[DDQ]

One week impression:

Stock tubes -quiet from moment of arrival
Swapped stock driver tube with NOS GE 6080 - still quiet. however I can't hear any improvement
Swapped stock signal tube with NOS RCA black plate, gray glass 6SN7GT - hummed (I have not given it any time to burn in just yet)
Swapped the black plate with a used RCA redbase, sjort glass 6SN7GT - quiet, noticeable improvement over stock tubes and stock signal and GE 6080 combo. (I'm happy with the set, at least until I hear something better)

 

[SonicDawg]

Quote:

Originally Posted by echo1 They hum when there new. I was told to make shure the tubes are seated all the way down and let it burn in for several hours and the hum would go away. It did go away. Also I found out that I like best leaving the back tube on a.c. voltage and using the power supply to just power the front tube with d.c. voltage.Powering both with D.C. made it to warm with loss of detail. Also sonicdawg I found a lot of tubes humed but leaving them in for several hours the hum went away. But some didnt.The d.c. voltage to the heaters fixed that.And the Ken rads just became my fav. tube. They sound real good with D.C.

How do you "burn in"? Do you mean with music on and phone connected or just leaving the amp on by itself? I would think that the hum will damage the connected headphones over a long period of time...

 

[swt61]

Quote:

Originally Posted by KevC Yay it's done and waiting for me in HKG. I just need to go pick it up... Has anyone tried GRADOs with this amp? I was always told that SS is slightly "faster" than tubes, but is less "smooth". However, I know you cannot just generalize tubes and SS amps just like that. GRADOs (say SR225) and Darkvoice sound good? Nice speed and impact?

I listened to an RS1 through mine, and it was quite nice. The Melos/RS1 combo rocks!

 

[swt61]

Quote:

Originally Posted by MrFaust I'm getting so anxious for my DV-336i. I can't wait to hear how my newly burned in RS-2's and my K701's sound through this amp. I just need to do some more reading on both of the Darkvoice threads to see which tubes echo suggested. Hopefully they won't cost too much. And once again, my wallet hates swt61 for bringing his 336 to the DFW meet.

The tube you heard at the Dallas meet was the Kenrad black glass 6SN7gt/vt231. I think I paid $45.00 from http://www.vacuumtubes.com/6sn7.html . The rear tube was a Sovtek 6AS7G from http://www.tubedepot.com/sovtek.html for $17.95

 

[SonicDawg]

I let the amp burn in through the night, and still it has a very audible hum with the stock tubes. Does anyone else knows what other causes can give hum in tube amp?

 

[Fitz]

Quote:

Originally Posted by swt61 Good work echo1, but when did Fitz become German?

I guess my family made a previously unknown side-trip to Germany on their way from Ireland to America.

Quote:

Originally Posted by echo1 I said I was done buying tubes, but I did anyway. Well here goes the story. I bought two identical hytron red label 6sn7gtb, and one humed and one didnt. Go figure. But when I put D.C. voltage on them both were quiet.If you guys can find a cheap used variable power supply or have one thats around its worth it considering that the price of a tube can be more than a power supply. All you need is 6.3 volts .6 amps to the front tube only. Bye all.

I've seen you on eBay lately for other tubes as well, your secret is out

. If only the Doc didn't keep showing up hovering over our auctions like bad news.


Quote:

Originally Posted by KevC awesome! thanks! i'm just worried about tubes taking away the classic grado "SPEED" and "IMPACT".

If anything, with the right combination, I feel there's more speed and impact on tubes. It takes away a lot of the grain and harshness from digital sources and lets the real music speed along unhampered. On what I've heard for SS the speed is usually accompanied by harshness and glare. Of course, with the wrong tubes for your tastes, it can just as easily be thick and syrupy. Depending on how I feel any given day, I like both ends of the spectrum

Quote:

Originally Posted by SonicDawg How do you "burn in"? Do you mean with music on and phone connected or just leaving the amp on by itself? I would think that the hum will damage the connected headphones over a long period of time...

Why would it damage them? It's no more harmful to the headphones than burning in with a bass test tone playing. I usually leave music playing when burning in an old tube that needs to be waken up, so the tubes aren't sitting idle, and always with some headphones connected.


Quote:

Originally Posted by swt61 The tube you heard at the Dallas meet was the Kenrad black glass 6SN7gt/vt231. I think I paid $45.00 from http://www.vacuumtubes.com/6sn7.html . The rear tube was a Sovtek 6AS7G from http://www.tubedepot.com/sovtek.html for $17.95

That's pretty much the only tube left that I'm interested in hearing that I haven't yet. I'm burning in a Sylvania 6SN7W metal base right now, to see if they're any good, given how much they usually go for. But I just can't seem to get a hold of a Ken-Rad for a price I like, since I always miss the boat on them.

Quote:

Originally Posted by SonicDawg I let the amp burn in through the night, and still it has a very audible hum with the stock tubes. Does anyone else knows what other causes can give hum in tube amp?

This is not good

Does it still do this with volume at minimum and nothing connected to the input at all? You may have a ground loop, but I'm wondering if the new PCB layout is more prone to hum, since it places components and wire paths slightly differently than before. Also try removing and snugly reinserting the tubes a couple times when you have it off and cool. If only you didn't live on the wrong side of the country, I could take a look at it

 

[SonicDawg]

I have switched from stock to some RCA tubes, and carefully inserted them, and all at no avail. And yes, the amp hums regardless of the volume I set at and with no input at all. I seriously doubt that all tubes are at fault, that it must be some flaw in the amp itself. I will continue to let it burn in for another night. But I would really hate to have to mail a brand new amp out for some issue that should have been addressed in quality control... I hope this doesn't end up to be the biggest disappointment in my hobby so far.

 

[SonicDawg]

Quote:

Originally Posted by Fitz If only you didn't live on the wrong side of the country, I could take a look at it

Thanks Fitz, I will take that as the last resort before mailing the whole package back to China..

btw, is there a simple way to check for ground loop?

 

[swt61]

Sonic Dawg, try using one of those cheap 3 prong - 2 prong adaptors. That might tell you if it's a ground loop. I'd also move it to another room and plug it in away from any other equipment.

 

[SonicDawg]

Quote:

Originally Posted by swt61 Sonic Dawg, try using one of those cheap 3 prong - 2 prong adaptors. That might tell you if it's a ground loop. I'd also move it to another room and plug it in away from any other equipment.

Do you mean for me to try plugging it in without ground? I will try to see if I can find one lying around somewhere, although I think this sounds very dangerous...

Btw, can I use a ground loop isolator kina thing? Will it kill SQ if I do?

 

[echo1]

A light bulb just went off in my head, by using the variable D.C. power supply on the front tube only I can use other variants of tubes without putting a series resistor into the heater curcuit. I think it sounds better keeping the back tube on A.C. anyway and just changing the front tube to D.C.
Ok off to ebay for some 12sn7 tubes. But............
Fitz please stop me if I am wrong.I will just watch a few auctions for now.

 

[Fitz]

Quote:

Originally Posted by echo1 Fitz please stop me if I am wrong.I will just watch a few auctions for now.

I just found it amusing that you were bidding on something, then I came in, then drarthurwells came in. It's as if Head-Fiers make up an unusual proportion of 6SN7 bids on eBay.

 

[echo1]

I was wrong. It sounds horrible!!!DC voltage causes a voltage reciprication that leads to total disentrigation of all voltage spikes causing power plant failure and a nuclear plant meltdown. Do not do this Mod!!!The feds will come looking for you!!!
Do not bid on 12sn7's on ebay!!!!

 

[heathkit]

Mine was packed exactly like the photos that Bosk posted. I probably took half an hour to unpack it. The amp really has the look and feel of a high-end component of at least twice the price.

OK folks, initial impressions are: This thing sounds almost too good to be true! I've had only about 25 -30 hours of burn-in so far and using stock tubes but, I've never heard my old K240's sound this good. And with a not-very-high-end source (PC and mp3's). Dead silent at any volume with foobar player paused. I really need to try it with my CD-63SE as a source, but I'd be happy for a while just re-listening to about 5000 or so songs on my PC!

Before I get into upgrading caps, resistors, etc. and rolling tubes, I really need a better set of cans. So far, from all I've read on Head-Fi and others such as HeadRoom, the AKG K701 might be my next 'phones. However the AT A900, Beyer DT-880, and Senn HD-595 are possible choices. I welcome any suggestions.

On order: Chaintech AV710 soundcard

 

[aznsensazian]

Quote:

Originally Posted by SonicDawg I have switched from stock to some RCA tubes, and carefully inserted them, and all at no avail. And yes, the amp hums regardless of the volume I set at and with no input at all. I seriously doubt that all tubes are at fault, that it must be some flaw in the amp itself. I will continue to let it burn in for another night. But I would really hate to have to mail a brand new amp out for some issue that should have been addressed in quality control... I hope this doesn't end up to be the biggest disappointment in my hobby so far.

Maybe some loose solder connection was broken off during shipment. Can you post some pictures of the internals?