If your source/pre have working output coupling caps you should be OK but a quick measure will not harm..
Yes, to DC couple you simply need to replace C13 with a jumper.
I suggest using small fastons tabs if you're planning to experiment, the K71 wil not survive to soldering /desoldering cycles...
PGND, unless you have problems should be left disconnected.
Trasnformer shield and chassis should be connected to safety earth.
I think it is interesting that many builders who listen carefully are reporting various impressions of the FE. Some say the TC is too sharp on highs, others, too dull. Some of this is personal taste or system variance. I think there is a more basic problem and these are all manifestations of it.
The cause of lack of high frequencies in the FE is the Riken resistor at R10. It obscures a lot of high frequency detail. I was shocked by the amount of information revealed when I replaced it. I believe this resistor was selected as a band-aid solution to the excessive edginess of the upper mids and highs caused by the alternate compensation. I have been experimenting with these components and their values, and I have determined in my system that the alternate compensation causes harsh upper frequencies. I know Dario disputes that claim, but my controlled listening experiments are conclusive for me. I have heard it right from the first time I played the FE, and I continue to hear it to the point that I don't enjoy listening to my stereo. Yes, it is accurate, but it sounds mechanical, electronic, like any other decent SS amp, nothing like the charming, live, open character of the MyRef Rev C. With the Riken at R10, it sounded more musical but muffled and flat. Sorry if that seems harsh, but something is wrong.
The TC capacitor at C13 is the best sounding capacitor I have heard for that price, and I have tried a lot of caps at C13, including various Mundorf's. I have not heard it, but perhaps the Rike S-Cap is also worth a try. The TC sounded superb in the Rev C, and it should sound just as good or better in the FE. It's not perfect, but its faults are much less than its attractions. If it does not sound good, perhaps there are other problems in the amplifier or system. The sound of a coupling cap does not change from one amp to another. The Riken resistor at R10 blocks 10 to 20% of the clarity and resolution of which the MyRef is capable. It also restricts the soundstage. It is not the TC at C13 that is causing problems.
By the way, using DC coupling to evaluate the sound of C13 caps in this amp is completely wrong. We have been told by Mauro that C13 contributes more to the operation of the circuit than merely blocking DC, that it somehow biases the LM318 and performs other duties. So removing it from the circuit changes the sound of the amplifier in more ways than simply removing a coupling cap normally would. Hence, DC coupling is NOT an accurate representation of the sound of this amp (this has been demonstrated by several builders), and a cap that sounds like it would not make for a good sounding amplifier. The only way to compare the sound of C13 caps is to live music or another known reference, NOT to DC coupling of this amp.
If you want to put tone control components into your amplifier, seek a capacitor with exaggerated high frequencies to try to replace what the R10 Riken obscures. If you really want high frequency clarity and resolution with expansive and deep soundstage, try a Caddock MK132 at R10. Unfortunately, this uncolored component will reveal the sad state of the alternate compensation. Solve that problem first, and all else should fall into place. Or you can keep putting on band-aids to fix the bad parts.
I will continue experimenting with comp values and report the results as I hear them. I can already say with significant confidence that 27pF is too high a value for C34. I have installed 22pF on one channel, and it is far more musical, with less edge than the other. The amp appears to be perfectly stable, but then I'm not sure how instability manifests itself. Can anyone inform me? I do not have analytical tools at my disposal other than a pair of ears and a decent LCR meter.
Peace,
Tom E
The cause of lack of high frequencies in the FE is the Riken resistor at R10. It obscures a lot of high frequency detail. I was shocked by the amount of information revealed when I replaced it. I believe this resistor was selected as a band-aid solution to the excessive edginess of the upper mids and highs caused by the alternate compensation. I have been experimenting with these components and their values, and I have determined in my system that the alternate compensation causes harsh upper frequencies. I know Dario disputes that claim, but my controlled listening experiments are conclusive for me. I have heard it right from the first time I played the FE, and I continue to hear it to the point that I don't enjoy listening to my stereo. Yes, it is accurate, but it sounds mechanical, electronic, like any other decent SS amp, nothing like the charming, live, open character of the MyRef Rev C. With the Riken at R10, it sounded more musical but muffled and flat. Sorry if that seems harsh, but something is wrong.
The TC capacitor at C13 is the best sounding capacitor I have heard for that price, and I have tried a lot of caps at C13, including various Mundorf's. I have not heard it, but perhaps the Rike S-Cap is also worth a try. The TC sounded superb in the Rev C, and it should sound just as good or better in the FE. It's not perfect, but its faults are much less than its attractions. If it does not sound good, perhaps there are other problems in the amplifier or system. The sound of a coupling cap does not change from one amp to another. The Riken resistor at R10 blocks 10 to 20% of the clarity and resolution of which the MyRef is capable. It also restricts the soundstage. It is not the TC at C13 that is causing problems.
By the way, using DC coupling to evaluate the sound of C13 caps in this amp is completely wrong. We have been told by Mauro that C13 contributes more to the operation of the circuit than merely blocking DC, that it somehow biases the LM318 and performs other duties. So removing it from the circuit changes the sound of the amplifier in more ways than simply removing a coupling cap normally would. Hence, DC coupling is NOT an accurate representation of the sound of this amp (this has been demonstrated by several builders), and a cap that sounds like it would not make for a good sounding amplifier. The only way to compare the sound of C13 caps is to live music or another known reference, NOT to DC coupling of this amp.
If you want to put tone control components into your amplifier, seek a capacitor with exaggerated high frequencies to try to replace what the R10 Riken obscures. If you really want high frequency clarity and resolution with expansive and deep soundstage, try a Caddock MK132 at R10. Unfortunately, this uncolored component will reveal the sad state of the alternate compensation. Solve that problem first, and all else should fall into place. Or you can keep putting on band-aids to fix the bad parts.
I will continue experimenting with comp values and report the results as I hear them. I can already say with significant confidence that 27pF is too high a value for C34. I have installed 22pF on one channel, and it is far more musical, with less edge than the other. The amp appears to be perfectly stable, but then I'm not sure how instability manifests itself. Can anyone inform me? I do not have analytical tools at my disposal other than a pair of ears and a decent LCR meter.
Peace,
Tom E
A few years ago I had an amplifier which was powered by 2 x 400 VA transformers and few 100.000 µF reservoir capacity. Every second or third power on activated the automatic circuit breaker.
Therefore I have used for this build two power inlets / switches to lower the in-rush current.
The potted transformers are 160 VA types from hifituning24.de (Schuro.de). They have a shop at ebay if you are intersted to buy some of them. diy-audio4you auf eBay
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Yes, Bob, I am always very careful to qualify my evaluations in a personal manner. I fully accept other's impressions are likely to be different. However, I see a pattern developing here. You yourself mentioned a few weeks ago that you experienced some listening fatigue. I had the same experience over the last few days, probably because I replaced those Riken mufflers with decent resistors.
I am building a pair of amps for my friend to be used with his Eggleston's, and that should be pretty definitive in terms of loudspeakers. I consider my speakers to be nearly their equal in terms of high frequency accuracy, but the Eggleston's are better at overall fidelity. I think my system is comparable but not quite equal. That's the biggest reason I am being so critical of the FE amps. They sound very good, but I know they can sound better. I have made some pretty big claims for them, which is why my friend is trusting me with up to a thousand dollars to build him the best amps I can. So far, with Rikens, I do not hear a thousand dollars worth of amplifier. With Caddocks, I am closer, but the sharp edge of highs and mids breaks the deal, and that aspect is certainly not listener or system dependent. It sounds bad, period. That is what I am trying to improve.
Peace,
Tom E
I am building a pair of amps for my friend to be used with his Eggleston's, and that should be pretty definitive in terms of loudspeakers. I consider my speakers to be nearly their equal in terms of high frequency accuracy, but the Eggleston's are better at overall fidelity. I think my system is comparable but not quite equal. That's the biggest reason I am being so critical of the FE amps. They sound very good, but I know they can sound better. I have made some pretty big claims for them, which is why my friend is trusting me with up to a thousand dollars to build him the best amps I can. So far, with Rikens, I do not hear a thousand dollars worth of amplifier. With Caddocks, I am closer, but the sharp edge of highs and mids breaks the deal, and that aspect is certainly not listener or system dependent. It sounds bad, period. That is what I am trying to improve.
Peace,
Tom E
IMHO the FE doesn't lack any HF content...BTW you're wrong about the reason I choose the Riken as the audiohpile choice...
I've thought about it and verified with other parts, and also compared the TCs with lots of other caps (I really wanted to confirm the TCs, as I told I consider them the most neutral , timbre-wise) .
Sadly the TCs were the only ones with that weird details hardness.
This is your opinion... Mauro told the amp is designed to work with a coupling cap (and I agree and discourage the use of DC coupling apart evaluating C13 alternates) but this impact performance numbers not timbre or details.
Sorry Tom, but this is non-sense... too many components and devices (and the recording choices...) are involved to even think you can compare the system with live performance.
The only known reference for a cap is no cap
There's nothing unfortunate, as I told when I suggested you to try them, I think they're the most neutral part you can use in that position...
Probably my ears work only with certain components...
No Tom, I wasn't poking at either your findings or system. As you may know I have been doing a lot with the discrete Pass style amps. I'm personally convinced there is no such thing as the best amp. They all have a signature and to me, trying to get one to sound like the other, or both design approaches to match is close to impossible. That opinion may change in time after some tweaking.
I really do appreciate your suggestion to try to compare all systems to live performances. I guess keeping that impression in mind while returning home and making adjustments is the trick - and needs to be done more than once. However, there are some mental gymnastics needed to compensate for room acoustics and reflections.
Like you, I don't have the lab or background for complete understanding and hopefully others will dig in at your suggestion. One thing I am curious about is why/how you determined the compensation is the band aided element. How did you narrow in on that?
Also, I know I sound like a broken record, but I'm hoping more members will dig into that Visual Analyzer program/thread. Still think it's promising for those of us without scopes.
EDIT: After reading Dario's comment I'll add a flavor on live music comparrisons. Hope it's not too far OT. A friend who passed away recently was the director of the local symphony. One of his favorite interview comments was " If one violin is playing the audience members hear a certain db. If 20 are playing the listener hears the same." Whether or not that's totally accurate, it convinced me I was looking for much higher volumes at home than were present in the concert hall. I now approach the entire topic differently ..and that's just one element.
I really do appreciate your suggestion to try to compare all systems to live performances. I guess keeping that impression in mind while returning home and making adjustments is the trick - and needs to be done more than once. However, there are some mental gymnastics needed to compensate for room acoustics and reflections.
Like you, I don't have the lab or background for complete understanding and hopefully others will dig in at your suggestion. One thing I am curious about is why/how you determined the compensation is the band aided element. How did you narrow in on that?
Also, I know I sound like a broken record, but I'm hoping more members will dig into that Visual Analyzer program/thread. Still think it's promising for those of us without scopes.
EDIT: After reading Dario's comment I'll add a flavor on live music comparrisons. Hope it's not too far OT. A friend who passed away recently was the director of the local symphony. One of his favorite interview comments was " If one violin is playing the audience members hear a certain db. If 20 are playing the listener hears the same." Whether or not that's totally accurate, it convinced me I was looking for much higher volumes at home than were present in the concert hall. I now approach the entire topic differently ..and that's just one element.
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It works with a wide variety of sound devices. I using the small (removable) section of the Mackie Satellite The forum pages give more information on that
Tom,
If you are having a problem with too much high frequency, then the Rike S-Cap is probably not your solution. I find it quite revealing, especially in the high frequencies, so it would likely bring any harshness you are hearing forward.
I certainly don't have all the answers, but I prefer to think about it like Tony Gee (humblehomemadehifi). He considers tuning an audio system as being like cooking. Each element adds its flavor and when blended properly, the result is a unique blend. First of all, that means each person's system is unique. Second, if the mk132 is giving you detail that you like, but shows too much harshness, then blend in some warmer components. In the end, it's all good.
Slightly off topic.
When working at the FE level, using C13 and C9, I found capacitors that opened up detail and soundstage, but only at the cost of mid-range or bass. This is a little like Ivan is experiencing. At the moment, I am playing with the passive crossover components of my satellites. By combining a Rike and an Obbligato in my tweeter filter, I have been able to open up the clarity and detail on the top without affecting the mid and bass. This was my original reason for trying a few Rike caps. As you say Tom, every component counts, but so does the way you mix them together.
Jac
Funny thing perception, very individual. I still cant get over how good the FE's with premium industrial BOM sound in my system, it makes me reluctant to mess about with them too much. Mind you I do prefer them when driven by the DCB1. I have had a load of commercial amps up to £1200.00 in the past, the FE's trash all of them. If I upgrade anything it will probably just be some Mundorfs at C13 and maybe some quieter transformers. Wish list stuff
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Promise I'll stop after this, but here is another confusing twist. I have combined the new Subbu DAC with the BrianGT monoblocks (W/Uriha's Resistor Replacer) and the improvement is staggering. As I PMed Dario a few days ago, that combination comes as close to the FE as anything I have. I never would have believed it, but the BGTs honestly sounds like a completely different amp. It's not just the onboard components that matter, what is fed makes an enormous impact.
So I'm fully in the camp that says "add vegetables and flavor to taste"
Attachments
I do not want to insult anyone or their taste, so please do not insult mine. We all make our choices and decisions based on the way we hear our own equipment in our own space. I use my memory of live acoustic instruments to attempt to tune my system toward what real instruments sound like. I know I will never achieve that goal, but I will continue to try to get closer to it. I listened to three new SACD's over the past few days, and all are superb remasterings of well known music. They all sound somewhat mechanical, slightly "hard" through the FE's, as does all of my other music. I know it is not the source material. I am well aware of the variances lurking there.
I am putting my efforts into the compensation network because those are the only components that have changed value between the Rev C amps and the FE's I now have playing. Everything else in these amps is the same value, and many are the same exact parts, actually removed from the Rev C and installed into the FE. If anything, the extra PS regulation and SMT technology should make the FE's sound better. In one important respect, they do not. I am on the verge of putting the Rev C's back together and putting them back into service. However, I have promised to build a pair of FE monoblocks for a friend with very nice speakers, and already spent a good deal of his money to obtain boards and a lot of parts. So I would rather find out what is making that one aspect of the FE's sound not as good as the Rev C. Do not misunderstand: I agree with all of you that the FE is a very fine amplifier as it stands. Perhaps it could be better. I think changing the compensation from Mauro's carefully selected values is an attempt to fix something that wasn't broken. I do not have a personal stake in whatever the values turn out to be. I am only trying to achieve the best performance with whatever combination of components of whatever value is optimal.
My opinion is not swayed by whatever parts are blessed by audiophiles. I use whatever is necessary to achieve good sound. If you are interested in my ability to do so, you might want to revisit some of the older MyRef threads to see the contributions I have made in the past. My opinion is not infallible, but I have a pretty good record of selecting components and mixing them effectively to make the MyRef sound better. With the FE amp, I am not sure why a part such as the Riken resistor that obscures some of the signal sounds "better" than parts that do not. That indicates to me that the amp is producing sound that needs to be flavored to sound good. I would prefer to fix whatever is wrong than try to cover it up. I'll liken using the Riken to covering everything with a layer of maple syrup that obscures natural flavors. I love maple syrup on pancakes and oatmeal, but I wouldn't think of putting it on lasagna or a steak.
I am very grateful for the level of discussion here, but there is no need to argue over this. I don't mean to be disruptive or dismissive. I'll carry on and report my findings. I hope that everyone can keep an open mind about the results. You learn only what you want to learn. I have built at least ten of these MyRef's in various configurations at several cost levels, and experimented with dozens of different parts. Not all trials have been successful, and admitting that is difficult but essential to improvement.
Peace,
Tom E
I am putting my efforts into the compensation network because those are the only components that have changed value between the Rev C amps and the FE's I now have playing. Everything else in these amps is the same value, and many are the same exact parts, actually removed from the Rev C and installed into the FE. If anything, the extra PS regulation and SMT technology should make the FE's sound better. In one important respect, they do not. I am on the verge of putting the Rev C's back together and putting them back into service. However, I have promised to build a pair of FE monoblocks for a friend with very nice speakers, and already spent a good deal of his money to obtain boards and a lot of parts. So I would rather find out what is making that one aspect of the FE's sound not as good as the Rev C. Do not misunderstand: I agree with all of you that the FE is a very fine amplifier as it stands. Perhaps it could be better. I think changing the compensation from Mauro's carefully selected values is an attempt to fix something that wasn't broken. I do not have a personal stake in whatever the values turn out to be. I am only trying to achieve the best performance with whatever combination of components of whatever value is optimal.
My opinion is not swayed by whatever parts are blessed by audiophiles. I use whatever is necessary to achieve good sound. If you are interested in my ability to do so, you might want to revisit some of the older MyRef threads to see the contributions I have made in the past. My opinion is not infallible, but I have a pretty good record of selecting components and mixing them effectively to make the MyRef sound better. With the FE amp, I am not sure why a part such as the Riken resistor that obscures some of the signal sounds "better" than parts that do not. That indicates to me that the amp is producing sound that needs to be flavored to sound good. I would prefer to fix whatever is wrong than try to cover it up. I'll liken using the Riken to covering everything with a layer of maple syrup that obscures natural flavors. I love maple syrup on pancakes and oatmeal, but I wouldn't think of putting it on lasagna or a steak.
I am very grateful for the level of discussion here, but there is no need to argue over this. I don't mean to be disruptive or dismissive. I'll carry on and report my findings. I hope that everyone can keep an open mind about the results. You learn only what you want to learn. I have built at least ten of these MyRef's in various configurations at several cost levels, and experimented with dozens of different parts. Not all trials have been successful, and admitting that is difficult but essential to improvement.
Peace,
Tom E