problem. I would suggest adding a source (MP3 player, computer sound card, etc.) with a volume control directly to the amp and see if there is an improvement.

just reread your post and you said it sounded better without the HK in the loop. I would try to find a better preamp IMHO.

Hardrock.ca

Thanks! I will try to measure the DC offset, I have a multi-meter

DaveHo wrote: »

Do you have a multi-meter? First thing I would do is check the DC output from the amp. With no source & no speakers connected, turn it on & let it sit for a bit to stabilize. 20 minutes should be enough. Set your meter to read DC voltage & measure the voltage between the + & - of each channel. Anything less than 50mV is considered OK. More than that, you should have it serviced.

-Dave

michaeljhsda2

Hardrock.ca wrote: »

Actually I only compare the sound from GFA-555II which uses HK3490 as preamp
and the sound directly from HK3490's speaker output. and I found the sound from GFA is not as good as the sound directly from the RECEIVER in terms of clarity and even volume!

I did not try hook it up with MP3 player yet. and I will try and thanks for the suggestions!

My hunch is that playing a source directly from the amp will yield much better results. Just make sure that the volume on the source is turned down before you power on the amp. You probably know this already but do not hook up a source directly to the amp unless it has a volume control!

heiney9

Hardrock.ca wrote: »

If listen this GFA-555II AMP alone, it seems it works fine, but just by comparing with the output from the HK3490 receiver.

This is why we are asking, now you say you only listened to the GFA hooked to the HK as a pre? What does the above statement mean if that's the case.

H9

michaeljhsda2

heiney9 wrote: »

This is why we are asking, now you say you only listened to the GFA hooked to the HK as a pre? What does the above statement mean if that's the case.

H9

It is confusing isn't it? :eek:

Hardrock.ca

I am definitely confused for this, as I add a power amplifier, I get a worse sound in terms of quality and volume , very sad

AsSiMiLaTeD wrote: »

I'll throw an alternative point of view in. The 3490 is a fantastic receiver, and has a great amp section built in. This is not your standard AVR, it's a 2 channel beast of a receiver. Perhaps you're just hearing how good the sound in the HK really is.

michaeljhsda2

Hardrock.ca wrote: »

I am definitely confused for this, as I add a power amplifier, I get a worse sound in terms of quality and volume , very sad

I wouldn't jump to that conclusion just yet. You can confirm this by hooking up a direct source to the amp as I suggested. This is an easy way to differentiate whether it's the HK that is the problem or the amp.

AsSiMiLaTeD

heiney9 wrote: »

Unlikely.

H9

OK, let me try to be more direct then. I'm not a fan of Adcom amps. I think the HK sounds better, and I've compared the 3480 and 555 side by side, have you?

Hardrock.ca

heiney9 wrote: »

This is why we are asking, now you say you only listened to the GFA hooked to the HK as a pre? What does the above statement mean if that's the case.

H9

You know HK3490 is kind of a powerful receiver, what I means is I got a worse sound(HK3490 preout + GFA 555) than the sound I can get from the sound( HK3490 working as receiver) in terms of quality and volume.

michaeljhsda2

In the past I used the preamp outputs from a Pioneer AVR that had decent sound quality. When I moved up to a better preamp (B&K Reference 5 S2) the sound quality improved by quite a bit.

michaeljhsda2

Hardrock.ca wrote: »

You know HK3490 is kind of a powerful receiver, what I means is I got a worse sound(HK3490 preout + GFA 555) than the sound I can get from the sound( HK3490 working as receiver) in terms of quality and volume.

Does the HK have a 2 channel direct mode?

AsSiMiLaTeD

michaeljhsda2 wrote: »

In the past I used the preamp outputs from a Pioneer AVR that had decent sound quality. When I moved up to a better preamp (B&K Reference 5 S2) the sound quality improved by quite a bit.

Uh, yeah I should hope so...

michaeljhsda2

AsSiMiLaTeD wrote: »

Uh, yeah I should hope so...

Then I would dump the HK. Why settle for crappy sound? In fact, I've yet to hear of an AVR that will pass a great 2 channel signal. A Sunfire Theatre Grand couldn't for example.

Hardrock.ca

HK is a 2-channel Receiver with preout, in term of mode, I didn't see a explicit '2-ch direct' mode, but I can have the Stereo mode and virtual Doubly mode

michaeljhsda2 wrote: »

Does the HK have a 2 channel direct mode?

heiney9

AsSiMiLaTeD wrote: »

OK, let me try to be more direct then. I'm not a fan of Adcom amps. I think the HK sounds better, and I've compared the 3480 and 555 side by side, have you?

Yes, and I happen to think a properly running and connected 555 sounds leagues better as far as dynamics, soundstage and timbre. It should play louder but it's not going to be a lot louder in terms of absolute dB's.

I still feel, subjective quality aside, the OP might have an issue with either hook-up or the amp itself. But there is not near enough information to go on and from the OP's post he's already given up and come to the conclusion the amp stinks.............so I'm outta this one.

H9

P.s. I have never listened to the 555 using the HK as a pre-amp. It was a side by side with a Nakamichi CA5 running pre-amp duty with the 555.

michaeljhsda2

heiney9 wrote: »

the OP's post he's already given up and come to the conclusion the amp stinks.............so I'm outta this one.

H9

I'm just about ready to do the same.

Hardrock.ca

Thanks a lot for the inputs

michaeljhsda2 wrote: »

Then I would dump the HK. Why settle for crappy sound? In fact, I've yet to hear of an AVR that will pass a great 2 channel signal. A Sunfire Theatre Grand couldn't for example.

I hope HK3490 is the problem but unlikely as the external preout is also used by the HK 3490 power amplifier portion and it ends up a better sound. If the preout of HK3490 is noisy, the sound of its speaker output should not be good too. This is my logic so far.
I means 'Better' just by comparing the sound from GFA-555, not means the sound from HK3490 is perfect.

nwohlford

Hardrock.ca wrote: »

HK is a 2-channel Receiver with preout, in term of mode, I didn't see a explicit '2-ch direct' mode, but I can have the Stereo mode and virtual Doubly mode

There is button on the remote labelled direct. Try pushing that.

michaeljhsda2

Did you try my suggestion yet? Hookup a source (with a volume control) directly to the amp and see if you get better sound.

michaeljhsda2

nwohlford wrote: »

There is button on the remote labelled direct. Try pushing that.

....

Hardrock.ca

I am in office right, but I check the manual online
The 'direct' button is not for purpose of '2-ch Direct'

its purpose is for Radio station selection:(Except form the manual is)
Direct: Press this button before using the Numeric Keys to directly
enter a radio station frequency. It is not necessary to press this button
before using the Numeric Keys to enter an XM Radio channel.

here is the link:
http://www.harmankardon.com/resources/Brands/harmankardon/Products/ProductRelatedDocuments/en-US/OwnersManual/HK_3490_OWNERS_MANUAL.pdf

michaeljhsda2 wrote: »

Did you try my suggestion yet? Hookup a source (with a volume control) directly to the amp and see if you get better sound.

nwohlford wrote: »

There is button on the remote labelled direct. Try pushing that.

CTTE

I have this amp. It doesn't sound good until it's warmed up for about 20 minutes.