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Post by bassnomo on Jul 26, 2010 11:43:23 GMT -7
So..... After much searching and incomplete answers, I would like to put this subject to sleep for me and I bet lots of Galaxie lovers out there...Are the main and extension speaker jacks wired in parallel or ? If so, is it ok to plug a 4 ohm cab into either the Main or Extension jacks, or are these jacks wired to separate transformer outputs, requiring an 8 ohm load to be plugged into each output? The majority of my cabs are 4 ohm, and I do not want to re-wire cabs unless necessary. A Manual would answer a lot of these questions.(Hint Hint). BNM
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Post by doctorice on Jul 26, 2010 13:45:49 GMT -7
In a PM Steve (bent top) confirmed that the jacks are in parallel. The output tranny is only tapped for 8 ohms. Steve also mentioned that DR Z indicated that the tranny is robust enough to handle a 4 ohm load. No doubt/disrespect to Steve, but an email to Brent in Z sales is probably wise.
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Post by T-R☼CK ♫ on Jul 26, 2010 15:06:56 GMT -7
Brent told me some years ago, that Gary Hooker(Brad Paisley) uses a 4ohm cab w/his regularly.
FWIW.....
The jacks are independent. No math required.
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Post by Martin60 on Jul 26, 2010 16:19:10 GMT -7
Just to be clear, i can hook up my Two Rock 2x12" 4ohm cab to my Galaxie? Because i would love to hear it with 12" speakers!
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Post by T-R☼CK ♫ on Jul 26, 2010 18:18:55 GMT -7
Just to be clear, i can hook up my Two Rock 2x12" 4ohm cab to my Galaxie? Because i would love to hear it with 12" speakers! yup.........
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Post by jimmysmith on Jul 27, 2010 17:21:10 GMT -7
thanks t rock for answering this question,, actually i decided against getting a galaxie (used) because i did not think you could use a 4 ohm cab,, but now i will try to find a used one,,
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Post by doctorice on Jul 28, 2010 6:28:34 GMT -7
thanks t rock for answering this question,, actually i decided against getting a galaxie (used) because i did not think you could use a 4 ohm cab,, but now i will try to find a used one,, Hope you find one. Great amp.
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Post by asmith9509 on Jul 28, 2010 7:46:34 GMT -7
So just to be clear- the two jacks are tied to two separate 8 ohm secondary taps on the output transformer?
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Post by Deleted on Jul 28, 2010 11:31:25 GMT -7
YEP!
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Post by doctorice on Jul 28, 2010 12:25:25 GMT -7
OK, here's what Steve (benttop) wrote me on this topic. I interpret this as one tap, not two.
Re: Galaxie « Message sent on Jul 18, 2010, 10:16am »
Yeah, it has come up multiple times. Dr. Z says that the output transformer has one 8 ohm output. The extension jack is wired in parallel with the output jack, so technically you should try to maintain an 8 ohm load there, but he also says the transformer is stout and will tolerate a 4 ohm load all day. So how do you put all of that in a table? I decided to leave it. I suppose I could put an asterisk there and indicate there is a parallel wired extension speaker jack....
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Post by bassnomo on Jul 28, 2010 17:26:40 GMT -7
Let's keep at it lads, looks like we are getting close to the bottom of this thing!I am feeling emboldened to use my two favorite cabs, a 4-ohm Zbest w/greenies and Harvey-converted 2xBlue open back with what is becoming one of my favorite Z amps. If it just had that master volume mod....reverb....BNM
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Post by asmith9509 on Jul 31, 2010 7:09:02 GMT -7
Ah... parallel wired jacks. In my experience building tube amps, it's not that big a deal to have a halving of impedance, I.e. using a 4 ohm cab with an 8 ohm tap. This is also working in the "safe" direction; more stress on the OT using a 16 ohm cab on an 8 ohm tap. Although relatively safe, it will probably sound different. A 4 ohm cab will probably sound a little looser/flabbier because the damping factor is cut in half. Could be good or bad; let us know how you like it.
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Post by mitch8686 on Aug 1, 2010 13:27:58 GMT -7
Man! Just when I thought I had the speaker jack situation figured out........ Guess not. Ok, so here's my question...... Can I put a 4ohm load into the main jack and an 8 ohm load into the extension jack? Right now, my 2-12 is wired up for 16ohms but if I can get away with running it at 4 ohms, I'd much rather do that. Mainly just in case one of the 12's happens to blow. Anyway, is this an acceptable combination? Thanks.
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Post by doctorice on Aug 1, 2010 15:59:44 GMT -7
Man! Just when I thought I had the speaker jack situation figured out........ Guess not. Ok, so here's my question...... Can I put a 4ohm load into the main jack and an 8 ohm load into the extension jack? Right now, my 2-12 is wired up for 16ohms but if I can get away with running it at 4 ohms, I'd much rather do that. Mainly just in case one of the 12's happens to blow. Anyway, is this an acceptable combination? Thanks. I believe if you an 8 and 4 in parallel the combined load is under 3 ohms, so probably not a good idea. If you put the 8 and 16 in parallel it's a bit over 5 ohms, which seems OK. Can someone double check my math just to be sure?
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Post by mitch8686 on Aug 1, 2010 19:29:55 GMT -7
The 16ohms + 8 ohms is the way I've been running it..... I emailed Doc about it awhile back and he said it was just fine to do so. IIRC, he also said something to the effect that the speaker jacks were independent of each other. In other words, that one didn't care how the other one was loaded. I took that to mean any combination was fine as long as the impedance was at or above 8 ohms for each tap. Of course, I didn't ask about 4 ohms or any combination that had a 4 ohm load. So, as you can see, I'm more confused now than I was before I read this thread :-)
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Post by doctorice on Aug 2, 2010 4:52:48 GMT -7
The 16ohms + 8 ohms is the way I've been running it..... I emailed Doc about it awhile back and he said it was just fine to do so. :-) I'll take that as confirmation. ;D
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Post by bassnomo on Aug 2, 2010 20:47:32 GMT -7
Here is a little more fuel for this fire, from Don Depew in customer service, a reply to my email about the MV mod and our present question: Dwight , Ok the master vol. mod is $150 - PayPal works best but we can take a check also I've attached an RA form - your number would be 080210D1 our address is DR Z Amps 17011 Broadway Maple Hts Ohio 44137 you can take the chassis out just make sure to pull the tubes and wrap them - make sure you do a good pcking job . As far as the Galaxie outs 4ohms is a nono - they can both run at the same time but both need 8ohms .Let me know if there's anything else ok ? Thanks, Don Depew
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Post by mitch8686 on Aug 2, 2010 21:45:09 GMT -7
Lol! .......and the conversation runs full-circle :-) I think I'll just keep my cabs wired the way they are, they sound just fine as-is.
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Post by asmith9509 on Aug 3, 2010 8:33:50 GMT -7
Next time I pull the chassis I need to have a look. I vaguely recall the jacks being wired in parallel, which would make some of the information above incorrect. If they are parallel, they would be dependent on one another. The equation for parallel resistance is: 1/equiv. R = 1/R1 + 1/R2...
So in the example above, a parallel 8 ohm and 4 ohm load has an equivalent impedance of 2.67 ohms; this would be bad.
A parallel 16 ohm and 8 ohm load would have an equivalent impedance of 5.33 ohms; this is probably OK.
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Post by bassnomo on Aug 3, 2010 9:27:31 GMT -7
I will be pulling the chassis for the mv mod,I will post my findings unless someone beats me to it..
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Post by gtrnstuff on Aug 16, 2010 17:34:25 GMT -7
My Galaxie has speaker jacks in parallel. One has red wire to NFB pot, red wire to the other one, which has red w/white lettering going to the OT. I accidentally ran it into 4 ohms for an hour or so once. No issue.
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Post by bassnomo on Aug 16, 2010 20:54:57 GMT -7
Well, I pulled the chassis to send off to the master volume school, and as gtrnstuff stated above, the jacks appear to be wired in parallel, though i cannot see where the wires enter the tran, so it is unclear if there be 2 taps on it... a schematic would go a long way in the right direction...
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Post by bassnomo on Aug 18, 2010 11:28:23 GMT -7
Here is further clarification from Don Depew:OK the Galaxie outputs - there is just a single 8 ohm tap on the transformer wired to a pair of jacks in parallel - the output section needs to see 8 ohms - so , (1) 8 ohm load or (2) 16 ohm loads would be acceptable but (2) 8 ohm loads would produce 4 ohms total so is probably not a good idea . Does this make sense ? I realize that the way it's labeled is confusing.....So, 1 ot tap, requiring 8 ohms total load for safety. I am going to get an impedance matcher as I have multiple 4 ohm cabs, and love to tinker with head/cab combinations. Thanks to all for the input. BNM
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Post by mitch8686 on Aug 20, 2010 13:57:10 GMT -7
Man, I swear that when I emailed the Doc, he told me that running an 8ohm load into one and a 16 into the other would be just fine. I'm not trying to dispute what Don said, but it seems to contradict what Dr. Z told me. I've also been told that 8ohms into each tap was fine, too. But apparently it's not..... Oh well.
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Post by Jan on Aug 20, 2010 15:36:43 GMT -7
From Mike, three years ago this week in this very forum: ubertone asked, Anyone know what ohm the extension cabinet for the galaxie needs to be if an 8ohm cabinet is already on it? I am guessing 8 ohms for a 4 ohm total load but I am not sure.Mike replied, Just use another 8 ohm cab plugged into the Extension Jack.See the thread here. He has hinted before about how studly the transformers are specd. The spec is 8 ohms. I doubt anything between 4 and 16 ohms is a problem.
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Post by bassnomo on Aug 20, 2010 17:58:00 GMT -7
Thanks for the research Jan, doesn't get any clearer than that. Could have saved everyone a lot of syllables if the search function had turned this up before my initial query. My concern was blowing an ot mid-gig, and the resulting difficulties. I am going to rock it, if she blows, she blows...
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