Daddy Dee Posted June 21, 2003 Share Posted June 21, 2003 I've been reading posts on this forum going back a couple of years on ST-70 rebuilds and mods. My interest in an ST-70 rebuild is to have a competent person do the work, lots of prospects there, but not me... and get the amp to the place where it doesn't have "vintage" problems. Most of my listening is jazz, vocals, and some rock. I do enjoy the whole range of music and not to neglect punch in bass. There seem to be several significant options for ST-70 rebuilds. Van Alstine does one for about $650, turn key job, including new binding posts. Read posts on this forum saying that this is a sound rebuild and a pretty good value. Wellborne Labs has a Alan Kimmel designed rebuild, which reads pretty well on the WL website. The parts for the whole deal are in the neighborhood of $800. In my case, that would be a basic cost, and paying for the labor of a competent pro is an additional consideration. Also have read several posts about Craig of NOSValves turning out a very nice ST-70. In their descriptions both Craig and AK talk about triode power. This would result in sound similar to SET? Also some parts from Curcio? I'd sure welcome hearing your take on these and other possible options, in terms of strengths, weakensses, etc. Does one do well to get rid of the EL34's? Don't the Mark III's retain those in most mods? As always, I sincerely appreciate individuals who are contributing to my tube education. Regards, Dee Quote Link to comment Share on other sites More sharing options...
Deang Posted June 21, 2003 Share Posted June 21, 2003 Hi Dee, The venerable Mark III's use the 6550. The Mark IV's use the EL-34. Typically, the 6550 will provide more bottom end grip and slam than the EL-34. The EL-34 is known for it's lush midrange and 'fat' soundstage. Having spent much time with the KT-88, a close relative of the 6550, and the EL-34 -- I prefer the EL-34. Realize this is purely subjective. I like the KT-88 very much also. Think of the ST-70 as the stereo version, lower powered version of the Mark IV's -- which are of course mono-blocks. Mind as well have Craig do it. At least if he screws up you can come here and publicly humiliate him. Seriously though, why the interest in this particular piece -- and what are you doing for a preamp? I'm one of those rare birds who believes it's best to leave things as designed. The ST-70 is an ultra-linear amp, it can of course be wired in "triode" -- but it's not true triode. It is system dependant though. Some people like it -- some people don't. http://db.audioasylum.com/cgi/m.pl?forum=tubediy&n=23245&highlight=wired+in+triode&r=&session= Quote Link to comment Share on other sites More sharing options...
NOSValves Posted June 21, 2003 Share Posted June 21, 2003 The Triode I do to a ST-70 is strictly in the front end board. I leave the output Ultra linear ! They can sound very nice if done right . Craig Quote Link to comment Share on other sites More sharing options...
tillmbil Posted June 21, 2003 Share Posted June 21, 2003 I also have a ST70. How much to rebuild leaving it the same? Tubes being separate. Quote Link to comment Share on other sites More sharing options...
kjohnsonhp Posted June 21, 2003 Share Posted June 21, 2003 I have a very nicely restored ST-70 using the factory board and circuit. I did the common modest mods but not triode mode nor the leveraged new circuit designs. I can even still switch it into mono mode. When Mallett's VanAlystine gets repaired I hope to A/B the two so to hear the delta. I've been told there can be a notable improvement but I haven't done the tests. I'm thinking of exploring updates but there is a point to where I might just find a new amp to be preferred. I have A/B'ed to Radio Craftsman. If Craig from Oklahoma would come down to Dallas for a DFW meeting then we could a/b the NOSValves mod to the VanAlstine leveraged mod to my basic restoration. The deltas would be very interesting and I'm assuming the three would sound different. Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted June 21, 2003 Author Share Posted June 21, 2003 Mind as well have Craig do it. At least if he screws up you can come here and publicly humiliate him. Seriously though, why the interest in this particular piece -- and what are you doing for a preamp? Dean, That is some serious accountability for Craig and it could take the fun out of his job! On the ST-70, ran across a pawn shop bargain, and it doesn't sound bad by itself... dumb luck. On the pre-amp: Sunfire Classic Tube, on trial to buy from a bud... potential good deal. It sounds pretty good. Mostly my interest is in hearing how different amps do the music. Next week sometime I should be able to experience Paramours 2A3. I like the idea people talk about getting emotionally involved with their music on SET amps. Basically wine tasting to see what is the most enjoyable. Regards, Dee Quote Link to comment Share on other sites More sharing options...
NOSValves Posted June 21, 2003 Share Posted June 21, 2003 tillmbil, Do you mean just freshen the ST-70 up and get rid of the stale parts with out a new board ? I would guess about $200 . A new replacement board would be another $40 to $50 (meaning the same factory circuit). Complete redesign with all triode front end and mods about $400 . Craig Quote Link to comment Share on other sites More sharing options...
kjohnsonhp Posted June 21, 2003 Share Posted June 21, 2003 If you spend around $300 on the ST-70 plus $400 on the full mod do you have a $700 amp that competes favorably with other $700-$1k amps from audiogon.com or new? I recall a thread where Kelly was advocating other amps but of course he never was an advocate of the ST-70. How much are the restored Mark III's running? I guess comparing to the Wright Sound mono8's or 2a3 mono blocks would be a different sound but they are around $1k on audiogon. Without listening to various options it's hard for me to select the right strategy. Would it make much sense to bridge these to mono and run a pair? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted June 21, 2003 Share Posted June 21, 2003 KJ, Depending on purchase price and tubes you could easily end up with anywhere from $900 to $1300 in a set of Mark III's complete. My own personal set I have a $1000 into plus $300 in a set of Tungsol 6550's and a set of EH KT-88's plus the tubes that were in them. I paid a $700 for mine but they are pristine and were in first class stock rebuilt state. I didn't really have to do anything to them but you know me. There is no way you can match this sound for under 2 grand !! I personally think kelly based is opinions on flawed setups with amps that were either bone stock or worked on by less then stellar techs. The entire Dynaco line with the right mods are great performers ! He also never thought much of Scott , Fisher and on and on. Craig Quote Link to comment Share on other sites More sharing options...
NOSValves Posted June 22, 2003 Share Posted June 22, 2003 Mark, great post but where did you come up with $1100 ?? If a person was to buy a ST-70 for even $350 which is what they go for and pay to have it rebuilt and modded it would only add up to about $800. Also the driver board upgrade and PS rework easily cost $175 to $200 in parts and tubes without labor to do it right. All your suggestion's were right on the money in my book but the figures are from the 70's Craig Quote Link to comment Share on other sites More sharing options...
NOSValves Posted June 22, 2003 Share Posted June 22, 2003 Dean, I can't believe you would base your opinion on that thread !! Tell me you have better info then that http://db.audioasylum.com/cgi/m.pl?forum=tubediy&n=23245&highlight=wired+in+triode&r=&session= Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted June 22, 2003 Author Share Posted June 22, 2003 Mark, Thanks for your post lining out options on the ST-70. That's some genuinely helpful info. Sometime next week I'm going to be able to listen to some 2A3 (Paramours) and I'm definitely looking forward to that. Hearing folks talking about listening to amps that are emotionally involving has got me certainly curious. I like being emotionally involved We'll just have to see if the lack of headroom leaves a satisfactory (to my ears) option. Also curious about the 300b, and hope to have a chance to audition of these sometime. In the price range of $1100, I'd sure be interested to hear from you and others as to some amps that are good bang for the buck candidates. Assuming a couple of given, taste in music is mostly jazz, vocals, and some classic rock. Not needing to shake the house often. Perhaps assuming a preamp already on site... Sunfire Classic Tube. I've got one for audition right now and listening to it on the ST-70. Sounds pretty good and has some friendly features like remote and some bass and treble contour available. Probably could assume used/good condition or some other turn key option. Appreciate your thoughts and any one else who would want to weigh in here. Regards, Dee Quote Link to comment Share on other sites More sharing options...
Deang Posted June 22, 2003 Share Posted June 22, 2003 No Craig, that thread is not entirely what I base my opinion on. That was purely for Dee's benefit. What, you want me to throw him a raw T-bone steak? "As for triode wiring the outputs, I happen to like this as a horn driver but I doubt it is useful as a full-range speaker amp unless you listen at the MOST polite levels." This really seems to be the consensus of most. If one goes through the archives at the tube asylum, they will run across many posts by those who own, or have heard the amps (mostly Cary) that have the UL/triode on the fly switching option. The great majority of these posts say UL sounds better. More extension into the bottom with more control, more dynamic, crisper highs, and generally a "livelier" sound. I did say it was hit or miss and system dependant, but this is what I mostly read and hear by objective folk. They are "objective" because they have both options readily at their fingertips, and just report what they hear. The triode freaks are hardly objective. They have a dinky triode amp and it just sounds SO MUCH BETTER THAN ANYTHING ON THE FREAKING PLANET! OH MY GAWD YOU'RE NOT LISTENING TO TRIODE ARE YOU OUT OF YOUR MIND! ITS THE FIRST WATT THE FIRST WATT -- and then you can almost hear the pacemaker kick in. Yeah, they're objective alright. Guess what? It ain't the first watt -- it's the last watt. The watt you need to complete the waveform without clipping. "Why people say this is not "true triode" I really don't know. My best guess is that they are confused between the definition "triode" as a tube-type classification and "triode" as an output configuration. Since it's perfectly valid to RCA, that's good enough for me." I'm not confused, and you answered the question better than I could of (which isn't surprising I realize) when you said, "The downside to wiring this in triode is that the transformers were wound to see an UL load, not a triode load." True triode to me is a 3 element, directly heated tube with a transformer to match. Everything I've read says that's what it is. Taking a pentode and emasculating it is not the same thing. It's "a sweet little midrange amp" because that's what your mostly left with. "Triode wiring radically alters the sound of the amp. Why? Because all the distortion characteristics change. You could say the order of predominence of each order of distortion is restacked. The triode mode (if done the way most people end up doing) also has less NFB and less sensitivity, and of course less power out. Because of the lower NFB, the bandwidth narrows. Ahhhh, sweet little midrange amp!" I just don't understand how less headroom, more distortion, and less bandwidth can be a good thing. It's kind of confusing stuff. Distortion is now 2nd order instead of third (I think), and I guess that's a good thing. There's less Class A, and I think that's a bad thing. You mentioned that it's triode at the RCA -- but there's more to it than that isn't there? Help me understand this. Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted June 22, 2003 Author Share Posted June 22, 2003 Dean, Was reading one of your posts from back in Feb. to someone who was considering a Cary Rocket 88. You were asking the person about their preamp, because there were quite a few folk selling their 88's due to a mis matched preamp, too low power for the 88. I was wondering what you'd look for in a competent preamp to match with the 88 and if the Sunfire Classic Tube Preamp would be a good candidate to match with the Cary 99? Appreciate your take on this and any others who would offer a comment. Regards, Dee Quote Link to comment Share on other sites More sharing options...
NOSValves Posted June 22, 2003 Share Posted June 22, 2003 Dean, What really kills me is your posting everything about what triode does and doesn't do from things you have read and you personally have never heard the amps that are being discussed in this thread. The statement that Mark made was directly related to the ST-70 which I agree should never be put in triode for most situations. I wired a Heathkit EL34 UL amp in triode for a customer that is a NYC apartment dweller and he absolutely loves it !! There is no clear cut answer as to what will sound best in each situation. Until you hear a Mark III's or ST-70 in triode you should just refrain from commenting derogatorily about it ! You don't like it because of a handful of asylum inmates that are running a amp that has a switch to change back and forth ? Well I can guarantee you the amp is setup to run perfect in one mode or the other so that is a really twisted comparison. If its not optimized for UL or Triode output then its less then what it could be in both situations. Whether to run in Triode or not depends on many factors. Like the room size , the speaker type , the music preference , the volume level required and on and on. Craig Quote Link to comment Share on other sites More sharing options...
Deang Posted June 23, 2003 Share Posted June 23, 2003 Your preamp needs to be able to produce 18-20 of gain to drive the 88 to full volume. '"Had (Dennis Had, the designer) believes that gain and buffer stages negatively affect transparency, so his goal was an amplifying device with minimal gain to provide the output power to drive the speakers. That means the Rocket 88 requires a high-output preamplifier. It took out my reference preamp, the Wyetech Opal (15dB gain) and substituted Carys SPL 2002, used in designing the Rocket 88. The 2002 has 20dB of gain, so I suggest that as the minimum matching requirement." A good amp for the Lascala. I'd love to have two of them in a vertical biamp configuration. Quote Link to comment Share on other sites More sharing options...
tillmbil Posted June 23, 2003 Share Posted June 23, 2003 Craig, sounds like I would like the freshen up with a possible new board. Looks like $300 to $400? I purchased the St-70 for $250.00, so for $650.00 I would say I would have a good amp. My goal is to have it sound original and be more reliable. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted June 23, 2003 Share Posted June 23, 2003 Sure will be ! When you say freshen with a new board are you still meaning keep the circuit stock ? That would only be about $250 . Craig Quote Link to comment Share on other sites More sharing options...
sunnysal Posted June 23, 2003 Share Posted June 23, 2003 here are my two cents. I think that mdeneen hit it pretty much on the head. the ST-70 is a great sounding amp, if you just freshen (new caps, a few key resistors) you will have a killer amp for less than $600. you could also mod lightly, some added puffs on the PS (via caps), perhaps a few multi dollar caps in key locations. but not much more. I think that plowing another $600 buck in mods is il-advised, at least to start, freshen and then see if you are not satisfied with the sound before going further. re: triode strapping the EL34s, I liked the results on my MkIVs, I did not percieve any loss in the frequency extremes but did sense I nice smoothness in the midrange with my k-horns, I could not listen for a long time in pentode after I made the mod (I have a switch installed that allows Pentode or Triode listening on the output tubes). the triode input boards I am sure sound nice (and nice 7199 are getting a little harder to find and cost about $30/each) but I was quite happy with my sound and never even thought about swapping input boards. YMMV, etc. best of luck, tony Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted June 23, 2003 Author Share Posted June 23, 2003 ---------------- On 6/23/2003 12:08:45 AM DeanG wrote: Your preamp needs to be able to produce 18-20 of gain to drive the 88 to full volume. '"Had ( Dennis Had, the designer ) believes that gain and buffer stages negatively affect transparency, so his goal was an “amplifying device with minimal gain to provide the output power to drive the speakers.” That means the Rocket 88 requires a high-output preamplifier. It took out my reference preamp, the Wyetech Opal (15dB gain) and substituted Cary’s SPL 2002, used in designing the Rocket 88. The 2002 has 20dB of gain, so I suggest that as the minimum matching requirement." A good amp for the Lascala. I'd love to have two of them in a vertical biamp configuration. ---------------- Dean, Here's what the Sunfire preamp manual says: (I share this because in my very lay understanding which is very close to confusion, I need some help interpreting it ) "The output inpedence of the Classic is a low 1.5K ohms, so it can drive power amplifiers having virtually any input impedence." Further states can use conventional cables as long as 30 feet, or low capacitance cables as long as 60 feet to drive power amps without difficulty. On the webpage, states 8 volts output, but no mention of how many db's of gain this would be. Tony, Thanks for your thoughts on your experience with the Mk IV's. That's helpful. Regards, Dee Quote Link to comment Share on other sites More sharing options...
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