parabellum wrote:
Did you run across any problems with the schematic? What transformer did you use?
parabellum wrote:Do I even need a preamp with a ST70? I saw some mod that puts a volume control on it, is that possible?
kheper wrote:parabellum:
If you are still looking for NOS 12au7 tubes,
the RCA clear-tops are a relatively good
bargin.
erichayes wrote:parabellum wrote:Do I even need a preamp with a ST70? I saw some mod that puts a volume control on it, is that possible?
No.
If you're working with "line level" devices, which are usually putting out a nominal 1 volt signal, all you need is a 100K gain control between the source and the input of the amp. Just so happens that Radio Shack carries an Alps dual 100K audio taper pot for around $4.00 that is excellent. Ignore the 40% loudness taps and wire it in: wiper to the amp input, high side to the source output, and low side to ground. Dont forget to ground the body of the pot, or you'll have hum problems.
If you want to get fancy, you can get a rotary switch from RS or Mouser, along with a handful of RCA jacks and a small chassis, and make a passive line switcher that will handle more than one source.
You have to determine what your goal is. If it's building stuff for its own sake, that's fine. If it's a desire to get as close to the original musical source as possible, then you have to take a minimalist approach, electronically. The more componentry you put between the source and the speaker, the less accurate the reproduction will be.
Thanks. I now have three options for
those ... the Tung Sol 12au7, JAN5814A and
the RCA's. That should ease the search I
guess.
+kheper wrote:Thanks. I now have three options for
those ... the Tung Sol 12au7, JAN5814A and
the RCA's. That should ease the search I
guess.
I just got 2 NOS Tung-Sol 12au7s and a
NOS RCA black plate off of an auction for
$17, including shipping. The date codes
are from 1956.
TomMcNally wrote:Angela does things the old fashioned way - I order almost every week,
and toward the end of the day you get a shipping notice from FedEx.
If it's on the site - that's the price, they clearly state they don't have
time to confirm, etc. Yeah, it's a bit different, but they get stuff to
you fast, in my case, ground is next day. A backorder might come
in another three days. I think the good prices and stocking on
Hammond is worth it.
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