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Old 6th June 2012, 05:32 PM   #311
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Good point.
I have not measured them recently, but they were correct a few weeks ago.
I am not really good at this, but my gut feeling is that a component regulating the heater supply is slowly failing after switching the unit on and recovering after switching it off.

joerg
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Old 3rd July 2012, 03:43 PM   #312
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Thorsten,

What corner frequency (-3dB) were you aiming for with 12uf output capacitor values?

Thanks
Anand.
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Old 17th July 2012, 09:52 AM   #313
GeirT is offline GeirT  Norway
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Have any one built the transformer and the rectifier into a separate enclosure?
I see that DIYSupply has a external power supply kit / chassis available for reasonable cost. The transformer included in that chassis is not compatible with the TRAM 2 requirements so the transformer has to be shifted.
The kit also includes a power cord w/connections. I gues that if the supply board is located in the external chassis, an additional power cord could be wise to keep AC feeds separate from the DC feeds.

Any thoughts on this?

Geir
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Old 26th July 2012, 08:42 AM   #314
Desmo is offline Desmo  Denmark
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OK, time for what I (kind of hope) is the final update on my Tram II

For me the DHT regulators has been the weak link in this wonderful preamp. The regulators that was delivered with the kit was quite noisy and replaced under warranty. The second pair was a little better, but still quite noisy. It helped when I installed better cooling as shown earlier in this thread, but still noisy..!

I then got a tip from another Tram II owner (beardman, thanks!) to check out the Rod Coleman DHT regulators. Long story short, I have installed them in my Tram II and first of all: The noise floor has dropped by quite a lot and I now need to be quite close to the speakers to hear the faint hiss and hum, before I could hear it from the listening position, especially in one channel.

But the lower noise floor is actually just a bonus because the major advantage is the sound that improves quite a lot with these Rod Coleman regulators..! I have always considered the Tram II to be one of the most natural sounding preamps I have ever tried, but when listening with these regulators installed I now realize that a thin ''electronic sounding haze'' has been removed. It was natural sounding before, and even more natural sounding now Furthermore ''images float in space'', these words (the Danish version ;-)) just kept popping up in my head when listening with these installed. There is a flow to the music and the images float in a 3 dimensional space in a totally different way than before. It's not that the soundstage is bigger as such, but it's more real, more there, more open, more natural and the music has better flow.

With this thin haze lifted away I also here more details, especially the ones that usually hides deep in the mix. For instance I listened to a jazz LP and during a guitar solo I could hear the guitar player humming his tunes while he was playing them. I have not heard that before on this record..! I give these regulators a strong recommendation to all you fellow Tram II owners - they set free even more of the potential in this amazing preamp

Here are a few pics of the installation and the custom heatsink / chassis arrangement that I made. It's made up of a heatsink I bought and then sheets of 10mm aluminum. I wanted to get the biggest cooling area possible, so I made this that is kind of heatsink and sub-chassis. It's connected to the inner rubber mounted aluminum sub-chassis so this aluminum plate is also part of the cooling system. I have then isolated the caps from this aluminum plate so they don't get hot (the two black Obbligato and my Duelund Cast input caps). The result is really good, it runs hot, but not crazy hot...

Also, since there are quite big currents running in such DHT regulators I wanted the best possible caps for the first set of caps after the rectifiers: I have used RIFA PEH200 - 10.000uF, 40V that can handle 12A ripple current. They are quite big, but I just managed to squeeze them in there and they will last

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Last edited by Desmo; 26th July 2012 at 08:53 AM.
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Old 28th July 2012, 02:08 AM   #315
GeirT is offline GeirT  Norway
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Wow, really nice build Desmo. I'm happy to hear that the pre-amp now is even better.
I tried to Google to find a source for the Coleman DHT regulators but did not find any promising links. Do you happend to have the link to a purchasing page?

Best regards from Geir
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Old 28th July 2012, 07:26 AM   #316
Desmo is offline Desmo  Denmark
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Hi Geir, sorry I forgot the link..! You buy them directly from Rod Coleman, just drop him a pb here in diyaudio. There is a long thread about these regulators: New DHT heater


After doing a bit more listening I can honestly say, that this upgrade with the regulators is the one that sonically makes the biggest improvement. More than different tubes, coupling caps etc. And as a big bonus, the noise is also gone with these.

Last edited by Desmo; 28th July 2012 at 07:48 AM.
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Old 28th July 2012, 08:54 AM   #317
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Hi
I will say the same as Desmo..this new Rod heater is the best i have done for my Tram2
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Old 28th July 2012, 10:02 PM   #318
GeirT is offline GeirT  Norway
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Just curious; the board between the DHT heaters containing capacitors, it contains part of the power supply for the DHT regulators? This board you have to supply/make yourself, not?

Geir
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Old 28th July 2012, 10:18 PM   #319
GeirT is offline GeirT  Norway
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I'm not sure it is a good character or not but when someone has invented the genious, I tend to copy the genious instead of inventing the wheel over again. Has a simple circuit diagram of the power supply for the Coleman DHT heaters been published?

Sorry for being lazy ;-)

Geir
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Old 29th July 2012, 06:04 AM   #320
Desmo is offline Desmo  Denmark
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Yes, the board between the two regulators contains the rectifiers, caps and resistors that forms the raw-dc supply for the regulators. This raw-dc supply you build yourself.

When you buy the regulators from Rod Coleman you get the two regulator boards + all components for them. You also get a build manual with lots of instructions on how to implement the regulators. In that build manual there are diagrams and specification for the components in the raw-dc supply. Once you have his build manual all is quite easy.
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