[compuryan]

When turning on my Cayin HA-1A even if the volume is turned down, it emits a loud buzzings through the left channel. (It might be the right too, its just so loud whenever it happens I instinctively turn off the amp immediately or unplug my headphones). I mess with it for a few seconds by turning it off and unplugging/replugging my headphones and everything is fine. I listen to music for hours. But I come back later and it buzzes, but after turning it off, unplugging/replugging a few times its perfectly fine.

Any ideas? Thanks all.

 

[Happy Camper]

Ryan,
Did this start with your new tube? Go back to your last tube and see if it goes away.

 

[compuryan]

Quote:

Originally Posted by Happy Camper /img/forum/go_quote.gif Ryan, Did this start with your new tube? Go back to your last tube and see if it goes away.

I am pretty sure thats not it because it was perfectly fine for over a month since I had installed that tube. Nonetheless, I will have to check to see if swapping tubes makes a difference.

 

[compuryan]

hey, great news! after pulling out both JJ EL84 tubes and replacing them with the stock Electro-Harmonix EL84s, there were no problems at all. Upon close inspection of the JJ tubes, I found that several of the metal pieces leading from the pins to the inner workings of the tube appeared to be burned and separated. I am puzzled how it happened, but I am just glad it wasn't something more serious.

 

[Tridacnid]

New production tube?

 

[compuryan]

Yeah I'm not sure, it makes me not want to buy any more JJ tubes. I was thinking about the reissue Mullard EL84, what do you think?

Mullard EL84 / 6BQ5 New Production

 

[Golden Monkey]

I'd avoid any of the reissues if at all possible. You can find really good NOS tubes, even less "glamorous" ones like Tungsram or Brimar, or relabelled ones at great prices if you know what to look for...it takes some learning, but reseach the type of tube you need and have at it. Here's some good info (prices are high, but you'll find some options) https://www.tubeworld.com/6bq5.htm

Oh, and Tube Depot has some really insane pricing on anything other than reissues...good for info, bad for your wallet.

 

[Ferbose]

I have rolled a lot of tubes with Cayin HA-1A, and still trying new tubes.
My latest experiment is to use European old 12AY7 and old GE 6829 for the 12AX7 position. Just got them from Ebay.
For the EL84 position, before you spend big bucks for NOS, try the Russian military NOS 6P14P-EV. In my experience genuine, matched NOS European and American EL84 are expensive, especially the good ones. I tried a pair of old American tubes but the Russian military tubes are better. 6P14P-EV has low noise and strong sound, better than modern tubes (EH, Sovtek, JJ).
You can find Russian tubes on EBAY (see below). Head-fier Jon L has tried many EL84 NOS tubes and he recommended to me Russian tubes.

6P14P-EV are still very affordable on Ebay:

6P14P-EV
6P14PEV

 

[ppl]

I have an Old 1950's era Stereo radio phonograph Console that used a pair of 12AX7's driving a couple of pair of EL-84's. I liked the 5751 a lot better than the 12AX7 the radio still had the original Bimar Tubes installed in it when i re tubed the Unit and i used all NOS of assorted American manufactures. IIRC the 5751 was an RCA and the EL84's were for sure NEC as i still have some of them Left over I get my Tubes from Antique radio Supply, they have great prices and i have always got good tubes from them.

 

[compuryan]

The 6P14P-EV has me curious. I think I might just have to go for it. That set of four on ebay would give me some extras if a pair dies on me. I really don't have plans of upgrading my other tubes right now. I'm using an RCA cleartop 12AU7 tube and a Sovtek 12AX7LPS and I am pretty happy with both of them.

 

[Ferbose]

Quote:

Originally Posted by compuryan /img/forum/go_quote.gif The 6P14P-EV has me curious. I think I might just have to go for it. That set of four on ebay would give me some extras if a pair dies on me. I really don't have plans of upgrading my other tubes right now. I'm using an RCA cleartop 12AU7 tube and a Sovtek 12AX7LPS and I am pretty happy with both of them.

I have Sovtek 12AX7LPS (a really good tube by any standard), but I really like any 5751 (Gain=70) at that position better than a whole bunch of 12AX7 (Gain=100) I have tried. I really think Cayin likes low-noise tubes, and it is even better to use low-gain low-noise tubes. You can get good NOS Philips 5751 from Tube Depot. That's what I am using and I got paid a $4 more for hand-selected low-noise tubes. For 12AU7 (Gain=20), Ray Samuels suggests everyone to try 12BH7 (Gain=16.5). And I have to say Ray is right, NOS American 12BH7 I have tried worked better than NOS American 12AU7. I have been using 5751 and 12BH7 for a year and folks at So-Calmeet thinks my HA-1A is better than other units they have heard. My latest experiment is to use 12AY7 (Gain=47) for the 12AX7 position, just got some from Ebay.

 

[Ferbose]

To continue my trial for tone modifications using lower-gain tubes, I tested 6 old production 12AT7 tubes from Ebay. The are probably used but test from good to strong, with 2 RCAs in original box. Not surprisingly, I like 12AT7 (gain =60) in general over 5751 (gain=70) in the 12AX7 (gain=100) position .

1 Telefunken (made in Germany): very good presence in midrange and bass, but a bit thin in the treble
2. Mullard (made in Britain): sweet midrange, but a bit subdued in the treble
3. RCA 12AZ7 (1955 made in USA): very low noise, very balanced across all frequencies, good resolution. My second favorite of the bunch.
4. RCA12AZA (1960 made in USA): warm and powerful sound, treble is a bit subdued, very similar sound to Philips ECG JAN 5751
5. Another Telefunken, high noise in the right channel.
6. Ameperex Bugle Boy, smeared branding. This one is the best. The tube has a flap foil attached to its "D" getter, a very distinct feature that allowed me to Google its origin back to Holland in the 50s and 60s.

To date, I have tried 19 different tubes in the 12AX7 position. Overall, best results are achieved with tubes of lower gain factors. As for individual tubes, everyone of them sounds different. Those that sound sweet in the midrange or strong have thin or subdued in the treble. Those sound super-detailed overemphasize the treble. So in my experience, unusually sweet sound, strong bass and surprising details all come at the price of some spectrum unbalance. Depending on the music and listening preferences, the trade-off can be good. But I want the faithful reproduction of acoustic violins, so I prefer more neutral presentations.
I also use sensitive headphones to evaluate the noise level, and in general low noise tubes give better clarity and resolution. In the end I prefer low-noise tubes with are even across different frequencies, the neutral, clean-sounding tubes at all positions in Cayin HA-1A.
The only surprise came with the Amperex 12AT7. At first it seems that it could enhance the ambiance, the spatial resolution, the warmth, and the clarity simultaneously. Yet it's noise level is not especially low still behaves balanced across different frequencies. I have tried thirty 12A*7 compatible tubes in the Cayin, and this is the only tube that gives surprising results. It is a mystery to me.

 

[compuryan]

I actually tried a RCA 12AT7 in the 12AX7 position and I very much prefer the Sovtek 12AX7LPS. The RCA sounded tired and flabby in comparison.

 

[sunseeker888]

Try a NOS RCA 7025 in the 12ax7 spot. You'll be pleasantly surprised. As for reissues: the Mullard EL84 reissues in my amp have been going strong for over a year and sound incredible.

But JJ is utter garbage most of the time. I've read thread after thread on a couple of different boards where they die, burn out, and make erratic noises. I bought some JJ 12ax7's and they just didn't sound right.

 

[compuryan]

yeah the JJs are in the trash can and four NOS military 6P14P-EV tubes are on their way from Russia! I bought them because Ferbose greatly preferred them after hearing the JJs and the 6P14P-EV. And I thought the JJs sounded great, well... until they broke. I'll have to let you all know how the 6P14P-EV tubes sound when they arrive.