Hi,
It is picked up via the radiated field from the rectifier tube. Some combinations do not work too well. Especially recent TJ 45's are very prone to picking up noise, which is why we no longer recommend for the Tram II.
The field is radiated and received via the top of the tubes, we tried "shielding hats" made from copper and grounded, these kill the hum completely.
Yes, there is no voltage regulation, different rectifiers have different voltage drops. The WE 274 IIRC is closer to a 5R4 in terms of electrical behaviour than a 5U4, so a 5U4 would have more voltage. We don't have any WE 274 at hand, so I cannot confirm if the difference is expected to be like what you have.
Otherwise the voltages and currents look okay.
The plate voltage and the voltage at the output cap are around 20V apart, so with a 5U4 things are spot on.
Yes, this is due to operation of the Active Bias System.
At startup the current through the tube is cut off totally (hence the rise of the Anode voltage to essentially equal +B) and is then slowly increased to nominal. This makes sure the cathode is up to temperature by the time we draw full current. You may have noticed that the heater voltage is also soft-started, as is the HT... You may have noticed that the final Anode current is the same, regardless of Anode voltage, this is due to the adjustment of the ABS.
It normally is plug/play, but it will do no harm checking the heater and anode voltages and re-adjusting.
In principle the CCS is set to 31mA and the ABS has it's internal thresholds (the tolerances in both are why adjustment is needed to get things "just so"), however if your 2A3's for example are far of normal spec, adjustment may be needed.
Ciao T
It is picked up via the radiated field from the rectifier tube. Some combinations do not work too well. Especially recent TJ 45's are very prone to picking up noise, which is why we no longer recommend for the Tram II.
The field is radiated and received via the top of the tubes, we tried "shielding hats" made from copper and grounded, these kill the hum completely.
Yes, there is no voltage regulation, different rectifiers have different voltage drops. The WE 274 IIRC is closer to a 5R4 in terms of electrical behaviour than a 5U4, so a 5U4 would have more voltage. We don't have any WE 274 at hand, so I cannot confirm if the difference is expected to be like what you have.
Otherwise the voltages and currents look okay.
The plate voltage and the voltage at the output cap are around 20V apart, so with a 5U4 things are spot on.
Yes, this is due to operation of the Active Bias System.
At startup the current through the tube is cut off totally (hence the rise of the Anode voltage to essentially equal +B) and is then slowly increased to nominal. This makes sure the cathode is up to temperature by the time we draw full current. You may have noticed that the heater voltage is also soft-started, as is the HT... You may have noticed that the final Anode current is the same, regardless of Anode voltage, this is due to the adjustment of the ABS.
It normally is plug/play, but it will do no harm checking the heater and anode voltages and re-adjusting.
In principle the CCS is set to 31mA and the ABS has it's internal thresholds (the tolerances in both are why adjustment is needed to get things "just so"), however if your 2A3's for example are far of normal spec, adjustment may be needed.
Ciao T
Hi Thorsten,
Thanks for your quick reply. It was a pleasure meeting you the other day I was at the workshop auditioning the Tram2.
My TJ45 was bought from Brian many years ago. I think the WE274B rectifier just radiated too much noise.
Interesting. There's probably a market for a mesh shield with hat. I bought graphite ones made by a local vendor but would have preferred a wired-mesh one if that's available.
Good to hear that.
I'll try that this weekend. I have a pair of Sovtek 2A3 and a pair of NU 2A3 somewhere in my stash.
I have two minor suggestions for the Tram2:
(a) Add a mute function;
(b) Add a power-up/power-down mute circuit to prevent thumping noises. I have two active subs connected to the Tram2 and I have to manually turn them on-off instead of using the auto-on feature to prevent thumping at Tram2 power-up/down.
Thanks.
Jack
Thanks for your quick reply. It was a pleasure meeting you the other day I was at the workshop auditioning the Tram2.
My TJ45 was bought from Brian many years ago. I think the WE274B rectifier just radiated too much noise.
Interesting. There's probably a market for a mesh shield with hat. I bought graphite ones made by a local vendor but would have preferred a wired-mesh one if that's available.
Good to hear that.
I'll try that this weekend. I have a pair of Sovtek 2A3 and a pair of NU 2A3 somewhere in my stash.
I have two minor suggestions for the Tram2:
(a) Add a mute function;
(b) Add a power-up/power-down mute circuit to prevent thumping noises. I have two active subs connected to the Tram2 and I have to manually turn them on-off instead of using the auto-on feature to prevent thumping at Tram2 power-up/down.
Thanks.
Jack
I've just gotten caught up on this thread. I've had a Tram since December (I posted in the thread about how much I loved it after getting it), built by DIYHiFi.
I have had EXACTLY the same problem described by two others in the thread - the "hum pulses". I was sent parts to "fix" it but after reading of others' experiences it's pretty clear this is a design issue with the filament supplies - right? Heat sinks not big/effective enough?
I've also been running 2A3s. I was never told to use 45s instead.
Why not enlarge the heat sinks and/or provide for better cooling? Why not make it a 45-only pre if they draw less current and eliminate the problem?
I have had EXACTLY the same problem described by two others in the thread - the "hum pulses". I was sent parts to "fix" it but after reading of others' experiences it's pretty clear this is a design issue with the filament supplies - right? Heat sinks not big/effective enough?
I've also been running 2A3s. I was never told to use 45s instead.
Why not enlarge the heat sinks and/or provide for better cooling? Why not make it a 45-only pre if they draw less current and eliminate the problem?
Hi Paul,
The Heatsinking of the "Filament Supply" is sufficient 2A3 use if:
1) The correct Heatsink is fitted
and
2) For extremely high mains voltages (> 120/240V) and 2A3 use the dropper resistors are fitted.
The problems that surfaced appear mainly because some Filament supplies that made their way into the Tram (diyhfs are still looking why and why this was not noticed), that had been fitted by the supplier with heat sinks that appeared superficially identical to the ones specified but in reality could handle only around 2/3rds of the needed dissipation and hence were actually insufficient.
This affected a small number of Trams Kits (and build up kits) during Dec to early March and AFAIK all these units have been fixed. This was for example the case for your unit, hence you received new supplies manufacturerd to the correct spec., which as you note fixed the problem.
Ciao T
The Heatsinking of the "Filament Supply" is sufficient 2A3 use if:
1) The correct Heatsink is fitted
and
2) For extremely high mains voltages (> 120/240V) and 2A3 use the dropper resistors are fitted.
The problems that surfaced appear mainly because some Filament supplies that made their way into the Tram (diyhfs are still looking why and why this was not noticed), that had been fitted by the supplier with heat sinks that appeared superficially identical to the ones specified but in reality could handle only around 2/3rds of the needed dissipation and hence were actually insufficient.
This affected a small number of Trams Kits (and build up kits) during Dec to early March and AFAIK all these units have been fixed. This was for example the case for your unit, hence you received new supplies manufacturerd to the correct spec., which as you note fixed the problem.
Ciao T
Paul,
Please do test fully and revert to diyhifisupply with any issues.
Also, what is you local wall voltage?
Ciao T
Please do test fully and revert to diyhifisupply with any issues.
Also, what is you local wall voltage?
Ciao T
Not positive but actually I just bought a PS Audio Premier AC regenerator and will be using that once it comes in a week.
Paul,
This should do nicely, you can just check the wall voltage using a normal multimeter set to AC...
Ciao T
This should do nicely, you can just check the wall voltage using a normal multimeter set to AC...
Ciao T
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.
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.
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.
Hi,
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
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
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.
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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Hi,
Just check the heater current with the TJ 2A3. 2.5A + 10% will work, but not much more.
Ciao T
Just check the heater current with the TJ 2A3. 2.5A + 10% will work, but not much more.
Ciao T
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.
Hi,
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
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
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?
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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