Torpedo III Build Thread

[dsavitsk]

I understand the need to ground it but couldn't that be done with a center tapped secondary and grounding the tap?

I know I have seen that done, but I don't see the benefit. And on the downside it would have made winding these transformers (and switching windings) a lot harder.

As for the second point, if balanced output doesn't give a benefit for short cable runs then what is your opinion of amps(Schiit Mjolnir1/2, Headamp GS-X, etc) that have a balanced topology and a balanced output? Should the balanced output only be used for long cable runs or in a professional setting?

Personally I just think that having an amp balanced all the way to the end has a sort of aesthetic appeal that you don't have with one that is balanced except for the last part. But that's just my bias.

I try not to have public opinions (positive or negative) of other people's amplifiers.

I will say that I use 4-pin connectors on amps all the time. I would prefer the whole headphone world move from TRS to 4-pin XLR,and where necessary simply ground 2 pins. So I agree with you on the aesthetic appeal. But here we are trying to keep costs as low as possible and appeal to as many people as possible, and everyone has a phone with a TRS jack. Maybe the T4 will have an XLR jack

I believe dsavitsk will want to weigh in on this, but my perspective is as follows - I suspect that in solid-state, the primary benefit of having differential all the way to the headphone is from the increased voltage swing that's created (slew rate, too, admittedly).

I like differential for the power supply isolation aspect. Phones need so little power that getting extra voltage swing or slew rate it are generally non-issues.

Although I think you are mistaken for the need to double everything to have a balanced output. I actually don't know of any tube amp with balanced output that uses two output transformers to create a differential signal.

You would never use 2 transformers.

 

[tomb]

Balancing Act -> Balanced (not differential) input via input transformer, single-ended gain stage, single-ended output stage feeding transformer for balanced output

Torp III -> Single-ended input, LTP differential input stage, differential follower feeding transformer for balanced output (that happens to have one leg grounded)

A reminder that differential is not the same as balanced.

Yes - and thanks. Although, for all intents and purposes, there is really only one individual who attempts to make that distinction: balanced not equal to differential. For most everyone else, they are the same.

 

[cspirou]

@dsavitsk-Ok so I am still trying to understand this. Even though you said that a balanced connection gives no benefit to a headphone user, if given the choice you would prefer to use 4pin XLR?

Or do XLR connections have a benefit with an ungrounded floating secondary? However you would only consider this for the low voltages in an SS amp and not the high voltages present in a tube amp?

And back to the torpedo III. After looking at the schematics you posted for the L-2 and the DSHA, it looks like the Torpedo III is a mix of both! Would you say that making both amps is what led you to making this design for the Torpedo III?

 

[dsavitsk]

For most everyone else, they are the same.

Balanced circuit and differential circuit are different, though often very related. The argument you are referencing was about balanced inputs versus balanced circuits and whether saying just "balanced" refers to the former or latter.

@dsavitsk-Ok so I am still trying to understand this. Even though you said that a balanced connection gives no benefit to a headphone user, if given the choice you would prefer to use 4pin XLR?

The big benefit of the 4pin is that it does not short the output while plugging and unplugging. And it allows for unreferenced differential outputs (see below.)

Or do XLR connections have a benefit with an ungrounded floating secondary? However you would only consider this for the low voltages in an SS amp and not the high voltages present in a tube amp?

This gets a little arcane With a high voltage circuit with an OPT, the secondaries must be grounded. With a high voltage circuit w/o an OPT, the output must be ground referenced.

In the DSHA2, since it is low voltage, this is not necessary. Using an XLR jack allows the circuit to be fully differential and not ground referenced without using an OPT.

The benefit here is not so much the balanced output, but the fact that the differential circuit can remain differential. If it needed to be ground referenced, it would either need a slightly different topology, or an OPT (both of which would raise the cost.)

And back to the torpedo III. After looking at the schematics you posted for the L-2 and the DSHA, it looks like the Torpedo III is a mix of both! Would you say that making both amps is what led you to making this design for the Torpedo III?

They are very related But the "innovation" of the T3 is that the OPT sort of works as a capacitance multiplier. That is, by running the buffer at high voltage we can use a low capacitance low current PS which I find to be quieter and easier to make sound good than a low voltage high current supply. The OPT converts everything down effectively increasing the output current by the turns ratio.

 

[tomb]

 

Although I think you are mistaken for the need to double everything to have a balanced output. I actually don't know of any tube amp with balanced output that uses two output transformers to create a differential signal.

You would never use 2 transformers.

 
It won't be the last time I embarrass myself with an assumption. 

 

[TheEnthusiast]

So, how soon 'till you take my money for this kit?! 

 

[HiGHFLYiN9]

Perhaps you gents could shed some light on a ballpark price for the kit?

 

[OJNeg]

Anxiety overload in this thread

 

[dsavitsk]

So, how soon 'till you take my money for this kit?! :atsmile:

Perhaps you gents could shed some light on a ballpark price for the kit?

I have shipped the nickel transformers to Tom, but he won't have them for a couple more days. I think he is very close to being ready to accept orders, but the number of i's to dot and t's to cross is enormous. So I think it will just be a couple of days, but I know we've said that before. Suffice it to say that we would like to accept your money even more than you'd like to give it to us, but we need to make sure that the process is seamless.

For pricing, I'll let Tom answer that since he is setting up the site, but I will say that the nickel OPTs add a ~$200 premium to the base price.

Anxiety overload in this thread :veryevil:

Indeed.

 

[tomb]

OK.  I received Doug's shipment.  The shipment included my first prototype that I sent him with the Edcors, plus a few Cinemag pairs.  I've listened to my prototype where he replaced the Edcors with the Cinemags.  Plus, I spent the last two days building another Torpedo III with the production PCB and a couple of the Cinemags he sent, just to be sure.  (There were some minor differences in the PCBs, plus, we spec'd a new PT from Edcor.)
 
The results?  I think he understated the sound quality, but maybe that's just me. 

 
 
 
P.S. One warning in a DIY build with the Cinemags.  They're taller than the Edcors, so: Do not forget to install the ground wire on the Alps BEFORE installing the Cinemags.  Guess why I know that.

  I will do my best to get the first few kits on sale this weekend, but the reference website may be a bit sketchy.  Still, this thread is perfectly valid for construction - Edcors or Cinemags. 

 

[Luckbad]

How much will the Torpedo III full kit be?

 

[drfindley]

I see the new kit is up, but I don't see how to get cinemag transformers. Did they already sell out?

 

[FlySweep]

I see the new kit is up, but I don't see how to get cinemag transformers. Did they already sell out?

My eyes are most likely broke.. But where do you see it available? I checked beezar.com & the Torpedo DIY page and didn't see it.

 

[tomb]

THE NEW KIT IS NOT UP.
 
You are seeing the Torpedo I with a price increase.  That's all there is right now.
 
I'm working feverishly.  Hopefully, there will be something up tomorrow and it will be perfectly clear which is which. 

 

[drfindley]

  THE NEW KIT IS NOT UP.

 
Ah, sorry to disturb the peace. Not all change means new