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Old 8th June 2011, 10:49 AM   #151
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I don't find my 2A3 hum relative to my 45s. I believe this will depend on the tubes used, including the rectifier.

My Tram ran ok with the std heatsinks and 2A3s once I installed dropper resistors feeding the regs. I have recently added 1 spikey heatsink per reg, the ones you can stick on chips. This is for piece of mind only as all was ok. If I can find some 45s to match the sound of my 2A3s I will swap so that I can reduce the thermal stress in the preamp.
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Old 9th June 2011, 12:23 AM   #152
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I guess the mains voltage can make a lot of difference. I tried new TJ 2A3s and United Electron NOS 45s. Although I made the heater voltage stable and heatsink temp at around 60deg the buzz is very prominent (I am guessing that is 100Hz dominated plus several higher harmonics) and I think this is because of the extreme load on the heater supplies ( I might be wrong). On the other hand - the 45s sound absolutely beautiful and the amp background noise in non-existent with them. Only a slight amount of valve hiss barely audible even on headphones. On top of that a pair of 45s cost under $100.
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Old 9th June 2011, 01:06 AM   #153
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> 45s cost under $100

Do you get your 45s: 2nd hand old ones off ebay?
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Old 9th June 2011, 04:40 AM   #154
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Hi,

Quote:
Originally Posted by DECKY999 View Post
I guess the mains voltage can make a lot of difference. I tried new TJ 2A3s and United Electron NOS 45s. Although I made the heater voltage stable and heatsink temp at around 60deg the buzz is very prominent (I am guessing that is 100Hz dominated plus several higher harmonics) and I think this is because of the extreme load on the heater supplies ( I might be wrong).
We incidentally use a pair of old pattern visually mismatched TJ 2A3 for testing and burn in, they do not require extra heatsinking.

I think you may one of two problems. TJ's production tends to be bit erratic and they often change details. Some batches of TJ Tubes draw a lot more heater current than specification. With the Filament Supplies you can measure the current bu measuring the voltage across the 0.1 Ohm resistor, a 3W through hole.

However, what I suspect as reason for the Hum is that some batches of TJ Tubes (all recent 45 ones) pick up hum from the fields radiated by the rectifier. You can check, if you touch the chassis with one hand, place the other above the tubes top (careful, hot) you may find the hum changes.

We have not found this with NOS 45's and 2A3's (we have a fair collection) or with the Valve Art 2A3's, nor with Emission Labs 2A3's and 45's., older pattern
TJ 45's and 2A3's also are fine.

However for some reason new pattern (there are clear visual differences) TJ 45's (we did not yet get any 2A3's but I suspect they will be the same) are very sensitive to picking up hum from the rectifier. Some Rectifiers are unusable (-40dBV Hum [dBV = re 1V out]), some are borderline usable (Valve Art 274B for example gives around -75dBV), but these tubes have a lot more hum than normal (better than -90dBV) and it is not oscillation or anything else we can find in the circuit. Shielding the top of these hummy TJ Tubes with copper (basically a copper cap) that is grounded removes the hum, but does not look good.

As a result we no longer recommend TJ Tubes with the Tram II.

Ciao T
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Old 9th June 2011, 06:04 AM   #155
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I agree with all of this. I did have a hum problem with a Shuguang rectifier that a bit of shielding solved and also changing that tube to a NOS mil spec one (Australian made) the hum disappeared. So, as you said - it is probably the TJ tubes themselves. I will be testing other 2A3s in the future. However the latest test was with the new regulator chips and after I replaced the CCS ships (thanks to Simon from DIY HiFi supply). This time the buzz was much higher frequency than before and louder. The test is not 100% accurate since I changed the rectifier in the meantime. So, it can be 2A3s/rectifier coupling , heater supply or combination of both.

As for the 45s - cannot say for sure since I got them from a friend but I think they are NOS and I am not sure if he got them from ebay or elsewhere. I will double check.
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Last edited by DECKY999; 9th June 2011 at 06:09 AM.
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Old 9th June 2011, 06:45 AM   #156
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Hi,

Quote:
Originally Posted by DECKY999 View Post
So, it can be 2A3s/rectifier coupling , heater supply or combination of both.
Just check the heater current with the TJ 2A3. 2.5A + 10% will work, but not much more.

Ciao T
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Old 9th June 2011, 07:22 AM   #157
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Quote:
Originally Posted by DECKY999 View Post
On the other hand - the 45s sound absolutely beautiful and the amp background noise in non-existent with them. Only a slight amount of valve hiss barely audible even on headphones. On top of that a pair of 45s cost under $100.
The NOS (or at least good testing) 45s will sound better than most new production 45s. I can't say all new production 45s as I've not heard all of them. When I got my NOS 2A3s (again, they may simply test like new) I found these sounded superior to my NOS 45s. Does this mean NOS 2A3 is the way to go with Tram II? I don't know, I would need to try many more samples, diyhifisupply will have the most experiences in this, although they aren't a major NOS vendor.
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Old 9th June 2011, 07:25 AM   #158
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Hi,

Quote:
Originally Posted by clivetjm View Post
diyhifisupply will have the most experiences in this, although they aren't a major NOS vendor.
There is a lot of NOS Stuff at the office, accumulated over years, but these are not for sale.

I would say which tube is preferred is at least in part a question of system context...

I PERSONALLY prefer 45's, but that's just me and with the Crescendo Speakers and with various Amp's of my design and either the Satch (TDA1541 Non-Os) or Cleo (192KHz/24Bit oversampling USB) as DAC.

But I can easily see it go the other way.

Ciao T
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Old 9th June 2011, 10:15 AM   #159
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I cannot believe but I have to scream for help again.

All the tests that I mentioned earlier I was doing with headphones attached to the Tram output (with a small battery powered head amp). Just to remind you, I had a major overheating issue before and that killed heater regulators and, as it looked, at least one of the CCSs. That is all replaced. Now, the heater V is stable, the bias V is stable with both 2A3 and 45s. However, I tried an hour ago to hook the amp up in the main system. There was quite a bit of hum with both valve sets and the level of signal was barely audible even on max volume setting. In the same system before the preamp was creating heaps of output with volume at 12oclock at -3dB output. I checked all the wiring inside. PSU voltages are fine (a bit high due to 246V mains) - B+ at around 270V. All LEDs are ON everything seams to be working but no sound this time. Any suggestions?
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Old 9th June 2011, 10:31 AM   #160
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The only other thing I noticed is that I have to readjust the bias when I am changing output valves. (going from 2A3s to 45s).
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