Gator aid. Or how to get the most from your Gator.

Hello there. I have been reading a lot of threads lately (possibly too many) as I'm laid up with a broken leg. Haven't come across any reference (other a pic somewhere) to using a hdam, eg a GD - Audio "Moon" that i used with a Zero 09 dac in lieu of the dual Burr Brown 2604 opamp. I use my caiman strictly as a dac from a macmini to a marantz pm7003.
I wonder whether i could 1) swap it? 2) if yes, do i need to ground it? as it comes with a ground wire with a metal ring at the end; 3) if yes, where would i ground it? I have the extension lead for it so i need to think about best positioning also if i proceed.
Any thoughts on whether it would be worth it? I am just an amateur when it comes to this stuff but the hdam certainly improved the sound of the Zero. I can't remember what opamp it replaced though. LM something i think.

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Originally Posted by allsorts

Hello there. I have been reading a lot of threads lately (possibly too many) as I'm laid up with a broken leg. Haven't come across any reference (other a pic somewhere) to using a hdam, eg a GD - Audio "Moon" that i used with a Zero 09 dac in lieu of the lm4562 opamp. I use my caiman strictly as a dac from a macmini to a marantz pm7003.
I wonder whether i could 1) swap it? 2) if yes, do i need to ground it? as it comes with a ground wire with a metal ring at the end; 3) if yes, where would i ground it? I have the extension lead for it so i need to think about best positioning also if i proceed.

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My first thought is that you need to be quite familiar with the Gator's power supply. The power is single-ended (+ve and gnd) and as I recall, the opamp is powered by the external p/s without additional regulation.

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Any thoughts on whether it would be worth it? I am just an amateur when it comes to this stuff but the hdam certainly improved the sound of the Zero. I can't remember what opamp it replaced though. LM something i think.

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I expect the answer is largely determined by what the power requirements are. If it requires dual rails + gnd, or has only moderate CMRR, then it will not work well or worse still not work at all.

Thanks Mervinb. The specifics of what you said elude me but I take on board the general idea . Here is some info on the Moon hdam: OPA - Moon : This discrete opamp uses dual differential gain stage and single ended output stage circuit design , we try and audition for a long period of time . The OPA-Moon sound characteristics is a bit of tube-like (vacuum valve) , soft and slightly thick, and full of emotions . THD Less than 0.0008%(1KHz), Operating voltage ：±9 TO ±25V，Open loop gain：33DB，Operating current：Approx. 28MA（Single OPA） ， Approx 58MA（Dual OPA）. I have a dual which was needed to replace the Burr Brown 2604 opamp in my Zero Dac.

I was having a problem with the passive mod in that my power amp and lightspeed combination has a very low input impedance. I needed around 90uf to get the bass response all the way down.

I've just received a gator and it has helped significantly, particularly with dynamics but still the bass extension is a little lacking. Better than small caps in the passive mod but less than with the big caps. Are there caps on the gator board I could change/add to that would help?

In My system the gator does sound much better than the passive mod, This may be largely due to better impedance matching.

On a friends very similar system but without the impedance issues the gator does sound very different to the passive mod. I personally prefer it. More etched, more detail etc but is quite a subtle difference and others may prefer the passive mod.

Any help much appreciated.

Brian

I'd like to clarify the above, I'm only interested in the line out. I don't use headphones at all.

Thanks again.

The bass on the Gator is relatively flat all the way down to 10Hz, with only a small decrease down to 4Hz on my spectrum analyser. If you are looking for a bass lift, then it will be a case of designing some sort of bass boost mod. I'll look into that.

Hi Stan, Thanks for the reply.

It isn't that I need a bass boost. Plugged into a pre-amp the sound is as close to perfect as I've ever heard. problem is the pre-amp isn't mine and has gone home.:scratch: With my passive attenuator I'm getting a bass roll off. It's quite low, I'd guess around 50-60Hz but that's where my speakers start to roll off so the resulting curve is pretty steep. The cause is my power amp's 5K input impedance. Together with the attenuator I think the Caiman is seeing around 1.2K. Yes I know that's really the problem but I can't afford to replace the power amp or buy a matching pre. Not right now anyway, maybe in the future.

If there is nothing that can be altered on the Gator to alter the roll-off then my best bet is to build a buffered version of my attenuator. That would take a bit of time and money so I was exploring the easier options first

The reasons I wondered if the gator could be tuned to this ridiculously low impedance was a post earlier by someone who bought a gator without caps to try the caps he used in his passive mod but he reported this left the sound rather thin, possibly because he used very small value caps where the 33uf oscons are on the gator? Also the 33uf caps in my gator are bipolar so I wondered if they were in the signal path and therefore reacting with the rest of my kit to cause the roll off, just as 33uf causes a similar roll off for me with the passive mod. Would replacing these with something nearer 100uf make any difference?

As you can probably tell I know just enough to be dangerous but not enough to really understand how the gator works.

Sorry if this is all twaddle but I feel as if I'm almost where I want to be. I know the caiman/gator/poweramp/speaker combination is capable of sounding truly excellent but the bass roll off bothers me, especially since I heard it going all the way down with the pre-amp in place.

So, re-cap the gator or build a buffered lightspeed?

P.S. the lightspeed is a sort of virtual pot made out of light dependent resistors in case you were wondering. Got the design from DIYAudio. Another user on here by the name of covenant mentioned having a problem with one before.

Covenant, if you see this you might be interested to know when I plugged my lightspeed into the caiman the other day I got some very bad distortion, like a guitar amp in overdrive. Turned out I had the caiman into the output and the power amp into the input. Switched them round and all in lovely now. Not suggesting you did anything this daft but thought I'd mention it anyway.

Brian

Hi Brian,
No its plugged in ok. I never did get to the bottom of this. ATM the LS is not used.

Since the TC-7520SEG case is about 2mm higher internally I have gone back to the THS4032 opamp for headphone listening. But I added an extra mod to the THS4032, which is an extra bit of HF filtering.
I also fitted a couple of WIMA caps since I prefer those when listening to my more detailed D7000 and HD800 headphones. The sound is a lot more 3D. Only really suitable for TOSLINK and Coax input feeds to the DAC though. The USB was less detailed.

http://www.beresford.me/images/TC-7400/g1.jpg

By the way, I got three sets of the WIMA caps left, so I can share them with three good quality headphone users who are skilled in modding.

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Originally Posted by bpcairns

Hi Stan, Thanks for the reply.

It isn't that I need a bass boost. Plugged into a pre-amp the sound is as close to perfect as I've ever heard. problem is the pre-amp isn't mine and has gone home.:scratch: With my passive attenuator I'm getting a bass roll off. It's quite low, I'd guess around 50-60Hz but that's where my speakers start to roll off so the resulting curve is pretty steep. The cause is my power amp's 5K input impedance. Together with the attenuator I think the Caiman is seeing around 1.2K. Yes I know that's really the problem but I can't afford to replace the power amp or buy a matching pre. Not right now anyway, maybe in the future.

If there is nothing that can be altered on the Gator to alter the roll-off then my best bet is to build a buffered version of my attenuator. That would take a bit of time and money so I was exploring the easier options first

The reasons I wondered if the gator could be tuned to this ridiculously low impedance was a post earlier by someone who bought a gator without caps to try the caps he used in his passive mod but he reported this left the sound rather thin, possibly because he used very small value caps where the 33uf oscons are on the gator? Also the 33uf caps in my gator are bipolar so I wondered if they were in the signal path and therefore reacting with the rest of my kit to cause the roll off, just as 33uf causes a similar roll off for me with the passive mod. Would replacing these with something nearer 100uf make any difference?

As you can probably tell I know just enough to be dangerous but not enough to really understand how the gator works.

Sorry if this is all twaddle but I feel as if I'm almost where I want to be. I know the caiman/gator/poweramp/speaker combination is capable of sounding truly excellent but the bass roll off bothers me, especially since I heard it going all the way down with the pre-amp in place.

So, re-cap the gator or build a buffered lightspeed?

P.S. the lightspeed is a sort of virtual pot made out of light dependent resistors in case you were wondering. Got the design from DIYAudio. Another user on here by the name of covenant mentioned having a problem with one before.

Covenant, if you see this you might be interested to know when I plugged my lightspeed into the caiman the other day I got some very bad distortion, like a guitar amp in overdrive. Turned out I had the caiman into the output and the power amp into the input. Switched them round and all in lovely now. Not suggesting you did anything this daft but thought I'd mention it anyway.

Brian

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Hi Brian,

From what you've said it's obvious to me that the main problem in your system is the 5K input impedance of your amp. This is extremely low and completely unsuitable for use with a passive attenuator of any kind. So modifying your DAC isn't the way forward although using the Gator will obviously help. Putting a buffer between source and Lightspeed may help, one between Lightspeed and amp would probably works better. However, by far the cheapest option would be to simply raise the input impedance of your amp, providing that's possible and something you could do. It's something that's worth looking into anyway. What's the make and model of your amp? :)