Search results

IMHO, this is #1 priority to figure out. It should NOT possible. First: IC 12 is the headphone amp, gets power directly from rectified +/-24v. ICs 9,10 and 11 are TL072s, are those what you meant? Power to the tone board comes from the maim board via ribbon cable. Pin 4 is +V. What does...

My PCB is marked "1500". That's what was and is installed. Changing it to 1000p causes an increased ultrasonic response. C18 & R20 comprise a low-pass filter, described in the manual sec. 4.3 "A single-pole RC filter composed of R20 and C18 continues to follow the high frequency roll-off at...

Well, you can stop chasing your tail now!:D Curious to know, what was the brand/part number of those sockets?

You're welcome Jan. The 2002s are gems and worth keeping alive. Keep us posted on your progress! Sean

Which "IC" are you referring to here? The "buffer" section opamps that had voltage anomalies earlier do NOT have any pins tied together. Those 3 opamps are output buffers for the tape and external processor loops, and not necessary for primary preamp functions. Are those 3 socketed? Suggest...

Jan: Sent you a PM with link.

From the horses mouth: Amp is Sony TAN-5550, 50 watt @ 8-ohm rated. Plays plenty loud enough for me, but ... 1) I don't need earth shaking volumes 2) Bi-amped, crossed over to subwoofers at 70 Hz (100W).

Yes it does. But I'm of the opinion that load values don't have to be precise, just "close" to recommendation (until I see evidence otherwise). eg. for MM, will 45k or 50k vs 47k be detrimental or even audible? I think not. for MC, will 90 or 110 vs 100 be detrimental or even audible? I...

Here's an Excel version. R values reversed so truth-table produces ascending final values, but otherwise the same.

Are there any pros and/or cons to series vs parallel connection? I've used parallel in the past, but with half the resulting values being less than the smallest resistor, and with very small stepping in-between, they are essentially equal. eg, would the difference between 63 and 99 ohm load be...

It's going to depend entirely on how the optimmum board layout shakes out, and too early to tell right now. As to labeling, it doesn't really matter. Either channel can be labeled L or R as the builder desires. If a balance control is used, simply connect the wire pins so L is L and R is R...

Don't confuse my spreadsheets with Wyns v4 design. Mine are just to illustrate how the "concept" RCA board would work, it's not a real thing (yet). Just as the pin-sockets did on previous boards.

Same with dip-switches :)

3-position dip switches give you EIGHT different combinations (2^3). One 3-dip switch for R per channel, another 3-dip switch for C per channel. So you have EIGHT possible load values of R and C per channel. Spreadsheets attached

3-position switches, providing 8 load values of R & C per channel. Parallel caps, series resistors. Lowest value R & C are permanently soldered, the other 3 switched summing to final value. This is only concept if I had my "druthers" to build a Wyn pre for myself. Also specific to v3 board...

I guess it's time to chime in. Way to early in the design process to say what might be possible. But offhand, as they are entirely different input stages than previously, I'd say that switch board as-is won't be suitable. But who knows, time will tell. I haven't yet discussed my ideas for...

Yes, but if you measure R90 AFTER it's all settled in, you WILL see a voltage drop. This is a transient situation, the Q19 surge circuit only takes 2-300 milliseconds to function, during which R90 is bypassed. It needs to be measured WHILE it's happening to see the effect (as in my simulation...

Two. Rabco ST-4 (Grado F1+), and Rabco ST-7 (Ortofon MC-20)

Yah, I already have that data sheet, and some others that can be more informative. In another IDEC data sheet it specifies: "Minimum Operating Voltage at 20ºC - 80% of rated voltage". 80% of 24v is 19.2v. The Apt mute circuit is already pushing that limit at 19.6-20v. If your power...

I got my Apt in 2000 w/a dead channel. 1/2 of the balance op amp had gone inop. Replaced it, continued to work fine with other originals until I replaced them all during 2019 overhaul. Hi-res schematic attached below. It has my own markups noted, as compared to actual board. You're...

My original is a bit inconsistent left, right and front are nominally 0.125" (0.122" lowest, 0.130" highest). rear measures from 0.155" to 0.160"

Nah, I'm not into furniture, prefer function over form. Metro shelving is quite functional: shelves adjustable for height, open-wire shelves allow free air circulation for amps & other electronics, and casters allow easy access to the back for changing/arranging connections.

Bought both new ('71 & '77), both still up & running

Signal ground is indeed tied to chassis (via PCB copper), but AC mains are not. A poor chassis connection can cause hum, as described in the manual. Unfortunately "screw G1" is NOT identified in "figure 6-1", but check them all. It might be that simple.

That's the part number listed in the ST-8 manual. If you found that in an ST-7 specific manual, then it's a 2nd publication where they had started to implement upgrades. re. the touch controls: I have the same issue. Lick your finger & try it. Haven't diagnosed it, but I suspect the contacts...