I've settled on the GE green base 6AS7 and the Australian AWA Radiotron 5U4G (5AS4).
Both are GT-shaped (straight-sided). They are therefore less microphonic than ST or globe types (but not as sexy) and the Radiotron in particular emits no RF interference. This is important with the Tram as the rectifier is right next to the 45s/2A3s.
GE 6AS7s are as cheap as chips and the Radiotron 5U4Gs can be had locally for about A$40 NOS.
No doubt someone will post singing the praises of some valves costing $$$s but I am sceptical of whether they would be an improvement.
Both are GT-shaped (straight-sided). They are therefore less microphonic than ST or globe types (but not as sexy) and the Radiotron in particular emits no RF interference. This is important with the Tram as the rectifier is right next to the 45s/2A3s.
GE 6AS7s are as cheap as chips and the Radiotron 5U4Gs can be had locally for about A$40 NOS.
No doubt someone will post singing the praises of some valves costing $$$s but I am sceptical of whether they would be an improvement.
I have been try to track down a 5AS4 around Brisbane and I ended up getting a Rogers 5AS4 with ST sides from Canada. When I was in Hong Kong two weeks ago, I picked up from WiWi Tubes the last two Fullmusic 45s with ST sides. They were dated Dec 2005. I also picked up the Tram2 kit from Simon at DIY Hifi Supply in Hong Kong. I have not started the kit as some of the major parts were on back ordered and are being sent. Can not wait to start.
Rolling in the Tram
My experience with the Tram has included a few rolls of each of the tubes. I've settled on 2 radiotron 45's a sylvania 6as7, and Rca 5u4g. The choice of output tubes had to include solid plate structures. Anything suspended or mesh was way too noisy and microphonic. The shuguang solid plate 2a3 worked well and is inexpensive. My preference for the 45 is based on that tube's slight detail improvement. They all sizzle a bit with the solid plates keeping it to a minimum.
As for the 6as7/5u4 I can't sense any real differences there. I never had RF problems or noise from any combination so I've kept them constant.
The final choice of output tubes is really based on what blends well with the rest of the system. The changes come in the finer points of HF details and noise. Some tubes I would avoid are the TJ 2a3 mesh. I can't get them quiet enough to enjoy regardless of the dampers used. You'll be happy with most choices as the Tram is a great front end. The decision to stay with one set of tubes really is based on fewest faults vs. detail and there are too many variables to pick a clear winning combination.
I recently changed my main speakers back to Horns with Heil AMT's. The tweeters are so detailed that I had to swap Tram tubes. Minor sizzle in one set became loud crackling with the Heils. I took a chance on the "NOS" 45's and they are perfect for this combination. They are just mellow enough to blend nicely. All this tube rolling is fun and the Tram makes it worthwhile. The differences are clear between sets and some work, others don't. To avoid wasting money, solid plates are a big plus, Nos can be risky but you may find a set that sounds good and is quiet. I have tried many combinations and solid choices are the Sovteks and plain vanilla Shuguangs.
Cheers
My experience with the Tram has included a few rolls of each of the tubes. I've settled on 2 radiotron 45's a sylvania 6as7, and Rca 5u4g. The choice of output tubes had to include solid plate structures. Anything suspended or mesh was way too noisy and microphonic. The shuguang solid plate 2a3 worked well and is inexpensive. My preference for the 45 is based on that tube's slight detail improvement. They all sizzle a bit with the solid plates keeping it to a minimum.
As for the 6as7/5u4 I can't sense any real differences there. I never had RF problems or noise from any combination so I've kept them constant.
The final choice of output tubes is really based on what blends well with the rest of the system. The changes come in the finer points of HF details and noise. Some tubes I would avoid are the TJ 2a3 mesh. I can't get them quiet enough to enjoy regardless of the dampers used. You'll be happy with most choices as the Tram is a great front end. The decision to stay with one set of tubes really is based on fewest faults vs. detail and there are too many variables to pick a clear winning combination.
I recently changed my main speakers back to Horns with Heil AMT's. The tweeters are so detailed that I had to swap Tram tubes. Minor sizzle in one set became loud crackling with the Heils. I took a chance on the "NOS" 45's and they are perfect for this combination. They are just mellow enough to blend nicely. All this tube rolling is fun and the Tram makes it worthwhile. The differences are clear between sets and some work, others don't. To avoid wasting money, solid plates are a big plus, Nos can be risky but you may find a set that sounds good and is quiet. I have tried many combinations and solid choices are the Sovteks and plain vanilla Shuguangs.
Cheers
Thanks D_arionj for your experience with the tubes for your Tram2. That is the sort of information necessary to try and get things right the first time. I am still waiting on parts from Simon at DIY Hifi Supply to start building the pre-amp. I bought two Full Music 45/N ST bottle shaped 2005 vintage tubes from WiWi Tubes in Hong Kong. I am going to use Sylvania 5AS4 tube and United Electron 6AS7. I have the Herbie Audio Guitar rings for the 45 tube.
Tram hints
Simon and Thorsten have been very helpful in support of those of us who choose to build the Tram. I'll admit to being frustrated at times with some issues but they have all been solved with patience and good communicating. The time difference has been the largest problem with builders in the US and getting help from HK. I think I've figured it out,, now that I'm done.
As for building advice, the screw terminals can be very tricky to get a strong secure connection. I understand the modular nature of the boards but with hindsight I should have removed them and soldered. My concern was damaging board traces with heat but a poor connection due to a twisting loose wire is much worse. Tinning the wires before tightening would help keeping them solid.
I had a bad filament supply (instantly replaced by DIYHIFI) and the screw terminals made the swap easy so there are some advantages to keeping them. Just be aware of this.
Secondly, final troubleshooting and voltage measurements need to be taken once the circuit settles down. This can take quite a while as the whole circuit takes time to stabilize. Trying to set 120v while things are still changing can be frustrating. Be patient. Good support under the transformer housing is critical to keeping things stable while you wait and measure so I'd suggest finding a nice thick book to keep things steady. The tubes are tall and the bases are weak so not putting any pressure on them will save $$$.
Clip leads are essential to monitor anode voltage safely during this process, and remember that the output caps carry a nice jolt for quite a while.
All the threads about potential heat problems made me concerned about the boards' longevity. I tried a flat laptop cooler under the chassis and it works like a charm and is reasonably quiet. The metal perforations allow for great airflow and the box stays cool. I thank other forum members for the idea.
That's about it. Remember to tighten the screws, pull on the wire and check again! I am, by no means, an expert on this but I have done it while making mistakes and learning from them so if I can do it...
Cheers
Simon and Thorsten have been very helpful in support of those of us who choose to build the Tram. I'll admit to being frustrated at times with some issues but they have all been solved with patience and good communicating. The time difference has been the largest problem with builders in the US and getting help from HK. I think I've figured it out,, now that I'm done.
As for building advice, the screw terminals can be very tricky to get a strong secure connection. I understand the modular nature of the boards but with hindsight I should have removed them and soldered. My concern was damaging board traces with heat but a poor connection due to a twisting loose wire is much worse. Tinning the wires before tightening would help keeping them solid.
I had a bad filament supply (instantly replaced by DIYHIFI) and the screw terminals made the swap easy so there are some advantages to keeping them. Just be aware of this.
Secondly, final troubleshooting and voltage measurements need to be taken once the circuit settles down. This can take quite a while as the whole circuit takes time to stabilize. Trying to set 120v while things are still changing can be frustrating. Be patient. Good support under the transformer housing is critical to keeping things stable while you wait and measure so I'd suggest finding a nice thick book to keep things steady. The tubes are tall and the bases are weak so not putting any pressure on them will save $$$.
Clip leads are essential to monitor anode voltage safely during this process, and remember that the output caps carry a nice jolt for quite a while.
All the threads about potential heat problems made me concerned about the boards' longevity. I tried a flat laptop cooler under the chassis and it works like a charm and is reasonably quiet. The metal perforations allow for great airflow and the box stays cool. I thank other forum members for the idea.
That's about it. Remember to tighten the screws, pull on the wire and check again! I am, by no means, an expert on this but I have done it while making mistakes and learning from them so if I can do it...
Cheers
Hi Thorsten (or others in the know...),
I found this nice old RCA black plate 5R4GY rectifier tube and wonder if this can be used as rectifier in the TRAM II?
Based on info I have been able to find on the Internet the main difference to the 5U4 seems to be a slightly different voltage drop across the diodes in the tubes, but I suppose this can be corrected with a simple adjustment of the CCS?
I found this nice old RCA black plate 5R4GY rectifier tube and wonder if this can be used as rectifier in the TRAM II?
Based on info I have been able to find on the Internet the main difference to the 5U4 seems to be a slightly different voltage drop across the diodes in the tubes, but I suppose this can be corrected with a simple adjustment of the CCS?
Hi Thorsten (or others in the know...),
I found this nice old RCA black plate 5R4GY rectifier tube and wonder if this can be used as rectifier in the TRAM II?
Based on info I have been able to find on the Internet the main difference to the 5U4 seems to be a slightly different voltage drop across the diodes in the tubes, but I suppose this can be corrected with a simple adjustment of the CCS?
Noone bites, so let me answer my own question
I've found some data indicating that the 5R4GY should be OK to use in the Tram II. If any difference it could be a larger voltage drop over the diodes in the rectifier. I have installed the tube and it works fine, and there is no change in B+ and the 120V DC from the CCS compared to my other rectifiers.At least this RCA 5R4GY seems to send out less hum than other rectifiers, so for now I will continue to use it. The level of hum is a bit lower than with the Svetlana I normally use.
The rectifiers I have tried so far are:
Valve Art 274 (with some triodes, there is quite a lot of hum with this one).
NOS Svetlana 5U3C (Highly recommended for less hum than the VA 274).
I should mention, that I don't have hum with all the tubes, just some of the NOS tubes. The dilemma is, that IMHO the NOS RCA 2A3 are the best sounding tubes I have tried, but they also seem to pick up more hum, so I'm searching for the most quiet rectifiers to use with the RCA triodes...
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