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Old 11th October 2012, 02:49 PM   #571
Desmo is offline Desmo  Denmark
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Originally Posted by clivetjm View Post
I'll stack the Tram on top of the identical phono chassis to judge the looks. This will probably be the deciding factor as to which route I go. The separate trafo seems like it ought to be a benefit but whether it's worth the effort and expense is hard to assess.
I can't see why a separate trafo should be a benefit, but it's not worse than using the existing one as long as the wires are short.

The Tram and the phono stage can look nice when stacked (I know) What you should consider is that you will have to bolt the two together so they form one unit. Having cables out the back of a power supply box, through cables to the preamp box, and then running through the preamp box is a no-go. If using a separate box the wires should go straight up from the box under the Tram...

Personally I think it's much better to have everything in one box, with short connections - but that's just me.
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Old 11th October 2012, 03:00 PM   #572
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Originally Posted by Desmo View Post
I can't see why a separate trafo should be a benefit, but it's not worse than using the existing one as long as the wires are short.

The Tram and the phono stage can look nice when stacked (I know) What you should consider is that you will have to bolt the two together so they form one unit. Having cables out the back of a power supply box, through cables to the preamp box, and then running through the preamp box is a no-go. If using a separate box the wires should go straight up from the box under the Tram...

Personally I think it's much better to have everything in one box, with short connections - but that's just me.
I would bolt the 2 chassis together to form one box, I would also cut large holes in the top to the PS chassis to let air through to the top chassis and out via the tube sub-chassis. There would be zero external wiring, it would all go through the large holes I would cut.

The wring to from the trafos would be shorter than if I used the TRAM trafo.

What am I missing here? This seems like a technically marginally more optimal solution and Rod feels there could be some benefit due to the heater recharge pulses not being coupled to the other windings in the TRAM trafo.
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Old 11th October 2012, 03:09 PM   #573
Desmo is offline Desmo  Denmark
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Quote:
Originally Posted by clivetjm View Post
I would bolt the 2 chassis together to form one box, I would also cut large holes in the top to the PS chassis to let air through to the top chassis and out via the tube sub-chassis. There would be zero external wiring, it would all go through the large holes I would cut.

The wring to from the trafos would be shorter than if I used the TRAM trafo.

What am I missing here? This seems like a technically marginally more optimal solution and Rod feels there could be some benefit due to the heater recharge pulses not being coupled to the other windings in the TRAM trafo.
I don't think that you are missing anyhing Clive. Notice that Rod does not say that it will be an improvement. He says that it's hard to predict, and that it might...

Again: If you like two chassis bolted together to form one unit and can keep the wiring short etc, then that will be a good technical solution and it will work well for sure. For me personally that's a technical/mechanical solution trying to fix a problem that is not there, but that's just me according to my priorities. You make your design of the DHT implementation according what you think is the best solution. That is the beauty of DIY

One thing is sure though: The improvements in both sound quality and noise performance is -more than-worth the effort..!
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Last edited by Desmo; 11th October 2012 at 03:26 PM.
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Old 11th October 2012, 03:58 PM   #574
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Originally Posted by Desmo View Post
I don't think that you are missing anyhing Clive. Notice that Rod does not say that it will be an improvement. He says that it's hard to predict, and that it might...

Again: If you like two chassis bolted together to form one unit and can keep the wiring short etc, then that will be a good technical solution and it will work well for sure. For me personally that's a technical/mechanical solution trying to fix a problem that is not there, but that's just me according to my priorities. You make your design of the DHT implementation according what you think is the best solution. That is the beauty of DIY

One thing is sure though: The improvements in both sound quality and noise performance is -more than-worth the effort..!
I take your point that the 2 chassis thing could be a solution looking for a problem. I just wanted to go through the process of thinking is through fully. I'm not wedded to the extra expense and work! I suspect I'll end up going down your route.
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Old 11th October 2012, 04:18 PM   #575
Desmo is offline Desmo  Denmark
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Originally Posted by clivetjm View Post
I take your point that the 2 chassis thing could be a solution looking for a problem. I just wanted to go through the process of thinking is through fully. I'm not wedded to the extra expense and work! I suspect I'll end up going down your route.
Thinking everything through is always the good thing to do. And I'm not saying there is one right way to implement these regulators in a Tram II. It's always looking for the best compromise. Things to consider on the two-box-bolted-together-as-one-unit route that are not related to the technical side of the two box solution are for instance:

What will happen with resale value? I think it will go down quite a bit on a Tram II that no longer looks like a Tram II and is based on two boxes with all kinds of holes cut in them.

How can decoupling be made in an efficient way that does not compromise the sound? (A box on top of a box is usually a bad solution sonically).

Etc...

Regarding the B+ supply: Remember that in our Tram II's there is done a lot to supply a very clean and good B+ to the triodes: First there is the tube rectifier and the very effective electronic choke supply. Then the Mu-follower tube and finally the FET based CCS. Not until after all that comes the tube.
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Old 11th October 2012, 04:39 PM   #576
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Resale's not really an issue, there would be no holes cut in the TRAM chassis, just the new lower chassis. The preamp could be returned to original spec in a few minutes.

As for decoupling, they would be rigidly bolted together via the 6 existing base plate holes, it would act as a single chassis.

The main issue is that the chances are that the benefits are not guaranteed to exist and if they do exist they may be very small.
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Old 11th October 2012, 04:47 PM   #577
Desmo is offline Desmo  Denmark
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There are never guarantees. I'm quite sure, that the benefits will be extremely small, if there will be any. Likewise the risk of a two box solution being worse sounding than a one box solution is also extremely small. But I think it's just as likely that a two-box can be marginally worse sounding as it can be marginally better... My honest opinion: No sonic difference, so choose the mechanical solution you like the best...
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Old 11th October 2012, 04:54 PM   #578
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Well-implemented B+ conditioning will certainly reduce the chances of any difference - I was not aware the TRAM had a FET choke.
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Old 11th October 2012, 04:59 PM   #579
Desmo is offline Desmo  Denmark
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Well-implemented B+ conditioning will certainly reduce the chances of any difference - I was not aware the TRAM had a FET choke.
Slightly off topic here, but this is the block schematic for the Tram II. The ''DIY HFS film capacitor universal PS'' after the rectifier tube is the electronic choke supply. After that the Mu-Follower tube and the CCS

Click the image to open in full size.
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Last edited by Desmo; 11th October 2012 at 05:04 PM.
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Old 12th October 2012, 01:31 PM   #580
disco is offline disco  Netherlands
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The use of chokes (without core or with iron core) replacing drop resistors for filament supplies isn't noval

Click the image to open in full size.
These puppies I use for years, up to 1A. They're effective outside AF, I never did an listening test*. No cure, no harm

Click the image to open in full size.
When distance is to be covered, I split the supply in a 'noisy part' near the transformer and a 'clean' part as close to the load as I can get.

*DHTrob reported progress with air wound coils on filament supplies.
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Last edited by disco; 12th October 2012 at 01:37 PM. Reason: *
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