Topic: New TS-2 Preamp ... under development (part II)

[JD]

Don't overlook the possibility of manufacturing in China.

Personally, I would rather pay a higher price than see this made in china.

You can specify whatever quality you need, and manufacturing costs would be 10-20% that of doing it in the US.

digifish

I understand you can get whatever quality you are willing to pay for from China, my reason for not wanting to purchase Chinese goods has more to do with political views and the fact that I work in the manufacturing sector and I am tired of seeing American jobs going offshore.

I have no problems paying a premium for domestically made goods.

[ScotK]

All right - noob question - what's all this talk about transformers and transfomer-less versions?
Where in the chain are the transformers used for what and why would one want/not want them?

thanks

s

[dactylus]

Don't overlook the possibility of manufacturing in China.

Personally, I would rather pay a higher price than see this made in china.

You can specify whatever quality you need, and manufacturing costs would be 10-20% that of doing it in the US.

digifish

I understand you can get whatever quality you are willing to pay for from China, my reason for not wanting to purchase Chinese goods has more to do with political views and the fact that I work in the manufacturing sector and I am tired of seeing American jobs going offshore.

I have no problems paying a premium for domestically made goods.

I agree.  I would prefer that this product designed in the USA be manufactured in the USA and I would pay to keep it that way.

[fivefishdiy]

Initial units will be manually assembled.

If the monthly volume demand is low, they'll continually to be manually assembled.

If the monthly volume is fairly consistent, assembly by a US based company and conversion to SMD is the next step. 

I'm not even thinking beyond that.

So to those who are worried about China assembly... there's nothing to worry about.  That will be like STEP 100, and I'm only on STEP 1. I don't even know if it will get to Step 100.

[muj]

you could run a series of 25 units at introduction price  with prepayment,then after evaluating the first sale , come to conclusion of whether getting these produced somewhere else ..

[MattD]

Jeeze - it's between this and the V3 - cant decide....hey could somebody go out and run over their V3 for me so I can do a true A/B comparison!!!???

This has nothing to do with anything, but Metric Halo ran over their devices with a front-end loader or similar equipment. Those little aluminum boxes can take a ton (literally)!

[ScotK]

Just re-reading this (and pt 1)... was there a final decision on offering an 1/8" output for those
with recorders that use them?

What I can gather about the transformers is that they're just another option (vs. passive resistors) to
attenuate the signal - that can be argued sound better/are better than a passive system. Am I even
on the right track here?

thanksm

scot

[stevetoney]

What I can gather about the transformers is that they're just another option (vs. passive resistors) to
attenuate the signal - that can be argued sound better/are better than a passive system. Am I even
on the right track here?

No, input transformers on a mic preamp usually serve one or more of the following purposes:

1) Eliminate the need for input capacitors
2) Provide very high common mode rejection ratio (rejection of interference in a balanced circuit)
3) Provide some amount of gain (not attenuation!), to improve the noise performance of the circuit
4) Provide a sonic benefit due to desirable nonlinearities
5) Convert the incoming balanced signal to unbalanced, for the following amplifier stage

You can use a transformer to attenuate a signal, but that's not usually done at the input stage, because it would degrade the noise performance of the circuit.  Also, there is nothing wrong with using resistors for attenuation, that's the way it's usually done, except it would be switchable.  It's also possible to use a multitap transformer for switchable attenuation, but I don't know if anybody does that.

#5 is handy for some preamp designs, because it saves you an amplifier stage.  It wouldn't matter in this design because of the use of the instrumentation amp.

OK, thanks for the response (if I can kibitz because I've wondered about transformers too).  However, for the people that aren't electricians or sound engineers, can I ask more questions in an attempt to translate (transform  ) your answer a little bit?

1) you said that transformers reduces capacitors...I guess that's a good thing from the standpoint of less parts needed in the design (less to solder onto a board and less that can go wrong)

2) I kinda understand this one...it's the concept of the opposite sound waves canceling each other out.  So, I guess what is happening is the transformers are using this concept to eliminate undesirable (maybe non-hearing range?) frequencies from passing by cancellation, but allowing the frequencies in the hearing range to pass?  Got a feeling I'm not on the right track here.

3) OK, number 3 is easy enough to understand.

4) In other words, the transformers can take specific frequencies and amplify them differently to provide different overall output 'flavors' (warm, transparent, cool, etc), rather than amplifying all frequencies exactly the same amount? 

5) You explained that one a bit, but frankly that seems more design related than anything and doesn't have any relationship to what the end user cares about.

Please explain if I'm on the right track with these elaborations.  Thanks!

[fivefishdiy]

1) you said that transformers reduces capacitors...I guess that's a good thing from the standpoint of less parts needed in the design (less to solder onto a board and less that can go wrong)

#1. Transformers block DC voltage (from the phantom power) going to the mic pre stage.  Because DC cannot travel from the primary winding to the secondary winding... only AC voltages can do that (which is the mic signal in this case.)  A tiny capacitor can do the same thing, DC blocking.

Yes, you have one less capacitor to solder but trafos bring its own kind of baggage. Trafos are expensive, bulky, heavy. And in a market where users are price conscious, trafo-based gear is usually out of the question.  So while a trafo will get rid of that small capacitor, it brings with it it's own set of "cons.".... $$$ of the part being the biggest thing. The bulkiness of it demands a bigger case, which is more $. The heaviness of it adds shipping weight, which adds to shipping cost, which is more $.

If the market is willing to pay for it, then trafos are used.


Got a feeling I'm not on the right track here.
#2. In simpler words, using a transformer on the input chain makes for a very quiet, clean signal with injected noise being cancelled out due to CMRR properties of the trafo.  Hum induced on the line is also cancelled out and does not get transferred to the secondary windings.

#4. The different materials used in the trafo core affects distortion and other things. Things that are then described as "flavor".  Some core materials have minimum distortion and sounds clean, while others add some bit of flavor. There is also some phase changes going on.

#5. Normally, a mic pre circuit is unbalanced and you use a transformer to convert from balanced to unbalanced.

With the THAT chips I'm using, it's a little different. The balanced signals of the microphone goes directly into the chip.  So a trafo is not necessary nor do I need a separate balanced receiver circuit to do the "unbalancing."

[ScotK]

Awesome- thanks all for the transformer discussion!

scot

[Kindguy]

Awesome- thanks all for the transformer discussion!

scot

Yes good stuff.

[ScotK]

Anyone else getting TS-2 withdrawls here?

scot

[fivefishdiy]

Update: Just waiting for the front panels from the prototype shop.  Won't be here until next week.

In the meantime, I found an old project I was working on back in 2005/06? 

(Not tapers related, but since we're talking preamps here.... This is old school discrete design, home-etch PCB, Ferric Chloride, manual drilling and none of that fancy silkscreen, no IC chips, just plain old fashioned transistors and input transformers and output transformers running on high voltage DC.... yup... this guy is not "green-friendly"...  Bigger is better, more is better, the more you live, the more you love.



Replaced and upgraded the PSU with my new PSU-4448 kit design. Replaced XLRs and just soldered all loose connections.


Output I measured is more than the limit on my oscilloscope.


Looking good at 50khz and I measured 46+ Volts peak-to-peak before clipping.


YES! 46+ Volts... which is not unusual since the whole preamp is running and requires a supply voltage of 48Volts. 
Absurd! Overkill! But whoa!... the sound... it's phat and beefy and just too much... 46Vpp!!!  Did you see the size of that output transformer?

This will bring into submission any AD converter that is unfortunate enough to be on the receiving end. It will slap that AD converter silly. 

and now back to regular programming....


.

[bugg100]

Well, why haven't you?    It sounds interesting, with all the new micro recorders seemingly most all with noisy pre sections...  We need companion pres for the Zooms, R-09's, DR-1 (gt-1), iRivers, Oly LS-10's etc, etc.

It really is a great time to be a taper!

+t to 5Fish and MSHilarious for the open design process.

[Church-Audio]

You really think 100 units is realistic?

Well, that depends on price, doesn't it?  But no, I don't think that's necessarily long-term demand, but initial demand, given the interest on this thread, could be quite high.  The difficulty is if one plans for production of ~5 units per month, and initial demand is say 50 units, then the backlog will never go away, at least for a very long time.  Then you end up with the 2-5 month lead time you see from other vendors.

I will say it's not an accurate gauge of demand to look at kit units sold.  The interest in assembled units is at least 10x kits.

Then it becomes a chicken-and-egg problem:  you can't fill demand without designing the process for that demand; you can't generate the demand without hitting the price point, which requires the higher quantity.  So then if you have a process designed for low unit volume, once you get tired of losing every evening to soldering, the backlog grows and demand slows down . . .

I dont think demand and price point have anything to do with each other. I build by hand 20-30 preamps a month + microphones... A product is in demand because its good not because its cheap especially in a market where the consumer knows the difference.