[peterpan188]

Hey Guys, I am still kind of a beginner for audio DIY, so please forgive the following questions that may seem dumb. I have made several CMoy and I feel like this is the time to work on something harder (well, for me more elements means more stuff to worry

), so I choose PIMETA, and here are some questions that I encounter during part selections:

1) Is the input capacitor C1 for left and right channel essential? I have measured the DC of my main sources (iPods, CD player and Audigy 2 ZS) and the DC offset is around less than 10mV. There is no part suggestion for C1 from Mouser by tangent(I like ordering from Mouser since its easier for me with the project builder, lazy like me

) Any suggestion on a sub of good SQ and low distortion for C1 that can be ordered from Mouser?

2) The C6G is out of stock from Mouser, any good sub for it?

2) I order a Blue Velvet from tangent, and now I have to worry about the knob. I would love the one used by James281, but I have no idea what that one's model is. Any other suggestion (if possible, from Mouser) would be very appreicated too. (I personally like the alumimum matte finish)

3) I am still undecided about the form of my first PIMETA, whether portable or just for home usage. So for portable usage, what is the smallest Hammond case would allow me to put a Blue Velvet and a Bulgin holder with 2 9V battery? (Am I asking too much for a portable?)

4)I dont have any RCA cable for now, so I guess I will stick to 3.5mm for input for now, I personally own a pair of Senn 497 and e3c, they both come with the 1/4" adaptor, but will I get better sound quality if I use a 1/4" jack for output? What is the ones that I see in almost every build I saw on the above linked thread? If 1/8" is a better choice, any good part from Mouser?

5)Is 18V enough to drive AD8620 and AD8610 combo? Do I have to go with 24V AC for AD843?

6) I am planning on getting a pair of HD650 soon, does the set up I have above looks enough for it?(I got the socket for resistor so I can tweak the gain fairly easily)

6) What is a good pick for R11 when I have 2xBUF per channel?

Heres about the questions I have in mind now (still alot, rit?

) Thank you for any kind response.

 

[Garbz]

1) 10mV with a gain of 11 is 110mV on the output of the Pimeta. Definitly bad for your headphones. C1 is essential in this respect. Any polypropelyne or polyeurathane cap of the desired value (bigger=better) should do.

5) Datasheets for thoes chips say 18V will be fine.

6) For the HD650s No. You want a Dynahi or balanced Dynalo. Mind you you're in a whole different leage here. You are talking about one of the best dynamic headphones money can buy, so if you really want to do them justice you need a best of an amp, definitly not a portable.
That said the PIMETA will sound eons better then no amp at all. Gain won't be a problem either.

 

[kwsuh]

2) I got this from mouser. It's same spec as the one in tagent's partlist.

140-500N2-100J

 

[peterpan188]

For more info, I will be using Vishay RN55 resistors, Wima and Elna caps from tangent, no class A bias. Thank you for your response.

 

[peterpan188]

Bump, can anyone please help with the questoins?
I guess I will use C1. C1 is at the signal path, so I would like to ask that for you guys recommandation on a good sounding cap for it.

Thank you

 

[peterpan188]

3) I am still undecided about the form of my first PIMETA, whether portable or just for home usage. So for portable usage, what is the smallest Hammond case would allow me to put a Blue Velvet and a Bulgin holder with 2 9V battery? (Am I asking too much for a portable?)

anyone? thanks

 

[bhjazz]

Once you decide, do a quick search of the forum. The Monkey, Mr. X, and n_maher have some nice photos of their pimeta builds. Get an idea of the case size they used from that. I'll bet that the elsewhere in those same threads will be someone asking which case it is...Voi'la!

 

[peterpan188]

Thanks guys for all your help.

I have gotten myself a 1455N1601, which seems like would hold everything I need (battery drawer, DC jack, TREAD, Neutrik 1/4" jack and RCA input) in my hands. The finish looks satisfactory to me.

Now I am just wondering, how do you guys drill the holes for all the components? I have a Dremel 400 with circuit cutter and stuff, but the drill it comes with gives me a pretty small hole. On my cmoy, i just open the hole up with the cutter, but it is pretty hard to control and i made some scratches. I dont really wanna do that on the Hammond, so how do you guys do it nice and neat?

Also, how do you guys mount the boards in the case? Open up a hold in the bottom of the case and put a screw through it? I found the Blue Velvet pretty resistant with banding, so i was thinking if i can just leave it with the Blue Velvet going through the front panel and screw on tight. Looks like can't do that with TREAD? Any suggestions?

THANKS again for all you kind help!

 

[rsabo]

I'm planning on using my school's drill press to drill out front panels, but it may not be an option for you. I've heard that there are some good cheap ones out there, might be a worthwhile investment.

I'm curious how most people mount boards as well. Right now I have my amp sitting on the floor of the case with electrical tape underneath.

 

[darkisz]

I picked up a stepped drill bit, AKA a unibit, that I use with my cordless drill. I was able to do all my case work with it. I'd highly recommend getting one if you can.

Mine is pretty small, I think it's 1/4" to 1/2".

 

[peterpan188]

Good idea! but will tat fit a dremel 400? I can't really wanna spend another fortune on another drill. I don't know much about the hand tools world, and to be honese, I took the dremel from my dad just for the casing of DIYs

.

Now the problem comes into how I can mount the board, should I drill holes in the bottom of the case, and put screws, spacer and bolts in? Wouldn't that affect the outlook of the case by quite a bit?

Thanks guys


Quote:

Originally Posted by darkisz I picked up a stepped drill bit, AKA a unibit, that I use with my cordless drill. I was able to do all my case work with it. I'd highly recommend getting one if you can. Mine is pretty small, I think it's 1/4" to 1/2".

 

[tangent]

Quote:

Originally Posted by peterpan188 but will tat fit a dremel 400?

A Dremel wouldn't have the torque to run a step bit even if it would fit. The larger the hole, the greater the resistance, so the higher torque you need to keep that bit turning.

 

[mono]

Yeah, there's sometimes a basic presumption one will have the basic tools such as a drill, and IMO, it would be good to get ANY drill, even the $20 corded generic type before risking cases. You might buddy up to your neighbors, somebody's bound to have a hand drill lying around if not a drill press.

 

[The Monkey]

The Unibit is your friend! It isn't cheap, but it has made my casework so much easier. Peter, I recommend getting a cheap cordless drill to go with it. The Dremel is useful for filing and widening holes.

Also, try to pick up a drill gauge so you can check to see what the exact hole measurements you should drill for your panel components.

As for mounting the board, mine basically stays in place due to the enormous Blue Velvet and the also enormous Neutrik jack. I though about using standoffs and screws, but I'm not really in the mood to drill through the case.

The Tread is just kind of, well, sitting there.

Not sure if that's the best solution. By the way, I suggest lining the bottom of the Hammond with some electric tape.

As for the knob, keep in mind that the Blue Velvet shaft is pretty long (25mm I think), so just make sure the knob is deep enough.

Also, I think it's smart to use C1. I am not using it right now, but I am going to change that soon, as I don't have the patience to check DC offset all the time.

 

[peterpan188]

After reading what you guys wrote, I went to a local Sears to check out drills and bits. I found this which they are having a sale on. It only has 1500rpm max, and it doesn't tell me the torque rating, am I missing something? I understand that the bigger diameter of the hole, the more torque required to drill through, but how can I tell if its strong enough on the specs? Please forgive me the lack of knowledge about tools

.

For step bits, I think for now I will get a 1/4" to 3/4", since for smaller holes I can work out with a dremel (well, if it comes to a point I find a 1/8" to 1/2" I will get it later). For the understanding I have, dremel is good for fine tunning, sanding, and making rectangular-shape holes with their cutters rit?

I personally found that the case work is the most time-cosuming task in DIY. We all want it look good, and there aren't really much other people can tell you with it, mostly your own experience. I found it hard to start out.

Thanks alot guys,
Peter