[FishHead]

Thanks for the update! Things are going swimmingly but I am now at the Hammond "choke" point :rolleyes: (couldn't resist). I have two questions. Is it secured with two of the short flat head socket screws and second is the orientation such that the leads are really short or are the leads looped back to the r2 holes?

As for the snubber caps. Those things are for the younger guys. I dropped one! Thank goodness it was on a tile floor and after a little groveling around I was able to find it. I only dropped one more after that one and got a lid to put them in. It was a relief to get them on the board.

 

[FishHead]

Renember that children song. One of these things is not like the others? Well I found a cap that is a smidgen too large.

 

[FishHead]

The impedance of the bias supply is a function of the the source impedance to the transistor's base, and the Hfe (~Rs/Hfe). With the LEDs, the Source Z is ~11 Ohms. Since Hfe is ~300, that means that the bias Z is less than an Ohm. This impedance is multiplied by the mu of the tube and added to the Zout of the plate which is why keeping it low is important here -- especially as the rp of the 6J6 is not particularly low.

But, bypassing the LEDs may lower this even more. We thought it was incidental, and neither of us could hear a difference. On the expensive version of this amp, I don't bypass.

I don't know what this is saying in laymens terms. Being a layman, I want to fill the holes unless I have a reason not to. What is the expensive version of the amp?

Just thought I'd ask as I'm in the middle of the build. :wink_face:

Oh, I have been playing with the choke. Please note, the tabs on it do not lie level with the bottom of the choke. I'm not sure just yet what I wish to do. The least stress on the pcb would be to put a washer under the tab between it and the board. But a washer at each point (above tab, below tab, under board) just does not give enough thread to start a nut with the short screw.

 

[tomb]

Thanks for the update! Things are going swimmingly but I am now at the Hammond "choke" point

(couldn't resist). I have two questions. Is it secured with two of the short flat head socket screws and second is the orientation such that the leads are really short or are the leads looped back to the r2 holes?

As for the snubber caps. Those things are for the younger guys. I dropped one! Thank goodness it was on a tile floor and after a little groveling around I was able to find it. I only dropped one more after that one and got a lid to put them in. It was a relief to get them on the board.

No, the flat head socket screws are only for the endplates.
 
Use the 4-40 x 3/8's for the choke.  Use a screw + washer on the top of the choke tab(s), then place a washer(s) between the tab(s) and the PCB.  Finish up with a washer, lock-washer, and nut on the bottom of the PCB.  Do this x 2 to get both tabs mounted.  Just an FYI, but every single 4-40 screw should have washer under its head, except for the endplate case screws.  Likewise, every single 4-40 screw assembly will have a lock-washer, except for the endplate case screws (flat-head socket screws) and the RCA jacks screw.  The standoff assemblies should have the lock-washer between the screw head above the PCB and a washer.  Just use a short 4-40 x 1/4 with a single washer on the bottom of the case to screw into the standoff from the other side. 
 
Cut the choke leads to fit to the holes next to the R2 holes.  Remember, though - measure twice, cut once!  If you get them too short, you can't get them back.  Anyway, the PCB pads for the choke leads are separate.  The R2 holes are way too close; there's quite a bit of bending of the leads as it is.  The choke lead holes are the very large pads on the edge of the choke square silkscreen - at the end of D4 and R1.
 
All SMD should be executed with tweezers.  You pre-tin one of the pads by melting solder on it, then grab the SMD part with tweezers in one hand and while melting the tinned pad with the soldering iron, position an end of the SMD part on the pad with the melted solder.  Remove the iron, wait till the solder cools, then remove the tweezers.  Go back and solder the other end of the part to the other pad and you're done.
 
FYI, but every DAC on diyforums.org has SMD soldering explained in excruciating detail.  Something like a 1206 capacitor is even easier than through-hole soldering once you learn how to do it.

 

 

[tomb]

Renember that children song. One of these things is not like the others? Well I found a cap that is a smidgen too large.

Try again. 

Renember that children song. One of these things is not like the others? Well I found a cap that is a smidgen too large.

Hmm ... I believe Auricap makes a 4.7uf in 400V.  That would work, but I can't seem to find one available right now. So, maybe they're not available in that voltage anymore.

 

 

[tomb]

 

The impedance of the bias supply is a function of the the source impedance to the transistor's base, and the Hfe (~Rs/Hfe). With the LEDs, the Source Z is ~11 Ohms. Since Hfe is ~300, that means that the bias Z is less than an Ohm. This impedance is multiplied by the mu of the tube and added to the Zout of the plate which is why keeping it low is important here -- especially as the rp of the 6J6 is not particularly low.

But, bypassing the LEDs may lower this even more. We thought it was incidental, and neither of us could hear a difference. On the expensive version of this amp, I don't bypass.

I don't know what this is saying in laymens terms. Being a layman, I want to fill the holes

unless I have a reason not to. What is the expensive version of the amp?

Just thought I'd ask as I'm in the middle of the build.

Oh, I have been playing with the choke. Please note, the tabs on it do not lie level with the bottom of the choke. I'm not sure just yet what I wish to do. The least stress on the pcb would be to put a washer under the tab between it and the board. But a washer at each point (above tab, below tab, under board) just does not give enough thread to start a nut with the short screw.

 
1. Believe me, capacitors at C7 and C8 make absolutely no difference at all.
 
2. The expensive version of the amp is based on a different tube type and a foreign toroid as the PT.  It's not economically feasible to build/sell it for the performance return.  It's quite a bit more expensive.  We've been toying with building one using the same Edcor PT, but results are a long way off, even assuming it works.
 
3. I've said this a few times, but maybe it hasn't caught on.

  Yes - the Hammond choke tabs are warped.  That's why you need washers between the tabs and the PCB.  DO NOT torque the tabs down without washers in those positions.  You will destroy the PCB.  You do not use the short screws - use the 3/8" long 4-40 socket head cap screws.  You have almost an inch below the PCB and an inch-and-a-half above the PCB.  There is absolutely nothing to gain by using a short screw.

  The only thing those are used for are the three standoffs.  That's because there's not enough thread length to work with screws going in on both sides of the standoffs and taller screws would stick further out the bottom than the rubber bumpers.

 

[FishHead]

Yep, you did say that but I guess it had not sunk in about the washers on the choke. I will post some pictures of the choke build later for guys like me who can read but not quite comprehend on some days

My problem was keeping track of ths SMD while on the table and picking them up. Tweezers! What a great invention. Just didn't have any at the time.

The caps may be available at thetubestore. That is where I got the big ones. I ordered a set of the 400v ones so I can compare against the other ones when I get back stateside.

Still having fun with the build.

 

[dsavitsk]

I don't know what this is saying in laymens terms. Being a layman, I want to fill the holes unless I have a reason not to. What is the expensive version of the amp?

This is just saying that you want the bias supply's impedance to be as low as possible, and that theoretically including the capacitors makes it lower. In practical terms, the difference is negligible. Using the caps may even be detrimental.

The expensive version of the amp is this one: http://www.ecpaudio.com/L2.shtml

 

[tomb]

Yep, you did say that but I guess it had not sunk in about the washers on the choke. I will post some pictures of the choke build later for guys like me who can read but not quite comprehend on some days

My problem was keeping track of ths SMD while on the table and picking them up. Tweezers! What a great invention. Just didn't have any at the time.

The caps may be available at thetubestore. That is where I got the big ones. I ordered a set of the 400v ones so I can compare against the other ones when I get back stateside.

Still having fun with the build.

Sounds good!

Make it a good pic on the choke and I'll post it on the website. I apologize for not having it detailed already.

 

[FishHead]

What you need


Top side stack


Bottom stack w/ lock washer.



Where I cut



All choked up.

 

[tomb]

All choked up -

 

[dpump]

This is just saying that you want the bias supply's impedance to be as low as possible, and that theoretically including the capacitors makes it lower. In practical terms, the difference is negligible. Using the caps may even be detrimental.

The expensive version of the amp is this one: http://www.ecpaudio.com/L2.shtml

This is confusing. If the capacitors are making the impedance lower and that's a good thing, how can they also be detrimental? I installed capacitors in my amp since I happened to have them. Should I remove them? What would be the detrimental effect of having them installed?

 

[FishHead]

Missed it by that much. I got it all cased up and ready to plug in and realized the fuses were 110 v. This weekend I will track some 220s down. I decided to go with the Mundorf Aluminum EVO caps first.

It was a fantastic and fun build experience. The finished product is very professional looking.

I have followed the development from the beginning and respect the significant sustained effort put in. I certainly bennifited from it. Thank you and props to everyone who contributed along the way.

 

[dsavitsk]

This is confusing. If the capacitors are making the impedance lower and that's a good thing, how can they also be detrimental? I installed capacitors in my amp since I happened to have them. Should I remove them? What would be the detrimental effect of having them installed?

If the impedance is different at different frequencies, it could cause phase issues. I feel like someone measured such an effect on a similar circuit, but I can't remember when or where I saw that, so I don't know if it is actually something to be concerned about here. The best I can say is to try it both ways and see.

 

[gabriel-dan]

Hi,
I read somewhere in this tread that the Torpedo might not be a suitable amp to drive orthodynamic headphones. Has someone actually used it with something like Hifiman HE 500 or LC2?. I am tempted to purchase the kit from Beezar , however not sure it will drive my orthos to a proper  volume. Tx