So, having Hexfred rectifiers, does that make the SLP 98 a hybrid?
@billpete , I make no claims to be an electronics or tube guru, but I’d say that a piece of tube gear that utilizes solid state rectification is NOT a hybrid. From what I have seen, there is an awful lot of tubed units using solid state rectification (perhaps the majority?) and I am just about sure that those are NOT considered hybrids. I had always thought of hybrids more in line with amps, and those were amps using input tubes but solid state output. But I may be mistaken--I often am.
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@billpete , I remembered a thread where someone was sort of considering/looking for a SLP-98, but I couldn’t remember the thread or who the OP was, so when I got the preowned notification email from Cary Direct this morning, I figured I’d pass the word.
Anyway, it sure reads as if you have got yourself a nice one. Although it wouldn’t be a factor for me, that Jaguar Red is pretty. A couple of things I was not aware of until I did a look on Cary’s site was that it uses 12au7s and ax7s for the phono stage, and I didn’t know that it used solid state rectification until you mentioned the Hexfreds. Btw, I have read that the Hexfreds make a big difference.
As far as the JJs and the EHs go: I have heard mixed about both of them. On the JJs, probably more bad than good. But I do have a tube guru friend on another site who swears by the JJ 12ax7s. I owe him more than one favor, so I had some Mullard 12ax7s I took out of an old Bogen receiver and I offered to send them to him as I have nothing that uses them. He emailed me back, thanks, but for his money the JJ12ax7s were as good as anything out there. I’ll dig through my emails back & forth from him and see if I can find that one and I’ll paste that content to this thread.
As far as the EHs, my SLP-05 came with EH 6sn7s, and I actually decided to try JJs in the phase splitter sockets. I cannot honestly say that I can hear a big difference in either direction. Vintage 6sn7s in those sockets are on my list. As far as the two balanced input sockets, the tube guru who I referred to a paragraph or so ago gave me a plethora of pairs of vintage 6sn7s (he no longer has equipment that uses those tubes, but when he did I believe he may have been a tad OCD) and I have found that some of those vintage pairs for the two balanced inputs transform the sound of that preamp. So, as I typed, a vintage quad is on my list. If the phase splitters had the sonic effect that the balanced inputs have . . .that should be another "wow!" moment.
Anyway, good luck with that new to you preamp; I am sure you are going to enjoy it, and feel free to keep us updated.
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Seems to me that Brent Jessee speaks well of the EH and JJ's but I may be mixing him up with another tube site that I go to.
Hmmm . . . I think that you may be mixing him up with another site.
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A friend of mine sent me a Moscode preamp and it is called a hybrid.
Well, as I typed, I may have been mistaken about that part.
You’re well ahead of me on this stuff.
I wouldn’t say that at all, @billpete .
When people start talking electronics to me, I feel like I’m back in kindergarten.
Me too. I can solder and de-solder, but I am really bereft when it comes to understanding the topology of the circuit that I am working on.
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@harpo75 , interesting read on adjusting the trim pots on the SLP-05. That sounds like it would be a lot of work to roll tubes. And I guess to perform the procedure the preamp would have to be setting on some type of open support box so that it could be upside down with the tubes installed and the bottom could be off (as I do not have a tube cage for mine). I suppose if I was going to do this, the best thing to do would be to buy a tube cage from Cary.
Anyway, as far as this goes
It’s super important to match the gain of the tubes to get correct channel balance.
forgive me for this question, but is the bottom line that the goal of this procedure is to get the output the same on both the left and right sides?
If that is so, here is what I have found with mine:
First of all I am using the balanced inputs, and I have what is literally a plethora of pairs of vintage 6sn7s that I can roll in those sockets.
I have used a test CD with "315 Hz System Setup and Balance Tone" and a voltmeter to check the output of the amp on both the L and R side. If the balance has not been equal I have found that swapping the phase buffer tubes from side to side has no effect on the readings I have gotten.
BUT, if I swap the balanced input tubes from side to side, I have found that the uneven AC voltage readings follow the (balanced input) tubes. I've actually found certain pairs of tubes in the balanced input sockets that give me very nearly equal AC voltage readings on both sides. So if I have nearly equal readings, there should be no need to do anything with the trim pots, correct?
Here is what I have been doing with pairs of balanced input tubes when I am getting unequal readings with my AC vm:
first I have noted that when I totally defeat one channel and check with my sound level meter and that I do not get equal db readings from both side of my room. Therefore, I put the strong tube on the weaker side of the room.
Secondly, I have played around with using the L & R "input level" knobs to achieve balanced readings on the AC vm, and after that adjust to achieve equal db readings with the sound level meter.
And I realize that using the "input level" knobs to tune the system is probably not optimal. Currently I have a pair of tubes in the balanced input sockets with the strong tube on the weak side and I am actually getting almost equal db readings with my sound level meter with both "input level" knobs turned completely up. As long as I am getting that is there any need to adjust the trim pots?
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@billpete , a few posts or so ago I referred to an email I sent to a benefactor who had blessed me with a literal plethora of vintage pairs of 6sn7s. I really wanted to do something nice for someone who had turned me on to so many tubes either at bargain basement prices or flat out gratis, so I offered to give him a bunch of Mullard 12ax7s I had removed from an old Bogen receiver, and he replied,
"I appreciate the offer of the 12AX7’s, but I’ve laid-in a lifetime supply of my favorite 12AX7. For my ears and money, there’s no better 12AX7 out there today than the frame-grid JJ E83CC. That’s a really good tube."
I am not trying to convince you of anything, good or bad; I am probably among the least audiophile members on this board, but I just figured I’d offer you another perspective. It may be worth noting that he does not use 12ax7s in a preamp, but in a Prima Luna Prologue Eight CDP.
As far as 6SN7s go, knowing his high opinion of the JJ 12ax7, I once queried him about JJ 6sn7s and he told me that he had no experience with their octal tubes, but he had heard some people say that they were not bad and that for the price, why not check them out. Therefore I did put a quad in the phase buffer sockets, and to begin with I thought I did like them better than the EHs, but now I don’t know if there was much difference at all and maybe it was just wishful thinking on my part.
I will quickly share a story about some 6sn7s I bought on ebay. Among those vintage pairs of 6sn7s my friend turned me on to were a pair of RCA black glass VT231s. For several nights I had been trying out different pairs and I thought that some were pleasant sounding and that some were nice sounding . . . but the night I put those RCA VT231s in it was a serious "wow!" night. I found the detail to be mesmerizing . . . with more detail came better imaging and with better imaging the sound stage became more tangible. So going down the road a bit, I was drinking wine one night while I was surfing ebay, and I came upon some guy in France who was selling a sextet of those black glass RCA VT231s. I was like I cannot let these get away! I can’t remember whether I paid him five or six hundred, but where running six of those tubes didn’t sound bad, it wasn’t like six sounded incredibly better than two (I had been running the EHs for the other four at the time). And then, they started going cold on me one at a time. What I learned from that is that I will never buy used tubes on ebay again.
And good to read that we now have an answer as to what a "hybrid preamp" is. As an aside, the preamp I upgraded from with the SLP-05 was a "modded by Dennis Had himself" SLP-90. The SLP-90 and SLP-94 both used tube rectification . . . the two rectifier tubes were on the main preamp chassis (as opposed to in the power supply box) on those two preamps. The SLP-05 uses only one rectifier tube (it is a different type, a 5AR4) and on the ’05 they put it inside the power supply box.
Anyway, @billpete , let us know your impressions with that slp-98. I have a feeling you are going to like it.
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@billpete , I am happy to read that you are up and running. I've made mistakes similar to that before and it was always a relief to figure out it was just my own stupid owner/operator error and not a serious product defect or malfunction that was going to require a lot of shipping and waiting.
@harpo75 , thanks for all of that in your above post. I am going to pate it to a word document and print it and keep it with my owner's manual. Although after my first quick read, it does seem to make casual tube rolling prohibitive. BTW, are you still in the tech service business?
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@harpo75 , I am going to hijack my own thread a little bit, but I guess since it is mine (the thread, that is) it is okay.
Anyway, a couple of generalized questions about the SLP-05, when the power supply is turned to 'ON', as I understand it (from the owners manual) all that is doing is putting it in a mode where turning the preamp knob to 'ON' will activate the power supply, but nothing else? In other words, with just the power supply knob turned to 'ON', the only thing that is happening is that the blue LED light on the knob comes on, but if I am reading the manual correctly, nothing else?
And I am pretty sure, but I will ask anyway, that the meters on the power supply are indicating plate voltage and plate current of ONLY the rectifier tube?
Sorry, pretty simpleton questions, but I am a simpleton, and I just wanted to make sure that I was understanding this correctly.
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I didn't mean to hijack your thread but I guess I more or less did take it over. I should be more mindful in the future. Sorry.
@billpete , that comment was not directed at you or anyone else! If you took it that way, I sincerely apologize! It was just kind of an offhand joke since I started the thread out as a heads up for anyone looking for a SLP-98 and then here I am asking Harpo SLP-05 questions. Honestly, @billpete , threads evolve into other topics all the time here on A'gon, I have done it on many other threads by other people, and I honestly don't care what anybody types about on a thread that I have started. Again, if you interpreted that as a snark I was directing at you, I aplogize because I did not intend it as a snark towards anyone, except maybe myself. And after I post this reply, I am about to divert my thread some more!
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Am I explaining that well?
@harpo75 , yes you are, and thanks for getting back to me on this! And from what you have typed, there would be no advantage to keeping the knob on the power supply turned to ’on’? As a matter of fact, if anything, it could be a disadvantage because the transformer could be a potential part to fail?
Where the meters are useful is if you suddenly notice a higher current draw. This would mean there is a short somewhere. Start by changing the rectifier tube. If a new tube doesn’t correct the high current draw then you either have a 6SN7 tube shorting or a bad PS capacitor. If you pull out all the 6SN7 tubes and turn it on and it still drawing high current with a good rectifier tube then you know you have a shorted capacitor somewhere.
And thanks for that also, @harpo75 , you are a wealth of information for me on this preamp and I appreciate it. I think Cary could have provided this in the owner’s manual, but anyway, thanks again.
except for the balanced input position tubes. Because my DAC tends to be a bit lean for my taste I really like the Sylvania 6F8G tubes (which need to be used in an adapter).
Via the generosity of a kind benefactor, I actually now own several pairs of 6F8Gs and I am currently running a pair of National Unions in the balanced input slots, and I love them. The same generous individual also turned me on to numerous pairs of 6SN7s and VT231s, and my favorite pair of 6SN7s in the balanced input slots were a pair of ’52 Bad Boys. My friend called the Bad Boys "the Iron Fists" and the National Unions "The Velvet Gloves."
Anyway, with that trivia aside, can I trouble you with another question? But this one is about the Hexfred rectifier diode(s) on the V-12. About five years ago I had a coupling cap go out and on start-up the bias would instantly run away high on that side, and to make a long story short, the way I troubleshot it was that I took the bottom of the amp off and took comparison (left versus right) readings on everything I could find . . . and of course, one of the coupling caps (they were the gold colored Jensens) read way off, so I replaced all of them with Mundorfs. But this is a rectifier diode question, and to the best of my recollection (and my recollection may be flawed) I only found one diode under there. How many rectifier diodes are there on the V-12, and if I did the Hexfred upgrade (which I would like to do) is this a one for one swap?
Hey, thanks a lot for your help on these Cary questions, @harpo75 , I truly appreciate it!
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Oops: double post for some reason. Removed on edit.
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@billpete , please rest assured that you did not take over the thread, and even if you had, it wouldn't have been a problem as it was kind of an open ended thread (open to anyone who was looking for a SLP-98). Anyway, on A'gon threads often evolve into threads within threads and can be quite helpful and informative in that manner, and that is one of the tings I like about A'gon threads. Anyway, I didn't intend to insult you or anyone else, so if it's all good, I'm happy.
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It’s not that you’re drawing a lot of current tube wise. It’s the turn-on surge to charge the capacitors. The more capacitors, the bigger, the surge, and the more the rectifiers see a short initially at turn on.
Thanks, @harpo75 , and that would explain why that when I had a Cary DIY external power bank (four more large caps) hooked up I was frequently blowing fuses on start up.
The V12 amps should have four strings of three diodes totaling 12 diodes for the high voltage supply.
And thanks for that; now I will know what to look for. If I can find the part in question, I can usually change it.
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