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Melos tube rolling thread - Page 9

post #121 of 137
I wasn't a big fan of the JJ/Teslas... to tell the truth, they sounded a little worse to me than the Sovteks I had in before. They sounded a little softer (not as tight) in the bass and had a little less "slam" or "energy" overall, though with a warmer image.

When I installed my Amperex USA Jan7308 (gold pin, orange label) tubes, the difference was astonishing. Much fuller body, deeper and yet tighter bass, smoother highs without loss of extension, more coherent image. I couldn't have believed that a pair of tubes could do so much.
post #122 of 137
You can also change how a Melos sounds by adjusting tube bias. If you look at the board from the side closest to the tubes you'll see two trim pots to the top right. They'll either be blue, yellow, or white in color, they are the bias pots. The Plate/Anode are pins 1 and 6 of the tube socket (counterclockwise* from the notch), adjust those pots to find what works best for you, measure the voltage, and match both channels. Obviously the higher you go the harder you drive the tube, usually around 60v for 6dj8s and 75-80v for 6922/7308 have been my preference with the amp. If one of your channels sounds slightly distorted, the channels imbalanced, and/or the tubes different in brightness (literally, not figuratively) adjusting bias usually solves the problem.

For those with an older SHA (blue board) the trim pots are above the tube sockets, perspective from the side closest to the tubes. I've seen blue and gray casings for those pots on those amps. Credit belongs to geom_tol for sharing the difference in board color.

While there are exceptions (the Amperex Bugle Boy for example) I very much recommend against using 6dj8s with the amp. The Melos will eat them, don't expect nearly as much life as with a 7308.

* edited due to a brain fart.
post #123 of 137
Thread Starter 
Quote:
Originally posted by carlo
The Plate/Anode are pins 1 and 6 of the tube socket (clockwise from the notch), adjust those pots to find what works best for you, measure the voltage, and match both channels.

While there are exceptions (the Amperex Bugle Boy for example) I very much recommend against using 6dj8s with the amp. The Melos will eat them, don't expect nearly as much life as with a 7308.
If you can find the output of those pins, and measure voltages with the tubes in place, you can theoretically match bias to your tubes, making a priori matching a bit less critical (correct me if wrong).

Add the Mullard 6DJ8 (ECC88) to the list of exceptions. I don't know how long they will last, but they're a great little tube for the Melos. If you find them, buy spares...
post #124 of 137
Quote:
If you can find the output of those pins, and measure voltages with the tubes in place, you can theoretically match bias to your tubes, making a priori matching a bit less critical (correct me if wrong).
- Hirsch
I'm not quite following Hirsch, what do you mean by prior matching? Adjusting plate/anode voltage won't make two tubes that are unmatched (lets say one about to die and one thats new) wear at the same rate or sound the same. Am I misinterpreting?
post #125 of 137
Just wondering if anyone's tried Gold Aero 7308 gold pins before? What about RAM 6DJ8 A's?

Any thoughts on either tube?

Thanks!
post #126 of 137
Thread Starter 
Hmmm...time to revive an old thread...


I've been using my carlo-modded SHA-1 to drive the AKG-1000. Initial sound was a bit harsh, so some tube-rolling was in order. At the NY Head-Fi meet, bozebuttons mentioned he was using 7DJ8's in his modded Melos, and they sounded good to me. So, I got a couple of sets of PCC88's. All are labelled Telefunken, but one set has the Telefunken diamond, while the other has a number in the glass at the bottom, indicating that Siemens made them for Telefunken.

The big difference between the 6DJ8 and the 7DJ8 is that the later tube was designed for a heater voltage of 7v (I'll leave it to you to work out the heater voltage of the 6DJ8). However, the PCC88 has no trouble operating with a lower heater voltage, and can be used as a drop-in substitute in most 6DJ8 circuits. The Telefunken Telefunkens are a very smooth tube. Great highs, liquid mids and very strong bass. I'm using them in my modded Melos, and the K-1000 is sounding very good. I'm not missing my RKV anywhere near as much as I used to The Siemens tubes are a bit brighter. There may be a touch more detail, but they don't have the lushiousness in the midrange of the other tubes.

Another important difference between the PCC88 and the ECC88 (6DJ8) is the price. A pair of Telefunken or Siemens ECC88's can be a bit expensive . These tubes ran less than $10 per tube for NOS that had never been used...
post #127 of 137
According to carlo the Melos plate voltage runs in the high 6s Thats why the the 7 volt heater tubes work well in the melos.
I am using the pcc88 amperex pinched waist holland tubes. A little rarer but cheaper then the 6922 pinched waist
amperex holland tubes I also have.
I prefer the pcc88 tubes in the melos.
close in sound to the 6922s but the pcc88s seem to have better bass and dynamics.
Anyone interested in tubes sound descriptions can go to audioasylum.com
click on FAQ and go to Joes tube lure.
Joe gives a pretty good description
of various tubes.
post #128 of 137
This thread will never die!

Could either of you help out with finding such tubes? I figure maybe I shouldn't sell my Melos after all.
post #129 of 137
Thread Starter 
Quote:
Originally posted by DanG
This thread will never die!

Could either of you help out with finding such tubes? I figure maybe I shouldn't sell my Melos after all.
I got mine at www.ebay.com and entering "PCC88" into the search function...
post #130 of 137
Want to buy 36 of the 38 tubes being sold together, and I'll just take the 2?

http://cgi.ebay.com/ws/eBayISAPI.dll...category=14947

$190's a bit much for me!
post #131 of 137
I have to say that gold pin Ei-Yugos are certainly gold in the Melos. I now understand why certain people dislike the JJs.

Eis are current production and not too expensive. Heard on AA that they compare to NOS but I haven't heard quality NOS myself so I can't comment on that... all I can say is that the Eis are an upgrade from sovtek, electro harmonix, and JJ.

The electro harmonix still have a tighter bass, though. oh well.
post #132 of 137
well ... i have been enjoying my melos for a few months now. the stock tubes* were starting to make some noise, however, so i thought it was time for a change. i picked up some amperex 7308s from upscale, and all i can say is that it is like a different amplifier. this is better sound than i think i have ever heard. had i just paid a few thousand for a new amp and it sounded like this i would not have been disappointed. these tubes are highly recommended. the fact that i am still below $600 total investment in this thing is amazing. now, if you'll excuse me, i have music to listen too ...


-d




* i bought it used, and my guess is that the original owner either never turned the thing on, or else he retubed with the cheapest thing he could find.
post #133 of 137
I recently tried a pair of Amperex 6922 USN-CEPs and they really seemed to open up the midrange. I have never tried the 7308. Might have to give Kevin a call.
post #134 of 137
Heh, I was just playing tube raider and contacted them and they didn't have any of the really good ones I was looking for. I hope you have better luck!
post #135 of 137
An update to my earlier post is in order -- My set of Amperex 7308's did not do well in the Melos. They developed a high pitched screech. I returned them to Kevin at Upscale who sent me a new pair (this time with "PQ" on the side). These also screech a bit, and according to Kevin he doesn't think that the Melos should have good tubes put in it. In fact, he says that the Melos is on the short list (with the Audible Illusions pre) of gear that he generally won't sell NOS tubes for -- he said it was a mistake to sell them to me in the first place.

Anyhow, I just got a set of JAN 6922's from the tube store (which cost $100 less than the Amperex, and Upscale sells the Amprex for less than many other places) and they are great. So far, there is very little noise, and they are warm, balanced, and only slightly less liquid than the Amperex. I might actually like them more in this amp. I'll post again after a few weeks of use, but so far they seem a good match.

-d
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