DiY AMI U47

[Melodeath00]

Ok so I'm reading a bit about polypropylene being pretty common in output capacitors in mics. I hear about WIMA a lot, and I have found Erse and Auricap as well. Auricap is a bit expensive ($22 per). Erse is a good price, but they are out of stock of the 1uF it looks like. WIMA I can get at mouser, but they look like boxes as opposed to cylinders. Is that typical for WIMA capacitors? I was considering paper in oil, but I can't find these except on ebay, so I may just go with polyprop.

I have read carbon resistors are typically noisier than metal, but might be more "musical." I don't necessarily believe that, but carbon would be more true to the vintage mic anyway, so I think I am going to use Carbon Resistors in the circuit, except for the high impedance section. I don't think you can find 1G carbon. In fact, I'm having trouble finding any 1G .5W resistors. Is it ok to go up in wattage? Again, due to inexperience, I have no idea, but I found some 5W 1G thick film resistors on mouser.

All comments are welcome!

 

[HellfireStudios]

The carbon resistors will most likely have more drift when heated by the tube. The musicality of the carbon comps is only applicable in tube guitar amps where they tend to sag the sound a bit more than the metal film variety. Better lifespan and a more consistent sound over that life is why metal film has surpassed the old carbon comp.

WIMA caps are good quality, and usually rectangular in shape. Wunder Audio have been using Illinois metallized polyester caps in there highly regarded U-47 clone. I like them for my signal caps too (the 400 volt ones are big so stick with 250 volt, if you can). Just be aware that sound differences in audiophile grade caps will be subtle. I would try the best cost-to-performance cap, and upgrade if you think it is needed.

-James-

 

[Melodeath00]

Thanks for that info. So maybe I'll just do all metal resistors. Carbon resistors don't look expensive, but it looks like there's carbon composition, as well as carbon film, and it's getting confusing...

Is upping the wattage in the resistors alright in the circuit? I can't find 1G .5W.

I've seen two 400V Auricaps fit side by side in the AMI body. It's good to know differences will be subtle. I just don't want to end up purchasing "low quality" pieces on mouser that end up sounding poor.

 

[HellfireStudios]

As far as resistors go, upping the wattage is ok. Again, size may be an issue, but that is doubtful.

-James-

 

[Melodeath00]

Many thanks!

I just started to wonder about those WIMA box-shaped caps. Are they easy enough to work with in a point to point setup? PCB makes sense, as there is a set distance between the ends of the cap, and you could fit it nicely into a PCB. But this is not a PCB build. Two caps will be underneath the transformer, connecting to 2 circuit boards. It seems like an axial form would be the only way to make it work. Am I wrong?

Am I going to need silver teflon wire for this build? I didn't think so at first, but now I think I'm beginning to see I will need it to travel up fromt he transformer deck to the high impedance and tube section.

 

[Moby]

Carbon resistors don't look expensive, but it looks like there's carbon composition, as well as carbon film, and it's getting confusing...

Just read this http://en.wikipedia.org/wiki/Resistor#Carbon_composition and everything will be clear. BTW, there is nothing wrong with carbon film resistors in this circuit 

 

[o3misha]

In the microphone very small currents are flowing. Only at high currents may appear sound quality resistors. The tolerance -important point. Older carbon composition resistors have poor tolerance and can change their resistance when heating is applied. There is nothing good about it. It is necessary to use a stable resistors. From modern I recommend Kiwame.

 

[Moby]

I agree about carbon composite resistors but  carbon film are different story. More precize, less noisy and just right for this kind of circuit. Just my 0,2c

 

[Melodeath00]

Thank you Moby and o3misha!

I have to ask, will a Radial capacitor work in this build? In all the internal pics I've seen, Axial-type capacitors are used below the transformer deck. But Erse is backordered for 45 days, and AuriCap is expensive, so I was thinking about WIMA, but they are all Radial like this - http://www.mouser.com/ProductDetail/WIMA/MKP4F041005D00JSSD/?qs=sGAEpiMZZMv1cc3ydrPrFwgzP98AO9idiZzKagcAeOU%3d

Is there enough lead to bend into "Axial" form?

 

[Moby]

I have to ask, will a Radial capacitor work in this build?

Of course, no problem with package, what you look is type of capacitor. In this case,  you choose MKP. Cool, but it sounds bit different from vintage MP or PIO.

 

[Melodeath00]

I have to ask, will a Radial capacitor work in this build?

Of course, no problem with package, what you look is type of capacitor. In this case,  you choose MKP. Cool, but it sounds bit different from vintage MP or PIO.

Yes. It's just that I've read good things about WIMA and polypropylene. I'm not sure I want to go into the realm of vintage capacitors for my first build. Vintage MP would be more true to the U47, but I'm already using an EF800 instead of VF14, which probably has a bigger effect anyway. It doesn't look like Mouser stocks any of their "paper" 1uF 250V caps, so that's another problem. I don't want to wait 14 weeks. I also doubt a modern "paper" cap is the same as vintage metal paper sound-wise.

I open to your comments. I can always replace the capacitors later once I know my build works 

 

[Moby]

I can always replace the capacitors later once I know my build works 

Exactly

 

[Melodeath00]

So I have made the decision that since this is my first build, I better buy a "test" capsule and transformer, so I don't blow up the expensive Beesneez K7 and Tab-Funkenwerk BV8.

What are my CHEAPEST options for test capsule and transformer? I've looked at microphone parts, advanced audio, and Peluso, and it seems the cheapest BV8 is Advanced Audio for $58, and the cheapest capsule is a $75 K67 from AA. Am I missing any cheaper options for testing?

 

[micaddict]

http://store.studio939.com/product/35mm-k67-style-capsule

 

[Melodeath00]

Thanks, micaddict. So that takes care of the capsule for sure. If there is a cheaper BV8 than $58, let me know!

Any advice on shockmounts is appreciated as well. The Cathedral Pipes is currently the cheapest at $30, but I could get a Peluso pretty easily if it's much nicer.

 

[Melodeath00]

Ok I should have a very cheap BV8 and K67 on the way just for testing. They probably wont be necessary, but this is my first build so I want to be very careful.

AMI kit is still on the way.

Can anyone let me know if this is a good soldering iron for mic building and PCB work? http://www.amazon.com/Weller-WLC100-40-Watt-Soldering-Station/dp/B000AS28UC/ref=sr_1_2?ie=UTF8&qid=1367888638&sr=8-2&keywords=soldering+iron+weller#productDetails

If it's not, could you suggest another? So far two people have mentioned that it doesn't have temperature control/feedback, so maybe this isn't so good? Much appreciated!

 

[Pip]

Can anyone let me know if this is a good soldering iron for mic building and PCB work? http://www.amazon.com/Weller-WLC100-40-Watt-Soldering-Station/dp/B000AS28UC/ref=sr_1_2?ie=UTF8&qid=1367888638&sr=8-2&keywords=soldering+iron+weller#productDetails

If it's not, could you suggest another? So far two people have mentioned that it doesn't have temperature control/feedback, so maybe this isn't so good? Much appreciated!

Better
http://www.amazon.com/Weller-WES51-Analog-Soldering-Station/dp/B000BRC2XU/ref=sr_1_1?s=hi&ie=UTF8&qid=1367906125&sr=1-1

Best
http://www.amazon.com/Weller-WESD51-Digital-Soldering-Station/dp/B000ARU9PO/ref=sr_1_8?s=hi&ie=UTF8&qid=1367906378&sr=1-8#productDetails

50 watts more than enough.

 

[Melodeath00]

Can anyone let me know if this is a good soldering iron for mic building and PCB work? http://www.amazon.com/Weller-WLC100-40-Watt-Soldering-Station/dp/B000AS28UC/ref=sr_1_2?ie=UTF8&qid=1367888638&sr=8-2&keywords=soldering+iron+weller#productDetails

If it's not, could you suggest another? So far two people have mentioned that it doesn't have temperature control/feedback, so maybe this isn't so good? Much appreciated!

Better
http://www.amazon.com/Weller-WES51-Analog-Soldering-Station/dp/B000BRC2XU/ref=sr_1_1?s=hi&ie=UTF8&qid=1367906125&sr=1-1

Best
http://www.amazon.com/Weller-WESD51-Digital-Soldering-Station/dp/B000ARU9PO/ref=sr_1_8?s=hi&ie=UTF8&qid=1367906378&sr=1-8#productDetails

50 watts more than enough.

Thank you! Is there any particular reason I would really need temperature control for mic building? Those look very nice, but they're a lot more expensive than that $40 iron, and I know people do a lot even with $20 irons.

My AMI Kit came in by the way! A small baggy of resistors and caps was included, which is great because I didn't think I would receive any circuit parts with the kit. However, I'm still trying to read the color bands on the resistors to see if they're all the correct value. Also the circuit has 10 resistors, and there are only 9 in the bag.

 

[tskguy]

These are the absolute super best awesome soldering tool you will ever own! They can be had or pretty darn cheap on eBay if you take the time to look. They heat up instantly and adjust their power depending on the amount of metal present. So if its a large ground plain it doesn't take forever for the solder to flow.
I have an older model and I can't imagine going back to the "normal" soldering iron.

http://www.amazon.com/Metcal-Soldering-Station-MX-5000-Series/dp/B001F7S5DG


Eric

 

[Melodeath00]

Wow that thing looks crazy haha. I just checked ebay and they're still way out of my league. This is baby's first soldering iron haha

It's probably between the $40 WLC100 and the $90 WES51 Analog. Just depends on if people think I need the temperature control or not.

So the local RadioShack has some 62/36 solder at 0.015". Is that too thin in your experience? I was planning to get some 63/37 at 0.032, but it's expensive and a huge 1 lb spool, which I don't need. Thanks!