Davec113 said:
Care to elaborate on this Dave? I've heard a couple rumors about a bad batch of JJ 5AR4's but those rumors also came from someone who was power cycling an amp with warmed up output tubes that were probably causing the tube to arc for reasons other than shoddy construction.
I've used a pair off an on for 6 months in a power supply that runs them pretty hard and provided that I don't try to hot-start the amp they've never been a problem.
Thanks, I'll do some searching.
I've only heard positive things about the TAD 5AR4 sold by AES and it's cheap enough at ~$20 a tube that I'll probably try it out in my SimpleSE during the testing phase. I have some other nice rectifiers to use once it's up and running.
One other rectifier related question - I haven't looked into it all that closely yet but has anyone else looked at using a 5U4 in the power supply? I know there are some applications where they are an acceptable substitute for each other but that it is not always the case. I think the 5U4 would result in lower Vout but that's all that comes to mind initially.
I've only heard positive things about the TAD 5AR4 sold by AES and it's cheap enough at ~$20 a tube that I'll probably try it out in my SimpleSE during the testing phase. I have some other nice rectifiers to use once it's up and running.
One other rectifier related question - I haven't looked into it all that closely yet but has anyone else looked at using a 5U4 in the power supply? I know there are some applications where they are an acceptable substitute for each other but that it is not always the case. I think the 5U4 would result in lower Vout but that's all that comes to mind initially.
I used a 5U4 for a short while. It works just fine, but I don't like how quickly it heats up. The rectifier is hot before the output tubes, and you get a relatively big surge on the supply caps. I prefer the 5AR4 with its nice, slow, gentle startup.
whitelabrat said:
Exactly. They just have a little better low end frequency response and should be fine for our audio use.
XSE: 70~18,000 Hz
GXSE: 40~18,000 Hz
All other specs are the same. They also have CXSE's rated for 25W with 20~20,000 Hz response. However, these are $50 more than GXSE's and probably overkill for the Simple SE circuit.
I bought a pair of the CXSE's for testing back when I was designing the Simple SE. I must admit that They tested out very good but I didn't really listen to them critically. Last year I got them out and connected them into a 300B amp. These have since become one of my favorite transformers. They sound really good. They are much larger than the XSE's and the GXSE's, about the size of the Hammond power transformer. If you have the space and the bucks, try them. If it were my amp, I would spring for the good transformers and start with lower cost output tubes. You can (and probably will) always upgrade the tubes but aren't likely to change the transformers. The transformers make the sound!
I have indeed tried a bunch of different tubes. The 5AR4 and the 5V4 both warm up slow which is good. The others will start up faster than the output tubes which can cause problems, though they are still slower than the solid state diodes. The 5R4 requires a fairly small filter cap to avoid sparking out. For these reasons the 5AR4 is the preferred choice.
There have been several reports of sporadic bad quality from the octal JJ tubes, especially the EL34 and the 5AR4. Some users love them and some have had them instantly blow up. I have been using JJ EL34's in one of my Simple SE's for about 3 years without any problems. I have received a few emails from users that had JJ 5AR4's spark out on initial power up. One user had two tubes blow instantly and thought something was wrong with the amp. A Chinese 5AR4 worked perfectly.
I have never bought tubes from him, but have never heard a bad thing from those who do. If he recommends a good Chinese 5AR4, try it.
Speaking of amateur radio, I am currently designing a monster transceiver for 902 MHz EME, about 600 watts. No tubes though
N1ESE said:
Well, shortly after I wrote this, I found some some audio curves on George's site of the CXSE's and now thinking of splurging on them.
Ty, sorry if I've hijacked your thread. Maybe I should start my own.
N1ESE said:
Well, shortly after I wrote this, I found some some audio curves on George's site of the CXSE's and now thinking of splurging on them.
Ty, sorry if I've hijacked your thread. Maybe I should start my own.
I highly recommend the CXSE's as I'm running them on my Simple SE (using EH KT88, per your other thread no less) and they sound incredibly good. The power of the bass is nothing short of impressive even with inefficient speakers.
The one critique of bigger transformers is that they sometimes drop at higher frequencies, but as someone with better HF hearing than average I can definitely say I notice no deficiency with a pair of older Telefunken speakers that have good HF response due to the tweeters (at least in comparison to anything I've heard to date).
I would spring for the best iron and upgrade tubes as you go - I'm glad I decided to use the bigger transformers.
George speaks on output transformers:
http://www.diyaudio.com/forums/showthread.php?postid=1113169#post1113169
Also be sure to follow the two links at the bottom of his post.
http://www.diyaudio.com/forums/showthread.php?postid=1113169#post1113169
Also be sure to follow the two links at the bottom of his post.
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