Just a quick word: after a week or so of careful listening, I must tell you that the amps sound fantastic. I want to thank you both for your efforts and your patience, because as far as I am concerned, it was all worthwhile. ... DM
I just wanted to thank you for your support and advise as well as congratulate you for not just an outstanding product, but for an informative and accessible website, as well as telephone availability. Saturday I was able to install the new driver board upgrade on my dynaco stereo 70 in a little bit over 3 hours. I had previously installed the capacitor replacement board. The sound is magnificent. You are absolutely right. Your modified PCB upgrade not only keeps the character of the original, but also improves on it. This is an impressive amp now; the music flows with the right amount of drive, the bass is plump and articulate, the tonalities are convincing and nuanced, but best of all the musicians performance is clear and engaging unlike most pieces of electronics out there. I am running the amp through a pair of spendor s3/5 monitors, and feeding it from a Quad QC-24 tube preamp, and is a great combination. I am curious now about the more powerful dynaco mono blocks... Thank you again for putting more better music in our lives! Best regards, RF
I'm writing primarily to thank you. My cousin used your kit to modify one of my 2 Dynakit ST70 amplifiers. He suggested that I write to you with my impressions and thanks. You gave him some email advice a few months ago and I'd like to express my appreciation for this as well. Now, I'm not an audio engineer, but simply a fan of recorded music. So I'll deal with subjective rather than objective, measurable assessments. The improvements my system has gained with your modification are, to my ears, quite measurable. I'd been running 2 ST70s, 'bridged' into mono, for about the past thirteen years. For about the past year I consolidated (good, operating) tubes and ran just one Dynakit. My system consists of a Linn LP12, Ortofon cartridge, Sonic Frontiers Anthem 1 pre, JVC XL-Z1010 cd player, Dahlquist DQ10s and of course, the ST-70 with Curcio modification, as of this past Tuesday. It's an aging system, but I'm tickled pink to see some of my components still mentioned by the audio press, which I've ignored for most of the past fifteen years or so. Here's what the mod has done in order of magnitude:
1. The Curcio mod has separated what was once a mass of instruments and vocalists into coherent 'compartments'. This is
actually the biggest difference, and the first thing I noticed. Never a particular fan of this before (I tend to seek out sound staging), but now that I hear it I want to keep it. This difference also means that two or more things can be playing at once and I hear them...separately. It's a real revelation, and quite unexpected.
2. The Curcio mod has extended the bass floor quite noticeably. I can tell this, because the floor shakes much more. But there are also bass NOTES. That means that I can now hear Eberhardt Weber's acoustic bass render differences between notes. The thumps are no longer just low-ish thumps, but notes. I hear bass notes. For a guy with a pair of DQ-10s, this is quite an accomplishment. I hear all sorts of little things happening down there. I've discovered why Jaco Pastorius is a genius, he does all kinds of interesting things in the nether regions of bass. On Joni Mitchell's "Blue" the opening drum can be heard as more than just a dull thump. I always thought it was someone's foot tapping on the floor. Now it sounds like a drum. Cassandra Wilson's "Strange Fruit" has bottom, real bass depth. It's quite frightening in a way. I can now play disco, if I really wanted to. My daughter will be so pleased.
3. The Curcio mod has extended the high end frequency floor. This is not as easily discernable as the bottom octave differences noted above, except for the fact that: a. I get more soundstaging. b. I get more image depth. But my system sounds brighter. This means I have to do something about my cd player, cause on some recordings, I get speaker fatigue. Maybe I should drop the little Dahlquist piezo tweeters into Lake Ontario..
4. The Curcio mod has given the system more detail..or, to put it more clearly, I now hear the very beginnings and endings of guitar strums, vocalists take breaths in-between passages, I hear small things in the mix not previously there, like bells for instance. Paul Simon's "Rhythm of the Saints" album has all this STUFF going on..it's very subtle, but it's very definitely
there. Singers lick their lips, tinny guitars sound tinny, fat guitars sound fat. I can hear the musician's fingers running up and down the frets, I can hear when the strings are sustained for an extra moment in an piano passage. Hell, that I can hear that at all makes the whole thing sound more real and enjoyable, and that's the point of the whole exercise, isn't it?
5. The Curcio mod has made my system able to reproduce the studio on some recordings. Here I think I'm being limited by my speakers, but I can definitely hear 'the room' on Kate & Anna, Roches, Simon, Jazz at the Pawnshop, Joni Mitchell, etc... it doesn't make bad recordings sound better though. I can hear the 'switch' from room to room, for example on "Blue" the difference in rooms between the piano track "My Old Man" and the next track, "Little Green" is quite easily heard. I can hear when a vocalist gets too close to the mic, I can hear more studio crap, I can hear whispers and asides in live recordings with much more clarity...that I'm not sure I want to hear.
6. I don't know if I'm imagining this one. The Curcio mod seems to have done something to the tempo on some recordings. The Roches seem to be speeding up and slowing down between choruses. They do this intentionally, I realize. I think I noticed this first when I got the Anthem preamp, but it's much more apparent now. The Indigo Girls and Joni Mitchell and others do this as well...
These are only preliminary impressions but I'm certain about their authenticity. Thanks again, RR
It's been a couple of week now since I finished upgrading my st-70 with your kits for power supply and driver board. After a period of time for break-in, and finding an appropriate interconnect and power cable, I can tell you that I am very comfortable with the sound my system is making. It's very musical and natural in a way that my high end solid state gear was not. Thanks for making these kits available and thanks for your help on the couple of occasions when I needed direction. It was comforting and essential to know that your help was just a phone call away. Best regards, G.
I have a fully modded ST70 and a PAS using both the driver and the power supply boards and love the sound. Tight bass, extended highs, very detailed and very 3D. I often listen at night with all of the lights turned off and frequently get startled out of my seat from hearing something in the music that sounded like it came from outside, or behind me. It's an unusual experience (a good one for sure). Joe provides exemplary service to his customers and his products are top rate.
I'm getting ready to fully mod a pair of MkIII's and can't wait to get them into my rig! My Impressions:
1. Sound is accurate and detailed. Not warm or cold, but right in the middle. Very wide, 3D soundstage with individual musical elements placed appropriately within the soundstage.
2. The rebuild is fairly straight forward. It is a full rebuild, the only items reused are the transformers, chassis, quad cap and some of the hardware. The replacement boards fit nicely. I used the premium semi-pack semiconductor upgrade as well as upgraded some caps with Wima's. The instructions that are included were slightly unclear for me, so spend some time and read through carefully.
3. Customer service with Curcio products is second to none. I was a complete electronics beginner when I rebuilt my ST-70 and had sent numerous newbie emails to Joe Curcio for assistance. Joe replied himself to every email answering my questions. He even provided some phone support when I was really stuck. That says much about a person/company commitment to their customer. KS
I rebuilt an old ST-70 using the full Curcio mod (power supply and driver boards) in 1992. The transformation was not subtle. I can't imagine anyone who has a system that can use a 30 WPC amplifier not being thrilled with this unit. The CAE mod has real, tight bass, smooth mids, and natural highs. Compared to a stock unit, well, there IS no comparison. I've also built and have extended listening experience with the Van Alstine and Audio Research mods. The AVA mod sounds good within its design parameters: bandwidth limited. The ARC sounds close to the CAE but is fond of eating 6L6 output tubes and is no longer available. Curcio's approach is certainly valid from an engineering standpoint. The regulated power supply provides strong legs to support the audio sections. Some may take issue with the 6DJ8 / 6922 tubes (4) in the phase splitter / driver section but I hear none of this tube's purported sonic signature (harshness, coldness, excessive sibilance) in the amp's overall sound. I have not had to replace a tube since the modification and it still sounds great. I highly recommend it. Regards, S
I am fellow LS3/5a owner, I have owned my speakers since 1978 and have been pleased with them since day one. Through the years I have had the opportunity to listen to many preamp and amp combinations, solid state and tube alike. Luxman Tube and Solid state, Audionics C22, Theta tube preamp, NAD 3020, APT Holman, DB Systems, All Dynacos, McIntosh, Haffler, Audio Research, Mark Levison, Old Marantz and HK, just to mention a few. I can truthfully say I like what I have now better than anything I've heard, and for a lot less money except the NAD 3020. I've noticed many owners inquiring about the best amp to use with the LS3/5a's. I whole heartedly suggest taking a look at Curcio Audio Engineering ( www.curcioaudio.com) Dyna ST-70 (FULL MOD amplifier) and the PAS (FULL MOD preamplifier) -Tremendous Combo. I finished my Curcio ST-70 amp about 2 years ago and the PAS about year later. I used the preamp section of a NAD 3020 until I finished the PAS - the PAS brought the ST-70 to a level I think most of us aspire to. Imaging is Unbelievable - on good recordings the LS3/5a's completely disappear - the depth is perfect - timbre right on - with the right tube combinations RCA 6fq7- Mullard EL-34(dual getter) for the ST-70's and a well balanced 12at7 (RCA or Telifunken (more money) for the line stage of the PAS they will SING. The ST-70 allows you to use a lot of different driver tubes - this gives you a lot of latitude when trying to get the sound that you like. I think these units will be the best price to performance our fellow LS3/5a users can purchase. These units are a great value and I don't mean cheap - I mean the biggest bang for the buck. If you get a chance, check these units out - you won't be disappointed. Oh by the way, I think Mr. Curcio also listens to LS3/5a's. To my ear this is the perfect combination for the LS3/5a's.
Equipment: Rogers Ls3/5a, Curcio ST-70 complete mod, Curcio PAS upgrade with DACT Volumn and selectors switched, Linn LP-12 - Grace 707 and Denon 103D Verion Step - up ,Marantz 63SE, Quad 57 ELS, Onkyo T-9 Tuner
Silver Sonic Speaker Cable, Belden 89259 IC's, Thanks, JB
I've used Curcio's St-70's since '92, one built with boards purchased from Sonic Frontiers, another built with stuffed boards purchased from Curcio Labs ( actually he built the entire amp, in return for a late delivery! How's that for service!). I've ended up wiring the outputs in triode on both of these amps. Simply put, I find the sound quality superb whether running pentode or triode, though the sound is a bit sweeter, the imaging a bit tighter, in triode mode. I have no comment about the bass as I've never used these amps full range; I tri-amp, using the Curcio's on mids and highs. Compared to an ARC D-76 (upgraded with MIT's, Holco resistors, and new 'lytics throughout), the Curcios offer far greater resolution of detail, again, better imaging (not EVEN close!), and much sweeter string reproduction without loss of "air" or, on excellent source, the natural string "bite." Some of this may be a reflection of my preference for EL-34's over 6550's, but, objectively, it is far more likely attributable to the power supply regulation - "total" plate regulation is, in my experience, something of a novelty, but, in conjunction with everything else, seems to manifest an order of magnitude improvement in sound quality - once more, most noticeably, with image specificity. I should also like to add that Joe Curcio has been more than willing to respond to any technical queries I've posed, and has been most gracious in dealing with my sometimes just plain stupid questions. One man's opinion. B
The 7199 tubes finally gave in and the cost to replace them was not to far from just getting a new driver board. I chose Joe Curcio's design for several reasons. First, this man really loves tweeking Dynaco gear and second the man is a saint. He helped me with several other problems my unit was having. I was even emailing pics of PC boards to him at one point. But mainly his driver board design employed newer technology while still maintaining the spirt of the true Dynaco design.
It was little hard to compare because the original design was pretty darn good. But I listened to some CD's that I was very familiar with. Again clarity and distortion wasn't a problem before but WOW there really was a difference. I tried several setups with direct input with the Dynaco FM3 tuner and a Marantz 2230 as a tuner preamp. I listened to a Pink Floyd song and actually heard a female technician giving directions in the background. On the Beatles White Album you can hear the usual chairs creaking and background "stuff". Beethoven's Pastoral, my favorite,was hauntingly beautiful. The change over from fragile soft passages to swelling crescendos were glowing and warm with detail incredible deep but subtle. It was almost like 3D sound. Loud rock is loud but the detail was still there even at increased volumes. One particular favorite rock album "Days of the new" is a very detailed piece, and it sounded wonderful with deep base and strong mids. Thanks Joe! C