Talk:Valve amplifier

Circuit diagrams

Anyone have any cct diagrams of valve amps? We could do with one in the article.--Light current 18:08, 19 March 2006 (UTC)[reply]

Author replies : I absolutely agree. Ideally imho the page should have AT LEAST a circuit for a DH-SET (with no feedback) plus probably a Class AB push pull design (with feedback) to be representative of the overwhelming majority of audio amplifier designs. However I am stymed by (a) ignorance of how to post images (and too lazy/busy to find out just now!) but more serious (b) concern about copyright for the "obvious" candidates to cite as examples (eg the williamson). I have some designs of my own for which copyright obviously isnt an issue, but I dont think that is acceptable for a wikipedia posting, which should above all be objective (in the view of most readers )!

Author: please sign and date your posts!--Light current 02:21, 10 April 2006 (UTC)[reply]

More current

Anyone know how to get more current out of a valve amp without using transformers? Can the valve anodes/cathodes be connected in parallel to do this?--Light current 18:12, 19 March 2006 (UTC)[reply]

Author replies : (I am answering this in the context of an audio power amp) Your question spans two only slighty overlapping issues : The use of transformers, and how to get more current (effectively more power) into a load that presents an arbitrary impedance. Dealing with the second point first, yes it is possible to connect tubes in parrallel, doing so will multiply the current in proportion, everything else being unchanged. But NB not everything else is unchanged, parralling tubes will reduce the effective output resistance - which is often also desirable in itself, not least because it permits a lower turns ratio from any coupling transformer.

Author: please sign and date your posts! --Light current 03:12, 10 April 2006 (UTC)[reply]

Is this artical biased against transistors ?

This article seems to imply that valve amplifiers are superior to solid state amplifiers. --KFP 14:20, 22 December 2005 (UTC)[reply]

Unknown wrote:Well, they are! Heh. Good point tho- it is appropriate for the article to say that valve amps have their fans who believe they sound better, but it shouldn't just say that they sound better. I agree that this article needs work, but a lot of it is over my head so I'm not sure I can be of too much help.

Author replies : I tried hard to qualify all subjective opinions to avoid such a bias by writing eg "some believe that .." , this matter is religious as well as technical and extremist views (and everything else in between) can be found (in both camps). My personal view is that (as usual in engineering) life isnt so simple as to say one is better than another in all respects. I believe that tubes offer remarkable open loop linearity and as a consequence of tht amplifier designs using them can be extremely simple and have a low component count, and this has sonic benefits for all kinds of good technical reasons. However the fact remains the are costly to produce (compared to transistors), typically require transformers to drive conventional loudspeakers, etc etc, that makes the expensive, large, hot, dangerous even, and generally impractical for other than enthusiasts. But the fact remains that amoung enthusisats for whom these concerns are minor issues - tubes retain a strong following. My best advise is that you listen to LOTS of ampliefiers built using both technologies, and let your ears decide.

Author: please sign and date your posts!--Light current 18:22, 9 April 2006 (UTC)[reply]

contradictions ?

One thing that stood out to me is a bit of contradiction: it says In fact this sound has more to do with the circuit topology and circuit design of the amplifier, than to the use of valves rather than transistors as the active gain devices. and then later, What most valve enthusiasts will agree on is that valves "sound better" than transistors, although there is less consensus about the explanation for this. I added some weasel words to try to fix this. Not ideal, I know, but it's the best I can do. In my opinion, as long as the article makes it clear that some high-end equipment still uses tubes, people can infer from this that apparently (at least some) people think they provide superior sound. Friday (talk) 15:31, 22 December 2005 (UTC)[reply]

Author replies : Yes, this is a problem. But the fact remains that while there are good technical explainations for eg the "sound" of class A vs class B, feedback vs non feedback, simple vs complex topology, (and I have my own personal views about these) ... there is not a concensous in the general tube amp community about which is best and which factors are the most important. If there were, a single class of desigsn would have become dominant. But in fact tube amps are notable for thier diversity - from < 1 watt minimalist DH-SET designs through a three or four stage push pull class AB (williamson decendents) mainstream of ~ 15 watts out to OTL (eg Graff) and massively parrallel monsters (eg from Jadis and Audio Research) to transmitting tube monsters (eg the Wavac 833)

Unknown wrote :This article does not discuss how they sound now but purely the technical aspects. For sound related material please visit Valve sound--Light current 01:29, 31 January 2006 (UTC)[reply]

Cut from page:

While some argue this is a good thing in terms of audio, (see valve sound, since its invention by Black, Negative Feedback (NFB) has been almost universally adoped to provide linear and repeatable performance irrespective of component variations. A side effect of NFB is that the output impedance (Z out) of the amplifier is effectively reduced as a function of the amount of NFB applied (which NB may vary as a function of frequency in some circuits). In consequence, non NFB designs (often DH-SETs) have very high output impedance (compared to modern transitor amplifier tyically using medium to high levels of NFB), and NFB designs (typically clas B push pull) have lower, but still sigificant output impendance

--Light current 00:23, 28 March 2006 (UTC)[reply]

Audiophile amplifiers

For diverse reasons, Although valves are today an obsolete technicnology except for specialist applications, there has been a resurgence in the popularity of valves for so-called "high end" audio amplification. There are doubtless aescetic and other supporting factors for this, but there is a strongly and widely held view that valve amplifiers simply sound.. preferable. (Audiofile electronics is a field where passions run high verging on religious, preclusing the use of terms such as "better"). The reasons why this is so are complex (for example being due to circuit topology, the transfer function of a valve compared to a transistor, and etc) and are heavily debated, nevertheless the effect is genuine, and is discussed at length in

In comparison with modern, primarily transistor amplifers, valve amplifiers tend to be rather low power, depending on the power tube used), and in particular and often low efficiency

The "classical" valve amplifier uses the Directly Heated Single Ended Triode topology (DH-SET), a topology that uses teh gain device in class A. The typical valve using this topology in (rare) current commercial production is the 300B, typically yielding ~ 5 watts. It should be noted however that the simplicity of the DH-SET circuit lends itself to hobbyist construction, so an unknown but perhaps majority of DH-SETs in use today are unique constructions, albeit usually variations of a small number of basic designs.

Many hobbyest constructors of audiofile amplifiers are (and are proud to consider themselves) extremists, and this is especially so for DH-SET constructors. A substantial minority of such constructors take minimalism and component selection to extremes, and many so called "flea powered" amplifiers in the 2 watt class are constructed, using tube types that became obsolete pre war, arguing that the minimalist designs have sonic benefits. However such low power output pushes complete replay system design problems firmly onto the louspeaker, requiring very high efficiencies, typically 10dB better than modern mainstream audio loudspeakers achieve, often horn speakers. A separate religious debate rages about the merits and demerits of different speaker technologies, but it is perhaps fair to say that whatever merits extremely low power DH-SET amplifiers may have are partly paid for by problems facing the loudspeaker.

A minority of home constructed DH-SETs use extreme tubes to yield up to 25 watts (or beyond) in class A, although the engineering considerations to achieve this are (notably constructing suitably massive coupling transformers while maintaining the desired wide bandwidth) as daunting. Class A amplifers are inherently very inefficient, so power supply and thermal considerations are also problementic for high power designs (which can be solved, but at a price, not purely financial.)

During the 1960's and 70's in particular (sometimes referred to as the "golden age" of valve amplifiers, (the height of thier development prior to the introduction of the transistor), the majority of commercial amplifiers adopted derivatives of the class B, push pull, negative feedback topology pioneered by Williamson, this yielding greater power and measured linearity despite using dramatically smaller (and cheaper) transformers. 12-20 watts were obtainable depending on the power tubes used (often EL84, KT66, EL34 or KT88), with high damping factors, and this facilitated the widespread introduction of relatively cheap to produce mutliway box speakers, and the "hi-fi" industry was born.

Signal amplifiers using tubes are capable of very high frequency response ranges - up to RF. Indeed many of the vavle types used in SET (Single Ended Triode) amplifiers are in fact designed to operate in the megahertz range in radio transmitters.

In practice however tube amplifier designs typically "couple" stages either capacitively or using transformers and these devices do limit the bandwidth at both high and low frequencies. Nevertheless audiofile power amplifiers have substantively flat frequency response accross and beyond the audio band, typically power amps having -3dB points order < 10 hz, > 65 khz. This contrasts with some transistor amplifiers that may go out far beyond 100 khz.

Some specialist valve preamplifiers amplifiers (e.g. microphone amplifiers) may be essentially flat to beyond 100 kHz, and remain excellent and amplifiers of chocie (still widely used in studio's).

However, the majority of comercial audio preamplifiers made during the "golden age" have complex filter circuits for equalisation and tone adjustment. Today many consider that these devices are fit only for scrap, having both appalling sonics (see valve sound) and also appalling measured performance, notably frequency response and phase linearity. However there are always exceptions, and a small number of excellent commercial designs remain on the market to this day, from e.g. Audio Research and others. Yet the role of "preamplifier" is increasingly tied to teh minority of audiofiles still using vinyl, all "modern" sources beling line level and requiring only switching, buffering and volume control.

Light Current please stop editting this page

It is obvious from your question "Anyone know how to get more current out of a valve amp without using transformers? Can the valve anodes/cathodes be connected in parallel to do this?--Light current 18:12, 19 March 2006 (UTC)" that you have a limited understanding of the subject matter.

What is the answer then? I wait with baited breath to glean some knowledge and pearls of wisdom from your superior intellect --Light current 19:02, 9 April 2006 (UTC)[reply]

notwithstanding, you have taken it upon yourself to remove a great deal of information from this page, leaving it containing almost no information at all, at the same time adding text about eg vibration amplifiers, which was only ever a tiny specialist application (many millions of audio amplifiers have been built using valves - it seems unlikely more than a few thousand vibration table amplifiers).

I have removed a great deal of unsubstantiated and unreferenced speculation that has nothing to do with valve amplifiers per se but only with what people think about their sound. The article valve sound exists for that sort of material. Other applications of valve type amplifiers are a valid contribution to this page.--Light current 03:17, 10 April 2006 (UTC)[reply]

Your guitar interest (cited on your user page) is readily apparent as a bias in the text you have added. I agree that guitar amplifers are today one of the main applications for valves, one which deserved to be described on this entry, however your comment "Properly designed modern tube amps are said to provide a warmer, richer sound" in bnaive, simplistic and in many cases inaccurate. Some valve amps do indeed sound "warm" but by no means all, and it is far from rigourous to state this is because they are improperly designed. The sound is a consequene of the compromises and ecisions taken by the designer. Something on which given your comment about *if* ubes can be parralleled it appears you do not yet have suffieicent expertise to comment on wit hany authority.

If you disagree with this comment, then change it!--Light current 03:20, 10 April 2006 (UTC)[reply]

If you wish to make any positive contributions to this page, please do, but please stop wholesale vandalisation of informative text on a subject you are not an expert in. I would politely suggest / request that you perhaps discuss any constructive comments with me by private email, and lts work together to make this entry better.

I take offence at your accusation of Wiki vandalism and I ask you to withdraw that charge forthwith!--Light current 03:20, 10 April 2006 (UTC)[reply]

Regards / tubenutdave

Welcome new editor

Welcome new editor! User:Tubenutdave!. Please dont forget to sign and date your posts using the siganture icon at the top of the edit screen or by typing 4 tildes { ~~~~ )

--Light current 03:00, 10 April 2006 (UTC)[reply]

New page - Valve audio amplifiers

There seems to be sufficient justification to put all the matl relating to valve audio amplifiers on its own page.--Light current 04:22, 10 April 2006 (UTC)[reply]

I have created such a page and put the disputed material there for valve amp enthusiasts to add to.--Light current 04:29, 10 April 2006 (UTC)[reply]