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Old 22nd September 2013, 12:27 AM   #911
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Hi Guys,
Firstly, thank you for all of your suggestions. I have managed to get a version 2 FCUPS board that was configured for use in an amplifier. I am currently getting it back to its original configuration. I am however still working on the v1 version to see if it can be simplified. I will keep you posted on my findings as it has to be modified to accept a centre tap from the transformer.

I will be using 2 external transformers which are rated for a 240v input. This ps will be housed either next I or underneath the Tram shielded with mu metal and very short runs.
The Coleman reg ps will be housed in the same box as the transformers, in a separate enclosure as close to the transformer as possible with an umbilical feeding the Coleman regs.

Cheers
Greg
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Old 22nd September 2013, 05:39 AM   #912
kazap is offline kazap  Australia
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Quote:
Originally Posted by PixelPlay View Post
This ps will be housed either next I or underneath the Tram shielded with mu metal and very short runs.
Nice.

You probably have read some valuable input earlier in the thread about two chassis designs. The benefits are enticing but expert opinion emphasised the benefits of a one box design allowing the power supply cables to be as short as possible to avoid inducing noise, especially with the filament heater supply wires.

I wonder how are you going to design your two boxes in order to have "very short runs" between the separated power supply chassis and the Tram2?

Ive got a design in mind if your interested.
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Old 22nd September 2013, 07:11 AM   #913
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Hi Kazap
Thanks for your reply. I was thinking that if it were directly below then a short umbilical straight through the roof of the bottom chassis into the tram, or if it is placed next to the tram then the connection could be made through the side walls of both the tram and ps chassis.

I would be interested in your design thoughts.
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Old 22nd September 2013, 08:53 AM   #914
kazap is offline kazap  Australia
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I do like the idea of a Tram2 Dual-chassis design but personally Im sticking to the mono-chassis for short power runs. So take my design musing as nothing more then fantasy.

a. Power chassis - you will note its identical to the Tram2 and has the thick aluminium to act as a heat sink - heat dispersing surface and EMF shielding.

b. Sit it directly under the Tram2 for matching good appearance and short power runs

c. Have the regulated DC supply fed vertically upward though the top of the power chassis with the power layout and exit locations chosen to be directly beneath where there they are needed on the Tram2

d. Dispose of the bottom plate of the Tram 2 and instead screw narrow aluminium bars transversely across the bottom of the Tram2 and screw power plugs into the bar so the are aligned vertically and slot straight into matching sockets on top of the power chassis. Alignment can be helped by replacing the Tram2 feet with spikes that fit into drill hole guides on the corners of the power chassis. The plugs could be something like ATX or

Click the image to open in full size.

e. I would also place a cement board painted black and with cut outs over the top of the power chassis and have it extend out a little from the sides so the heat of the power chassis does not radiate or convect heat straight up into the Tram2 but instead is forced to conduct heat out to the sides and bottom of the power chassis.

Last edited by kazap; 22nd September 2013 at 09:00 AM.
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Old 22nd September 2013, 09:07 AM   #915
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Exactly what I was thinking as a stacked version. I have the additional chassis from diyhifi and was looking into some military connectors almost like the plugs that you posted. I was then going to put the mu metal on the underside of the ps chassis. I was thinking of how I was going to attach the feet and your idea of bars will work well. The Coleman DC raw supply will be housed in the bottom chassis close to the transformer and then it will feed the Coleman regs in the tram.

I will keep you posted.

Cheers
Greg
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Old 13th October 2013, 11:35 AM   #916
rab28 is offline rab28  Australia
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Hi all, yesterday I finally got around to changing the secondary windings on the Tram2 transformer so that my Coleman regulators can now supply 2.5V across the filaments of my Emission Labs globe 45's.

I also took the opportunity to once again correct the bias voltages to 120+-5 VDC, which eliminated the tube rush-type noise that returned recently in the right channel.

However, the motivation for this post is that, when no music is playing, i can now hear a low level oscillation/feedback type whine that appears occasionally (i would guess something like every 5 minutes or so), lasts for something like 30 seconds, and then disappears again. At first i thought it was microphony following music, but then i discovered it comes and goes even when no music is playing. It also seems independent of tapping the 45's with a fingernail. It's as though the amplifier is very slightly going into oscillation and then out again... but it must be said the level is very low, so in any case it's not a big problem.

I had never noticed this before, and I believe it is a new phenomenon related somehow to the transformer winding change/filament voltage adjustment/bias re-adjustment. My first thought is to re-check all of the voltages, in case, say, the bias voltages have drifted way off.

Has anyone else noticed this or something similar with their Tram2?

- r.

Last edited by rab28; 13th October 2013 at 11:38 AM.
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Old 13th October 2013, 09:41 PM   #917
rab28 is offline rab28  Australia
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... actually, i just remembered that i also replaced my Philips rectifier tube with an EML 5U4G... will also try swapping back...
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Old 15th October 2013, 07:02 PM   #918
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This whining have i often heard on my Tram....have no idear where it comes from..just like yours it is not there all the time..
Bjarne
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Old 4th November 2013, 08:32 AM   #919
rab28 is offline rab28  Australia
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Quote:
Originally Posted by beardman View Post
This whining have i often heard on my Tram....have no idear where it comes from..just like yours it is not there all the time..
Thanks Bjarne, i suppose i'm glad to learn i'm not alone! Sure would be nice to get rid of it though! My friend's Tram2 using the same tubes (except for the 6AS7) does not have it...

Incidentally, yesterday I finally managed to get around to changing my Tram2 volume control board to shunt mode, in my case using a Rhopoint series resistor (as used by Thorsten as an I-V resistor in his DAC). Folks, this is not a subtle improvement! For example, the staccato strums on Doug McLeod's Come to Find used to sound a bit harsh and unclear; now I can hear every string of his guitar without harshness.

Next up is to substitute the Mills resistor and Amtrans cap in the Coleman boards. Parts ordered and on the way!

Thanks again Morten!

- r.
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Old 9th November 2013, 08:34 AM   #920
Desmo is offline Desmo  Denmark
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Originally Posted by rab28 View Post
Thanks again Morten!

- r.
You're welcome..! Glad you tried it...

It's funny why many are so reluctant to try the shunt option in the Tram and stick to ''normal mode''. The shunt is a free option, fully implemented in the design, it's just to move two jumpers and the volume is in shunt mode.

Also, choosing the series resistors for shunt mode gives another possibility in the voicing of the preamp. This resistor is in a very sensitive position in the circuit, so differences between resistors is about as big as differences between caps on the output.
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