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DR504 output impedance : 4-8-16 ohms ?
Posted: Mon May 10, 2010 3:43 pm
by 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 ?
Re: DR504 output impedance : 4-8-16 ohms ?
Posted: Mon May 10, 2010 4:19 pm
by mikhailwatt
thames wrote: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.
Re: DR504 output impedance : 4-8-16 ohms ?
Posted: Mon May 10, 2010 4:37 pm
by 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
Re: DR504 output impedance : 4-8-16 ohms ?
Posted: Mon May 10, 2010 5:35 pm
by mikhailwatt
mikhailwatt wrote:Yes, 4 wires off the OT secondary: 3 taps plus the common.
Or, what the Professor said...
mhuss wrote:Many of the earlier 50 watt OTs only had two pairs of secondary windings.
So, no shared "common" with these?
Re: DR504 output impedance : 4-8-16 ohms ?
Posted: Tue May 11, 2010 3:25 am
by 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
Re: DR504 output impedance : 4-8-16 ohms ?
Posted: Tue May 11, 2010 11:41 am
by 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
Re: DR504 output impedance : 4-8-16 ohms ?
Posted: Tue May 11, 2010 5:27 pm
by thames
mhuss wrote: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 ?
Re: DR504 output impedance : 4-8-16 ohms ?
Posted: Wed May 12, 2010 11:46 am
by mhuss
thames wrote:So, no "real" 4 ohms tap, right ?
Right.
--mark