[Dr. Lloyd]

Thanks in great measure to the communicators on this forum, I am indeed busy these days--soldering iron and drill press are my best friends. This is good for me but does slow down the turnaround time from ordering to shipping. I did manage to get a special version of the Ear+ built to commerorate the 25th unit--a personal model for when I have time to listen. You can see some photos at http://hollowstate.netfirms.com/earplus25commem.jpg. I have enough of the Russian paper/oil caps to build one more--but not for a few weeks please. Thanks again to AudioCircle members for the excellent forum.

Lloyd

[dado5]

Looks real nice.

Thanks for the replacement capacitor. Seems my 2 year old got a hold of it and it went the way of odd socks and car keys.

I am nearly done putting the Ear together. It has been lots of fun. My 7 year old is helping with the soldering and component placement. She is getting a good grasp of the circuit operation in the process. A great learning experience!

I have done a little personalization; swapping the coupling caps with Auricaps (expensive on the headphone output!). Along these lines I have a question: Is the value of the fixed resistor in the balance control circuit critical?  I would like to experiment with a carbon comp resistor here as well as the metal film. I refurbed a Dynaco 35 a few years ago and found the sound to be more pleasing and fuller with the  cheap carbon resistors over the pricier film ones. I have not found a 24.3K carbon comp resistor yet. Would you recommend rounding up or down?

Thanks for the help and the great pics!

Rob

[/img][/i][/b]

[Dr. Lloyd]

Rob:

I am awaiting your report of a successful completion of your Ear+. I considered using a 30 uF or so polypropylene cap (e.g. Solen) and getting rid of the electrolytics in the No. 25 special, but the physical size was just too large. I am wondering if you replaced the electrolytic bypass or the whole thing. The total value is somewhat critical (see my design article on the Ear+). Use of black gate electrolytics would be an interesting mod but pricey too.

Nothing critical about the 24.3K resistors--they form a voltage divider with the balance control pot which gives better control that having no series resistance (also avoids shorting out the source at full balance position). You can use 22K with no problem. It would be good to have 1% matching though--you could do this with 5% resistors and an ohmmeter. You will see a lot of wierd values of 1% resistors used in circuits--the actal values are usually not critical but the 1% allows matching between channels. I use carbon film resistors in the Octal 6 for warmth and have no plans to change. It would be nice to get the tolerance down from 5% to 1% though.

Let me know how the mods turn out.

Lloyd

[dado5]

thanks doc.

I am replacing both caps on the headphone output with a single 33uf Auricap.  I figured the value was critical and this was as close as i could come to the 34uf total. Actually the guy I spoke to at Audience measured a few 33uf caps while I was on the phone and they all averaged around 33.5 -34uf....can't get much closer than that. I just direct swapped the 1uf on the preamp out with a 1uf Auricap. The 1uf caps are $7 each but the 33uf are $60.00 a piece. I debated that for a while, but I knew I would do it eventually so I just went for it since I had the cash. I am putting those in right off the bat so I will not be able to compare the supplied caps with the Auricaps, but I have used Auricaps before in a few CD player outputs and they make a noticable improvement...more dramatic than many cable swaps I have done. They increase the 3D aspect of good recordings and the sweeten and extend the upper ranges on most every record.  They are nearly as sweet as Jensen aluminums, and they have a quicker, punchier bass....the Jensen's come off as boomy and slow in comparison.

I ordered 22K and 27K carbon comp resistors so I will slap in the 22K as you suggest.

The resistors and the big Auricaps are due to arive on Tuesday, so I sould be finished by the end of next week latest.

Thanks again for such a fun and rewarding project.

Rob

[dado5]

The 33uf Auricaps just ain't gonna fit in the chasis as is.  I am toying with the idea of mounting the transformers or the caps on the top of the chasis.  Does Hammond make covers for these trannies?  

A cover at the front of the chasis  may have a side  benifit  for me....it  may help keep the tubes out of the reach of curious little hands.

I will try to make it work somehow and I will post my results.

Thanks,

Rob

[Dr. Lloyd]

I was dubious about fitting in the large poly caps under the chassis. You can put the transformers on top using the same mounting holes and drill holes for the leads, or you could move the caps to the top and feed their leads through small grommets. Hammond makes a tube cage for this size of chassis that will enclose everything. I think it should fit right over the rear transformer cover box as well. If you put the caps on top, they will look cool and be a topic of conversation. If you do this, I can send you shield rings for the tube sockets (attach over the sockets) and three tube shields to reduce the danger of exposed tubes.  

Lloyd

[dado5]

Hi Doc,

Thanks for the suggestion.  The caps will fit on top basically flanking the input tube.  My daughters all liked the look of it with the caps on top, the wife thought it looked silly.  

What would you reccomend to make the holes for the wire feed-through?  The smallest manageable gromit I can find is for a 1/4" hole.  I am thinking a punch will be better than a drilled hole, but I have not used one before (not that this would stop me, I 'll just by one of the little enclosures at Radical Shock and practice).  Any other ideas?

Thanks,

Rob

[Dr. Lloyd]

Rob:

I think a 1/4" drilled hole is fine. Just be careful putting in the grommet not to scratch the finish, right? The grommet has about an 1/8" hole. You will definitely want to use insulation tubing on the cap leads right up to the capacitor body as there is over 100 V on one lead. The 1/8" hole will be about right to let the insulation tubing pass through. If the leads don't hold the caps tightly against the chassis, you might use a drop of crazy glue or epoxy. The grommets should be as close to the ends of the body as possible with the leads going straight down. There won't be much lead showing. If the high voltage on the one lead is a problem for you, then I guess the caps will have to go underneath and the transformers on top. BTW, I think the Hammond cages have lips on the short ends to fasten to the chassis--just where the controls and jacks are on the Ear+ unfortunately. Let us know what you come up with.

Lloyd

[dado5]

Thanks Doc.

securing the caps with epoxy was just what I had in mind.  The Auricaps come with the leads insulated (black and red for polarity indication) and they are made with stranded wire so they are very flexible...very well designed caps...can't say enough good about them.  They are also colorful, that's why the girls liked them.

I am concerned about flexing the chasis and/or damaging the paint with a drill.  I think I might try locate a machinist to make the holes with a drill press.  Which side would you recommend drilling from, the top or the inside?

Thanks,
Rob