You're welcome.
The RS 'no-clean' solder it's pretty easy to clean with isopropyl alcohol.
The Oyade is normal and on the contrary requires more effort to clean PCBs.
Possibly or maybe the alloy or both.
fet op amps and C9 and C13
I wanted to better understand the effects of the new fet opamps and how they combined with C9 and C13. Because of the DC offset issue I am finding on the old boards, I can't do the combination of shorted C9 and normal C13 with the fet opamps because it gives me too much DC, but I could manage other combinations and compare them to LM318 boards with the same components.
At present, I have the fet boards built with OPA627. Although not a back to back comparison, I would have to say that the ADA4627 is a noticeable bit better than the OPA627, so there is no reason, at least for me, to pay more to get the old OPA627. I look forward to learning more about the OPA827 and, maybe others.
I would also say that the LM318 boards are still very good. When comparing the LM318 and OPA627 with both C9 and C13 in place, I definitely prefer the LM318. It's more present and more dynamic. I would even say it's slightly quieter. All of that was a surprise for me because I have preferred and used OPA627 in many projects.
Of course, what that means is that eliminating the caps is a big part of what is going on here. I expected that for C9, just because electrolytic caps shouldn't be in an audio signal path, IMHO. The surprise was how much C13 also changes the sound. I would say that for me, C13 has a bigger change on the fet amps than it had when I tried it on the LM318.
In my mind, that means we need to be careful with this mod. If part of getting the best out of the fet opamp is removing C13 and going DC coupled, the person doing it better be willing trade off the sound for the risk. I know I'm glad that I put in my speaker protection mod. Popping some chips doesn't scare me, but speakers get expensive fast.
Overall ranking by my opinion;
OPA627/shorted C9/shorted C13 - LM318/normal C9 and C13 - OPA627/normal C9/shorted C13 - OPA627/normal C9 and C13
With C9 and C13 shorted, the OPA627 has a lot of what I liked in the ADA4627 in the same configuration. Very clean, fairly dynamic (I think the 4627 was better), better separation of instruments/voices (Instruments don't blend together, but are there as individuals), and very low background noise. I would say that the LM318/normal combination was probably a bit more dynamic, but didn't have the same instrument separation.
With C9 normal and C13 shorted, the OPA627 was a step down but fairly close to the level of the LM318. The instrument separation was lost as was some of the dynamic response. I think the background noise was a bit higher than the LM318.
With C9 and C13 normal, the OPA627 was just disappointing. I even noticed that the very first time I listened to it. Almost no dynamics and there is a hazy feeling behind all music. Instrument separation is completely lost.
In sum, C9 is very important and was the biggest factor with the OPA627, in my opinion. C13 is also very important and represent a risk/choice for the person building with an fet opamp. But when C9 and C13 are shorted and the OPA627 is on it's own, there is a worthwhile improvement. Finally, the original LM318/C9/C13 design is safe and still really very good.
Jac
PS You may have noticed that others on this thread have commented that C9 didn't change much for them with an fet opamp. Systems and people vary, as do other component choices, which means both answers are valid. To me, it means that these are worthwhile experiments for each person who is going to try an fet opamp.
Jac
I wanted to better understand the effects of the new fet opamps and how they combined with C9 and C13. Because of the DC offset issue I am finding on the old boards, I can't do the combination of shorted C9 and normal C13 with the fet opamps because it gives me too much DC, but I could manage other combinations and compare them to LM318 boards with the same components.
At present, I have the fet boards built with OPA627. Although not a back to back comparison, I would have to say that the ADA4627 is a noticeable bit better than the OPA627, so there is no reason, at least for me, to pay more to get the old OPA627. I look forward to learning more about the OPA827 and, maybe others.
I would also say that the LM318 boards are still very good. When comparing the LM318 and OPA627 with both C9 and C13 in place, I definitely prefer the LM318. It's more present and more dynamic. I would even say it's slightly quieter. All of that was a surprise for me because I have preferred and used OPA627 in many projects.
Of course, what that means is that eliminating the caps is a big part of what is going on here. I expected that for C9, just because electrolytic caps shouldn't be in an audio signal path, IMHO. The surprise was how much C13 also changes the sound. I would say that for me, C13 has a bigger change on the fet amps than it had when I tried it on the LM318.
In my mind, that means we need to be careful with this mod. If part of getting the best out of the fet opamp is removing C13 and going DC coupled, the person doing it better be willing trade off the sound for the risk. I know I'm glad that I put in my speaker protection mod. Popping some chips doesn't scare me, but speakers get expensive fast.
Overall ranking by my opinion;
OPA627/shorted C9/shorted C13 - LM318/normal C9 and C13 - OPA627/normal C9/shorted C13 - OPA627/normal C9 and C13
With C9 and C13 shorted, the OPA627 has a lot of what I liked in the ADA4627 in the same configuration. Very clean, fairly dynamic (I think the 4627 was better), better separation of instruments/voices (Instruments don't blend together, but are there as individuals), and very low background noise. I would say that the LM318/normal combination was probably a bit more dynamic, but didn't have the same instrument separation.
With C9 normal and C13 shorted, the OPA627 was a step down but fairly close to the level of the LM318. The instrument separation was lost as was some of the dynamic response. I think the background noise was a bit higher than the LM318.
With C9 and C13 normal, the OPA627 was just disappointing. I even noticed that the very first time I listened to it. Almost no dynamics and there is a hazy feeling behind all music. Instrument separation is completely lost.
In sum, C9 is very important and was the biggest factor with the OPA627, in my opinion. C13 is also very important and represent a risk/choice for the person building with an fet opamp. But when C9 and C13 are shorted and the OPA627 is on it's own, there is a worthwhile improvement. Finally, the original LM318/C9/C13 design is safe and still really very good.
Jac
PS You may have noticed that others on this thread have commented that C9 didn't change much for them with an fet opamp. Systems and people vary, as do other component choices, which means both answers are valid. To me, it means that these are worthwhile experiments for each person who is going to try an fet opamp.
Jac
Pretty much the same I think.
We can get good sounding and very expensive boutique caps, but the best cap is still no cap.
Suggestion on speaker pairing
Not sure if this is right place. I ordered one kit (12th run) and I have been looking around for some suggestions in terms of speaker pairing. Overall the consensus of LM3886 pairing seems to be "high-sensitivity full range speakers".
I'm wondering if there are any specific performance characteristics of the My_Ref Fremen edition that favour a certain brand?
Thank you.
Not sure if this is right place. I ordered one kit (12th run) and I have been looking around for some suggestions in terms of speaker pairing. Overall the consensus of LM3886 pairing seems to be "high-sensitivity full range speakers".
I'm wondering if there are any specific performance characteristics of the My_Ref Fremen edition that favour a certain brand?
Thank you.
I would not say that any of the My_Ref amps are limited to only high sensitivity full range speakers. It wouldn't work well with a very low sensitivity speaker that required high power. After all, we are talking about approximately 45W per channel. In the end, the gain is high enough that you should be fine generating enough voltage to be loud enough for most speakers. The limitation comes from the current limits of the LM3886. I would say that any speaker that you like which has a sensitivity in the mid-80's dB/1W should be fine.
I don't have any experience with commercially available speakers since I have been diy for speakers for some time. I can say that I recently built the Linkwitz LXmini from the Madisound kit and powered it with 4 channels of FE and it works very well. The LXmini is not a particularly sensitive speaker, but it does require 4 amps due to it's DSP crossover and EQ.
Anyone else care to comment on speaker choices or sensitivity?
I seem to remember Tom building some FE amps for his friend and those powering some pretty big speakers. I don't recall if they were bi-amped or not.
Jac
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Not particularly, I've tuned the amp using Infinity Alpha and Monitor Audio Bronze 5 (2015 version) but builders seems to use a variety of different Brands and DIY speakers with great results.
From 86/87dB sensitivity and up you should be fine.
I've used the MyRef in TP and FE configurations with quite a few different speakers, and they all sounded better than commercial products. Full range: B&W 802 Matrix rev 3, Thor transmission line floorstanders, Eggleston Andra II where they almost run out of gas when cranking really demanding program material, and Fostex single-driver back-loaded horns. Now I primarily use them actively crossed @ 400hz for the midrange/treble of three-ways that dip down to about 5 ohms, and they never run out of power before my ears surrender. My buddy still loves them with his Andra's.
Some of these set-ups are pretty demanding loads, with impedance falling slightly below 4 ohms for limited portions of the range. The amps don't even really get warm, but I guess that's the point of 22V transformers and big heatsinks. Actually, the transformers and PS caps get warmer than the chip case!
Peace,
Tom E
Some of these set-ups are pretty demanding loads, with impedance falling slightly below 4 ohms for limited portions of the range. The amps don't even really get warm, but I guess that's the point of 22V transformers and big heatsinks. Actually, the transformers and PS caps get warmer than the chip case!
Peace,
Tom E
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Good to read that the FE can power some "serious" speakers.
I'm looking into the Q Acoustics 3050 and the Monitor Audio Bronze 2. Both are just below the 400 EUR price point.
But than I'm seeing all the interesting DIY speaker builds. Tempting!
Anyway, going off-topic. Thank you all for your input. That was actually my first post. This really is a great community!
I'm looking into the Q Acoustics 3050 and the Monitor Audio Bronze 2. Both are just below the 400 EUR price point.
But than I'm seeing all the interesting DIY speaker builds. Tempting!
Anyway, going off-topic. Thank you all for your input. That was actually my first post. This really is a great community!
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Welcome! It is a great community with people from beginners to experts and many willing to help. At 92 and 90 dB sensitivity, the two speakers you mentioned should have no trouble at all.
One other question, what do you plan for a pre-amp or just volume control? At 90 dB sensitivity or higher, you could just use a stereo potentiometer for volume control.
Jac
One other question, what do you plan for a pre-amp or just volume control? At 90 dB sensitivity or higher, you could just use a stereo potentiometer for volume control.
Jac
I'll start with a stero potentiometer, maybe later I'll add a pre-amp. Step-by-step
I'll start with a stero potentiometer, maybe later I'll add a pre-amp. Step-by-step
There is no need of an active preamp with this amp or any high-gain amp for the matter. You can achieve higher performance (i.e. transparency) with high quality attenuators and transformers.
Hello guys, after a few weeks seeing the nice projects performed in this forum I decided to start to build my first amp with the MyRef FE. I got the schematics (v1.7) from the drive and I'm trying to understand every circuit's component. In the Original MyRef there was a technical document explaining most of the building blocks, but I haven't been able to find in MyRef FE, and there are some differences from the original design. I think that going through hundred of pages of the post is far from optimized. So, is there any document like that?
Regards,
Regards,
AFAIK there isn't any specific document like that... but conceptually there are basically no differences. There are only a few improvements, mostly inspired by Mauro's "My Evolution" amplifier.
The main difference are:
1) the power supply for the first stage, which on the original MyRef was just a simple resistor+Zener while on the FE there is a CCS + a more elaborated shunt regulator (see the PSU block on the top-left of the FE schematic);
2) the internal limiter network (those Zeners between the first stage and the current pump), for better clipping control.
Another (obvious) difference WRT to the original MyRef (but not WRT some other implementation, such as the one by TP) is the full "dual-mono" configuration of the FE (the original MyRef was configured as a stereo amp on a single board, with some ancillary parts in common for both channels).
There are also some minor differences in the compensation networks.
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Hi, you can find the document in the original post by mauro penasa. Or here PROGETTO“MY_REF”
Also, I’ve been struggling to find what’s the goal of C10, can anybody tell what’s it goal?
Regards,
Nicolas.
Also, I’ve been struggling to find what’s the goal of C10, can anybody tell what’s it goal?
Regards,
Nicolas.
Hello guys, can you please explain what is the goal of C10?
It’s part of the compensation scheme.