olds1959special Posted May 13 Share Posted May 13 I recently got some Sparkos SS3602 op-amps from Sparkos Labs. Andrew was very helpful and they sound great. I have also tried the MUSE02 and these are better. I am using them in a Fosi BT20A Pro amp. I have thought of trying a couple of Fosi ZA3 mono amps with my Vandersteen 2ci's (rolled with Sparkos op-amps, of course.) I don't think there is a reason these digital amps would not perform as well or better than class a or class a/b. For now I'm not going to go that route, but this amp sounds amazing with my bookshelf speakers with sub. Link to comment Share on other sites More sharing options...
Holmz Posted May 13 Share Posted May 13 6 hours ago, olds1959special said: I recently got some Sparkos SS3602 op-amps from Sparkos Labs. Andrew was very helpful and they sound great. I have also tried the MUSE02 and these are better. I am using them in a Fosi BT20A Pro amp. I have thought of trying a couple of Fosi ZA3 mono amps with my Vandersteen 2ci's (rolled with Sparkos op-amps, of course.) I don't think there is a reason these digital amps would not perform as well or better than class a or class a/b. For now I'm not going to go that route, but this amp sounds amazing with my bookshelf speakers with sub. Yeah just give it a try… I used an AIYAMA $80 class-D, which I have on the surround speakers. It was remarkably good, and one can keep the cables short with monoblocks. For the same $ I would probably suggest running them and a powered sub (2W?), over some schmicko amp. Which begs the question of how hard is it to overamp say a Treo-CT? With “Over amping” being in terms of cost rather than wattage… Link to comment Share on other sites More sharing options...
GdnrBob Posted May 13 Share Posted May 13 Can anyone explain to me what OP amps are and why they used in stereo systems?- Like, do they do something better than conventional amps? Bob Link to comment Share on other sites More sharing options...
olds1959special Posted May 13 Author Share Posted May 13 (edited) 3 hours ago, GdnrBob said: Can anyone explain to me what OP amps are and why they used in stereo systems?- Like, do they do something better than conventional amps? Bob Op amps are chips that amplify sound. They are found in lots of audio gear, DAC's, pre-amps, headphone amps, etc. Some manufacturers allow us to change out the op-amps to get a different sound. The digital amp (Fosi) I was referring to allows op-amp rolling (changing op-amps). Edited May 13 by olds1959special Link to comment Share on other sites More sharing options...
Holmz Posted May 14 Share Posted May 14 4 hours ago, GdnrBob said: Can anyone explain to me what OP amps are and why they used in stereo systems?- Like, do they do something better than conventional amps? Bob “operation amp” == OP AMP. They are usually high gain, and like all designs trying to approach infinite gain, they use feedback. As they are on the same piece of substrate the temperature is consistent, so in some ways it is better than separate discrete components. It may not be correct, but I always associate Bob Widar with OP-Amps. https://en.wikipedia.org/wiki/Bob_Widlar 1 Link to comment Share on other sites More sharing options...
GdnrBob Posted May 14 Share Posted May 14 Thanks guys, I tried to Google it, but it was a bit beyond my grasp. It still is, unfortunately. I really need a simplified description, if possible. I am reading the linked article, too. B Link to comment Share on other sites More sharing options...
olds1959special Posted May 15 Author Share Posted May 15 I found this cool picture of Bob Widlar! 2 Link to comment Share on other sites More sharing options...
TomicTime Posted May 15 Share Posted May 15 Operational Amplifier as in complete gain on an integrated circuit typically in a DIP dual inline pin configuration… Just add a power supply… 1 Link to comment Share on other sites More sharing options...
Holmz Posted May 15 Share Posted May 15 (edited) 1 hour ago, olds1959special said: I found this cool picture of Bob Widlar! Even better… (And in a magazine advert) Edited May 15 by Holmz 2 1 Link to comment Share on other sites More sharing options...
olds1959special Posted May 18 Author Share Posted May 18 I couldn't contain my curiosity so I got 2 Fosi ZA3 amps and replaced the right channel op amp with Sparkos SS3602 for using them in dual mono. First I tried the XLR connection from my DAC, but this didn't sound that good, so I pulled out my Schiit Saga S pre-amp and hooked that up using the RCA inputs. The Saga sounds better without the active circuitry enabled in this case. The two Fosi amps are turned all the way up, and I'm controlling volume with the pre-amp. The sound is noticeably better than before when I was using the Hafler DH120 mono amps, which sounded a bit dark and not as open sounding. I think these amps are worth trying, and Fosi just came out with a newer model, the V3 mono (although it's not on Amazon yet) which looks good and has no volume control. Link to comment Share on other sites More sharing options...
olds1959special Posted May 18 Author Share Posted May 18 (edited) Sorry, I meant to say I'm trying the Fosi ZA3 mono amps with my Vandersteen 2Ci's. I do like the sound now but I'll see how my ears adjust after a few days! Edited May 18 by olds1959special Link to comment Share on other sites More sharing options...
GdnrBob Posted May 18 Share Posted May 18 My limited EE knowledge, and some Google reading seems to indicate that OP amps use feedback in their circuitry, does this affect the sound? I ask as I know that Vandy speakers seem to work best when not using feedback (negative). Sorry if this is newbie stuff... Bob Link to comment Share on other sites More sharing options...
stratocaster Posted May 18 Share Posted May 18 1 hour ago, GdnrBob said: Sorry if this is newbie stuff... Bob Bob, Rest assured, you sound more experienced in this matter based on your questions 😄 All this opamp experimentation sounds like another cash burning rabbit hole that needs to be avoided.. I am going to grab a bowl of popcorn and follow this thread… 1 Link to comment Share on other sites More sharing options...
Richard Vandersteen Posted May 18 Share Posted May 18 OP amps use lots of feedback, this is why they are rarely used in Hi End products in the audio signal path. We use lots of them in our electronics for the analog protection circuits and general housekeeping but never if it even touches the signal path. RV 1 1 Link to comment Share on other sites More sharing options...
olds1959special Posted May 19 Author Share Posted May 19 (edited) Here's a pic of the setup. I'm currently enjoying some jazz, the Wild Bill Davison "Solo Flight" record on Quboz, played through my iPad. Before starting listening and I went ahead and pulled out all the unused op amps except the Sparkos in the right channel. Supposedly this improves things, (why, I don't know?) although I can't say I heard a big difference, if any. But it does function this way. The DAC is the SMSL DO100 Pro using the linear phase fast roll-off filter, going to the Schiit pre-amp, and I'm currently finding the active mode on the pre works better. I have the tweeter level boosted by 1db on the speakers. My overall impression compared to how it was before with the Hafler amps is that I'm getting more raw detail, and a spacious airy sound with lots of treble extension. It is possible there is less heft to the bass, but it worth it for the overall coherency of the sound. I read these amps are load-dependent which might cause a rise in high frequencies with some speakers. Edited May 19 by olds1959special Link to comment Share on other sites More sharing options...
olds1959special Posted May 19 Author Share Posted May 19 My other dac, the SMSL SU-1 sounds good with this setup too, and is based on an AKM chip instead of the SABRE, which to me sounds less hollow. The bass may be a bit better this way. Link to comment Share on other sites More sharing options...
olds1959special Posted May 20 Author Share Posted May 20 (edited) I am now using the Fosi ZA3's (with the single Sparkos op-amp installed) for the midrange/treble drivers only. I'm using the Hafler DH120's for the bass. I had to reduce the volume of the Fosi amps to match the levels. I've pretty much maxed out my desk space for amps now. I am enjoying the feeling of added power to the sound. Everything feels bigger now. With TV, the dialogue sounds super clear. I thought that the treble was a bit excessive for music though? I tried playing with reducing the tweeter contour control, but didn't find this helped TV sound, so I set it back to flat. I'm looking forward to doing some more testing with music. Edited May 20 by olds1959special Link to comment Share on other sites More sharing options...
olds1959special Posted May 20 Author Share Posted May 20 (edited) I think I just had the midrange/treble turned up too much. It's sounding pretty good now after spending some time making adjustments to levels. I'm wondering if having the Hafler only plugged into one side means only half the power is being delivered? Even in mono mode? Edited May 20 by olds1959special Link to comment Share on other sites More sharing options...
olds1959special Posted May 20 Author Share Posted May 20 (edited) On 5/18/2024 at 4:28 PM, Richard Vandersteen said: OP amps use lots of feedback, this is why they are rarely used in Hi End products in the audio signal path. We use lots of them in our electronics for the analog protection circuits and general housekeeping but never if it even touches the signal path. RV Can someone explain why feedback is bad? Edited May 20 by olds1959special Link to comment Share on other sites More sharing options...
GdnrBob Posted May 20 Share Posted May 20 I believe it will accentuate timing inaccuracies, but I think Mr. V. will provide the best explanation. B Link to comment Share on other sites More sharing options...
Holmz Posted May 20 Share Posted May 20 6 hours ago, olds1959special said: Can someone explain why feedback is bad? I am not sure it is, but I recall my PSE Studio I and II made a big deal about using minimal amount of feedback. And Dean is also involved with the new amps, some 40 years later. Your Sparko OP-Amps, and most of the other OP-Amps, have a finite gain, so they only can provide feedback control to some given frequency. If one does not have enough gain bandwidth product, then as the frequency gets higher the circuit is playing catch-up. If it was some super higher frequency, like radio, then you would just use a choke to get rid of the harmonics from a non linear amp. Or one would use a feed-forward control to predistort the signal to account for (aka equalise) the distortion from the amp/speaker/whateva. Speaker drivers are also not completely linear, so there is an opportunity for IMD and HD from them. So the feed-forward seems like it should become more common. ^This^ should tide you over, until a grown up answer arrives. Link to comment Share on other sites More sharing options...
Richard Vandersteen Posted May 21 Share Posted May 21 7 hours ago, olds1959special said: Can someone explain why feedback is bad? Feedback makes its corrections after the fact! We all may like that choice in life so when we make a mistake just fix it and act nobody noticed. Over simplified to the max but that is what it is. Its only bad if you don't like its nonlinear effects. RV Link to comment Share on other sites More sharing options...
TomicTime Posted May 21 Share Posted May 21 Take a simplistic view of music = sine wave, a a = input signal >>>>> amplifier makes A bigger but adds D where D is the sum of fractions of Asquared, etc… this is THD on top of A. = A+THD Thd is total harmonic distortion. Negative feedback takes a % of the A+THD, flips it out of phase ( this is the negative part ) and then puts it back into the input So now you have a minue ( some % of A+THD flipped out of phase.note both gain and THD as measured go down. However… music = input does not equal sine waves…or if it does, you belong in a lab… Throw agbdf at this…. and vary amplitude…. so the negative feedback a note gets mixed w g… and so on… Its worse for transients Link to comment Share on other sites More sharing options...
Holmz Posted May 21 Share Posted May 21 @olds1959special https://circuitdigest.com/electronic-circuits/positive-and-negative-feedback-in-op-amp-circuits You’ll ^See^ those circuits literally have the input connected to the output. That signal travels at the speed of light, with some inductance and capacitance to limit the gain-bandwidth product. For feedback to work over the entire operating range, you’ll need a high gain-bandwidth product. https://en.wikipedia.org/wiki/Gain–bandwidth_product The fact is that the gain-bandwidth product is often somewhat lacking, and then we get into the place where the signal is crashing its tail and never catching up. If the feedback is worst (higher distortion) than the NON-linearity of circuit then you are better off without feedback. And if the amp is really non-linear, then you are better off with using feedback. Usually I liken ^all this^ to worrying about whether the fleas and ticks on a Rottweiler that is running towards me, are carrying some disease. Unless the speakers are pretty low in distortion, then worrying about the distortion of the amps and preamps is a bit “of polishing the turd” work. But Everyone likes nice amps, and they do make a bit of a difference. For a fixed amount of $, I still rate better speakers, HPFs and subs, as more of a primary focus for attention. Then later amps, preamps, and cables. (But some speakers just are difficult to drive, and sort of define which amps will be needed.) I could never figure out what gave me a grainy sound on my original setup… I sort of changed the preamp and the cartridge at the same time… and it could even have been the LPs. It was not super distressing, but once one heard it, then it is was back to “the fleas and ticks”. And that was a low feedback amp/preamp. At some point the theory falls away and there is music or not. Either the Haflers or Sparkos sound fine enough, or not. Since you are already running subs, you are further down the road than some. If they sound fine, then I would not be concerning myself with whether they have feedback… and then whether it is a lot of feedback, or just a little bit. If you are replacing them though, then it makes sense to be concerned. Link to comment Share on other sites More sharing options...
olds1959special Posted May 22 Author Share Posted May 22 14 hours ago, Holmz said: At some point the theory falls away and there is music or not. Either the Haflers or Sparkos sound fine enough, or not. Since you are already running subs, you are further down the road than some. If they sound fine, then I would not be concerning myself with whether they have feedback… and then whether it is a lot of feedback, or just a little bit. If you are replacing them though, then it makes sense to be concerned. This is how I feel: if it sounds good, it's working for me. I have been pretty impressed with overall sound the last few days, but I believe this is mostly because of the combined power of the four amps, class D or whatever. So I decided to order two more of the Fosi amps. That way, I don't have to match volume levels, I can just turn them all up all the way. Plus, I'll be adding even more power. (btw, I'm not running a sub with my Vandersteens, just with my ELAC bookshelf desktop near field setup.) 1 Link to comment Share on other sites More sharing options...
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