Volume pots

[leadtower]

I was wondering if anyone has built a 70 with mono volume pots for each channel? I am thinking of putting one in each of the octal sockets in the front of the chassis. Then drilling a small hole in each corner of the top plate for a bias adjustment pin. Route the leads to that pin for bias adjustment and install a pot in the holes where the socket was for level changes.. Does anyone know if thats been done on a 70? I would like to use the amp exclusively for CD playback so i don't need a pre.
Or would an outboard passive pot control be a better solution? Maybe wired with a jack where the sockets are. I could use a DAC with a level control but i would like to try a pair of quality pots that sit on the chassis.. What value of resistance would i need for mono pots?
Also is there a noticeable sound change with a bigger PS transformer? or just keep the stock unit. I use the SDS cap board for rectification.
BTW; this amp is dead quiet; even at pretty high levels. Nice quiet hiss on high volume.
Also I saved all the stock parts from this amp. if anyone needs something let me know. I have no use for them. They are in good shape. Except the trans' I used them. I don't plan on going back; this is a good amp.

[Shannon Parks]

You could set it up like an Eico HF87. No prob, though a stereo pot would probably be less of a PITA. :)

[leadtower]

I'm not sure how you mean with the Eico. I'm wondering how difficult the mono pots would be? Would I have to change circuit values much? It seems to be a good place to put a couple pots; so am I not seeing something I should? How about the input impedance for CD and other digital sources?
Thanks Shannon

[Shannon Parks]

http://www.freeinfosociety.com/electron ... hp?id=2343

Two 470k mono pots were in the front connected to the RCA jacks.

[leadtower]

Is 470K correct for the ST 70? I see the little slotted pots on a HF 87; do you know if anyone has tried this on a 70? I don't see it in the literature.

[EWBrown]

Anything between 100K and 500K audio taper (log taper) pots should work fine.

/ed B in NH

[leadtower]

Thanks Ed; how about the 100K RS pots?

[erichayes]

The RS/ ALPS stereo pot is a great little pot. I stick with 100k, because higher values tend to cause the Miller effect to rear its ugly head at any setting other than full-on.

[leadtower]

I looked at this last night; the two RS pots would be a tight fit.

[EWBrown]

THere isn't much spare room under the ST-70 chassis, they managed to get it about as small as humanly possible... Talk about jamming 40 pounds of "stuff" into a ten pound box ... :o Yellow_Light_Colorz_PDT_06

If you use the original RCA input jacks location, the pots could then be mounted where the two octal "test" sockets are on the front, some sheet metal or scrap fiberglass PC board could be used to "fill" the holes and mount the two 100K pots.

It'll still be a tight squeeze, but it shuld all fit in OK.

/ed B in NH

[leadtower]

Yes; I am trying to fashion a small extension from PVC to hold the pot and make wiring a little less cramped.