ECP Torpedo III [indexed in first post]

Your builder certainly can

TomB - if you read this, please share an update on the output CCS boards

 

Yes please As I understood Tom when he mentioned them recently, they should be ready soon.

 

Thank you. If I'm understanding correctly, you're using these resistors in place of the electronic choke, correct?

Awesome.. thank you, Mike!

 

Not correct... The electronic choke is part of the power supply and replaces 1 resistor. These 12 resistors are in the signal path - see my post on P36 where I give my impression on the resistors, the specific resistors are mentioned in that post.

 

Ooer. Where in the circuit will we insert these output CCS boards?

@MortenB not everyone fled from your resistor post. I'm going to try some AMRGs in those positions as well, just haven't gotten around to it. Too busy selling a MicroZOTL2 and enjoying the T3 as is. But I did just toss a set of them in my Hifi Collective cart with a bunch of other junk I needed... ;-)

 

Great Start with the 4 plate load resistors (100K / 2W), they are the most important ones, and then go from there...

 

Looks like i can start the build this weekend, my kit has cleared customs

 

The output CCS boards replace R19, R20, R21, & R22.

 

Ah, so that probably means removing the Mundorfs to get in there. Okie dokie then!!

 

D'Oh! Corrected. See above.

 

Ah OK... the Mundorfs are safe! LOL

 

Hey, quick question about the OPT (Cinemag or Edcor, doesn't matter)... I noticed in the schematic the secondary is just wired up directly to the J1, but for some reason I had it in my head that a light parallel load like a 1k resistor and maybe a Transzorb across the headphone connections would be desired for protection. If you remove the headphones from the jack while the amp is running otherwise, is there any concern of damaging the OPTs?

 

Received the kit, somehow thought it would be bigger! Packaging was excellent and i only got semi shafted by customs. Had to pay 175€ for taxes and handling. So not to bad i guess, looking forward to starting the build tomorrow

 

There is some thought that in speaker world with highish power single feed topologies, running an OPT with open secondaries can lead to extremely high voltages that can damage the transformers. In reality, I have never heard of this actually happening, and there are practical reasons for why it probably can't - namely the DCR of the secondary acts as a sort of load. When we get to the point that there is superconducting wire to wind our transformers with, it will be more of an issue.

But more to the point, this is not that topology so it is not an issue here. In particular, besides the fact that the power levels are simply too low, a parafeed OPT does not store energy in the same way that a single feed OPT does, so even with the load removed it will never swing more than the signal level. So you are free to run the thing however you want, and to plug and unplug with impunity.

 

Good for you..! That's 120€ less than I had to pay here in tax-hell-denmark. And good luck with the build

 

For the 4 plate resistors.. I plan to go with the same Amtrans you mentioned, Morten.

For the Shinko's in R5/6/7/8 & R9/10, do you recommend either 820 ohm or 1.3K ohm for all six resistors?; or a mix of those two values (like you did in your build)? I'm considering the Takman carbon film resistors for these positions, as well.. but I sense that having carbon film resistors in all these positions could be a little heavy handed, no? If so, any other (non uber pricey) Tantalums you'd recommend?

 

Thanks!

 

The plate load resistors gives the biggest sonic impact, so go with the Amtrans AMRG there if you want the fuller and punchier sound I described.

I used 1K5 and 820 ohm because that was what I had, and it's impossible to find 1K Shinko's now. If you go with Shinkoh's then buy what you can get. If there are 6 of the same value then fine. If not you can mix like I did. However R9/10 must be the same value of course. And R5/6/7/8 also must be the same value. If you buy other resistors, then stay with the 1K.

For some reason the Takman only had minimal effect in the T3, I would not bother to replace the standard 1K resistors with those. Remember, I had the Takman carbons from the beginning, so the changes in sound I described was going from Takman carbon to the combinations of Amtrans and Shinkoh. What you could do is to buy a pair of 0.75W Amtrans AMRG to use for R9/10 (the grid stoppers) and then test, if you think it becomes too much or not.

This is all about the fine tuning of the sound and we have to try things out to learn what works.

 

Any idea if going with some nice metal film resistors (instead of carbon film) in R5-8 and/or R9/10 is worth chasing? I'm essentially after the exact same type of sound you've illustrated. Natural, organic, yet highly resolving, transparent, and balanced (not that gooey, slow, thick sound).

Have you rolled the stock tubes into your TIII since the resistor and choke upgrade? I'd be interested in those impressions since the stock EH tube were, for the most part, considered bright-ish and thin with a stock (or even slightly modded) TIII.

 

Have you bought the Mundorf caps Riotvan..!? If not, then you can buy my pre-bend and burned in caps