bobro
New Member
Posts: 35
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Post by bobro on Sept 18, 2023 13:54:25 GMT -7
I have a 2015 version of the Z-Lux that came without a fan. I have been running 5881 power tubes in the amp from April 2022 until today, Sep 18, 2023. These tubes were running really hot. I had to put some computer fans on the outside of the grill on the back of the amp to dissipate the heat. I have been playing shows with the Z-Lux and was a little concerned about reliability and also the longevity of these tubes. The fans operate off of a USB connector, which is plugged in to a 3 port USB power supply that's sketchy on at least one of the ports, causing the fan to work intermittently.
So, today, I took the 5881s out and put the original 6V6s back. The amp now runs with an expected and manageable level of heat emanating from the tubes. I'm happy about that, but I think the amp sounds better with the 5881s.
5881s - less low end, seems slightly compressed and sounds warmer. More manageable EQ. Overdrive from turning up the Volume to about 12 and up sounds better. Pedals work better with these tubes. I personally think it breaks up quicker than the 6v6s and has an awesome slight growl to it. To my ears, these tubes make the amp sound better.
6V6's - lots of bass end, bloomy, bold sound, more dynamic, don't run as hot, so I'm guessing the amp and the tubes will last longer? More headroom in my opinion, although both have lots of headroom. Seems like the amp has more volume. The amp doesn't need pedals in front of it with 6V6s. And it doesn't seem to get along with them as well. I used to think the quality of components inside of the amp exceeded the quality of components inside of the pedals, and that's why the pedals didn't sound as good - because they were detracting from the sound the amp was outputting by having cheap components in the signal. But now I'm starting to wonder if it's because of the big bass response that the 6v6s are outputting.
Does anyone have any insights? Does what I've said make sense?
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Post by scottunzicker on Sept 18, 2023 14:03:17 GMT -7
Which 5881s and 6V6s are you running?
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Post by nmz on Sept 18, 2023 14:46:27 GMT -7
I going to try the 5881’s with my next tube swap. But from the beginning I remember Doc saying it runs hot (they did end up adding a fan) and that was with the 6v6. Mine has the fan and I haven’t experienced short lived tubes. Others run 5881’s and should chime in soon.
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Post by Chilly Gibbons (Todd T.) on Sept 18, 2023 15:03:07 GMT -7
I’m sticking with JJ 6V6s. Love the power, almost like a 6L6.
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Post by Ed M. on Sept 18, 2023 15:43:55 GMT -7
I prefer the jj 6v6 in mine also, although it's been a few years since I had the 5881 in there so I don't remember the exact sonic differences
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bobro
New Member
Posts: 35
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Post by bobro on Sept 19, 2023 8:08:09 GMT -7
Which 5881s and 6V6s are you running? Scott, Man... You were right on with your description about the 5881s as you stated here - ztalk.proboards.com/thread/75581/5881-impressions.. I got the same impression about the tightness of the bass. It's almost compressed in comparison to the loose bass response in the 6V6s. It's a warmer sound with the 5881s, and the grit/grind from these tubes is so nice. The boost channel sounds better to me with the 5881s. I've already decided to swap back to the 5881s and fortunately, I have a new quartet of them I bought when I was paranoid about the supply chain that I came across today. As I said before, I'm using the Tong Sol (mediums). I guess I'll put up with a little heat dissipating out of the back of the amp. And yes, they are louder than the 6V6s. I keep editing to add to my observations. I've deleted a couple of posts to consolidate the information. This new set of 5881s is running much cooler than the previous set, and it has more breakup. Thanks for your input. If I remember correctly, I read your thread and then got the 5881s.
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Post by frankie on Sept 19, 2023 8:53:13 GMT -7
Which 5881s and 6V6s are you running? Scott, Man... You were right on with your description about the 5881s as you stated here - ztalk.proboards.com/thread/75581/5881-impressions.. I got the same impression about the tightness of the bass. It's almost compressed in comparison to the loose bass response in the 6V6s. It's a warmer sound with the 5881s, and the grit/grind from these tubes is so nice. The boost channel sounds better to me with the 5881s. I've already decided to swap back to the 5881s and fortunately, I have a new quartet of them I bought when I was paranoid about the supply chain that I came across today. As I said before, I'm using the Tong Sol (mediums). I guess I'll put up with a little heat dissipating out of the back of the amp. And yes, they are louder than the 6V6s. Thanks for your input. If I remember correctly, I read your thread and then got the 5881s. Don in repairs has taken a couple Z-Luxes that people have insisted on running 5881s in and optimized them to do so. There are also a few other tricks available for this amp, a "MK II" reworking if you will. Given yours is a 2015, it would be in the range where there could be some adjustments and improvements to the circuit. I'm sure some folks will chime in to give a report on the update.
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Post by Don A on Sept 19, 2023 9:14:31 GMT -7
The Z-Lux is a cathode biased amp? Does the cathode resistor need to be changed when replacing the 6V6s with 5881s so that the bias is correct? I know that's the case with the Cure.
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Post by nmz on Sept 19, 2023 11:45:36 GMT -7
Yes, MKII is awesome
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Post by Stephen on Sept 19, 2023 15:08:13 GMT -7
I have an early Z-Lux too. Mine came with a fan. I had the MKII update last year. It is definitely an improvement.
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Post by Chilly Gibbons (Todd T.) on Sept 19, 2023 16:23:41 GMT -7
Yep. MKII rules.
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bobro
New Member
Posts: 35
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Post by bobro on Sept 20, 2023 8:41:56 GMT -7
The Z-Lux is a cathode biased amp? Does the cathode resistor need to be changed when replacing the 6V6s with 5881s so that the bias is correct? I know that's the case with the Cure. I can't answer this. Sorry. I know that Dr Z said that he just swapped out the tubes. I didn't hear anything about biasing. Also, there was a drastic difference in how hot these 5881s were burning. The first set was very hot, but the fans kept it under control. This second set is rated lower and isn't getting very hot, probably about the same as the 6V6s, so that's a nice surprise. The JTM45, the Dirty Shirley, the Twin Sister, and several Dr Z amps use 5881s.
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Post by frankie on Sept 20, 2023 9:24:19 GMT -7
The Z-Lux is a cathode biased amp? Does the cathode resistor need to be changed when replacing the 6V6s with 5881s so that the bias is correct? I know that's the case with the Cure. It is. 5881s will run in it safely, but not optimally. That's part of the refinement Don will do for people who want to run 5881s permanently in their amps.
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