The Opamp thread

[ROBSCIX]

Quote:

Originally Posted by diditmyself /img/forum/go_quote.gif I stopped class A biasing of opamps after I did some blind tests. All testing was with constant current sources. I couldn't hear any improvement. In fact I heard no difference at all. Before that I experimented with restistors, and at that time I thought I could hear the difference, and it was to the better. Now I think that it might have been placebo. Those tests were with the opamps in front of diamond buffers, a very light load, 100's of kOhm. I've tried 15 mA class A biasing of AD8397, driving high impedance phones, and I could hear no difference in blind tests. Maybe I didn't give it enough time. Flipping back and forth with a switch isn't the same as long time listening. All my discrete amps are class A. I think I'm sure that they sound less fatiguing in the long run at higher bias.

I have to run tests for myself and gauge the results. Some suggest this mod as a good option and others not so much so I need to check for myself.
The testing never ends around here...

 

[crapback]

Ok, I went for the bypass cap switch with some k40y9's. I've only done the earth in the dac so far cause with the pio's on there they take up a lot more space. I'll have to figure out how to fit them in the case. I'm not sure if the bass has actually improved or not but I'm going to keep them on there just for the fact that the hdams now look like tiny versions of shark diving cages.

I really need more free time if I'm going to get a chance to legitimately compare the hdams with and without bypass caps and with the different bypass caps. I guess I'll throw some more k40y9's on the amp hdams and see how she sounds.

 

[ROBSCIX]

Quote:

Originally Posted by crapback /img/forum/go_quote.gif Ok, I went for the bypass cap switch with some k40y9's. I've only done the earth in the dac so far cause with the pio's on there they take up a lot more space. I'll have to figure out how to fit them in the case. I'm not sure if the bass has actually improved or not but I'm going to keep them on there just for the fact that the hdams now look like tiny versions of shark diving cages. I really need more free time if I'm going to get a chance to legitimately compare the hdams with and without bypass caps and with the different bypass caps. I guess I'll throw some more k40y9's on the amp hdams and see how she sounds.

Great stuff.
Post you listening impression when you get a chance to have a listen.

 

[crapback]

I now have k40y9's on all 3 earth's. I really wish I had ordered some clear heatshrink that would've fit over the k40's. I shouldn't admit to liking the look of any capacitors but I think the k40's look sweet. Maybe it's just placebo effect but I swear I can hear a difference already. This is going to take a while and I think I'm going to enjoy every minute of it.

I included some more pictures of the modules crammed into the zero case. There's also a pic with the k40y9 and one of the stock evox caps so you can really see the difference in size. I also threw in a picture so you can see the el cheapo stepper I put in there with a solder job only a plumber could be proud of.

DACT Type 21 Stepped Attenuator Potentiometer 100K 2A3 - eBay (item 120471954152 end time Sep-27-09 14:56:18 PDT)

 

[murrays]

Quote:

Originally Posted by crapback /img/forum/go_quote.gif I now have k40y9's on all 3 earth's. I really wish I had ordered some clear heatshrink that would've fit over the k40's. I shouldn't admit to liking the look of any capacitors but I think the k40's look sweet. Maybe it's just placebo effect but I swear I can hear a difference already. This is going to take a while and I think I'm going to enjoy every minute of it. I included some more pictures of the modules crammed into the zero case. There's also a pic with the k40y9 and one of the stock evox caps so you can really see the difference in size.

Are you picking up noise from that transformer? You may hear a buzz or humm when no music is playing? I say that because I am in the middle of shielding & re-positioning components to cure such noise in my amp - and my components are further away from the transformer. I see you have one capacitor resting right against it. I am finding that just moving some of the larger capacitors around is helping to eliminate most of it. You may be lucky with a better quality transformer (or just lucky...).

With bypassing caps you want to keep the leads as short as possible. Long leads (and large size) can impede the HF characteristics.

 

[crapback]

I guess I'm just lucky then. There is a very slightly audible hiss when I turn the volume to maximum with no music playing but no buzzing or humming. That's what I was worried about when I first put the hdams in my zero. I bring it with me during the week in my truck at work so I need to be able to keep it closed up. That doesn't leave me any better options for now until I find a better job that'll let me actually live in an apartment again.

As for short leads, I can't really make them much shorter and still solder them onto the hdams. I could trim off about 7-8mm off each, but I don't really think that would make any real audible difference. There really is no lack of high frequency extension of detail with my zero now. 22 k40y9 bypass caps in total and a cheap stepper have made huge improvements in my little monster. That and add about 2 pounds to the weight of the thing.

When it becomes a stationary zero I'll work on repositioning the hdams for a cleaner install. For now, I can live with any noise generated by the proximity of the components cause I can't hear it having any effect on my music at the volumes I listen at.

I also wanted to add that it might be the rather heavy metal casing of the k40's that is providing some decent shielding in my situation. Or I guess it could just be luck.

 

[leeperry]

damn, it's a major pain to reuse browndogs...I've had one of the browdog tracks dying on me, so I had to desolder the 2*LT1363 to put them back on another one...even w/ desoldering braid it was a major PITA to take them off in one piece

I really don't see how you can reuse these things..

and going LT1364>2*LT1363 improves the stereo separation pretty drastically! but I still feel that these cheapo browndogs are poorly shielded to EMI...so DIP8 is definitely better if the chip does the +/- polarities of the same channel...but a dual chip for stereo is indeed worthless.

 

[ROBSCIX]

Why would you reuse them? Your going to ruin the adapter and the opamp.
Just buy new ones.

 

[ROBSCIX]

Quote:

Originally Posted by crapback /img/forum/go_quote.gif I guess I'm just lucky then. There is a very slightly audible hiss when I turn the volume to maximum with no music playing but no buzzing or humming. That's what I was worried about when I first put the hdams in my zero. I bring it with me during the week in my truck at work so I need to be able to keep it closed up. That doesn't leave me any better options for now until I find a better job that'll let me actually live in an apartment again. As for short leads, I can't really make them much shorter and still solder them onto the hdams. I could trim off about 7-8mm off each, but I don't really think that would make any real audible difference. There really is no lack of high frequency extension of detail with my zero now. 22 k40y9 bypass caps in total and a cheap stepper have made huge improvements in my little monster. That and add about 2 pounds to the weight of the thing. When it becomes a stationary zero I'll work on repositioning the hdams for a cleaner install. For now, I can live with any noise generated by the proximity of the components cause I can't hear it having any effect on my music at the volumes I listen at. I also wanted to add that it might be the rather heavy metal casing of the k40's that is providing some decent shielding in my situation. Or I guess it could just be luck.

You could always add some sheilding, if you find it is a issue.

 

[crapback]

I don't think I need to shield anything just yet, there isn't enough noise to affect my enjoyment of the music. Now I'm intrigued by the audio changes,(if in fact they are real), of the new bypass caps on my hdams. I'm back to playing with my compass again to check things out. Looks like I'm back to rolling opamps again, even if they are discreet.

If head-fi itself is an addiction, what drug would opamp rolling be?

 

[ROBSCIX]

Quote:

Originally Posted by crapback /img/forum/go_quote.gif I don't think I need to shield anything just yet, there isn't enough noise to affect my enjoyment of the music. Now I'm intrigued by the audio changes,(if in fact they are real), of the new bypass caps on my hdams. I'm back to playing with my compass again to check things out. Looks like I'm back to rolling opamps again, even if they are discreet. If head-fi itself is an addiction, what drug would opamp rolling be?

It was just a suggestions if the noise bothered you. So your hearing differences?
They are positive or you haven't had time to compare yet?

 

[crapback]

I didn't mean to come off snotty in any way. I forget sometimes how I need to add more smilies to convey my tone of voice.

I would have put the emphasis on the "just yet" to say that I haven't screwed the pooch so far.

I swear I hear better detail with my compass now both in the high and low range. There was a lot of the resonance of cymbals missing before that I'm noticing now. Bass guitars also sound better like the tone of Geddy Lee's Rickenbacker. Or I might just be looking for more detail now that I've changed something in my setup. I don't know for sure. I don't really feel like swapping bypass caps over and over to compare them properly. I like how they sound and if the k40y9's give me a placebo effect I'll take it.

I should have more than enough hours on both the compass and the earth in it to pass any burn-in standards for audio-gd gear so that shouldn't be part of it. I'm still keeping an open mind on the whole electronics burn-in issue.

 

[ROBSCIX]

Oh no, I didn't think you were being "snotty". Post your results when you have more time to compare.

 

[murrays]

Quote:

Originally Posted by leeperry /img/forum/go_quote.gif ... but I still feel that these cheapo browndogs are poorly shielded to EMI.

I was thinking of ordering some of these - can you explain what is the problem with them? I wasn't aware they had any shielding.

 

[diditmyself]

Quote:

Originally Posted by murrays /img/forum/go_quote.gif I was thinking of ordering some of these - can you explain what is the problem with them? I wasn't aware they had any shielding.

I've never seen an adapter with shield. Opamps don't have ground pins. I guess you could connect a shield to one of the rails. Is this how it's done in the metal can opamps?

I've just ordered some of those cheap SOIC to DIP adapters from Hong Kong. The traces are much shorter and look sturdier than Browndogs.

If usual care is taken with decoupling caps as close to the power pins as possible, short feedback path, an input resistor and maybe an input filtering cap, I think you'll be fine. The use of an output resistor and/or a zobel network make the amp more stable driving capacitive loads. The use of a compensation cap when needed, or choosing "the right" value for feedback resistors also increase stability.