I agree that op amps can take on great character-- possibly surpassing tubes-- when powered by an optimal power source. The AD744 is a particularly good one (also used in the Merlin BBAM). Unfortunately in most commercial gear op amps are powered on the cheap.
Possibly the best pre-amp one can have
Category: Preamps
Title: May be the best pre-amp ever
“Your Parasound amp is fixed,” said Charlie in his usual calm voice.
“Oh great, what was the problem?” I asked
“Nothing,” He said.
“Nothing?” I asked
“It was just its heat sink that had come off, so I attached it back and it stopped heating up. It won’t shut off by itself now,” Charlie replied.
“I see, thank you,” I said, looking at him with a praising smile. Even though I am technically handy, I had not been able to figure out why my amp was shutting itself off.
This was not the first time Charlie had come to my and my audio friends’ rescue. He worked in a nearby audio store in the Dallas Fort-Worth area. He had been a full-time electrical engineer at Motorola and worked part-time at the store which sold hi-fi audio and home theatre equipment. He had a full-scale workshop at the back of the store and was often busy with repair orders from all kinds of customers. Charlie had a reputation of being extremely skillful and was known to always fix your faulty audio components. He knew all the parts, where to get them from, and what price and how to find compatibles if the original was not available. He did not talk much and appeared to be a man of few words. With all white hair but manly looks, he reminds me of Bob Knight, the basketball coach, but in total contrast when it comes to personality -- Charlie is extremely soft spoken and polite. He also does not brag. We did have few chats on audio. He had been to my home for listening to my system along with another friend (in fact twice, once with the Divas, and once with the Centaur-Fullrange, which is still my main system). During these visits, I noticed he had good ears and he was a smart audiophile. But again, he spoke only when he needed to. He was totally impressed with the sound of my system though and he expressed it objectively with right observations. I knew he was a serious listener. This is what I knew of Charlie.
“Ok, Charlie, I gotta go now, thanks for a nice job, I will first go to the front to pay the service charges, see ya,’ I said.
“Did you see this pre-amp?” Charlie said pointing to a simple looking black case.
“No,” I said.
“This belongs to Chris, our main salesperson, I made it and now I am replacing an LED in it. It sounds good” Charlie said.
“I see, good, see ya” I replied and waved at Charlie to say goodbye.
About a month later, I had to go to the store to get something from Chris. Chris is the guy who also made the wooden panels for my Centaur-Diva and Centaur-Fullrange. And as you have seen from the pictures, what a nice job he has done. He is also an audiophile and has passion for it. Chris was going to come to my home to install a mount for a projector that I bought from the store,”
“So I will see you on Saturday, Chris,” I said.
“Yes, see you then. By the way, I want to listen to your system again and I have free time on Saturday.”
“Sure, we will have a listening session after you install the mount,” I said.
“ok,” Chris said.
“Hey, what is that?” I pointed to a black box.
“Oh, it is a pre-amp that Charlie made for me. It’s been here since Charlie placed an LED in it.” Chris replied.
“Oh yeah, I remember last time I was here, Charlie mentioned,” I remembered.
“Ok, Chris, see you. And bring that pre-amp with you, will ya?” I said.
“okay, bye,” Chris chirped.
Chris came on Saturday and installed the mount. After that we had some coffee and then sat down for listening. The system was Centaur-Fullrange, driven by 4 Tube Research Labs GT-400 monoblocks, Lamm L2 Reference pre-amp, and Meridian 808 Reference CD player.
Chris was totally lost in sound, song after song, shaking his head in disbelief.
“If our customers listen to this, we will be out of business as no one will like the equipment that we have,” Chris said, “It is just amazing, and I have no words to explain how good it is”
“Thank you,” I replied.
We continued to listen for about 2 hours and I totally forgot that he had also brought his pre-amp.
“If you do not mind, can we try my pre-amp?” Chris asked.
“Oh, yes, sure,” I said apologetically.
Chris had been nice and I wanted to be nice too, otherwise I had no interest in listening to his home-made toy. But being an audiophile, I have always been open minded and curious. And in fact, I was the one who asked him to bring the pre-amp.
We disconnected the Lamm and inserted Charlie’s pre-amp. We listened to it for about 15 minute, during which time my mind was somewhere else. We changed some CDs and played a couple of my favorite tracks. I was paying attention now.
“Hey, this sounds good,” I could not help stop my surprise.
“Hahahaha, yeah, I am thinking the same,” Chris said.
My curiosity increased. We switched back and forth between Charlie’s pre-amp and the Lamm, and every time I found myself moving in my chair restlessly, scratching my head and looking at Chris.
The Lamm was easily the best pre-amp that I had listened to. I had recently installed new tubes (purchased from Lamm Inc.) and it sounded even better than when I had bought it a few month ago. The Lamm L2 was an upgrade over the Audio Valve Ecklipse, which was an upgrade over the Conrad Johnson 17LS (which disappointed me), which was an upgrade over the Conrad Johnson PF-2 (one of my favorites), which was an upgrade over a Counterpoint, Parasound, and so on and so forth. The Lamm L2 gave a huge improvement over the Audio Valve. It gave the impression that all of my CDs had come back from a dry cleaning shop after a complete cleaning. The vocals were so touching that I had tears in my eyes at times. Apart from vocals, the Lamm also excelled in other aspects. I had no complaint. The only reservation one could come up with was its bass, which I found to be a very marginally lighter. I had a detailed talk with ‘Richard’, a forum member, who also owned the Lamm L2. According to Richard, the Lamm bass was true and authentic, in contrast to other pre-amps that inflated bass artificially. I had to concur with this. Later, I read its review in Stereophile (which I normally do not) and it said the same thing. Overall, I loved the Lamm L2; no wonder that many people consider it to be state-of-the-art. Despite its hefty price tag, I was going to keep it and was not looking for any upgrade.
So a home-made amateur toy giving the Lamm L2 a good run for money? Gimmie a break, I thought to myself. It is just that we are reaching the listening fatigue now or something else.
May be it is just psychological that Charlie’s pre-amp was appearing to be better, I told myself.
“Ok, Chris, can you leave it with me for a few days please?” I asked.
“Sure, I am setting up my home theatre now, so do not need it for now,” Chris said.
“Nay,” I thought to myself. Charlie’s pre-amp could not be better, I told myself.
For the next two weeks I was making very serious comparisons between the two pre-amps. Every time, my conclusion was Charle’s pre-amp sounded better. Better how? Well, the first observation was improved transparency, then the dynamics. Finally, the bass, which is what had been something that could be discussed and debated about the Lamm, depending upon who you talk to and of course your own taste and expectations. With Charlie’ pre-amp, the bass was more weighty but not too much. The tonal balance of Charlie’s pre-amp was just perfect.
Every time I made a comparison, my ears decided I preferred Charlie’s pre-amp but my mind did not accept it. It was like a boxing match in which the referee was hesitating to give the nod to the challenger who was knocking down the favorite champion. I was thinking may be the comparison was unfair to the Lamm. So I decided to try out all the permutations of cables, tubes, interconnects, power chords. The harder I tried to give the edge to the Lamm, more clear winner became the little Charlie. Two weeks later, I thought it was time to return the pre-amp. So I cleaned up my audio rack of all the extra cables and placed the Lamm in its original and permanent position. After listening to the Lamm for 2 days, I was depressed. Now both my ears and my mind were shouting “we need Charlie back”
I called Chris and asked him if I could keep the pre-amp a little longer. He said I could keep it as long as I wanted, until he wad done with his home theatre setup.
During the next month, I invited several friends and made comparisons. Most people could identify the difference easily, not that the Lamm was doing anything wrong. In fact, the sound was still outstanding with the Lamm. But the little Charlie would remove every bit of veil from the sound, and add more dynamics and details. It was as if it was removing everything between you and the sound. The Lamm was doing one thing better though. The vocals were sweeter with the Lamm. Clearly, it was the FET color of the Lamm, which was doing the trick. Vocals are extremely important to me, perhaps more than anything else in music. Yet, the little Charlie was not doing anything wrong with the vocals. It was not as sweet but it was more clear, meaning it was revealing what was on recorded. Besides, it was doing everything else better than the Lamm, and hence was winner.
I called up Sal, a buddy of mine who owns the Divas and drives them with Sim Moon Audio gear, including their top of the line pre-amp.
“Hmmm, I trust your opinion,” Sal said after I told him the whole story.
“But, I do not believe in these homemade gimmicks, as they have no quality control,” he remarked.
“Well, let’s compare it with yours,” was my answer.
On the following Sunday I went to his house, taking Charlie’s pre-amp with me. It weighed about 15 pounds or so, with a detachable power chord, so wasn’t a problem to carry. We warmed up his system and listened for about 30 minutes.
“Now, you will hear the magic,” I said with a cheeky smile.
“Well, I am not sure about the magic,” Sal laughed.
We replaced the Sim Moon with Charlie pre-amp and turned on the system and started the same CD. I did not say any word. Nor did Sal. We were both silent, dead silent. After 10 minutes, Sal stood up and said “Yeah, it is better”.
“What the hell is inside it? Tubes” He asked.
“I know it has no tubes but to be honest I have no idea what is inside it,” I said.
We listened more and now it was my turn to laugh as there was no contest in soundstaging, imaging, bass, dynamics, details, and transparency. The Sim Moon sounded dull. Charlie sounded live.
“Yes, but it is marginally better, which is not a big deal, Sal said.
“Marginally better? Everything in high end is marginally better, depending upon how you define your margin,” I said.
“Look, can you see the image of the singer in this recording”, I asked.
“Yes, it is right there,” Sal said.
“Ok, now let’s put the Sim Moon Audio back,” I said.
We changed the pre-amps and played the same track.
“Now, where is the singer,” I asked.
“I cannot tell now, hahahahah,” Sal said with a sheepish smile.
A couple of weeks later, I called another buddy, the owner of B&W 800 Diamonds, driven by Lamm M1.1 and BAT VK 51, top of the line from BAT. He brought to my house his BAT, a heavy duty pre-amp with more than a dozen tubes and weighing 60-70 pounds. We warmed up the BAT and listened, then compared. I never said any word. In making such comparisons, it is my principle to let the listener decide for themselves. I do not chip in with my own instructions for them or to tell them what I want them to believe. So I said nothing.
After 15 minutes, my buddy said: “There is no contest, what a surprise”
“Can Charlie make one for me,” he asked.
“He should. I will ask him,” I said.
I had been with this pre-amp for more than two months now. I called Charlie up and told him I wanted to buy him a lunch. We ate at an “authentic” Tex-Max restaurant.
“Why you never told me about this pre-amp, Charlie,” I asked.
“Well, I did but you did not pay any attention,” Charlie said.
“Oh yes, I remember, but you could have told me more” I said embarrassingly.
“I did not know it would meet your expectations as you have some of the most astonishing gear,” Charlie said.
“What is inside it?” I asked.
Charlie is a man of few words but now it seems that Charlie did not know how to stop -- all I could do was to listen. The pre-amp was a solid state pre-amp using video op-amp. Charlie had been reading the research papers published by Walt Jung, a well respected name in audio who has written tens of professional and amateur audio papers as well as books. Charlie himself has been with Motorola for some 35 years. A veteran of Vietnam, with a B.Sc. degree in Electrical Engineering, and a genuine audiophile, Charlie has listened to and experimented with countless amps and speakers, not to mention his repairing skills. Charlie has been in audio for more than 40 years.
What caught Charlie’s attention was Walt’ Jung’s paper on using video op-amps for designing pre-amps. For 2-3 years, Charlie tried various topologies based on Jung’s publications, with additional modifications.
The heart of a pre-amp is the power supply. No matter how good a topology is, it won’t sound good without a good regulated power supply. Often op-amps are used incorrectly. No wonder op-amp have bad reputation among audiophiles. Charlie first built this pre-amp for Craig (owner of Legacy Whispers). Craig needed a pre-amp that could drive the signal with long runs of interconnects. Since this is a high-current pre-amp, it can drive very long interconnects (single-ended). According to Charlie, even 100 feet is no problem. According to Craig, his jaw dropped after he first listened to the new pre-amp, as his objective was just to find something that could solve his problem of long interconnects. He did not expect a huge improvement.
“The pre-amp has the most regulated power supply that one can possibly design,” Charlie said.
“Can it be improved if money is no objection,” I asked a naïve question.
“Nope, this is the best that can be done, and it is already an overkill,” Charlie answered.
The pre-amp has the flattest frequency response with no distortion (because of the wide bandwidth of the video op-amp). Furthermore, it does not change gain at any frequency.
“The input signal is virtually untouched and is amplified in its purest form” Charlie added.
“It is like a passive pre-amp but on steroids, isn’t it? “I remarked.
“Yeah, you can say that,” Charlie said.
“Ok, Charlie, make me one please, but I want a dual mono with best components, separate volume control for each channel and better case, better LEDs,” I said.
“Should we go for a balanced design,” I asked.
“No, the noise is already the minimum possible and you can run as long an interconnect as you wish without any loss in signal. By making it balanced you will only increase the circuit complexity three times and the cost,” Charlie said.
During the next two weeks, we met a few more times, and discussed all the details. I simply wanted the best that could be done. Charlie was going to add ladder resistors for volume control which keep the impedance constant without touching the signal. The power supply was also going to be separate for each channel. We also looked at some cases from a catalog and chose a simple but elegant one. I paid $1000 to Charlie to order components. Charlie was going to charge another $900 or so for the labor. The whole pre-amp was going to be hand-made by Charlie himself, so the cost was justified.
A few days later, I received some disturbing news. The store was going to be closed and Charlie was going to be laid off. The store was not making profit in retail audio and video. The owner had decided to build media rooms instead, with consulting service and supply of audio-visual equipment as needed. Charlie told me not to worry. He promised he could work at home. He had recently retired from Motorola. But they had offered him a temporary contract. The store was soon shut down. I was feeling sad for Charlie, so I did no push him. I sold the Lamm L2 though. Chris had been nice enough not ask his pre-amp back, which is what I was listening to now.
After 2 months I called Charlie. Charlie was never home. His wife said he was working 70 hours a week. After several tries, I got hold of Charlie and asked for my pre-amp. Charlie said he had all the parts now and he was working on it but had very little spare time. He had to work even on weekend as he had no permanent job and wanted to benefit from the contract as much as he could. I understood his position.
The next 8-9 months passed by during which time I found myself gradually getting upset as I did not get my pre-amp. But it was a difficult situation because Charlie’s contract was being renewed on a monthly basis. Charlie promised he would finish it soon. I had to wait for a total of 14-15 months all in all. Meanwhile, I called Chris and asked if I could buy his pre-amp. Chris agreed. I paid him what his cost was. At least I had the original one now.
Finally, Charlie called me one day and said he was done. The first thing on my mind after I brought the new pre-amp home was to compare it with the original one. They sounded the same except that the newer one quieter and even more smooth sounding – it also looked better.
“Turn on the volume all the way up without playing any music, and see if you hear any hiss” Charlie said.
“None, the pre-amp is dead quiet” I said.
“Does it need any breakin?” I asked.
“No,” Charlie said.
The end of the story. The next match of Charlie pre-amp (now I call it X-2) is with the CAT Ultimate mark II and I have no doubt it will win. But I have no interest in any pre-amp upgrade, not even auditioing.
The X-2 features a very direct signal path, a precision high current drive output stage, and a very high quality power supply. Specifically it uses and AD811 current feedback video op-amp and an AD744 FET input op-amp output stage to drive the 811. All components are of the highest quality, such as metal film resistors, polypropylene film and high frequency low ESR electrolytic caps. Charlie made extensive efforts in the power supply to provide as complete isolation from AC power line noise as is possible and to keep the regulated supply impedances extremely low.
The power transformers used are dual bobbin types with a “Hi-Pot” rating of 4000V ensuring minimal transfer of AC line high frequency noise. In addition, common mode chokes are used before the transformer primary and after the soft recovery rectifiers as well. The high frequency electrolytic filter capacitors smooth the rectified voltage of the raw dc supply that then feeds the sophisticated regulators, which have extremely low impedance even at high frequencies. The result is effortless dynamics as well as extremely well-defined imaging and detail.
Several configurations can be utilized as far as power supply complexity, volume control configuration, number of inputs, and output stage drive circuitry. The ultimate configuration is dual mono with separate dual-secondary power transformers for each channel, with four separate bridge rectifiers and filter capacitors providing DC to two pairs of +/- regulators (one pair of regulators per channel). As I mentioned above, this is a true dual mono configuration with the grounds from each channel run separately back to their respective DC supply filter capacitor center points. The only common connection between the two channels is at the common ground at the center point of the two DC supplies.
The result of the quality of the power supplies and the care taken with the grounding is high dynamic range, high channel separation with no crosstalk, and extremely low noise.
The standard line driver circuitry is capable of driving low impedance and capacitive loads to high levels at high frequencies with no slew limiting. Overall, the gain can be adjusted to your requirements during construction.
To me, all other pre-amps seem to have some color. The X2 pre-amp is crystal clear, like water, which is what a pre-amp should be.
Last Friday was the last day for Charlie at Motorola. He might have time for building more pre-amps.
Please contact Charlie directly:
calex1044@sbcglobal.net
Anyone who is interested is free to communicate with him. Consider me out of the loop please.
The picture of the pre-amp can be seen at my system:
http://forum.audiogon.com/cgi-bin/fr.pl?vaslt&1066703453&read&3&4&
Title: May be the best pre-amp ever
“Your Parasound amp is fixed,” said Charlie in his usual calm voice.
“Oh great, what was the problem?” I asked
“Nothing,” He said.
“Nothing?” I asked
“It was just its heat sink that had come off, so I attached it back and it stopped heating up. It won’t shut off by itself now,” Charlie replied.
“I see, thank you,” I said, looking at him with a praising smile. Even though I am technically handy, I had not been able to figure out why my amp was shutting itself off.
This was not the first time Charlie had come to my and my audio friends’ rescue. He worked in a nearby audio store in the Dallas Fort-Worth area. He had been a full-time electrical engineer at Motorola and worked part-time at the store which sold hi-fi audio and home theatre equipment. He had a full-scale workshop at the back of the store and was often busy with repair orders from all kinds of customers. Charlie had a reputation of being extremely skillful and was known to always fix your faulty audio components. He knew all the parts, where to get them from, and what price and how to find compatibles if the original was not available. He did not talk much and appeared to be a man of few words. With all white hair but manly looks, he reminds me of Bob Knight, the basketball coach, but in total contrast when it comes to personality -- Charlie is extremely soft spoken and polite. He also does not brag. We did have few chats on audio. He had been to my home for listening to my system along with another friend (in fact twice, once with the Divas, and once with the Centaur-Fullrange, which is still my main system). During these visits, I noticed he had good ears and he was a smart audiophile. But again, he spoke only when he needed to. He was totally impressed with the sound of my system though and he expressed it objectively with right observations. I knew he was a serious listener. This is what I knew of Charlie.
“Ok, Charlie, I gotta go now, thanks for a nice job, I will first go to the front to pay the service charges, see ya,’ I said.
“Did you see this pre-amp?” Charlie said pointing to a simple looking black case.
“No,” I said.
“This belongs to Chris, our main salesperson, I made it and now I am replacing an LED in it. It sounds good” Charlie said.
“I see, good, see ya” I replied and waved at Charlie to say goodbye.
About a month later, I had to go to the store to get something from Chris. Chris is the guy who also made the wooden panels for my Centaur-Diva and Centaur-Fullrange. And as you have seen from the pictures, what a nice job he has done. He is also an audiophile and has passion for it. Chris was going to come to my home to install a mount for a projector that I bought from the store,”
“So I will see you on Saturday, Chris,” I said.
“Yes, see you then. By the way, I want to listen to your system again and I have free time on Saturday.”
“Sure, we will have a listening session after you install the mount,” I said.
“ok,” Chris said.
“Hey, what is that?” I pointed to a black box.
“Oh, it is a pre-amp that Charlie made for me. It’s been here since Charlie placed an LED in it.” Chris replied.
“Oh yeah, I remember last time I was here, Charlie mentioned,” I remembered.
“Ok, Chris, see you. And bring that pre-amp with you, will ya?” I said.
“okay, bye,” Chris chirped.
Chris came on Saturday and installed the mount. After that we had some coffee and then sat down for listening. The system was Centaur-Fullrange, driven by 4 Tube Research Labs GT-400 monoblocks, Lamm L2 Reference pre-amp, and Meridian 808 Reference CD player.
Chris was totally lost in sound, song after song, shaking his head in disbelief.
“If our customers listen to this, we will be out of business as no one will like the equipment that we have,” Chris said, “It is just amazing, and I have no words to explain how good it is”
“Thank you,” I replied.
We continued to listen for about 2 hours and I totally forgot that he had also brought his pre-amp.
“If you do not mind, can we try my pre-amp?” Chris asked.
“Oh, yes, sure,” I said apologetically.
Chris had been nice and I wanted to be nice too, otherwise I had no interest in listening to his home-made toy. But being an audiophile, I have always been open minded and curious. And in fact, I was the one who asked him to bring the pre-amp.
We disconnected the Lamm and inserted Charlie’s pre-amp. We listened to it for about 15 minute, during which time my mind was somewhere else. We changed some CDs and played a couple of my favorite tracks. I was paying attention now.
“Hey, this sounds good,” I could not help stop my surprise.
“Hahahaha, yeah, I am thinking the same,” Chris said.
My curiosity increased. We switched back and forth between Charlie’s pre-amp and the Lamm, and every time I found myself moving in my chair restlessly, scratching my head and looking at Chris.
The Lamm was easily the best pre-amp that I had listened to. I had recently installed new tubes (purchased from Lamm Inc.) and it sounded even better than when I had bought it a few month ago. The Lamm L2 was an upgrade over the Audio Valve Ecklipse, which was an upgrade over the Conrad Johnson 17LS (which disappointed me), which was an upgrade over the Conrad Johnson PF-2 (one of my favorites), which was an upgrade over a Counterpoint, Parasound, and so on and so forth. The Lamm L2 gave a huge improvement over the Audio Valve. It gave the impression that all of my CDs had come back from a dry cleaning shop after a complete cleaning. The vocals were so touching that I had tears in my eyes at times. Apart from vocals, the Lamm also excelled in other aspects. I had no complaint. The only reservation one could come up with was its bass, which I found to be a very marginally lighter. I had a detailed talk with ‘Richard’, a forum member, who also owned the Lamm L2. According to Richard, the Lamm bass was true and authentic, in contrast to other pre-amps that inflated bass artificially. I had to concur with this. Later, I read its review in Stereophile (which I normally do not) and it said the same thing. Overall, I loved the Lamm L2; no wonder that many people consider it to be state-of-the-art. Despite its hefty price tag, I was going to keep it and was not looking for any upgrade.
So a home-made amateur toy giving the Lamm L2 a good run for money? Gimmie a break, I thought to myself. It is just that we are reaching the listening fatigue now or something else.
May be it is just psychological that Charlie’s pre-amp was appearing to be better, I told myself.
“Ok, Chris, can you leave it with me for a few days please?” I asked.
“Sure, I am setting up my home theatre now, so do not need it for now,” Chris said.
“Nay,” I thought to myself. Charlie’s pre-amp could not be better, I told myself.
For the next two weeks I was making very serious comparisons between the two pre-amps. Every time, my conclusion was Charle’s pre-amp sounded better. Better how? Well, the first observation was improved transparency, then the dynamics. Finally, the bass, which is what had been something that could be discussed and debated about the Lamm, depending upon who you talk to and of course your own taste and expectations. With Charlie’ pre-amp, the bass was more weighty but not too much. The tonal balance of Charlie’s pre-amp was just perfect.
Every time I made a comparison, my ears decided I preferred Charlie’s pre-amp but my mind did not accept it. It was like a boxing match in which the referee was hesitating to give the nod to the challenger who was knocking down the favorite champion. I was thinking may be the comparison was unfair to the Lamm. So I decided to try out all the permutations of cables, tubes, interconnects, power chords. The harder I tried to give the edge to the Lamm, more clear winner became the little Charlie. Two weeks later, I thought it was time to return the pre-amp. So I cleaned up my audio rack of all the extra cables and placed the Lamm in its original and permanent position. After listening to the Lamm for 2 days, I was depressed. Now both my ears and my mind were shouting “we need Charlie back”
I called Chris and asked him if I could keep the pre-amp a little longer. He said I could keep it as long as I wanted, until he wad done with his home theatre setup.
During the next month, I invited several friends and made comparisons. Most people could identify the difference easily, not that the Lamm was doing anything wrong. In fact, the sound was still outstanding with the Lamm. But the little Charlie would remove every bit of veil from the sound, and add more dynamics and details. It was as if it was removing everything between you and the sound. The Lamm was doing one thing better though. The vocals were sweeter with the Lamm. Clearly, it was the FET color of the Lamm, which was doing the trick. Vocals are extremely important to me, perhaps more than anything else in music. Yet, the little Charlie was not doing anything wrong with the vocals. It was not as sweet but it was more clear, meaning it was revealing what was on recorded. Besides, it was doing everything else better than the Lamm, and hence was winner.
I called up Sal, a buddy of mine who owns the Divas and drives them with Sim Moon Audio gear, including their top of the line pre-amp.
“Hmmm, I trust your opinion,” Sal said after I told him the whole story.
“But, I do not believe in these homemade gimmicks, as they have no quality control,” he remarked.
“Well, let’s compare it with yours,” was my answer.
On the following Sunday I went to his house, taking Charlie’s pre-amp with me. It weighed about 15 pounds or so, with a detachable power chord, so wasn’t a problem to carry. We warmed up his system and listened for about 30 minutes.
“Now, you will hear the magic,” I said with a cheeky smile.
“Well, I am not sure about the magic,” Sal laughed.
We replaced the Sim Moon with Charlie pre-amp and turned on the system and started the same CD. I did not say any word. Nor did Sal. We were both silent, dead silent. After 10 minutes, Sal stood up and said “Yeah, it is better”.
“What the hell is inside it? Tubes” He asked.
“I know it has no tubes but to be honest I have no idea what is inside it,” I said.
We listened more and now it was my turn to laugh as there was no contest in soundstaging, imaging, bass, dynamics, details, and transparency. The Sim Moon sounded dull. Charlie sounded live.
“Yes, but it is marginally better, which is not a big deal, Sal said.
“Marginally better? Everything in high end is marginally better, depending upon how you define your margin,” I said.
“Look, can you see the image of the singer in this recording”, I asked.
“Yes, it is right there,” Sal said.
“Ok, now let’s put the Sim Moon Audio back,” I said.
We changed the pre-amps and played the same track.
“Now, where is the singer,” I asked.
“I cannot tell now, hahahahah,” Sal said with a sheepish smile.
A couple of weeks later, I called another buddy, the owner of B&W 800 Diamonds, driven by Lamm M1.1 and BAT VK 51, top of the line from BAT. He brought to my house his BAT, a heavy duty pre-amp with more than a dozen tubes and weighing 60-70 pounds. We warmed up the BAT and listened, then compared. I never said any word. In making such comparisons, it is my principle to let the listener decide for themselves. I do not chip in with my own instructions for them or to tell them what I want them to believe. So I said nothing.
After 15 minutes, my buddy said: “There is no contest, what a surprise”
“Can Charlie make one for me,” he asked.
“He should. I will ask him,” I said.
I had been with this pre-amp for more than two months now. I called Charlie up and told him I wanted to buy him a lunch. We ate at an “authentic” Tex-Max restaurant.
“Why you never told me about this pre-amp, Charlie,” I asked.
“Well, I did but you did not pay any attention,” Charlie said.
“Oh yes, I remember, but you could have told me more” I said embarrassingly.
“I did not know it would meet your expectations as you have some of the most astonishing gear,” Charlie said.
“What is inside it?” I asked.
Charlie is a man of few words but now it seems that Charlie did not know how to stop -- all I could do was to listen. The pre-amp was a solid state pre-amp using video op-amp. Charlie had been reading the research papers published by Walt Jung, a well respected name in audio who has written tens of professional and amateur audio papers as well as books. Charlie himself has been with Motorola for some 35 years. A veteran of Vietnam, with a B.Sc. degree in Electrical Engineering, and a genuine audiophile, Charlie has listened to and experimented with countless amps and speakers, not to mention his repairing skills. Charlie has been in audio for more than 40 years.
What caught Charlie’s attention was Walt’ Jung’s paper on using video op-amps for designing pre-amps. For 2-3 years, Charlie tried various topologies based on Jung’s publications, with additional modifications.
The heart of a pre-amp is the power supply. No matter how good a topology is, it won’t sound good without a good regulated power supply. Often op-amps are used incorrectly. No wonder op-amp have bad reputation among audiophiles. Charlie first built this pre-amp for Craig (owner of Legacy Whispers). Craig needed a pre-amp that could drive the signal with long runs of interconnects. Since this is a high-current pre-amp, it can drive very long interconnects (single-ended). According to Charlie, even 100 feet is no problem. According to Craig, his jaw dropped after he first listened to the new pre-amp, as his objective was just to find something that could solve his problem of long interconnects. He did not expect a huge improvement.
“The pre-amp has the most regulated power supply that one can possibly design,” Charlie said.
“Can it be improved if money is no objection,” I asked a naïve question.
“Nope, this is the best that can be done, and it is already an overkill,” Charlie answered.
The pre-amp has the flattest frequency response with no distortion (because of the wide bandwidth of the video op-amp). Furthermore, it does not change gain at any frequency.
“The input signal is virtually untouched and is amplified in its purest form” Charlie added.
“It is like a passive pre-amp but on steroids, isn’t it? “I remarked.
“Yeah, you can say that,” Charlie said.
“Ok, Charlie, make me one please, but I want a dual mono with best components, separate volume control for each channel and better case, better LEDs,” I said.
“Should we go for a balanced design,” I asked.
“No, the noise is already the minimum possible and you can run as long an interconnect as you wish without any loss in signal. By making it balanced you will only increase the circuit complexity three times and the cost,” Charlie said.
During the next two weeks, we met a few more times, and discussed all the details. I simply wanted the best that could be done. Charlie was going to add ladder resistors for volume control which keep the impedance constant without touching the signal. The power supply was also going to be separate for each channel. We also looked at some cases from a catalog and chose a simple but elegant one. I paid $1000 to Charlie to order components. Charlie was going to charge another $900 or so for the labor. The whole pre-amp was going to be hand-made by Charlie himself, so the cost was justified.
A few days later, I received some disturbing news. The store was going to be closed and Charlie was going to be laid off. The store was not making profit in retail audio and video. The owner had decided to build media rooms instead, with consulting service and supply of audio-visual equipment as needed. Charlie told me not to worry. He promised he could work at home. He had recently retired from Motorola. But they had offered him a temporary contract. The store was soon shut down. I was feeling sad for Charlie, so I did no push him. I sold the Lamm L2 though. Chris had been nice enough not ask his pre-amp back, which is what I was listening to now.
After 2 months I called Charlie. Charlie was never home. His wife said he was working 70 hours a week. After several tries, I got hold of Charlie and asked for my pre-amp. Charlie said he had all the parts now and he was working on it but had very little spare time. He had to work even on weekend as he had no permanent job and wanted to benefit from the contract as much as he could. I understood his position.
The next 8-9 months passed by during which time I found myself gradually getting upset as I did not get my pre-amp. But it was a difficult situation because Charlie’s contract was being renewed on a monthly basis. Charlie promised he would finish it soon. I had to wait for a total of 14-15 months all in all. Meanwhile, I called Chris and asked if I could buy his pre-amp. Chris agreed. I paid him what his cost was. At least I had the original one now.
Finally, Charlie called me one day and said he was done. The first thing on my mind after I brought the new pre-amp home was to compare it with the original one. They sounded the same except that the newer one quieter and even more smooth sounding – it also looked better.
“Turn on the volume all the way up without playing any music, and see if you hear any hiss” Charlie said.
“None, the pre-amp is dead quiet” I said.
“Does it need any breakin?” I asked.
“No,” Charlie said.
The end of the story. The next match of Charlie pre-amp (now I call it X-2) is with the CAT Ultimate mark II and I have no doubt it will win. But I have no interest in any pre-amp upgrade, not even auditioing.
The X-2 features a very direct signal path, a precision high current drive output stage, and a very high quality power supply. Specifically it uses and AD811 current feedback video op-amp and an AD744 FET input op-amp output stage to drive the 811. All components are of the highest quality, such as metal film resistors, polypropylene film and high frequency low ESR electrolytic caps. Charlie made extensive efforts in the power supply to provide as complete isolation from AC power line noise as is possible and to keep the regulated supply impedances extremely low.
The power transformers used are dual bobbin types with a “Hi-Pot” rating of 4000V ensuring minimal transfer of AC line high frequency noise. In addition, common mode chokes are used before the transformer primary and after the soft recovery rectifiers as well. The high frequency electrolytic filter capacitors smooth the rectified voltage of the raw dc supply that then feeds the sophisticated regulators, which have extremely low impedance even at high frequencies. The result is effortless dynamics as well as extremely well-defined imaging and detail.
Several configurations can be utilized as far as power supply complexity, volume control configuration, number of inputs, and output stage drive circuitry. The ultimate configuration is dual mono with separate dual-secondary power transformers for each channel, with four separate bridge rectifiers and filter capacitors providing DC to two pairs of +/- regulators (one pair of regulators per channel). As I mentioned above, this is a true dual mono configuration with the grounds from each channel run separately back to their respective DC supply filter capacitor center points. The only common connection between the two channels is at the common ground at the center point of the two DC supplies.
The result of the quality of the power supplies and the care taken with the grounding is high dynamic range, high channel separation with no crosstalk, and extremely low noise.
The standard line driver circuitry is capable of driving low impedance and capacitive loads to high levels at high frequencies with no slew limiting. Overall, the gain can be adjusted to your requirements during construction.
To me, all other pre-amps seem to have some color. The X2 pre-amp is crystal clear, like water, which is what a pre-amp should be.
Last Friday was the last day for Charlie at Motorola. He might have time for building more pre-amps.
Please contact Charlie directly:
calex1044@sbcglobal.net
Anyone who is interested is free to communicate with him. Consider me out of the loop please.
The picture of the pre-amp can be seen at my system:
http://forum.audiogon.com/cgi-bin/fr.pl?vaslt&1066703453&read&3&4&
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- 25 posts total
- 25 posts total