Jeez, if we're building exact copies of Ralph's amp, why not just pony up and buy the amp from him? Enjoy it sooner. Take out a little loan if needed. Better than taking out a loan on a car which will loose 90% of it's value in 10 years.
Just sayin.....
Thx Ralph,
If I understand you correctly its $450 for the chassis and $800 for the transformers so we are talking about a kit cost around $1,250. Am i hitting it right? Kit meaning for chassis and transformer set all other parts on us.
Thx again
Not sure what your count is now, but I'd be #3 or #4 for the group buy of chassis @ $450. Can we get 10 people to commit (and pay)?
Anyone who has done some amp work knows what a pain it is to get a chassis cut to measure which looks good (for the wife) too. I am 110% in.
I am also fond of the toroid offer, and fully back this one too.
guys spread the word around
I am also fond of the toroid offer, and fully back this one too.
guys spread the word around
Obviously you have a point, but everything at the end of the day depreciates.
The kit will make sense to someone who has the time to experiment and benefit from the added satisfaction of tweaking, as and when one pleases.
To someone who is cost conscious, there is also a saving of the manufacturers mark up not being a charitable organisation (thankfully we have the chief designer to advise us in the process).
Unless you are an electronics buff like the rest of the people on this forum, enjoying the "ride" more than the destination, then the ready made option is financially more viable for you.
Is there any reason why atma has not embraced El509 and chosen 6AS7G instead for the last so many decades?
Transcendent seems to argue that the 6as7 is more prone to internal sparking and not as rugged as the 509. This has to do with the internal tolerances of the tube and its manufacturing specs. Additionally they (he) claim(s) that there is some adverse effect on the sound quality of the amplifier which is avoided altogether by using 509 instead.
I am curious to hear your views on this subject and if there is any "legitimate" basis for these arguments, in your view.
Transcendent seems to argue that the 6as7 is more prone to internal sparking and not as rugged as the 509. This has to do with the internal tolerances of the tube and its manufacturing specs. Additionally they (he) claim(s) that there is some adverse effect on the sound quality of the amplifier which is avoided altogether by using 509 instead.
I am curious to hear your views on this subject and if there is any "legitimate" basis for these arguments, in your view.
i had a question...i wondered if this topology could be adapted to employ the WE feedforward distortion cancellation ala stephie bench?
see here
:: View topic - 45 Watts per channel push pull 801As
you mention that the amp doesn't use much if any feedback and results in a predominately 3rd harmonic distortion profile. i am wondering if this technique can be used to make the profile more 2nd and cancel the 3rd?
you already have the cathode followers in place.
see here
:: View topic - 45 Watts per channel push pull 801As
you mention that the amp doesn't use much if any feedback and results in a predominately 3rd harmonic distortion profile. i am wondering if this technique can be used to make the profile more 2nd and cancel the 3rd?
you already have the cathode followers in place.
The 3rd harmonic is very hard to cancel out, and any amplifier that is fully differential will always have some 3rd harmonic. However it is kept at a lower level and the ear sees the 2nd, 3rd and 4th as musically related to the fundamental so its not been seen as a problem.
Have you built the amp at the link?
Have you built the amp at the link?
I have not built the amp in the link. The engineering i still have a hard time getting my head around. Its a variation on western electric's harmonic balancer (equalizer) which was specifically designed to cancel out the odd harmonics, namely the third.
I find the concept fancinating but relatively unexplored. I've always wondered why.
I find the concept fancinating but relatively unexplored. I've always wondered why.
Don't know why this awesome thread went quiet......
in any case I have a question: the power tube heaters are floating in the schematic, is there any need to reference them to the cathodes?
Steve
in any case I have a question: the power tube heaters are floating in the schematic, is there any need to reference them to the cathodes?
Steve
I was looking at the Western Electric 86 circuit trying to find the harmonic cancellation people were mentioning. The only thing I've spotted so far is a cap between the driver / output B+, and a tap halfway up the "cathode" resistor (the one from the center of the heater winding since 300A's are directly heated). I don't think I'd call that feedforward cancellation since it isn't derived from earlier-stage audio. It's basically canceling out a current increase/drop resulting from a rise/drop in B+ by shifting the bias at the cathode to move the current in the other direction. That reduces the hummy garbled intermod effects from the 120 Hz power harmonic and the low frequency audio-induced ripple from a varying load on the supply line. Since the B+ does have the usual filter cap (this is just after the first choke of a choke input filter) it's not broadband audio/distortion at that point, but low frequency bounce and what would look like heavily filtered full-wave rectified audio (since current from either positive or negative audio peaks would make the voltage dip, that is full of even harmonics with even the hum being 120 Hz). Since a push-pull output cancels hum/noise from the power supply when the tube currents are balanced (equal noise at ends of transformer primary) it is actually intermodulation with even harmonics and grunge, not simple THD, that is prevented. In essence the PP triode output stage acts like a balanced modulator with supply grunge as a single-ended input on one port. The WE addition effectively feeds the noise into an opposite input of the same port turning the grunge into an ignored common mode signal. A stiffly regulated or at least well filtered power supply (maybe even with a few caps that are especially low loss at high frequencies) weren't a viable option in the W.E. oil-cap era which saw 8 mF as big. They did have some beefy power supplies at times though. The 1 kW model 100B was available with a three-phase power supply.
The circuit in the HE801 is interesting. Since it is essentially full-wave rectifying some audio (responding to positive peaks from either side of the drive) to make bias less negative it is also a balanced modulating type of effect. Since tubes generally have much lower transconductance near cutoff (particularly a problem with class B), shifting the bias up that way should reduce what amounts to intermodulation distortion near the crossover point. Another way to look at it is the audio itself being used to push the bias more in the class A or AB direction (away from class B) when there's audio. With audio-rate bias modulation (the WE signal was taken from across a filter cap, but this isn't filtered) there is inverse intermodulation which certainly could provide some cancellation. I'm referring to the bias as modulated instead of regulated to emphasize that the circuit is not intended to keep bias constant. Of course dynamic bias can potentially also help reduce energy waste and tube cooking at idle or low signal levels too.
The circuit in the HE801 is interesting. Since it is essentially full-wave rectifying some audio (responding to positive peaks from either side of the drive) to make bias less negative it is also a balanced modulating type of effect. Since tubes generally have much lower transconductance near cutoff (particularly a problem with class B), shifting the bias up that way should reduce what amounts to intermodulation distortion near the crossover point. Another way to look at it is the audio itself being used to push the bias more in the class A or AB direction (away from class B) when there's audio. With audio-rate bias modulation (the WE signal was taken from across a filter cap, but this isn't filtered) there is inverse intermodulation which certainly could provide some cancellation. I'm referring to the bias as modulated instead of regulated to emphasize that the circuit is not intended to keep bias constant. Of course dynamic bias can potentially also help reduce energy waste and tube cooking at idle or low signal levels too.
Hi,
I just found this fantastic thread a few days ago and have managed to brows through it, understanding about half of what is being said. There are certainly a lot of clever and knowledgeable guys participating here.
First a big thank you to Ralph for being so generous and sharing his knowledge in those matters.
Secondly, thank you Desperateaudio for defending Futterman and his pioneering work, in Post 425. I have tried to do the same on OTL Asylum where a lot of silly things are being said about the stability of the Futtermans. I am now in to my second pair of H3AA.
This thread has really inspired me in considering building a pair of the M-60s. There are a few questions that I have concerning this and the first is:
1. Could the 36KD6 be used. I have a number of those as I previously used a pair of Beveridge SW-2 where they are part of the circuitry?
2. If one were to stay with the original type for the M-60, are there any brands that are preferable, any that should be avoided? In the Beveridge and also in the Futtermans, tubes from General Electric and Sylvania are in my experience much superior to other (even well known) brands.
3. When matching tubes, what criteria should one use, matching on a certain input giving a certain output or a certain change in input giving the same rate of change (steepness?) in the output of the two tubes? Or both perhaps? I understand that matching is not an issue with the M-60 but I had to grab this opportunity as there are so many people here that would know the correct answer.
How far have you people come, any one close to finalisation?
I just found this fantastic thread a few days ago and have managed to brows through it, understanding about half of what is being said. There are certainly a lot of clever and knowledgeable guys participating here.
First a big thank you to Ralph for being so generous and sharing his knowledge in those matters.
Secondly, thank you Desperateaudio for defending Futterman and his pioneering work, in Post 425. I have tried to do the same on OTL Asylum where a lot of silly things are being said about the stability of the Futtermans. I am now in to my second pair of H3AA.
This thread has really inspired me in considering building a pair of the M-60s. There are a few questions that I have concerning this and the first is:
1. Could the 36KD6 be used. I have a number of those as I previously used a pair of Beveridge SW-2 where they are part of the circuitry?
2. If one were to stay with the original type for the M-60, are there any brands that are preferable, any that should be avoided? In the Beveridge and also in the Futtermans, tubes from General Electric and Sylvania are in my experience much superior to other (even well known) brands.
3. When matching tubes, what criteria should one use, matching on a certain input giving a certain output or a certain change in input giving the same rate of change (steepness?) in the output of the two tubes? Or both perhaps? I understand that matching is not an issue with the M-60 but I had to grab this opportunity as there are so many people here that would know the correct answer.
How far have you people come, any one close to finalisation?