ECP Torpedo III [indexed in first post]

The Vishay Naked Z foils are (probably) the most transparent and neutral resistors avaliable. Very, very good stuff. They are not 0,6W though, they are 0,4W as can be seen when clicking the official spec sheet from Vishay at the partsconnexion site. They might survive as plate loads, but they will be running hot.

I choose the Amtrans carbons to balance out the slightly lean bass and slightly bright treble of the T3 with Mundorf parafeed caps. The Amtrans resistors has a relatively full bass and a slightly rolled off treble giving great synergy and tonality at that time. It's great that the output CCS has improved the tonality of the T3, and this will of course mean, that other resistors are now a better choice for a neutral balance.

The Vishay naked Z foil are IMHO the best resistors (also the most expensive). Will they last? Bazelio will know soon

Another very neutral and transparent option is the TDK 2W metal films I posted about earlier. See pics earlier in the thread. They are quite big... I found them too bright, but more transparent, than the stock resistors. The Amtrans gave better tonality. This was before the output CCS boards. http://www.partsconnexion.com/resistors_tkd_two_watt.html

My main point all along has been, that resistors matter for best sound (many believe they don't), and that the plate loads are an important spot in the circuit where the sound can be tweaked and optimized giving changes equal/more than tube changes, but for a lot less money. I realized, that I have not managed to communicate this well enough, I simply don't have the vocabulary in a second language to get more complex matters across - very frustrating - so I mostly stay offline now.

 

I've read the datasheet for the parts I obtained prior to obtaining them. They have a 0.6W peak rating, and 0.4W RMS, assuming 70C temp. Both ratings are within the calculations posted by Doug; found in the manufacturer datasheet here. And they're working well for 16+ hours straight. I'm living life on the edge, though, I know.

I've been liking the naked z foils a lot. They seem to have no character of their own, as did the AMRG resistors. The bass quantity might seem slightly reduced at first listen, but after extended listening, I now realize that it's a cleaner bass than the AMRGs, and that merely gives the perception of less output. The AMRGs did their job for a while, but I do like final sound signature from the combo of CCS output boards and z foils better.

Edit - And by the way, the naked foils are available in higher power ratings in the multi-chip models. Didn't see any of those available on discount.

 

Aren't plate load resistors usually up-rated in wattage to reduce noise? I guess the Z foil's are very high end so they are going to be quiet.

http://www.diyaudio.com/forums/tubes-valves/119683-where-low-noise-resistors-matter.html

 

I just installed all 6 CCS boards. I worked with the bottom of the board facing up. On the output CCS boards I couldn't get any solder to flow all the way through to the top of the board. Is this going to be a problem? The bottom of the board looks good, but not sure if I need solder through the entire hole. Super hard to get access to them from the top of the board, and those pins are all very heat hungry.

 

My $0.02, it's a good idea to get it to flow through on these boards or solder from both sides if you can not. I made sure it flowed through on my boards. You could try boosting the tip temp a bit for better flow but there are a lot of variables here, including temperature, tip type, solder type, solder diameter, flux, etc. For example, I really dislike lead-free solder as I find it harder to get good flow. I stick with standard eutectic solder (though I've started using Cardas quad eutectic recently) and I have a few different diameters which can make it easier to apply the right amount to the specific application, chisel tips in a couple different sizes, and I vary the temp from time to time as needed (particularly when desoldering).

@Mr.Sneis :

 

If I am to flow all the way through, I would have to desolder these boards and start again. After desoldering the resistors I don't really want to put that strain on those holes. I was able to apply a small amount of solder on top, so hopefully that takes care of it. Everything went fine on the initial build, but this rework was a bit more challenging.

 

That reference has a dead link for the Vishay metal foil document. This one is current:
http://www.vishaypg.com/docs/49997/49997.pdf
[Edit: I like the Fig. 2 graph in this doc, because it shows metal in the context of carbon - both film and comp.]


I had found the Vishay article a while ago, but for some reason, couldn't find it again when I posted the results of the Amtrans in the T3. The Fig. 2 graph in that article is pretty illustrative. The "Deposited Carbon" bar is essentially carbon-film resistors. It's pretty obvious that their noise is very slightly better than carbon comp, which pretty much everyone agrees is the worst.

According to the graph, bulk-foil appear to have the advantage, but the thin metal films we use as standard will equal the bulk-foil if they're in the low noise range of metal films. Wirewound is slightly better in noise, but as the article describes, they come with so much inductance that they cause a whole host of other issues. So, I agree the foil resistors could be an advantage, but if the thin metal films that we use as standard are on the low end of their noise range, the advantage may not be there.

Note that the standard metal films used in the T3, both assembled and kits, are Vishay BC, PR020002 series. They have 0.78 Cu wire leads (the rest is Pb and Tin - no Fe).

 

Solder on top does the same thing. If you've heated enough to melt solder on top and solder on bottom, you can be pretty certain that the through-hole plating has been melted into the joint, too.*

What's most important, really, is to ensure those Output CCS boards are flush to the PCB. After initially soldering them into place, I put the T3 board up on its side. While pushing on the top of the Output CCS boards with my fingers, I melt the solder again on the bottom of the PCB, then remove the heat while still pushing down with my fingers. That ensures that the CCS boards are tight against the PCB and cuts down on the potential wiggle.

EDIT: Bazelio is correct that flow-through is best, but as he said, there are a lot of variables in play that work together sometimes to prevent you from doing that.

* Just to be clear, I'm referring to "flowing" the solder on top, too. It's not enough to simply apply solder on top like a paste. You need to "flow" it into the joint. If done correctly, it pretty much melts the solder on the other side, too. Anyway - give it a shot.

 

The voltage is on the edge too. The max rated voltage of 200V is below what Dough recommended earlier in the thread (I think it was 300 volt). Using them as plate loads is living on the edge for sure, it will be really interesting if they last. If they do it's great news - I agree that they are the most transparent resistors avaliable.

As seen on the power deration curve in the datasheet their power rating drops with ambien temperature above 70 degrees: 0,4W at 70 deg (0,6W peak), and 0,2W at 125 deg (0,3W peak). As Dougs calculations showed there will be more power running through the plate load resistors with signal than at idle. Dougs calculation says 0.484W peak with signal. I know we don't have these kind of ambient temperatures inside the chassis, but air moves slow and the ambient temperature will be relatively high just around the resistors, and at the resistor element.

Do you have any way of measuring the temperature of the resistor element itself after playing music through the amp for a few hours with the top cover in place? It would be interesting to know the temperature...

 

Voltage is regulated at 225V. With V*I being inside limits, it's probably OK. Welcome to life on the edge. Not recommended for the feeble or weak at heart. And to anyone wanting naked metal foils, I highly recommend the 2 chip module version to remove all doubt. EDIT: That part number is TX2575-2 I believe, whereas I am using TX2575.

Now back to listening to music instead of talking about resistors... I need all the listening time I can get before mine blow up, too.

 

lol that's great. Can't say what (if any) difference there is with the TKD 2w resistors there since I did the output ccs at the same time, but this thing is so killer.

 

You mention resistors, but we can't talk about resistors

If the temperature is high enough you might be close to max spec or outside spec. That's why it would be helpful for the rest of us, if you would check the temperature...

 

For those who will only use the very best: http://www.mouser.com/ProductDetail/Vishay-Precision-Group/Y0028100K000T0L/?qs=INhxIttfpiA5%2bshy6EbBkA==

Best = most expensive, right?

 

According to the spec sheets, those TKDs should not be much different than the metal films we're already using. I suspect most everyone else is hearing the same thing you are.

 

This part number might be better, it's rated for .6W instead of .5 - Y0785100K000T9L

datasheet here

 

@Smitty , @TheloniuSnoop - Those parts don't match up to the naked z foils in all categories. Example, while 5ppm TCR is certainly very good, it's not in the same league as the naked metal foils.

@MortenB - Ok just because I love you, I asked my buddy to borrow his Flir E4 which he modded the firmware to enable all Flir E8 features. He will bring it in tomorrow. This will be an effective tool for these measurements. I will take some measurements from outside the chassis and detect temp through the vent slots, as well as try to quickly remove the cover after warmup and take a quick image.

 

Yes I expect you are quite correct. Such an awesome amp.

 

Ok, I decided to desolder and redo the output CCS boards to get good flow-through. Mission accomplished.

Any recommendations on adhesive? Tom was kind enough to send a generous glob along with the boards, but by the time it got to me it was already cured. Dow Corning 748 is not easily obtained from a reliable source. I haven't fired the amp up because of a lack of adhesive, but I'm itching to hear the improvements.

 

Amazon non corrosive electronics grade silicone. MG chemicals brand iirc.

 

Thanks, ordered. Any worries about firing this up a few times without it? Won't have the silicone for 2 days.