Then that is where one puts in design effort to select an appropriate component that suits that duty.
An example of such a part has already been given. The NFB upper and lower resistor voltage divider cannot correct for errors in these two components. They NEED to operate as closely as possible to perfect resistors.
Small variations due to parasitics will change the amplifier performance. It will be measurable if one knows what to measure, how to measure it and has the equipment with sufficient resolution to reveal it.
The cartridge loading resistor at the front end is a quite different duty, as are most other resistors in the amplifier.
I have no idea. I used to read about the flat earth audio manufacturers in the UK 'voicing' their amplifiers in the 80s. I have absolutely no idea how one would do this though. Plenty of people on this thread seem to claim to be quite adept at it.
Vary device bias randomly until it sounds 'good'. Never, ever, try to draw a load line.
Design some stages with an LF or HF droop, and others with the opposite. Try to balance one off against the other. This can be done accidentally. The really clever (or clumsy) can make this balance vary with volume pot position, thus allowing close 'focussing' of sound. An alternative strategy is to ensure that device parasitic capacitances play a significant role (valve guitar amps do this) so that 'tube' or 'chip' rolling can be used as a form of tone control.
Ensure that input impedances are low and nonlinear, and output impedances are high and nonlinear. Then the equipment will be very fussy about what other items appear in the system - it is well known that this is a sign of 'fine discrimination' and really impresses audio journalists and salesmen.
Design some stages with an LF or HF droop, and others with the opposite. Try to balance one off against the other. This can be done accidentally. The really clever (or clumsy) can make this balance vary with volume pot position, thus allowing close 'focussing' of sound. An alternative strategy is to ensure that device parasitic capacitances play a significant role (valve guitar amps do this) so that 'tube' or 'chip' rolling can be used as a form of tone control.
Ensure that input impedances are low and nonlinear, and output impedances are high and nonlinear. Then the equipment will be very fussy about what other items appear in the system - it is well known that this is a sign of 'fine discrimination' and really impresses audio journalists and salesmen.
Feedback Resistor/NFB upper and lower resistor voltage divider
Ugh! NFB resistor; is that the same as feedback resistor?
http://www.diyaudio.com/forums/solid-state/101321-3-stage-lin-topology-nfb-tappings-3.html
(head exploding reading the above thread)
NFB seems to apply to ICs. Is this just an issue for the amplifier (speaker connection?) or does this apply to all gain stages?
Many tube devices have negative feedback. Is the feedback resistor critical for tube circuits.
For the hacker with a soldering iron are these resistors easily identified in typical IC schematic?
Riken is the resistor of choice for this app?
Kudos for these responses.
Ugh! NFB resistor; is that the same as feedback resistor?
http://www.diyaudio.com/forums/solid-state/101321-3-stage-lin-topology-nfb-tappings-3.html
(head exploding reading the above thread)
NFB seems to apply to ICs. Is this just an issue for the amplifier (speaker connection?) or does this apply to all gain stages?
Many tube devices have negative feedback. Is the feedback resistor critical for tube circuits.
For the hacker with a soldering iron are these resistors easily identified in typical IC schematic?
Riken is the resistor of choice for this app?
So Simple
So, the important differences I hear rolling 12ax7 types in a Lambda tube power supplies of my preamp are due to its poor design?
Ugh! Complex trolling I see since the author recommends a high output impedance driving a low input impedance.
So, the important differences I hear rolling 12ax7 types in a Lambda tube power supplies of my preamp are due to its poor design?
Hi billshurv,
Completely agree with you.
This is more of a problem with recent design efforts than the way engineers approached design in the earlier years ending perhaps in the early 70's. Oh, there's the answer! Engineers used to design products!
Tubes don't have a sound. It is the reaction between the tube characteristics and the circuit design that will create a sound. The more accurate the cube in circuit, the less of a "sound" it sill have operating in its linear region.
Tubes from any manufacturer are supposed to be close to the industry standard curves (or a "bogey" tube). Due to manufacturing tolerances, these characteristics will vary from tube to tube in the same lot even. Tube differences for the same type number are supposed to be minimal across different manufacturers. If the characteristics are too variable, you get a tube make that is variable in sound. The amount of variation with different tubes also depends on design. You can go from a Counterpoint (the sound depends entirely on the tube) to something like an old Fisher or McIntosh where different tubes produce a minimal sound variation.
Power supply circuits should be in the last group, especially since you do not want the voltage to change much with different tubes!
-Chris
Completely agree with you.
This is more of a problem with recent design efforts than the way engineers approached design in the earlier years ending perhaps in the early 70's. Oh, there's the answer! Engineers used to design products!
Tubes don't have a sound. It is the reaction between the tube characteristics and the circuit design that will create a sound. The more accurate the cube in circuit, the less of a "sound" it sill have operating in its linear region.
Tubes from any manufacturer are supposed to be close to the industry standard curves (or a "bogey" tube). Due to manufacturing tolerances, these characteristics will vary from tube to tube in the same lot even. Tube differences for the same type number are supposed to be minimal across different manufacturers. If the characteristics are too variable, you get a tube make that is variable in sound. The amount of variation with different tubes also depends on design. You can go from a Counterpoint (the sound depends entirely on the tube) to something like an old Fisher or McIntosh where different tubes produce a minimal sound variation.
Power supply circuits should be in the last group, especially since you do not want the voltage to change much with different tubes!
-Chris
Thx. Might be happening, but have had some DC like issues on occaision. Pretty rare not to hear differences in tubes in my experience, so:
An externally hosted image should be here but it was not working when we last tested it.
Tube rolling does add up and really should be part of any design.
There is worse (e.g. a Counterpoint hybrid power amp.)
Yup that's the one. I was young and needed a new power amp in a hurry. It's done 20 years service but it slowly dying now. It's replacement needs a teeny bit of work then I can pension it off for a rebuild as and when Chris finds some time.
I take pride in owning not one but two power amps that got bad reviews from stereophile
I take pride in owning not one but two power amps that got bad reviews from stereophile
...have you had cause to listen to any gear recently? I must show you this I just acquired it..its about the size of a 5p with mounting screw..
Regards
M. Gregg
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Oddly I listen to music
I have somewhat of a backlog in projects. kids does that to you, esp babies. The replacement is barely 15 years old and that's only temporary until I go active.
Is the active bit tubes in a speaker enclosure or a sound bar?
Regards
M. Gregg
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