Intact Audio

Hi-
I’m going to a strictly mono system meaning- one speaker, mono amp and eventually mono preamp. I’m currently using a Fisher 400CX-2 which gives me a few different ways to achieve this using a stereo cartridge and most for my vinyl is not mono. Would a transformer be the best way to convert the stereo signal to mono and can this be built? I tried out a Denon DL-102 and was not impressed so I'm sticking with my stereo cartridges. I see Sakuma uses a transformer input for his CD player converting R-L to mono but I have not seen anything on phono play back. Would a mixer be a better way to go? The RCA manual has a simple mixer circuit.

For a long time I thought a transformer was the way to do it... then spice talked me out of it.

dave

dave slagle wrote:For a long time I thought a transformer was the way to do it... then spice talked me out of it.

dave

Any thoughts on the best way to do this?

series summing resistors are all I have in the passive realm.

if you are vinyl only you can try wiring the channels of the cartridge in series to add the lateral and offset the vertical.

dave

dave slagle wrote:series summing resistors are all I have in the passive realm.

if you are vinyl only you can try wiring the channels of the cartridge in series to add the lateral and offset the vertical.

dave

Yes, vinyl only. I'll try the series connection.

Thx

dave slagle wrote:series summing resistors are all I have in the passive realm.

if you are vinyl only you can try wiring the channels of the cartridge in series to add the lateral and offset the vertical.

dave

Interesting. I've always heard a transformer was the best method. I'm currently using a UTC A20 to sum stereo to mono in my big mono system in the workshop....

maybe I need to try resistor summing...?

It has been a while since I went over this but I don't think the transformer is the ideal way. The problem arises when you start to look at the loads presented to the common mono info vs the stereo info and how it is loaded.

everyone seems to run the numbers for mono and that works out perfectly even if you simply parallel the outputs. looking at dissimilar info for the left and right channels gets to be a complex mess pretty quickly. I came to the conclusion that there really isn't a good passive way to do it.

For phono only I still think the series coils of the cartridge is the best.

dave

dave slagle wrote:It has been a while since I went over this but I don't think the transformer is the ideal way. The problem arises when you start to look at the loads presented to the common mono info vs the stereo info and how it is loaded.

everyone seems to run the numbers for mono and that works out perfectly even if you simply parallel the outputs. looking at dissimilar info for the left and right channels gets to be a complex mess pretty quickly. I came to the conclusion that there really isn't a good passive way to do it.

For phono only I still think the series coils of the cartridge is the best.

dave

Thank you for the insights Dave. That makes a lot of sense. This system is just my workshop system, my phone streaming Tidal.

I think I'll try the resistor method, see if it sounds better for me in the workshop.

Cheers,
Gable

a good solution to this is Mid/Side processing. a pair of transformers or a specially constructed tranny can do it.

hey JC!

I don't think a single transformer will ever do it properly. I spent a lot of time in spice trying to crack that nut and coupling through a common core always unduly loaded down the stereo info.

Now two transformers with the secondaries in series would be my goto solution at this point.

If you are going to stick around for a bit I would love a discussion about how the mac bifilar unity coupling works. Not a discussion on whether it is good or bad.... but what is actually going on.

dave

"Now two transformers with the secondaries in series would be my goto solution at this point."

I am currently using a summing transformer at the input of my mono amp. Would two transformers with the secondaries in series give a 1:2 stepup?

If I ordered two 1:1 full range input transformers they would probably be a size up from the AVCs, wouldn't they?

since these are simple input transformers the autoformer size would be fine. you should get 1:2 My first thought would be bifilar but I think the ground shift would "get you" at high frequencies.

dave