DR504 output impedance : 4-8-16 ohms ?

[thames]

Hello!

Im quite new on DR504, I noticed that there's only 2 twisted pairs coming out of the OT, which seems to connect to 8 and 16 ohms taps only ... what about 4 ohms ? Is it truly 4-8-16 ?

[mikhailwatt]

I noticed that there's only 2 twisted pairs coming out of the OT, which seems to connect to 8 and 16 ohms taps only ... what about 4 ohms ? Is it truly 4-8-16 ?

Yes, 4 wires off the OT secondary: 3 taps plus the common.

[mhuss]

Many of the earlier 50 watt OTs only had two pairs of secondary windings. See, for example:
http://hiwatt.org/pix.php?p=DR504_75_pwrL

In these amps, the 4 & 8 ohm selector settings were tied together. Obviously the designer was not worried about overloading anything, and 4-ohm loads were rare back in those days of "4x12 or nothing."

--mark

[mikhailwatt]

Yes, 4 wires off the OT secondary: 3 taps plus the common.

Or, what the Professor said...

Many of the earlier 50 watt OTs only had two pairs of secondary windings.

So, no shared "common" with these?

[gldtp99]

Yes i've seen this in DR504's, too----- 16 and 8 ohm taps are twisted pairs---- no 4 ohm tap---- 4 and 8 ohm tabs on switch connected together.
So only three sets of wires coming from OT secondary: 16 ohm tap, 8 ohm tap, and Common.
I sometimes get to work on real Hiwatts--- not just my clones and Sound City conversions-- ...........gldtp99

[mhuss]

Ok, two windings, tapped once, six wires total,

There are two "bifilar" windings connected in parallel, 16 ohms total (green (2) and black (2))
A tap on each of these windings (blue (2)) provides an 8 ohm output.

--mark

[thames]

Many of the earlier 50 watt OTs only had two pairs of secondary windings. See, for example:
http://hiwatt.org/pix.php?p=DR504_75_pwrL

In these amps, the 4 & 8 ohm selector settings were tied together. Obviously the designer was not worried about overloading anything, and 4-ohm loads were rare back in those days of "4x12 or nothing."

--mark

That is exactly what Im refering to. So, no "real" 4 ohms tap, right ?

[mhuss]

So, no "real" 4 ohms tap, right ?

Right.

--mark