[newbie23]

I currently have Oris 150 which are rated at 109 db sensitivity. Will the turn on thump be too loud for the speakers? Is there an output relay or snubber in the circuit to prevent overshoot? My other question is concerning the DACT volume control. I already have a TVC which I would like to use instead and I am assuming the DACT is rated at 10k. Could I use a high quality 10k Caddock resistor in the signal path and bypass the DACT to use the TVC? As you can tell I am a purist when it comes to sound.

[Vinnie R.]

Hi newbie23,

Welcome to audiocircle and the RWA forum!

The Sig 30 and 70s have a small turn on pop (more like a higher frequency transient instead of a thump), but nothing that will come close to doing any damage to speakers... even 109dB speakers.  Sure, you'll hear it more with 109dB speakers vs. 89dB speakers, but it still not powerful enough to damage your speakers.

Yes, I could have designed the output with a relay to wait for full power up before switching the speaker outputs on (and have actually tested a few of them during the prototype stage), but I have found that even high quality relays add some degradation (as well as adding a mechanical part) and I decided that the small turn on transient is minimal enough that it doesn't justify the use of a relay in the speaker output path.

Regarding the DACT, it is 20k (not 10k).  I do not build the Sig 30 or Sig 70s without it.  In theory, you could remove it but will will void the 5-year warranty. 

Could I use a high quality 10k Caddock resistor in the signal path and bypass the DACT to use the TVC?

 

There would be no reason to do this, as the DACT is already very high quality.  Use it to set the gain of the Sig 30 ("set it and forget it") that would allow you to obtain the most useable range out of your TVC, and use your TVC to control the volume.  I do recommend that you also try simply using the DACT (without the TVC) to control the volume, as you will probably prefer the results of doing so over using the TVC in front of the Sig 30... especially if you are a purist as you mention.     I don't recommend using two passive volume controls (the TVC followed by the DACT) in the signal path. but feel free to experiment.

I know TVCs are nice and a lot of people like them, but you need to take my word that the Sig 30 was voiced with the DACT in the input stage and you will throw off the tonal balance if you were to remove it.  The Sig 30 and 70s use carefully selected parts that were not just chosen for their high quality and reliability, but were mainly chosen to give the sound that I was looking for... working together as a whole (a synergy of parts in the signal path, ie, "voicing the amp").  Most of this process was done via listening, trial and error, tweaking, changing, refining, trying different combinations of parts, etc.  It took a long time but it was well worth it! 

Plus, using the Sig 30 would allow you to not need the TVC, so you could sell it  aa

Best regards,

Vinnie



 

[newbie23]

The only way I figure the DACT sounding better in your Signature 30 is leaving out the 20k input resistors in the circuit. Is this why it is neccesary to have? Thanks for the quick response.

[Vinnie R.]

The only way I figure the DACT sounding better in your Signature 30 is leaving out the 20k input resistors in the circuit. Is this why it is neccesary to have?

Hi newbie23,

Not quite... but I do not wish to go into detail about the design of the
Sig 30's input stage. 

Thank you for your understanding,

Vinnie

[newbie23]

I can only assume you use a 10k resistor in the input stage, since this would provide the most usable range. I have more question concerning the brand of the big power electrolytic cap used in the signature 30. How much capacitance is it rated for? My guess is it a four pole Jensen or standard blackgate.

[Vinnie R.]

I can only assume you use a 10k resistor in the input stage, since this would provide the most usable range. I have more question concerning the brand of the big power electrolytic cap used in the signature 30. How much capacitance is it rated for? My guess is it a four pole Jensen or standard blackgate.

Hi newbie23,

I do not use a 10k resistor in the input stage. 

Regarding the power supply cap, I do not wish to disclose the brand or capacitance/voltage.  I have tried MANY different caps (brands and sizes) and invested A LOT of time and effort into voicing the Signature 30 to make it sound totally unique to any other amp out there (even other tripath amps and DIY kits using the similar 2050 chip... I use the 2051, which again, I have found to sound a little different even though they are very similar). 

I do not wish to disclose any more details about the components and the design (ex, inductors, caps, resistors, values, configuration, etc.).  The most that I will go into detail is already listed on the Sig 30 website.

Thank you again for your understanding,

Vinnie