babadono Posted October 7, 2020 Share Posted October 7, 2020 That's the original part, there a dime a dozen. Still not opposed to sending you a couple if you wish. Still won't be stock as Mark changed the gain structure and other things as well. Quote Link to comment Share on other sites More sharing options...
babadono Posted October 7, 2020 Share Posted October 7, 2020 Qual est hashy? Quote Link to comment Share on other sites More sharing options...
Marvel Posted October 8, 2020 Author Share Posted October 8, 2020 4 hours ago, babadono said: That's the original part, there a dime a dozen. Ah, never mind. But that's weird... I thought he put in a quad that would up the slew rate a bit without making it unstable. What all did you do with your D-75? 1 Quote Link to comment Share on other sites More sharing options...
Panelhead Posted October 8, 2020 Share Posted October 8, 2020 I doubt the use of MC33079 is a weak link. I have a dac that uses them on all balanced outputs. Replaced with every higher specced quad opamp I could get. None made an improvement. Some degraded the sound. Tried bipolar and FET input types. Ended up going back with the MC33079. They are old and cheap. Crown and others used this part for a reason. There were lots of options. Changing out the opamps may not do anything for rise times. The output stage may be the bottleneck. Quote Link to comment Share on other sites More sharing options...
babadono Posted October 8, 2020 Share Posted October 8, 2020 1 hour ago, Panelhead said: Tried bipolar and FET input types Did you try an LME49740? Mark changed the amp to a Fet input type because he increased the input impedance of the diff to single ended input to work better with tube preamps. He upped the input impedance to 47k from the 10k standard. I agree that the limiting factor primarily on the slew rate(speed) of these amps is the output devices. I was able to get mine up to about 10v/us by careful changing of compensation throughout the amp. Quote Link to comment Share on other sites More sharing options...
babadono Posted October 8, 2020 Share Posted October 8, 2020 4 hours ago, Marvel said: What all did you do with your D-75? I've got a list in my work computer, let me try to dig it up. I needed to write it down cuz i did 4 of 'em this thread has a lot of info: Quote Link to comment Share on other sites More sharing options...
Panelhead Posted October 8, 2020 Share Posted October 8, 2020 1 hour ago, babadono said: Did you try an LME49740? Mark changed the amp to a Fet input type because he increased the input impedance of the diff to single ended input to work better with tube preamps. He upped the input impedance to 47k from the 10k standard. I agree that the limiting factor primarily on the slew rate(speed) of these amps is the output devices. I was able to get mine up to about 10v/us be careful changing of compensation throughout the amp. This was the first one tried. Hoped to hear angels singing. To my ears the dac sounded the same. The dac uses surface mount chips. Swapping these in and out was challenging. Quote Link to comment Share on other sites More sharing options...
babadono Posted October 8, 2020 Share Posted October 8, 2020 4 minutes ago, Panelhead said: This was the first one tried. Hoped to hear angels singing. To my ears the dac sounded the same. The dac uses surface mount chips. Swapping these in and out was challenging. Did the P.S. rails support it? I had to modify the P.S. in the Crown D75s to use the singles and duals from that family of amps. Quote Link to comment Share on other sites More sharing options...
babadono Posted October 8, 2020 Share Posted October 8, 2020 Here's my list: Crown D75 Modifications.doc Quote Link to comment Share on other sites More sharing options...
babadono Posted October 8, 2020 Share Posted October 8, 2020 These are first gen. D75s not the D45/D75as.You'll need this schematic to follow along: D75_J0116-4_original.pdf Quote Link to comment Share on other sites More sharing options...
Marvel Posted October 8, 2020 Author Share Posted October 8, 2020 I've thought of getting the Parasound Z-amp.. For $350, would be pretty nice. https://parasound.com/zamp-v3.php 1 Quote Link to comment Share on other sites More sharing options...
ben. Posted October 8, 2020 Share Posted October 8, 2020 22 hours ago, babadono said: Qual est hashy? Lack of clarity in the mids & highs. Audible distortion. 1 Quote Link to comment Share on other sites More sharing options...
Marvel Posted October 9, 2020 Author Share Posted October 9, 2020 So... Mark used a TL085 in the Duke. They're cheap enough, too. It can't be those Black Gates that made all the difverence. Whatever be did, it sounds really nice. Thinking hard about selling the Moondogs. Maybe if I cleaned them up I would be more inclined to keep them They sound great, too. The lacquer on the brass chassis plates is getting a little old and shabby looking. 🙄 1 Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted October 9, 2020 Share Posted October 9, 2020 2 hours ago, Marvel said: So... Mark used a TL085 in the Duke. They're cheap enough, too. It can't be those Black Gates that made all the difverence. Whatever be did, it sounds really nice. Thinking hard about selling the Moondogs. Maybe if I cleaned them up I would be more inclined to keep them They sound great, too. The lacquer on the brass chassis plates is getting a little old and shabby looking. 🙄 PM sent Quote Link to comment Share on other sites More sharing options...
babadono Posted October 9, 2020 Share Posted October 9, 2020 3 hours ago, Marvel said: It can't be those Black Gates that made all the difverence. DJK commented in the thread I linked to yesterday that the quality of the input coupling caps had more to do with the sound of the amp than the input opamp. I personally don't know if I could hear the difference in coupling caps unless maybe I had 2 identical in every other way amps with different input coupling caps that i could switch between very quickly to compare. No way I could trust my hearing memory to take the time to switch the caps. Quote Link to comment Share on other sites More sharing options...
The Dude Posted October 12, 2020 Share Posted October 12, 2020 If anyone is looking for op amp sockets, and Black Gate caps, let me know as I may have some. Just need to know what cap specs to verify. I thought I bought them for this project, but don't recall. Sent from my SM-G986U using Tapatalk Quote Link to comment Share on other sites More sharing options...
The Dude Posted October 15, 2020 Share Posted October 15, 2020 I've thought of getting the Parasound Z-amp.. For $350, would be pretty nice. https://parasound.com/zamp-v3.phpI've actually switched to Parasound HCA amps from Crown D45s. I wanted a little extra umph. I am using that exact amp you linked on my zone 2 outside with Klipsch KSB 1.1Sent from my SM-G986U using Tapatalk Quote Link to comment Share on other sites More sharing options...
OO1 Posted October 31, 2020 Share Posted October 31, 2020 On 10/8/2020 at 12:44 AM, babadono said: I've got a list in my work computer, let me try to dig it up. I needed to write it down cuz i did 4 of 'em this thread has a lot of info: cool thread ------tx Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.