@jaddie , does that mean that in your experience, these transformers give a reasonably flat response when the primary is driven from the intended impedance and the secondary is loaded with a much higher impedance? That would be nice, as it simplifies things.
I also don't see the point of the whole exercise, although I think sound quality improvements were more something of the first century of audio, or maybe the first 110 years. The quality of at least popular recordings have been in steady decline over the last few decades, the same holds for the equipment most people use to listen to them.
Anyway, I wonder if you won't need even more voltage to drive the transformer in saturation with music. Unless the music is church organ music or synthesizer music with very deep bass, chances are that the number of volt-seconds is smaller than with a 30 Hz sine wave.
By the way, the amplifier is 60 W into 4 ohm when you use it as a stereo amplifier, like Obe1cannoli intends to do.
I also don't see the point of the whole exercise, although I think sound quality improvements were more something of the first century of audio, or maybe the first 110 years. The quality of at least popular recordings have been in steady decline over the last few decades, the same holds for the equipment most people use to listen to them.
Anyway, I wonder if you won't need even more voltage to drive the transformer in saturation with music. Unless the music is church organ music or synthesizer music with very deep bass, chances are that the number of volt-seconds is smaller than with a 30 Hz sine wave.
By the way, the amplifier is 60 W into 4 ohm when you use it as a stereo amplifier, like Obe1cannoli intends to do.
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I would drop the 150 ohm resistor to a pair of 33 ohm ones to make a lower impedance balanced source. 1/2 watt carbon composition ones should be fine.
As to the output load capacitors, .022 uF should provide the load at the upper frequencies to prevent ringing. You don’t need to load the secondary across the entire bandwidth to accomplish that. Although trying.01 uF might show more of what is wanted. Switching in a second .01 or even larger across the first one might give a flavor switch to see what is preferred.
Normally the use of this type of distortion is to make the low end stand out more. The increase in distortion is frequency dependent thus emphasizing the LF.
Using diodes or say germanium transistors will give a fuzz box effect which is quite different.
Does the dB loss by terminating the transformer with 600R even matter when the point here is to drive the 111C to saturation? Isn't that just determined by the input voltage?
Since I'm still learning about transformers, I was reading that the source impedance has an effect on low end distortion. Maybe a 1-2k rheostat could be used on the input to help "tune" things?
Since I'm still learning about transformers, I was reading that the source impedance has an effect on low end distortion. Maybe a 1-2k rheostat could be used on the input to help "tune" things?
The load resistance will drop the voltage to the transformer as there is a source resistance.
True, but not much more when the secondary winding sees a high load impedance.
You've gotta be thinking of a different Jim Williams. The one I'm talking about has a website called audioupgrades.com and a phone number. You can call him and talk to him yourself if you want.
I had mentioned the 60w into 4ohm (peak) thing and asked if that was overlooked and no one answered me. If so, I presume that could change the recommendations by Marcel and Simon.
Your point about peak is very important. This thing will start to distort at low frequencies with peaks. As soon as I hear low end distortion from peaks I will not push it any further, so there will be no need to put any more power into it at that point. Im not going to use this as a send effect where I only send midrange to it or something, that causes delay problems. I'm just going to slap it on the mix bus.
Thank you for taking the time to draw these schematics. I appreciate the time and effort.
I think my plan A will be to go with the simple setup Jaddie suggested as it will not take long at all to put together. I'll rig it up and see how much I can get out of it. If it's not enough, I will start working on the above schematic.
Thanks for your input. I really wish I had more knowledge with making circuits because it would be much more fun to design my own tailored solution, but I don't. Even though the circuit looked pretty simple in the link you provided, it's still out of my league. The power amp route only requires me to add a couple of resistors to the output, which is something I can handle. Thanks again though!
I'm on vacation and a little bored, so I think I'll build the OPA552 circuit I proposed and see how it turns out. The simulation says it can output 39.5Vrms @ 0.016% THD into a 600Ω load before clipping.
Not sure if the PDIP version can handle ~1.3W output though. I also have the DDPAK version that I could attach heat sinks to, but those would be alittle more difficult to work with on a perfboard.
Let's say I build it, it works as planned, and I want to donate it to someone
. What value output resistor should I use? Something low so the recipient can add more resistance in series if needed?
Not sure if the PDIP version can handle ~1.3W output though. I also have the DDPAK version that I could attach heat sinks to, but those would be alittle more difficult to work with on a perfboard.
Let's say I build it, it works as planned, and I want to donate it to someone
. What value output resistor should I use? Something low so the recipient can add more resistance in series if needed?
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I hope you're talking about me lol. If you are, and you're talking about the output resistance that will go to the transformer, I've been keeping everything at 600ohms. If you're not talking about me, then I will look very sillyI'm on vacation and a little bored, so I think I'll build the OPA552 circuit I proposed and see how it turns out. The simulation says it can output 39.5Vrms @ 0.016% THD into a 600Ω load before clipping.
Not sure if the PDIP version can handle ~1.3W output though. I also have the DDPAK version that I could attach heat sinks to, but those would be alittle more difficult to work with on a perfboard.
Let's say I build it, it works as planned, and I want to donate it to someone
There are more than one "Jim Williams". The one with Audio Upgrades seems to be still kicking.
100% still kicking. Spoke with him this week. Kicking so much in fact that he can't take on any new custom requests because he's so busy.
Hmmmm.
I'm still trying to wrap my head around using transformers myself, but I don't think 600R is ideal if the secondary is loaded with 600R. That would cause the low end response to be down -3dB I think. The source output impedance should be at least 10x lower(?). I'll let the pros weigh in on that one though.