300b's for Kaiju

[drewh1]

Hi Paul - BTW, I really appreciate you spending this much time on this issue. I am really trying to keep my system simple. unfortunately my DAC has been made with the same philosophy and does not have a volume control. I would prefer to build an external passive volume control since I do not need additional gain or source switching. If you could tell me the input impedance of the Kaiju, I'll figure out what I need to use and build it into a separate box. I can use my servo on any Goldpoint and can build one to match the necessary impedance. I am able to keep the interconnects very short so that shouldn't be a big issue. 

thanks again for your time with this.

[Paul Birkeland]

Your DAC has a heroically low output impedance (something like 70 Ohms), and the Kaiju has 100K input impedance.

A passive control that was in the 10-15K range between the two should work well. 

If you need long cabling anywhere in the chain, I would recommend having it between your DAC and whatever is feeding the DAC, which would allow for the DAC itself, level control, and amplifier all to be fairly close together.

-PB

[drewh1]

thanks Paul!  I also may have found a solution that takes out any additional circuitry in the signal path. I can control the volume digitally with J-River. Should have no impact on quality at all. I have been playing with it with my Stereomour. I just have to find a convenient way to access it remotely. So I have options. Anyway, I am now super excited about building this amp and can't wait to start ordering (after the first of the year!)

Really glad you guys do what you do. Happy New Year.

[jdm]

drewh1

I am using dual 10K mono Goldpoint ladder type attenuators between an Ayre QB9 and Paramount 300B amps (original version with 12at7) with no problems. Interconnects are 2 feet long from dac to attenuators and 3 feet from attenuators to amps.

Jim   

[drewh1]

Great to know Jim - thanks.  I am going to go with Goldpoint so I can attach my servo motor to it. I have my DAC and amp located next to each so I can get away with very short interconnects.

I am interested in the digital volume with J-River, but am reading conflicting reports about quality impacts. imagine that in the audiophile world

BTW, I just got the DSD upgrade. I had the old 96k version. It really is worth the money, takes the QB-9 DAC to a whole new level. Not a subtle improvement, and way cheaper than buying a new DAC. Highly recommend it.

[Doc B.]

I am interested in the digital volume with J-River, but am reading conflicting reports about quality impacts. imagine that in the audiophile world

The only way you can resolve this is to try it for yourself. You get what you pay for when it comes to opinions on the internet.

[drewh1]

Ain't that the truth!

So I just put my order in.  One more question.

Knowing I'll be using the EML Mesh Plates, I did not order tubes. I assume I will need to make sure the Filament Voltage and current are correct prior to using the tubes. Can I measure this without tubes, or will I need a cheap set of tubes to set things up?

thanks again, when does it ship?  (joking of course)

[jdm]

drewh1

Have had the dsd upgrade for just over a year now.  Use Cd's (44.1) ripped to external HD with mac mini running Pure Music and the difference/improvement is worthwhile to me.  Must try some high rez PCM and dsd soon.

Jim

[drewh1]

It is amazing how well 44.1 sounds through this DAC. I keep going through my old CD rips and it is like hearing them for the first time. I have downloaded comparison DSD and 192 PCM files. I couldn't hear any audible differences. J-River (which I use) converts DSD to PCM anyway. Charlie Hanson prefers PCM so the DAC probably does a better job with it anyway!

[Paul Birkeland]

Knowing I'll be using the EML Mesh Plates, I did not order tubes. I assume I will need to make sure the Filament Voltage and current are correct prior to using the tubes. Can I measure this without tubes, or will I need a cheap set of tubes to set things up?

Provided the instructions are followed in the manual for measuring your AC line voltage and selecting the appropriate power transformer wiring, no additional testing is necessary.

[drewh1]

Got my kit!  It includes the DC Regulated filament kit - Given that I will be using EML's from the start do you still recommend building the kit stock and then adding the DC circuit board?  l

I won't have my tubes for a couple of weeks, so I could probably get everything done prior to the arrival of the tubes. I  can't measure voltages before getting the tubes and would prefer to have the circuit in place prior to firing up the tubes.

thanks for the advice.

drew.

[fullheadofnothing]

Read p. 10 of the DC manual.

[drewh1]

Well, of course I did read that page. The reason I am asking is that Paul J. recommended that I utilize the DC Filament circuit for use with the EML's.  So I am just making sure it is reasonable to start using the EML's safely with the AC then switch over.

I also need to modify the circuit after getting some measurements. So, I also imagine the measurements won't be accurate until I have the DC circuit in place.

[Paul Joppa]

In the best of all worlds, I myself would use cheap, worn tubes until everything is running correctly and the filament voltages look perfect. I can do that, because we have plenty of tubes lying around. The only reason for such care is that the EMLs are really expensive, and I have a substantial portion of Scottish DNA. My grandfather used to say we were descended from the finest horse thieves in Scotland - also the reason my ancestor moved to America...  :^)

But I'm assuming you don't have a spare pair of used 300Bs. So yeah, build it stock, take it slow and careful, and do all the tests. Be extra careful about the power transformer input voltage (starts on page 29). If there are any questions, this is the place to bring them up. We will be paying special attention to any confusion or problems, until there are a few successful builds.

A few hours at a slightly wrong filament voltage will not harm most tubes, but EML specifies a very tight +/-4% on the filament voltage, and conforming to that spec is important to retain their warranty.

[Doc B.]

Just to give a little of our rationale here, what we can give competent tech support for is an amp assembled by the method we describe in the manual. Which is to say assemble it with the AC supply first, make sure it is functioning properly, and then install the DC upgrade. If the amp is built with the DC supply from the get-go, our tech support advice in the case of it not working is to tell the builder to complete the amp with the AC supply first, make sure it works right, and then install the DC supply.  When part or assembly changes are made to a first run kit you will have to wear your pioneer hat.
(https://americanhistory.si.edu/sites/default/files/styles/large/public/Fess%20parker%20cap%20b.jpg?itok=zxO6ofxf)