Bruce,
That's all fine and dandy - yes, you successfully "beefed up" the PS. But please list the numbers of before and after, but at 1 watt output. Since this is the max output level that most people will ever use.
Unless you have speakers with a 40dB efficiency rating!....
Do you listen to the amp at 65W? I think not.
Let's start using some real numbers here.
That's all fine and dandy - yes, you successfully "beefed up" the PS. But please list the numbers of before and after, but at 1 watt output. Since this is the max output level that most people will ever use.
Unless you have speakers with a 40dB efficiency rating!....
Do you listen to the amp at 65W? I think not.
Let's start using some real numbers here.
Joel, for 1 watt just look at the idle hum and noise. It's very hard to measure .025 VPP @ 425 VDC. With the regulator the noise on the power supply only starts to climb when you start to get near clipping the amp.
Oh, by the way, think of the 15 watts more output before clipping you get by way of stable B+ as added head room. I'm still running the same 20 year old tubes.
The speakers I have are 87 dBspl @ 1 meter and I run about 1 - 2 watts average power per channel with peaks to 40 watts or so depending in the soure.
Later
Bruce
PS Joel, why are you so mad? Is it a New Yorker thing?
Oh, by the way, think of the 15 watts more output before clipping you get by way of stable B+ as added head room. I'm still running the same 20 year old tubes.
The speakers I have are 87 dBspl @ 1 meter and I run about 1 - 2 watts average power per channel with peaks to 40 watts or so depending in the soure.
Later
Bruce
PS Joel, why are you so mad? Is it a New Yorker thing?
CHALLENGED?
"It is from numberless diverse acts of courage and belief that human history is shaped. Each time a person stands up for an ideal, or acts to improve the lot of others, or strikes out against injustice, he sends forth a tiny ripple of hope, and crossing each other from a million different centers of energy and daring, those ripples build a current which can sweep down the mightiest walls of oppression and resistance."
- Robert Kennedy
"It is from numberless diverse acts of courage and belief that human history is shaped. Each time a person stands up for an ideal, or acts to improve the lot of others, or strikes out against injustice, he sends forth a tiny ripple of hope, and crossing each other from a million different centers of energy and daring, those ripples build a current which can sweep down the mightiest walls of oppression and resistance."
- Robert Kennedy
FOR JOEL ONLY
An African chieftain flew to the United States to visit the president. When he arrived at the airport, a host of newsmen and television cameramen met him. One of the reporters asked the chief if he had a comfortable flight.
The chief made a series of weird noises: "Screech, scratch, honk, buzz, whistle, z-z-z-z..." Then he added in perfect English, "Yes, I had a very nice flight."
Another reporter asked, "Chief, do you plan to visit the Washington Monument while you're in the area?"
The chief made the same noises: "Screech, scratch, honk, buzz, whistle, z-z-z-z..." Then he said, "Yes, and I also plan to visit the White House and the Capitol Building."
"Where did you learn to speak such flawless English?" asked the next reporter.
The chief replied, "Screech, scratch, honk, buzz, whistle, z-z-z-z... From the short-wave radio."
Cheers,
An African chieftain flew to the United States to visit the president. When he arrived at the airport, a host of newsmen and television cameramen met him. One of the reporters asked the chief if he had a comfortable flight.
The chief made a series of weird noises: "Screech, scratch, honk, buzz, whistle, z-z-z-z..." Then he added in perfect English, "Yes, I had a very nice flight."
Another reporter asked, "Chief, do you plan to visit the Washington Monument while you're in the area?"
The chief made the same noises: "Screech, scratch, honk, buzz, whistle, z-z-z-z..." Then he said, "Yes, and I also plan to visit the White House and the Capitol Building."
"Where did you learn to speak such flawless English?" asked the next reporter.
The chief replied, "Screech, scratch, honk, buzz, whistle, z-z-z-z... From the short-wave radio."
Cheers,
Frank - that's funny. Yes, shortwave can drive me batty after an hour or so...
Bruce - Your 15 watts extra gave you an additional headroom margin of not even +1dB. This is inaudible. Now, as to whether the additional cost and power usage is worth it - well, that's a subjective call.
As far as the lowered hum level - I've never heard MkIII's descibed as underfiltered - but I also don't own one, so I can't comment further. But I sincerely doubt Hafler would have shipped a buzzy amp. Again, this is a case of "guilding the lilly", and is your perogative if you have the extra cash, and don't mind placing additional strain on your power transformer (to charge the additional capacitance).
Nick - did you pick a rectifier yet? And what is the circuit?
Bruce - Your 15 watts extra gave you an additional headroom margin of not even +1dB. This is inaudible. Now, as to whether the additional cost and power usage is worth it - well, that's a subjective call.
As far as the lowered hum level - I've never heard MkIII's descibed as underfiltered - but I also don't own one, so I can't comment further. But I sincerely doubt Hafler would have shipped a buzzy amp. Again, this is a case of "guilding the lilly", and is your perogative if you have the extra cash, and don't mind placing additional strain on your power transformer (to charge the additional capacitance).
Nick - did you pick a rectifier yet? And what is the circuit?
Well I tell ya. Before I did these mods to the Dynacos they required a tuneup about evey 6 months. Now I don't know when the last time is checked the bias was, it just never changes any more.
Lets see, more power usage? No more rectifier tube so the wattage of the filiment of that tube is gone. Still have the same voltage drop from transformer secondary peak voltage to DC supplied to amp so that loss is the same. The transformer runs cooler now.
Slow turn on circuit. It takes about 5 seconds before the relay closes for full power. The measured inrush current is much lower now if I remember correctly. Starting up those cold filiments makes for a good surge. All of this seams like less strain on the transformer and less power usage to me.
I agree that the 15 watts is small patatoes BUT it came for free when what I was tring to do was lower the power supply impedance to extened the power bandwidth of the amp. These amps will now produce fair square waves down to 15 Hz into a 8 ohm resistive load. Before the mods a square wave input looked like a sign wave output up to about 60 Hz or so, big improvement in the low end response. The high end was improved also by an octive or a little more. The sound of these amps is just tighter and cleaner now.
Where did I say that these amps buzzed? I love David Hafler's stuff, but it can be improved. Power supply is an easy place for most of us to make improvements in production equipment. Manufactures only spend what they have to. We can jazz things up a little if we want and make a big difference to the sound of an already good amp. I've done this type of mod to several different amps and it always helps long term stability and just seems to clean up the sound of the amp.
Later
Bruce
Lets see, more power usage? No more rectifier tube so the wattage of the filiment of that tube is gone. Still have the same voltage drop from transformer secondary peak voltage to DC supplied to amp so that loss is the same. The transformer runs cooler now.
Slow turn on circuit. It takes about 5 seconds before the relay closes for full power. The measured inrush current is much lower now if I remember correctly. Starting up those cold filiments makes for a good surge. All of this seams like less strain on the transformer and less power usage to me.
I agree that the 15 watts is small patatoes BUT it came for free when what I was tring to do was lower the power supply impedance to extened the power bandwidth of the amp. These amps will now produce fair square waves down to 15 Hz into a 8 ohm resistive load. Before the mods a square wave input looked like a sign wave output up to about 60 Hz or so, big improvement in the low end response. The high end was improved also by an octive or a little more. The sound of these amps is just tighter and cleaner now.
Where did I say that these amps buzzed? I love David Hafler's stuff, but it can be improved. Power supply is an easy place for most of us to make improvements in production equipment. Manufactures only spend what they have to. We can jazz things up a little if we want and make a big difference to the sound of an already good amp. I've done this type of mod to several different amps and it always helps long term stability and just seems to clean up the sound of the amp.
Later
Bruce
THE PROOF IS IN THE PUDDING.
Hi fellows,
Over the ten years or so I ran my company I modded about 350 of all kind of tube amps even guitar amps and pro gear a long the same lines as Bruce did to his Dyna.
At the end people look at you as if you're a god so amazed were they at perceived sound improvement and reliability.
You do this kind of work a few times on guitar amps and I tell you
before know it you're swamped with work.
Never had the need to run an add,never.
Most gratifying job I ever did.
Cheers,
Hi fellows,
Over the ten years or so I ran my company I modded about 350 of all kind of tube amps even guitar amps and pro gear a long the same lines as Bruce did to his Dyna.
At the end people look at you as if you're a god so amazed were they at perceived sound improvement and reliability.
You do this kind of work a few times on guitar amps and I tell you
before know it you're swamped with work.
Never had the need to run an add,never.
Most gratifying job I ever did.
Cheers,
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