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chris1973
PostPosted: June 28th, 2017, 4:16 pm 
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Posts: 270
Hi all,

I have a great Pacific Creek E34I MK2. ( Retail about $950 for the standard version, MK2 was a limited edition intended as sort of an executive product) It's a little bit nicer!

It's in perfect working condition. I recently have spent a lot of money on defective tubes, and I'm just a little fed up that the tube I like the sound of best comes from China, and I'm having a hard time getting a reliable set.

I want to go back to Solid State, but I'm a little bit spoiled now with the musicality of tubes.

I'm looking for low wattage (100W or under) super high quality sound that is "analog like". It has to be Hi Res and brilliant with a lot of subtle details!

MY CD PLAYER HAS A HIGH QUALITY PREAMP, SO I'M LOOKIN SPECIFICALLY FOR A POWER AMP!

It should be relatively new, and I would certainly consider something modest that has been modded by some of you who know what you are doing, or built from scratch altogether (as long as it looks pretty!)

The Pacific Creek like I said, is in stunning condition 9/10, and an all over very high quality piece of equipment. I'm looking for a direct trade. I would require an audition! That would give you a chance to evaluate my claims too.

Anyway, let me know if you think you are interested.

Thanks,

Chris


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SoundMods
PostPosted: June 28th, 2017, 7:51 pm 
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Location: Parkville, Maryland
I can do one of two things -- relieve your tube pain -or- if you're patient you can take possession of a Quad 405-2 that I will be modding once I gather the parts I need.

I would have been done with it much sooner but benched it to play with a Krell PAM-5 pre-amp that turned out better than expected -- much better.

Anyhow -- in stock form the 100-watt/channel Quad impressed me with its musical playback that actually got the "blat" in brass sections right. It has slam and a delicate tube-like nature.

My modification should improve on the deficiencies and leave the good stuff alone.

Your tube complement appears to be EL-34s with 6SN7s -- Yes? No? If your amp. has fixed bias on power tubes you may have it set for a higher bias current than what is needed for good sound and long-term reliability.

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chris1973
PostPosted: June 28th, 2017, 8:24 pm 
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Posts: 270
Hey, so with the new tubes, the lowest tube was around 435mv, so I tuned the rest to 440. I have had other tubes and I usually tuned to around 350mv or so. The amp sounds beautiful either way. I don't have any sense that the tubes are being over, or under driven in this range in any way based on listening. it's just that the new tubes are not keeping a stable bias current from one day to the next, and I'm getting frustrated with the process. It's really more of a mental problem, than a constructive complaint of what the amp sounds like. The amp sounds great!

I'm just a little bit superstitious, and it seems like a solid state amp would have a couple less things to worry about!

Can you send me a picture of the Quad. I have seen them on ebay, and I'm a little bit critical that they don't have a typical profile.
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SoundMods
PostPosted: June 28th, 2017, 9:57 pm 
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Should I presume that the 440-mv represents 44-ma cathode current? EL-34s have a sweet spot and that is 38-ma. Although 44-ma is not too aggressive not all EL-34s are created equal some can't tolerate heavy bias current . The best out there that not only sound good but are reliable are the JJs formally known as Tesla.

http://www.ebay.com/itm/NEW-Matched-Qua ... rkt%3D1%26

I've attached a picture of a Quad 405-2.


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Walt
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chris1973
PostPosted: June 29th, 2017, 7:13 pm 
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Posts: 270
Hey Walt,

I have been buying $60-$80 Psvane tubes, would the JJ's out perform these?

What I have found with the Psvane's is almost perfect sound in my system, but with kind of unreliability consisting of pops and crackles, and unstable bias current readings.

Do you know anything about the Blue JJ's (parts express)

I would like to keep the amp. I'm just getting frustrated with unstable tubes and the resulting paranoia of keeping the bias consistent by constantly checking and adjusting.

I want to be able to rely on my equipment, and not have to fuss around with it too much. I'm a speaker builder, so I don't have any problems being radical and breaking down or rebuilding a speaker, because I know how to do it, but I like the equipment in my rack to be the constant variable in my system!

Thanks,

Chris
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Cogito
PostPosted: June 29th, 2017, 7:24 pm 
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How often do adjust the bias and by how much?
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SoundMods
PostPosted: June 29th, 2017, 7:44 pm 
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Typically when you first install new tubes you make sure the bias isn't anything aggressive. Give the amp. about an hour to settle in then adjust the bias to the desired value. After maybe a couple of weeks of play time you might want to check it and adjust it if necessary. After that just enjoy -- most well-made power tubes are fairly stable. After about a year you can check it again -- or if you're anal about it check it more often. A lot depends on the ease with which you can do it. Some manufacturers bury the damn bias pots inside the chassis to force you to make a career out a simple bias setting. If the passive parts have good thermal characteristics and don't drift you should be fine based on what I've said.

I have not seen a schematic of your amplifier or even a user manual. Sometimes that information is on the WEB, but as it turns not in this case.

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SoundMods
PostPosted: June 29th, 2017, 7:53 pm 
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Hey Chris!

I have used JJs and a friend of mine have used JJs and they go the distance. My experience has been based on a 38-ma cathode current was good. They were open and muiscal. Since your concern is sound quality (that goes without saying) you might get away from those fat 6SN7s that have a reputation for micro-phonic issues and go with U.S. surplus tubes like Raytheon or Sylvania. Also the Russian EL-34s do a good job as well.

I find that PSVane is not consistent -- I've used PSVane 300Bs and they were reliable and had a musical yet transparent sound -- then I tried the PSVane 845s and in my opinion they were crap and I sent them back.

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Cogito
PostPosted: June 29th, 2017, 7:58 pm 
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SoundMods wrote:
Typically when you first install new tubes you make sure the bias isn't anything aggressive. Give the amp. about an hour to settle in then adjust the bias to the desired value. After maybe a couple of weeks of play time you might want to check it and adjust it if necessary. After that just enjoy -- most well-made power tubes are fairly stable. After about a year you can check it again -- or if you're anal about it check it more often. A lot depends on the ease with which you can do it. Some manufacturers bury the damn bias pots inside the chassis to force you to make a career out a simple bias setting. If the passive parts have good thermal characteristics and don't drift you should be fine based on what I've said.

I have not seen a schematic of your amplifier or even a user manual. Sometimes that information is on the WEB, but as it turns not in this case.


Right. After the burn in period of about 100hrs, I don't see a need to adjust again. I check about a couple of times a year, rarely adjust.
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