The ask dsavitsk thread

[Pars]

I just wanted to chime in and say how excellent Doug is. II emailed him a while back about my amp and seeked his opinion on what he saw with the schematic and my description. The man seems to have a very thorough understanding of tube circuits and maximising performance. We got together for him to check out and implement some of the things he felt needed addressing. This included bypassing the cathode bypass caps which were electrolytics with some obbligato films. Doug measured voltage levels and made sure that generally speaking things were running to spec as I had concerns of resistors and caps drifting a bit and whatnot.

Doug saw the biggest improvement in my amp to be the input stage, and I agree. I have always thought that Craig with his designs could have delved more into maximising the input stage. The majority of his amps lean on using the 6SN7/6Sl7 resistor plate loaded into the output stage, sometimes with a cap sometimes DC coupled. In my case with the 6J5 though the amp has never disappointed me I always felt and heard that the tube was not running optimally, and never was truly driving the 2a3 or 45 as well as it could. After almost a year with the amp the sound manifested itself simply as a traditional, SE DHT type of sound, a slight softness to tone and just a lack of pop for lack of a better word.

Doug sent me some info and links as well as his own experience with using an active load CCS for the plate of the input tube 6J5 (specifically a depletion mode cascoded CCS I believe). I felt this would be a step in the right direction. An led bias was also put in, and current was doubled running through the tube to operate it in a more linear part of its curve. Other than cool red LED lights popping through the hood and portholes I am pretty giddy and startled at the results. More gain for one thing, which was very noticeable on speakers, and a sense of more focus and definitely more clarity. The proverbial "wiping another layer" of grunge that exists in our audio path. The amp was quiet before but I do notice that there is a sense of vividness and contrast that I don't think was there before. I am looking forward to living with the tweaks a bit and just soaking it in and enjoying the music.

Doug was really nice and gracious with his time and thoughts, and he is just a super nice laid back guy. In fact we have other ideas and thoughts for the next time we get together, he truly is a perfectionist and he seems to be able to see lots of different angles on how to approach things. The amps that he built, especially his espressivo, are fantastic. That little balanced mosfet follower he has sounded great.

That was really nice of Doug to take the time to do this. I would really appreciate it if he would ever have the time to take a look at my Counterpoint preamp that I have been working on with limited success for quite some time to eradicate a bit of noise.

[recstar24]

That was really nice of Doug to take the time to do this. I would really appreciate it if he would ever have the time to take a look at my Counterpoint preamp that I have been working on with limited success for quite some time to eradicate a bit of noise.

I agree, couldn't ask for a better friend. Doug and I plan on getting together sometime within the next couple of weeks to check out his new amp he is designing and building, I will shoot you a PM and I am sure we can all get together.

[dsavitsk]

I didn't know if there would be an issue tying the shield to ground (or earth) if the heater is floated above ground (by ~ 60V). So, I suppose this is my first question, is this okay?

So far as I know, the shield is not connected to anything else. But, you can just AC couple it to ground or earth or whatever.

Now, lets say I want to use a ECC99 or 12AT7, in which pin 9 is a center tap, not a shield. To do this, I swap out my 0-6.3V heater winding with a 0-12.6V windings as well. Can I really connect this to ground (or, is earth more appropriate) since the heater is raised? Reason says that this needs to be tied to the voltage divider instead.

If I understand what you are saying, then no. You would have one side of the heater tied to 60V and the other, or the center, tied to ground, which would mean 60V across the heater. You'd have a race to see whether the heater or the resistors would burn up first.

Finally, does any of this change (100R false center tap, raising said center tap up 60V, pair of ceramic caps at socket pins, and whatever arragement you propose for the shield/CT) if this 0-6.3VAC and 0-12.6VAC winding becomes a DC heater? I agree that a +-3.15VDC and +-6.3VDC bipolar DC supply would be better since it takes care of common-mode noise, not just differential mode... but assuming I don't have that luxury, does the above arrangement still work well?

I think you are fine, AC or DC.

Are you really getting noise from the heaters that requires all this effort to eliminate?

[luvdunhill]

Are you really getting noise from the heaters that requires all this effort to eliminate?

no, it works fine. I'd just like to try some 12V tubes. It looks like I need to add a jumper from pin 9 of the noval tube that allows the pin to be floated (in the case a 12V tube is used, where pin 9 is a CT) or connected to earth (in the case a 6V tube is used, where pin 9 is a shield), since I cannot connect the CT to ground / earth due to floating the heaters up 60V. Sound reasonable?

[Looser101]

.1uF cap from pin 9 to ground.

[luvdunhill]

hey doug:

I remember you having a website that you recommend that has a number of test tones that can be burned to a CD.. i've created a few of my own, but would like to see what they offer and what other tones I might add to my CD.

Thanks!

[deepak]

hey doug:

I remember you having a website that you recommend that has a number of test tones that can be burned to a CD.. i've created a few of my own, but would like to see what they offer and what other tones I might add to my CD.

Thanks!

Bink Test cd by any chance?

Michael Knowles: Extras

[Grahame]

Or this perhaps

Audiophile MFSL Gold CD 24-Karat SPCD-015 / Alan Parsons & Stephen Court / Sound Check

(check out the track listing in the link)

[dsavitsk]

I remember you having a website that you recommend that has a number of test tones that can be burned to a CD

Nothing magical from me -- I've used these but I can't vouch for the quality.

Realm of Excursion - Audio Downloads

I've also downloaded tone generation software and used it to make tones -- but I can't remember which software.

Oh, and I have one of these:

[dsavitsk]

A little teaser ...

[n_maher]

That amp is officially looooooooooooooooong, can't wait to hear more about it.

[luvdunhill]

that's really, not LESSSSSSSSSSSSSSSSSSSSSSSSSS very sweet though!

[TomB]

A little teaser ...

<img]http://www.ecp.cc/images/L'es4-1.jpg[/img>

<img]http://www.ecp.cc/images/L'es4-2.jpg[/img>

Yep it's long. I had to beg Hammond to send us a couple of special length extrusions of the 1455-series cases. They actually sent Doug and I two for free! They're hoping we'll order a lot more like them.

I'm looking forward to this one.

[n_maher]

Yep it's long. I had to beg Hammond to send us a couple of special length extrusions of the 1455-series cases. They actually sent Doug and I two for free! They're hoping we'll order a lot more like them.

I'm looking forward to this one.

The case is about 12" long, right?

[TomB]

The case is about 12" long, right?

13", to be exact. That's a d*mn good guess just from the pics.

[digger945]

Are the opts socketed?

Very cool

[aerius]

Thanks for posting those latest pics, I finally know what to do with the wooden boxes that my bottles of whiskey came in. I've been struggling to find a use for them and now I know.

[recstar24]

Nate,

I don't want to speak for Doug or Tom, but I believe it is going to be a pretty sick project that would be able to compete with the Starving Student for best tube based budget project, and something easy enough where even a newbie like myself could tackle it as a 1st project. However it appears luvdunhill gave away a nice hint at the circuit of the amp.

[luvdunhill]

Well, in all fairness, it was quite evident from the name of the photo itself

http://www.ecp.cc/images/L'es4-2.jpg

[dsavitsk]

13", to be exact. That's a d*mn good guess just from the pics.

To be even more exact, it is 0.5mm shorter than it needs to be

Are the opts socketed?

No, just PCB mount -- you could probably socket them if you really wanted, but I'm not sure the benefit ...

able to compete with the Starving Student for best tube based budget project, and something easy enough where even a newbie like myself could tackle it as a 1st project.

That's the idea -- the parts cost is remarkably low -- $1 tube, which is still a secret for now , $9 OPT. The most expensive things there are the IEC and the Alps pot (unless you use Auricaps, I suppose).

Well, in all fairness, it was quite evident from the name of the photo itself

I need to shoot Gary an email to be sure that it isn't going to step on any toes.

[Beefy]

That's the idea -- the parts cost is remarkably low -- $1 tube, which is still a secret for now , $9 OPT. The most expensive things there are the IEC and the Alps pot (unless you use Auricaps, I suppose).

Sweet, I'd love to build one then for shits'n'giggles. Here's hoping it doesn't have a ridiculously high gain like the Starving Student did

[n_maher]

Sweet, I'd love to build one then for shits'n'giggles. Here's hoping it doesn't have a ridiculously high gain like the Starving Student did

Knowing Doug I'd be somewhat surprised if it had gain.

[TomB]

To be even more exact, it is 0.5mm shorter than it needs to be.

</snip>

Once they anodize them, that'll probably add back the 0.5mm. ;)

[Bidoux]

That's the idea -- the parts cost is remarkably low -- $1 tube, which is still a secret for now , $9 OPT.

A cheap OPT headphone amp is a really cool idea. Are the tubes NOS or in production ?

[dsavitsk]

Sweet, I'd love to build one then for shits'n'giggles. Here's hoping it doesn't have a ridiculously high gain like the Starving Student did

Knowing Doug I'd be somewhat surprised if it had gain.

Here are the curves of the secret tube ...

We use a custom made transformer with 300 and 32 ohm taps on the secondary. Without accounting for copper losses, etc, this gives an overall gain of just under 2 into 32 ohms, and just under 6 into 300 ohm loads. In reality, this probably turns into 1.5x and 4x, or something like that. But, I've been using an old TDA1545 DAC with very low output, and there is plenty of gain for that, but with a dac with normal output, there is still enough play in the pot.