Soldering components in parallel
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Author:  adamgggg [ Tue Feb 16, 2010 11:07 am ]
Post subject:  Soldering components in parallel

Hi, I am in the middle of building the tube mic pre. I am following the mods that were listed in a Tape Op article.

One of the mod instructions is "C21 and C22 were replaced with 10uf 16v Black Gate "N" types and .1uf Sprague Orange Drops placed in parallel"

How do I fit these components "in parallel"? Does it mean squeeze 2 components into the slot for one component?

Otherwise, really enjoying building the kit so far!


Author:  PAiA-Scott [ Wed Feb 17, 2010 11:07 am ]
Post subject:  Re: Soldering components in parallel

Yes, that's right, just line them up side-by-side, twist the legs of one to the other, flow a bit of solder to the twist, and clip the extra excess leaving one set of leads to put through the two holes.

This photo is of similar sized parts and is an example of the way they can paralleled to go in the closely spaced holes and area on the 9407 printed-circuit-board.

ParallelC.png [ 13.54 KiB | Viewed 16663 times ]

Check out this other PAiA Talk topic related to the 9407 Tube MicPreAmp:


Author:  adamgggg [ Wed Feb 17, 2010 10:56 pm ]
Post subject:  Re: Soldering components in parallel

Thank you so much, Scott. I was envisioning something like in the photo in the strange dreams about soldering PCBs that I have been having :geek:

Although I heard that it is common to have dreams about new motor skills that the brain is learning...

Anyway the other part of the Tape Op mod I am wondering about is this:-

"Pin four of the tube connects to the AC side of the preamp's power supply, at a spot marked "F2", and pin five ties to the circuit ground. The noise floor will improve once the filament pins are heated with filtered DC. To achieve this, disconnect pin 4 from the AC supply, and connect a 1W 15-ohm resistor from pin 4 to the junction of D2, C3, and R2"

I am wondering about the junction of D2 C3 R2. Where can I make the connection? I read on the Tape Op forum:-

"the resistor goes to the junction. an easy way to connect it is to loop the resistor lead around the lead of the diode, then solder to that. that way you don't have to worry about trying to solder to the pad or trying to double up the leads in one pcb hole".

If this is the best way, which side of the diode should I connect the resistor to? Should I also try to insulate the resistor?

Your advice is really appreciated Scott. I am sure that many people who buy this Kit are interested in doing these mods. Hopefully when I have everything successfully working I will post some advice on here with some photos etc.


Author:  PAiA-Scott [ Thu Feb 18, 2010 11:45 am ]
Post subject:  Re: Soldering components in parallel

Aren't dreams great?

I dug-up this old sketch I used to mail along with the 9407 Tube MicPreAmp tips/suggestions that I now have to send as a pdf (note to self...update this file) which you might find useful in implementing the modification. The Sovteks we send now don't benefit from this so much as the tubes we had for a while, marked with red paint "Made in China". If you're going all out though and want even better results with connection of dc to the filament, regulate it to about 8vdc.

9407 Tube MicPreAmp tips/suggestions
9407ts.pdf [73.65 KiB]
Downloaded 1475 times

9407tsSketch.pdf [95.18 KiB]
Downloaded 1494 times

And for the benefit of others, its always best to build a kit as instructed first, then alter/improve things from this point. The most noticeble improvements come from the wire routing, the greater valued C14 and the set-and-forget "calibration" for symmetry.

Author:  adamgggg [ Thu Feb 18, 2010 11:58 pm ]
Post subject:  Re: Soldering components in parallel

Thanks again. The Pdf is great- you don't need to make a new one.

I get all the hints about learning to walk before you run or not diving in at the deep end etc, and sure that is the better way to do things. I am just being a bit extra careful and patient with it, so hopefully this will make up for my lack of common sense... ;)

So the first channel is basically done- I just am a bit worried about a few of the connections on the tube socket being really close together, so I think I should do something to insulate them. What can I use to do this with? My google searches suggested shrink wrap. Is this ok to use or is there something better out there? some kind of tape?


Author:  PAiA-Scott [ Fri Feb 19, 2010 10:58 am ]
Post subject:  Re: Soldering components in parallel

Tape would be OK but tubing would keep things looking neat and tidy.

It would be difficult working with heat shrink in the closely spaced area. Just a piece of tubing about the size of the grey outer insulation of the two-conductor shielded cable would do the job, or, maybe some aquarium tubing???

Notice on this image the way the wires aren't crimped or twisted around the terminals, but just smoothed/trained/positioned to be at rest in the eyelet prior to flowing solder. If you can make yours look like this, insulating the terminals shouldn't be a concern.

Vsocket.png [ 726.28 KiB | Viewed 16646 times ]

Author:  PAiA-Cliff [ Tue Mar 02, 2010 6:33 pm ]
Post subject:  Re: Soldering components in parallel

I always thought the paralleled output capacitor trick was kinda pointless. I agree that upgrading the output caps to a higher quality cap works wonders but that 0.1uF cap really isn't going to have an audible effect when it's swamped out by a 10uF cap. The best thing to do IMO is to simply replace that output capacitor (it's 33uF, right?) with a 10-22uF Nichicon audio grade capacitor.

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