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Post by osostrings on Nov 29, 2006 10:20:58 GMT -7
I got a Route 66 in yesterday - awesome amp! Super rich and muscular midrange, huge but tight low-end, and silky smooth highs - I have missed this amp so badly since I unwisely traded it away a year ago.
Anyway, the NOS Mullard GZ34 that is was loaded with was dead on arrival so after I threw in a basic GT/Sovtek (I think), it's firing up fine. Which leads me to my first question(s): Are there any particular NOS 5AR4/GZ34 rectifiers that y'all recommend, and do I have to rebias the output tubes with every rectifier change?
Second, I found a Mullard 12AT7 in another amp that I forgot what tubes it was loaded with - I tried this in the phase inverter position and it was really weird. With the amp cranked but the guitar volume low, the tone was really spitty and farty, but when I turned the guitar back up it smoothed out to the familiar Rt66 tone but with added upper-midrange grind. It was a pretty cool sound, but I of course changed it back to the Ei 12AX7 the amp was loaded with so that my clean tones would function again. Second question: Any cool phase inverter ideas for this amp?
Thanks!
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Post by John on Nov 29, 2006 12:30:12 GMT -7
The only thing I can recomend is that you use a Matched Phase Inverter. (MPI) They cost a few dollars more, but the PI needs to be balanced.
You should contact KCA Tubes for suggestions for your rectifier tube. He can be contacted in the 'ask the experts' area of this forum.
As far as I know, you do not have to rebias when using a new rec tube. But better get the official word from someone who knows.
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Post by iggs on Nov 29, 2006 13:04:24 GMT -7
Yup ... e-mail Mike from KCA NOS and he will (most likely) suggest the same one he suggested I get, which is the JAN Phillips/Sylvania 5AR4 mislabelled as 5VG4. I got two of those from him and they made a HUGE difference in the sound and feel of my Route 66 when compared to the Sovtek 5AR4 and JJ GZ34. The price is definitelly worth the admission. The amp sounds tighter, quicker response and feel, much more "open" sounding.
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Post by matcaster on Nov 29, 2006 13:12:16 GMT -7
what is a Matched Phase Inverter ?
thanks
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Post by rcrecelius on Nov 29, 2006 13:27:59 GMT -7
what is a Matched Phase Inverter ? thanks Basically its a 12AX7(or whatever) that is balanced...both sides of the tube are equal...this is important for getting proper voltage(?) to the power tubes...it makes a huge difference in the sustain dept.
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Post by matcaster on Nov 29, 2006 14:21:56 GMT -7
is it the same in the Z-28 between the 2 preamp tubes ?
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Post by John on Nov 29, 2006 14:50:41 GMT -7
Maybe I can expand upon what rcrecelius has said....
A 12ax7 actually has two independent functioning units inside it. When this tube is used for the phase inverter, one side controls 1/2 of the signal going to one power tube, the other side of the phase inverter controls the signal going to the other power tube. These two 'sides' of a 12ax7 usually do not operate at the exact same levels...in a perfect world they're supposed to, but they don't.
If one side of the 12ax7 operates at a different level than the other, the result is one power tube will be getting a different level of power/signal than the other. This uneven power tube operation is not good and causes some problems, most notably, loss of sustain.
So... It's pretty important that both sides of this 12ax7 tube operate at the same level....they must 'match'...as in Matched Phase Inverter.
....and furthermore, now you may guess why you should have matched power tubes....for the same reason. When the phase inverter (even if it's a matched one) sends the signal to the power tubes, if the power tubes themselves are not matched, you will have the same problem of uneven power operation. (the power tubes are matched to all other power tubes in the amp...they are not matched to the phase inverter)
All amps that I know of have only one phase inverter, and it's usually the one closest to the power tubes.
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Post by matcaster on Nov 29, 2006 15:10:03 GMT -7
i learnt something today ? So is it the same with the 5751 in my z-28.....i have a couple of NOS ones, how do i know if they are balanced ?
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Post by rcrecelius on Nov 29, 2006 15:53:52 GMT -7
Thanks for taking that a step further gtrman...I knew what to say, I just didnt say it all Yes, the 5751 in your Z28 needs to be a matched tube as well...youd have to get someone to test it for you...or, just stick one in there and try it...if the amp sounds good and sustains well I'd go with it.
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Post by hipfan on Nov 29, 2006 16:12:34 GMT -7
I've used "matched" and non-matched tubes in the PI slot of various amps, and my experience is that tonal goodness does not necessarily flow with either configuration. There are a lot of other variables involved. Although I'm far from an expert on the topic, it seems that a "matched" or "balanced" PI tube actually functions more to preserve inherent imbalances in the PI circuit, rather than creating or preserving any kind of actual balance. Here's an interesting discussion of the topic, with commentary from several very knowledgeable folks: www.thegearpage.net/board/showthread.php?t=134825 . As far as choosing a phase inverter tube for your Route 66, I don't have one of those, so I don't have any specific recommendations. However, in general, I've had great success with Sovtek 12ax7LPS's, old RCA 12ax7's, and old Brimar ECC83's in various amps. I would advise getting a few different kinds of 12ax7/ECC83's, without regard to "matching" or not, and test them out methodically. I also generally prefer the tone of my amp with intentionally mis-matched power tubes, fwiw.
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Post by John on Nov 29, 2006 17:55:37 GMT -7
You can read about Matched Phase Inverters from someone who knows what they're talking about (Myles Rose) at the following string: www.guitaramplifierblueprinting.com/pastinfo.htmlYou have to page down a few times. What also seems to be the case (as reported by Myles Rose) is that if your amp is full of electronics (such as my three channel Marshall with Direct Out, two reverb settings, deep switches, three separate master volumes....etc.), then the signal is so squashed and processed that you probably won't notice the difference in matched tubes or a matched phase inverter. But the more simple the amp, such as Dr. Z's...you will.
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Post by hipfan on Nov 30, 2006 11:29:19 GMT -7
You can read about Matched Phase Inverters from someone who knows what they're talking about... Whoa! Didn't mean to soil anyone's morning Cheerios! Just offering a different perspective for the sake of the discussion. For the record, my experience is with relatively straight-forward amp circuits (DST U34, Dr. Z 6545, SRZ65, Maz38, Mojo Tone Machine, Traynor Bassmaster YBA-1, Cage Corsa), not complex channel switchers. All I was trying to point out is that there seems to be genuine disagreement on this topic between people "who know what they're talking about." There are more than one of those type of cats out there, you know. Myles certainly is a well-documented proponent of the matched phase inverter. Respected amp builders and techs such as Paul Cochrane, Roccaforte, John Phillips, Lord Valve seem to disagree in a well-supported way. The disagreement is very interesting to me and leaves me with no concrete conclusions, so I just go by my own experience. I don't take any of these guys' word necessarily as gospel (must be the agnostic in me), but my experience seems to be more in line with the "matched phase inverter is unnecessary" group. Gtrman3's experience apparently is more in-line with the other group. Cool with me. I'll keep working with my not necessarily-matched ones, and he can keep working with the matched ones. The original poster probably should try a couple of each in the PI position and see what he likes most. Can we agree that that is a decent idea, funds permitting?
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Post by iggs on Nov 30, 2006 11:40:18 GMT -7
I think the sound of the tube itself will have a major impact on the overall sound and feel of the amp more so then matched sides. I find a lot of people think that since the PI is not a part of the initial gain and tone shaping stage per se it will not impact the sound as much. I find it does very much so. Not "as much" as a pre-amp tube change but even in my limited tube changing experience I could hear the difference right away. Especially in a simple amp (and I do mean that in the best way possible) like Route 66 or my Bümbox Lead50. I do like getting the matched sides PI ... could be my obsessive-compulsive nature getting the best of me.
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Post by hipfan on Nov 30, 2006 11:45:08 GMT -7
I think the sound of the tube itself will have a major impact on the overall sound and feel of the amp more so then matched sides. I find a lot of people think that since the PI is not a part of the initial gain and tone shaping stage per se it will not impact the sound as much. I find it does very much so. Not "as much" as a pre-amp tube change but even in my limited tube changing experience I could hear the difference right away. Agreed completely! I've noticed that swapping the PI tube seems to make a difference in the tone and feel of every amp I've owned.
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Post by John on Nov 30, 2006 13:12:06 GMT -7
Sorry hipfan,
I re-read what I wrote and it sounded way too snotty...and that was not my intent.
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Post by hipfan on Nov 30, 2006 14:17:10 GMT -7
Sorry hipfan, I re-read what I wrote and it sounded way too snotty...and that was not my intent. No worries, man! Cheers!
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Post by taswegian on Nov 30, 2006 21:29:20 GMT -7
. Anyway, the NOS Mullard GZ34 that is was loaded with was dead on arrival That's kinda like finding a hen's tooth, a NOS Mullard GZ34 that has died. They are my recommendation. I have a steel based Mullard from 1954 in mine.
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Post by myles on Dec 6, 2006 19:26:30 GMT -7
I just posted a bit on rectifiers in the general forum and SRZ area.
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