Hi all,
Refering to the DLite layout, what purpose does the green wire serve that runs from the 6.2k res. to the the selector switch terminal(4ohm) serve I'm using a hammond 1620 OT for this build. I'm a little confused on where to run that wire. Also, are there any good alternatives for the Sheilded coax(RG174) I created a layout of the impedance selector switch so I could at least use the 4 ohm and 8 ohm section of this OT. I think it might work.
THANKS,
DAVE
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That wire is the negative feedback loop. On the D'Lite it is attached to the 4 ohm output tap.
I'm not sure what Moss included in the D'Lite kits, but it was a very small diameter cable with a braided shield. Difficult to work with, but very little was required.
Hi Ampdoc,
Will I be able to hook this wire up to my OPT's config? If I was to just use the 8 ohm taps on my OPT, what happens to the feedback loop? Is it just left un-attached? I'm new at this and I appreciate your help greatly.
By connecting the NFB to a different tap changes the initial negative feedback voltage and hence changes the amount of feedback. The 4 ohm tap will give you the least feedback voltage in a given NFB circuit with a 4/8/16 secondary OT. The 8 ohm tap is going to give you a little more voltage than the 4 ohm tap, which will increase the amount of signal reduction. This reduction is not linear at all, so if you want double the signal reduction of what you get on the 4 ohm tap, you'd use the 16 ohm tap. You could change the feedback resistors to compensate if you want to, but this slight increase in signal reduction wouldn't be that noticeable (4 to 8 ).
way too complicated - if you look at the connection diagram for the transformer the only difference between 4 and 8 is whether you connect the speaker positive to yel or grn/yel that is the only choice the switch has to make and all other connections can be made permanent and not use the switch. Just connect the NFB to GRN/YEL.
Perfect! - if you question whether the amp rating of the switch contacts is adequate for the speaker current you could run another section (or 2 or 3) of the switch in parallel.
The amp rating for the switch is .3 A 125VAC per pole. I think that should be adequate. I'm going to give it a shot. I'm almost done with my build. I just need to get my hands on some RG174 Coax. I could order it, but I'm trying to find some locally. Some people said I could use audio or mic wire. I striped a piece of audio cable and it just looked cheap, not braided, more like strands of copper over a pvc jacket. I assume capacitance and resistance plays a big roll in choosing the right sheilded wire. But with such short lengths, is there much of a difference? I was able too find alot of RG50 and 58. Would guitar wire work? I know the OD is a little bulky to be using inside the chassis. I'll keep searching for RG174 if need be.
RG174/U has become pretty much the standard for most of us, but there are lots of alternatives with very low capacitance per foot. I've measured the cheap coax used in RCA patch cords and it's actually lower than RG174 in some cases.
Steve at apexjr has some really nice shielded cable with a Teflon jacket. Give him a call. In the meantime, no harm in chopping up an old RCA patch cord.
I'm using a hammond 1620 OT for this build. I'm a little confused on where to run that wire. Also, are there any good alternatives for the Sheilded coax(RG174) 
