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Post by plexed on Oct 18, 2008 6:13:35 GMT -7
I was not quite sure if I can safely replace my Jan 5y3 with a JJ GZ34. I tried it and loved the sound, but do not want to hurt the amp, I can accept shorter tube life. I am running V1 GT12AX7 V2 JAN 5751 and JJ el84s. This is going into a avatar 16ohm 1x12 closed back cab with a V30. I should mention I use a THD 16 ohm hotplate as well.
The GZ34 seems to tighten up the sound, increase the low end, and increase the dynamic range of the amp. Any comments or experience if this is a safe move very much appreciated!
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Post by myles on Oct 20, 2008 13:22:06 GMT -7
I was not quite sure if I can safely replace my Jan 5y3 with a JJ GZ34. I tried it and loved the sound, but do not want to hurt the amp, I can accept shorter tube life. I am running V1 GT12AX7 V2 JAN 5751 and JJ el84s. This is going into a avatar 16ohm 1x12 closed back cab with a V30. I should mention I use a THD 16 ohm hotplate as well. The GZ34 seems to tighten up the sound, increase the low end, and increase the dynamic range of the amp. Any comments or experience if this is a safe move very much appreciated! There is no problem in using this rectifier at all. You will have more headroom, more wattage and the amp will be tighter and faster. Tube wear will be a bit faster, about the same as the life in a MAZ Jr. which is normal for EL84 cathode biased amps. Happy playing.
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Post by plexed on Oct 24, 2008 7:15:26 GMT -7
Thanks Myles!
This is good news, as I really liked the sound of the GZ34 but removed it for fear that I was pushing the envelope on the head too much. I agree the amp has more headroom, tighter and faster response. Since I am more of a rock player then a bluesman - I appreciate the GZ.
I am very pleased with the Ghia. I just switched the head from my Avatar 1x12 to an Avatar 2x12 openback - the sound really took off. I can't say enough good things about these amps!
Much appreciation to all the good folks here on the forum. I am looking into either the SRZ-65 or the GT in the future.
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Post by myles on Oct 27, 2008 10:45:20 GMT -7
Thanks Myles! This is good news, as I really liked the sound of the GZ34 but removed it for fear that I was pushing the envelope on the head too much. I agree the amp has more headroom, tighter and faster response. Since I am more of a rock player then a bluesman - I appreciate the GZ. I am very pleased with the Ghia. I just switched the head from my Avatar 1x12 to an Avatar 2x12 openback - the sound really took off. I can't say enough good things about these amps! Much appreciation to all the good folks here on the forum. I am looking into either the SRZ-65 or the GT in the future. Happy playing and no worries .... a GZ34/5AR4 works great and has no adverse side effects.
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Post by tookermel on Oct 28, 2008 7:10:28 GMT -7
According to you, Myles (whether scientifically, or first-hand experience)......between the JJ GZ34 and a NOS Philips/Sylvania mislabeled 5AR4, which should give the most headroom?
Thanks! -Tookermel
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Post by myles on Oct 28, 2008 9:19:42 GMT -7
According to you, Myles (whether scientifically, or first-hand experience)......between the JJ GZ34 and a NOS Philips/Sylvania mislabeled 5AR4, which should give the most headroom? Thanks! -Tookermel If they are both at design spec there probably will be no difference at all. They are the same rectifier.
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Post by tookermel on Oct 28, 2008 13:13:10 GMT -7
Oh, ok.....makes sense. Thanks a lot! I thought I had read before there was a difference, but there's so many variables. I'll take your word for it! I have both, and tried to A/B 'em, but that's REALLY hard to do - near impossible since you have about a minute of down time swapping 'em. I thought my ears were telling me the JJ had more bass, and was a little more loose in the bass, and a voicing or EQ difference might make sense, but I couldn't notice a difference in headroom.
-Tookermel
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Post by myles on Oct 28, 2008 14:20:42 GMT -7
Oh, ok.....makes sense. Thanks a lot! I thought I had read before there was a difference, but there's so many variables. I'll take your word for it! I have both, and tried to A/B 'em, but that's REALLY hard to do - near impossible since you have about a minute of down time swapping 'em. I thought my ears were telling me the JJ had more bass, and was a little more loose in the bass, and a voicing or EQ difference might make sense, but I couldn't notice a difference in headroom. -Tookermel Just like two different 12AX7s even from the same vendor you will find differences. A 5AR4 is a GZ34 ... one label is a USA designation and the other Europe. They are the same item.
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Post by tookermel on Oct 29, 2008 6:08:43 GMT -7
Gotcha.....so, probably the biggest variable is consistency in design specs for within different brands and types. For example, if one were to more properly compare or A/B two rectifier tubes from two different brands, you should get about 10 of each brand, maybe find an average in specs within that brand, then compare the averages between the two brands, since even within brands the specs can vary (obviously the NOS tubes will/should be more consistent). My little comparison really doesn't make a whole lotta sense.
Main thing.......just play! Lol...
-Tookermel
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Post by myles on Oct 29, 2008 10:01:36 GMT -7
Gotcha.....so, probably the biggest variable is consistency in design specs for within different brands and types. For example, if one were to more properly compare or A/B two rectifier tubes from two different brands, you should get about 10 of each brand, maybe find an average in specs within that brand, then compare the averages between the two brands, since even within brands the specs can vary (obviously the NOS tubes will/should be more consistent). My little comparison really doesn't make a whole lotta sense. Main thing.......just play! Lol... -Tookermel Rectifers are no different than preamp tubes or output tubes ... they vary widely. Here is a little piece I wrote in response to a fellow comparing two different 12AX7 tubes but it applies to rectifiers as well. As a side note, there was a batch of Sovtek 5Y3 rectifiers about a year ago that had higher output than a spec 5AR4 and this would have been a big problem in amps designed for 5Y3 voltages. This is a question I received over at Guitar Player and I thought it might be of interest to some here .... Hi Myles! Newbie alert! I have recently purchased a Rivera K-Tre 55-watt combo purely on the basis of the spectacular clean channel. When I got the amp home, I discovered it actually had a dirty channel too -- one for which I hold no particular love. I've tried a number of things with greater or lesser success: - I returned the combo to a near-original tube setup (12AX7WBs across the board), and the clean was great, but the dirt was staccato as opposed to smooth -I replaced the tubes with 12AX7EHs across the board, and the whole thing went dark -I put back the 12AX7WBs and added a 12AX7EH in position 1. It all got better, but I still find it a bit staccato-sounding For what it's worth, my other rig is driven by a JMP-1 in which the dirty preamp is run through a 12AX7LPS. It is by far (to my ears) the smoothest gain/overdrive I've heard so far, and is more or less the quality I'm going for in the drive side of the Rivera. Alas, the LPS does not do particularly well in combos. I'm about to order another raft of tubes (probably just in pairs for position 1 and 2) and I'm looking for advice. I'm considering Tung-Sols, JJs, and in an interesting twist, 5751s. Anything else I might like to try? Joe Joe, The biggest problem in swapping preamp tubes is one does not know what an off the shelf preamp tube is doing. Trying to compare a 12AX7EH to a 12AX7WB will yield untrue results if the WB is close to design spec and the EH is not close. You need to compare tubes that have their specs close .... transconductance, true gain, plate resistance and current output. You said that the EHs made the amp dark and this tells me you had some weak ones as the EH is brighter and more articulate than a WB. A recent test of a lot of EH's showed this: 1.0 1160 0.014 82.9 1.1 1430 0.016 89.4 1.1 1510 0.017 88.8 1.3 1610 0.018 89.4 0.8 1260 0.014 90.0 0.8 1120 0.013 86.2 1.3 1580 0.0165 95.8 1.3 1560 0.0165 94.5 1.1 1540 0.017 90.6 1.1 1540 0.017 90.6 0.8 1310 0.015 87.3 1.2 1570 0.0165 95.2 1.3 1540 0.017 90.6 0.9 1370 0.015 91.3 1.1 1470 0.017 86.5 1.2 1590 0.017 93.5 0.6 1160 0.014 82.9 0.8 1280 0.014 91.4 1.0 1430 0.0155 92.3 1.4 1670 0.018 92.8 0.8 1200 0.014 85.7 0.9 1290 0.014 92.1 1.1 1480 0.0165 89.7 1.2 1490 0.016 93.1 0.8 1340 0.015 89.3 1.0 1540 0.0165 93.3 1.0 1370 0.015 91.3 1.3 1620 0.018 90.0 0.8 1300 0.0145 89.7 0.6 1170 0.013 90.0 1.0 1500 0.017 88.2 0.9 1370 0.0155 88.4 Output TC Gain 1.0 1418 90.09 84.9% 88.6% 90.1% 1610 100.6% 1120 70.0% 30.6% 1.4 116.7% 0.6 50.0% 66.7% 95.8 95.8% 82.9 82.9% 12.9% This might not make a lot of sense but the important factor here is that these vary 66.7% in regard to spec current and the average tube is down 15% from spec and that is like turning a 50 watt amp into a 30 watter depending on position in the circuit. Transconductance has a 30% spread and this is not good either. You need to be able to compare apples to apples as today's production preamp tubes are a crap shoot and the odds are NOT in your favor.
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