Daddy Dee Posted November 8, 2005 Share Posted November 8, 2005 DM. Those Sound Valves are beauty amps. about what was the year of manufacture? Are you the first owner? Quote Link to comment Share on other sites More sharing options...
D-MAN Posted November 8, 2005 Share Posted November 8, 2005 Yep, got them new. Used about a year to 18 mos. or so. Back in the original boxes with all original packing. Been there every since. I did not have horn speakers at the time. I would guess about 1997 or 98 or so. Tne thing I wish they had was a balanced input ; they are RCA only. DM Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted November 8, 2005 Share Posted November 8, 2005 They do look sweet. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 8, 2005 Share Posted November 8, 2005 Yep, got them new. Used about a year to 18 mos. or so. Back in the original boxes with all original packing. Been there every since. I did not have horn speakers at the time. I would guess about 1997 or 98 or so. Tne thing I wish they had was a balanced input ; they are RCA only. DM D-MAN, Its really not a good idea to let amps like that sit without at least firing them up every six months or so. You propably would be better off bringing them up on a variac after 5 or 6 years of sitting idle. They may fire up just fine but the longevity of the PS caps will be lowered. I happen to have a variac if you need it done and want them checked over[6]. If they prove to be working fine all you will have cost wise is the shipping and a $50 bench fee. This just because I would love to check out the circuit and see what they did with them. They look to have a two tube front end you wouldn't happen to remember what the two small signal tubes are in them do you? Craig Quote Link to comment Share on other sites More sharing options...
D-MAN Posted November 8, 2005 Share Posted November 8, 2005 Seems to me its a 12ax7 as a phase splitter (guess) and a 12au something. I don't quite remember. I've got all new tubes in the boxes for them too, all the way around. (I'm at work or I'd go and look). Yes, the variac is a good idea. I think they've got cheasy caps anyway. When I get around to it, I'll send them to you to get them "checked out", "freshened" and otherwise ready to rock. No time now, though. Trade? DM Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 8, 2005 Share Posted November 8, 2005 Trade for what? Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 8, 2005 Author Share Posted November 8, 2005 There a couple of different issues being discussed here -- one of which has to do with high voltage spikes and max voltage ratings of electrolytic filter capacitors, the other with using a current limiter on the PT primary winding, or a standby switch on the plate supply center tap to make life a little easier (and longer) for ones tubes. If that distinction wasn't clear in my response to this, that's my fault. It's kind of crazy in the morning before work around here. Craig: Your description of using a current limiter with a 5AR4 rectifier is unclear to me. What are you talking about, and/or where were you picturing it in the circuit? Thanks for the description of what a thermistor is and how it works. In fact, why are you proposing the use of a soft start device on this particular rectifier? It's probably your description that's not clear to me. Lastly, Is it necessary to once again make comments about being cheap? I said nothing of the kind to you, or about you in this thread. If the reference is to the builder of these amplifiers, he was doing professional tube amp repair when you and I were a little boys. These MKIIIs are outstanding for the price. Same goes for the Dyna 70s. Thanks, Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 8, 2005 Author Share Posted November 8, 2005 D-Man: Variacs are very easy to use and come by. I have a couple of here, and they are useful tools. If this is all you need, you could do it yourself. For more work, send them to Craig. The Variac really doesn't take any specialized skill, though. Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 8, 2005 Author Share Posted November 8, 2005 Craig: I've got it. Your saying it's of little use on a 5AR4. I wasn't proposing one use a current limiter with that tube. Thanks, Erik Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 8, 2005 Share Posted November 8, 2005 D-Man, Those M60Is always looked like nice amps. Never heard a pair myself though. Its too bad Sound Valves/Values is gone. They looked like they had good products at great prices. http://web.archive.org/web/20010401000804/www.soundvalves.com/m60i.html Shawn Quote Link to comment Share on other sites More sharing options...
Marvel Posted November 8, 2005 Share Posted November 8, 2005 I was seriously interested in their ST70 amp. Mostly because of my real ST-70 I suppose. Erik, I know that Shawn has a current limiter in his spec for his DIY 35 amp, but it has a solid state PS. He also had comments on his forums about the use if a switch on the center tap being dangerous. Maybe because of the ss power supply. Here are a couple of ways to get around the spike they were having (from the DIY tube forum - I make no claim to these ideas): 1. I tried wiring the 1M resistor across the standby switch today. So far, so good. I do not have a scope so I wouldn't see any really fast transients, but what I do see - is that the voltage at B+ rises from 0 to 6V in about 15 seconds after power switch is turned on and stays there. Each leg of the transformer secodary measured to ground is about 340 VAC - the ground reference is there. 2. Cathode Switching The most common "new" stand-by method is called "cathode switching". This is simply a ground-interrupt switch in series with the cathode circuit of the output stage. To reduce the switch transient, and more importantly, to avoid the risk of cathode stripping, a resistance is wired across the switch contact. Any value from 4K7-2W to 10K-2W is suitable. This is equally applicable to both cathode bias and fixed bias amplifiers, with any type of output tube. O'Connor, K. 1996 Principles of Power.Power Press Publishing. p3-25. Later, Bruce Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 9, 2005 Author Share Posted November 9, 2005 Marvel: "1. I tried wiring the 1M resistor across the standby switch today. So far, so good. I do not have a scope so I wouldn't see any really fast transients, but what I do see - is that the voltage at B+ rises from 0 to 6V in about 15 seconds after power switch is turned on and stays there. Each leg of the transformer secodary measured to ground is about 340 VAC - the ground reference is there." You are right -- I neglected to mention that a resistor can be used in conjunction with the stanby switch. Thanks for adding that detail. Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 9, 2005 Author Share Posted November 9, 2005 and Marvel: TNX for the information on the cathode switch. Interesting -- I haven't done that before! Erik edit: Marvel: Just thought of something that is sort of a relative of this approach. No time no, but later! E Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 9, 2005 Share Posted November 9, 2005 There a couple of different issues being discussed here -- one of which has to do with high voltage spikes and max voltage ratings of electrolytic filter capacitors, the other with using a current limiter on the PT primary winding, or a standby switch on the plate supply center tap to make life a little easier (and longer) for ones tubes. If that distinction wasn't clear in my response to this, that's my fault. It's kind of crazy in the morning before work around here. Craig: Your description of using a current limiter with a 5AR4 rectifier is unclear to me. What are you talking about, and/or where were you picturing it in the circuit? Thanks for the description of what a thermistor is and how it works. In fact, why are you proposing the use of a soft start device on this particular rectifier? It's probably your description that's not clear to me. Lastly, Is it necessary to once again make comments about being cheap? I said nothing of the kind to you, or about you in this thread. If the reference is to the builder of these amplifiers, he was doing professional tube amp repair when you and I were a little boys. These MKIIIs are outstanding for the price. Same goes for the Dyna 70s. Thanks, Erik Erik, Answer a few questions for yourself 1) Did you build the amp were discussing? 2)Did you advise who ever did build it on the design? I believe both answers are no to these two questions. So my final question is how do you figure I was calling you cheap? You need to re-read what I posted about thermistors (in rush current limiters) you still have it wrong. They work well with a 5AR4 and do little good with a 5U4 or SS rectifier at stopping the voltage spike presented to the power supply. They work off current so with any instant on rectifier setup they won't really kick in until the heaters of all tubes in the amp warm up. Now if they used a stand by switch and thermistor then it would work. I say just put the proper 5AR4 rectifier in, proper rated PS can and a thermistor. Then you have a long lasting well designed product that doesn't need a stand by switch. Remember this amp is being sold as fresh and ready to roll to me this should mean for 15 to 20 years of service with that 500V can it's just not the case. Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 9, 2005 Author Share Posted November 9, 2005 Craig: Are you sure you want me to reply? "So my final question is how do you figure I was calling you cheap?" Shucks, I don't....umh.....'no' I had gotten used to it, I guess. You're right, I still don't understand your description. The builder is not a 'cheap' guy, and if YOU would read a little more carefully, I think I made it clear that I wasn't sure if you were calling me 'cheap' (remember? God of the Cheap Seats or President of the Anal Analyzer Society) LOL![] or the person who redid these amps. Sure, anyone can make a mistake, altough he tests these things for quite awhile before sending them out. If something fails to work right, he is very approachable with highly regarded customer satisfaction. If someone on this forum bought it, and the filter cap blew up, I would replace for them for free, with just shipping and parts costs covered. I'm pretty sure I could even handle this complex task without the aid of a scope! Also, You indicated something about the possible lack of test instrumentation. This person was working with scopes and signal generators while you and I were still playing with Tonka trucks (the good metal Tonkas!). D-Man: Those amps really do look nice! My feeling is that the filter caps are probably still perfectly fine. If not, they can be replaced. BTW: That triode front end looks interesting. I have several old schematics of MKIII modifications with that aspect in common. I'm glad Shawn posted the link so I can have a closer look Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 9, 2005 Author Share Posted November 9, 2005 D-Man: Get those amps up and running! I'd love to have a look at them myself! Too bad they aren't offered any more. Erik Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 9, 2005 Share Posted November 9, 2005 Erik, you just don't get it do you? A professional does a "professional job" and when designing gives plenty of comfort zone in the parts they specify. A 500V can has no place in the amp that runs at, near or above 500V that is simply sloppy design to save a buck nothing more nothing less 525V cans are readily available for just $20 more or you can double the caps up and use balancing resistors. Why would someone want to buy an amp and then have to send it to you for a free can replacement when it fails? I'm sure the amp will hold up for a year or two as is but what about 5 or 10 years? I'm all about quality and that is what works if you plan too stay in business or have a descent reputation. You jump to recommending things WAY to easily in my opinion without truly knowing that your recommending something that is built to a reasonable standard. Of course you couldn't just say that I have a point which I absolutely do you would rather try to side step the issue. You don't know this seller personally or have any extended experience with him. How the heck do you know what he will say 6 or 8 months after the sale? I wrote the guy weeks ago and ask for his explaination of this power supply issue, his answer was it works fine and he plays them for 3 or 4 weeks before selling them. Well I'm telling you that isn't good enough for me because I know this is trouble waiting to happen. I still can not believe you can't understand how a In rush current limiter does no good if little current is being drawn by a cold compliment of tubes in the amp. They only work by the current being drawn through them heating them up. They could careless if the rectifier is making 500V or 50V. no current no help. Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 9, 2005 Author Share Posted November 9, 2005 Craig: You have a point, and you are right, and I am wrong, and I don't know how a current limiter works. I completely withdraw and or retract everything I have said now and in the past as baseless, and nothing more than nonsense blabber from the throne of 'cheap seats.' Hey, wait! Can that work, Craig? It's sort of an interesting situation, isn't it?! -- an oxymoron of sorts! 'Throne of Cheap Seats' I like it![] The game is yours! Erik Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted November 9, 2005 Share Posted November 9, 2005 Oh well, at least I can honestly say I have no earthly clue how any of it works, and I know I'm right too![] Can't argue with that... Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 9, 2005 Share Posted November 9, 2005 Jim, Trust me your better off. Craig Quote Link to comment Share on other sites More sharing options...
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