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PostPosted: Sat Apr 22, 2017 11:52 pm 
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I just noticed that the Tramp Layout and Schematic were revised last back on Jan 5 2014 (Layout Rev #17 and Schematic Rev #15). Primarily I see the removal of resistor (R25) and the change of the VRM resistor (R22) from 100k to 220k, as well as some suggestions for shielded wiring options to lower noise.

Can you give us any info on what these revisions do and specifically are the resistor changes an improvement the Tramp's VRM circuit?

I completed my kit (Layout Rev #14) back in early 2013. For a couple months now I have been wanting to get my Tramp “back on the bench” to clean some solder connections, to work at quieting noise around v1 (shortening some of those leads) and to make the mid boost mod. Since I will have my Tramp on the bench, I thought I would also bring my Tramp (my layout version #14) up-to-date with Schematic Rev#15 (2014) specs.

I do have two specific questions:

1) Regarding the resistor changes, shouldn't the removal of old R25 and the change of R22 from 100k to 220k (1w) both need to be done at performed at the same time?

2) I noticed that for optimum “low noise” at “max gain” you recommend an option of using shielded cables in a couple additional places now. Would it be a problem for me also to add a shielded cable from C1 (.1uf) on the board over to R1 (10k) (your yellow wire on your new color Rev 17 Layout)? The leads to V1 and back to the board seems very sensitive to noise (that is why I am “cleaning” things up in that corner and shortening those leads on my Tramp). So, would it hurt also to add a shielded cable from C1 to R1? If so should the shield be grounded back to the common preamp ground star or is it okay to ground it to the the other shielded cable going to the 330k resistor (R6)? I would want to avoid multiple ground points.

I apologize if all of this has been covered in another thread. I could not find one, but if there is one, just point me to it.

Thanks

Cecelius2


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PostPosted: Sun Apr 23, 2017 3:44 am 
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Hey mate how's things? Interesting you should bring this up because I just noticed the change to R22 a couple of weeks ago (My amp works great so I wasn't thinking about actually doing it but wondering more about the mechanics behind the revision) so thanks for raising this. I hadn't noticed added shielding but that is interesting too because my Tramp is the quietest amp I have ever used, I mean idle noise is unnoticeable even when cranked. I built my amp in 2012 (wow where did that time go).


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PostPosted: Sun Apr 23, 2017 8:00 am 
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Coax wont hurt but in the extra position, it is very short and wont really make a difference. Best palce is where there are long runs at low voltages.
Best thing for noise is to shorten up the low level leads.
The VRM resistor was changed to increase the lower voltage floor of the VRM because it was too unusable at lowest settings.
No Need to remove that resistor. It was a redundant voltage draining resistor. Just leave it there, won't hurt anything.

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PostPosted: Sun Apr 23, 2017 5:08 pm 
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Thanks Coco for your reply. This is very helpful information.

C2


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PostPosted: Sun Apr 23, 2017 6:12 pm 
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No457 Snowy wrote:
Hey mate how's things? Interesting you should bring this up because I just noticed the change to R22 a couple of weeks ago (My amp works great so I wasn't thinking about actually doing it but wondering more about the mechanics behind the revision) so thanks for raising this. I hadn't noticed added shielding but that is interesting too because my Tramp is the quietest amp I have ever used, I mean idle noise is unnoticeable even when cranked. I built my amp in 2012 (wow where did that time go).


Thanks. I just sent you a PM.


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PostPosted: Mon May 08, 2017 10:19 pm 
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I finished these mods and really like them. The VRM resistor change definitely helped widen/increase the usable range of the VRM potentiometer. Before this fix, mine was okay between 8&10, but lower than 8 was grainy and distorted; now I can go down to about 5 and still have good clarity and good volume reduction; below 5 it still lowers the volume but does get distorted. I also replaced the mosfet with a new one as well as a new zener dioded. All of this has made the VRM much more usable.


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