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Tube amp with cheap transformers 'useless' ? - Page 5

post #61 of 106
Thread Starter 
Quote:
Originally Posted by wakibaki View Post

Setting issues of profit margin aside and regardless of absolute prices, there is no reason why a tube headphone amp with comparatively cheap transformers should be considered 'useless'. Why everybody seems determined to argue the contrary is a mystery to me, but I do notice amongst the respondents a commitment to tube amp ownership or involvement in tube amp production.

 

As the OP, I am guilty of neither - I have heard tube speaker amps in a dealer's showroom, but have never owned a tube-based component of any kind. I posed the initial question in good faith, and the majority of responses seem to have been posted in the same spirit. I dont know of a single amp designer who is prepared to come out and disavow the importance of quality transformers to the performance of their products, but I am in no position to buy a cheap amp and an expensive amp simply to prove or disprove a point. 

 
post #62 of 106
Quote:
Originally Posted by wakibaki View Post

Do you deny that there is a radical improvement in OP transformer performance when used at power levels significantly below their maximum rated power? Did you even bother to look at the manufacturers figures in post #51 and compare them with the figures produced by nikongod at reduced power? This is not a ''DIY discovery', this is a well known fact and simply a consequence of physics.
 
These are improvements obtained in a 1W transformer with a 300Hz -3db rolloff. The performance improves to -1dB at 50Hz. Consider instead the likely performance of a 10W transformer with a 50Hz etc. etc.

One of my earlier posts did defend the use of less expensive transformers designed for 70V speakers as output transformers in a tube preamp or headphone amp with fantastic measured results, Si steel laminations not withstanding. These 4W transformers operate at less than a watt, and yes the response is much wider (about 10Hz to 30KHz) at this level, as expected.

 

By the way, my 66-001 preamp also sells for around 3K, there's much more involved putting it together and more casework due to the separate PSU. I could go lower in price on these units if I did not pay myself to build them. All my products are point to point wiring and do not use exotic parts. I've designed a headphone amp using a circuit board and less elaborate PSU built in, but with the casework and shipping pack in the small runs that I do the price wouldn't be below $1.5K.

 

So, if you're doing something that is solid state on a PCB that fits nicely into a stock extruded aluminum case and it only takes an hour to build with no elaborate shipping container because it only weighs 15oz then yes, you could sell them for $300.00 a pop and maybe keep the lights on.

post #63 of 106
Thread Starter 
Quote:
Originally Posted by elliottstudio View Post

One of my earlier posts did defend the use of less expensive transformers designed for 70V speakers as output transformers in a tube preamp or headphone amp with fantastic measured results, Si steel laminations not withstanding. These 4W transformers operate at less than a watt, and yes the response is much wider (about 10Hz to 30KHz) at this level, as expected.

 

By the way, my 66-001 preamp also sells for around 3K, there's much more involved putting it together and more casework due to the separate PSU. I could go lower in price on these units if I did not pay myself to build them. All my products are point to point wiring and do not use exotic parts. I've designed a headphone amp using a circuit board and less elaborate PSU built in, but with the casework and shipping pack in the small runs that I do the price wouldn't be below $1.5K.

 

So, if you're doing something that is solid state on a PCB that fits nicely into a stock extruded aluminum case and it only takes an hour to build with no elaborate shipping container because it only weighs 15oz then yes, you could sell them for $300.00 a pop and maybe keep the lights on.

 

Thank you.  

post #64 of 106

Quote:
Originally Posted by estreeter View Post
I posed the initial question in good faith, and the majority of responses seem to have been posted in the same spirit.

 

Given the effort I have put into researching both sales data and component specifications and pricing, to say nothing of extensive reading of design manuals and datasheets to ensure that I am not talking complete nonsense, I hope you feel that my contribution has been in good faith.

 

I've got a design drawn up here that I'm working at simulating (I haven't done a sim with valves and transformers before), that I'm working on with a view to buying the components, building and testing it. For no other reason than to prove a point. Not that I don't benefit from the effort, but I'm not doing it because I'm insincere.

 

I saw the comment about Bottlehead charging $65 per hour. I can hire a contractor here with an MSc and 10 years of experience of GSM and UMTS handset development for £35 ($55) per hour. I know, because I get the job adverts in my inbox. That's flat rate. I don't pay taxes, National Insurance, benefits, holidays, anything. He's self-employed.

 

3 years ago I was working for a company that was paying guys on the assembly line building point-to-point wired instrument panels £10 per hour. No two panels identical. This is not the 3rd. world. This is the Westcountry of England. The rate was depressed because they could get guys with service pensions, but not everybody had one. That was the rate. £4 over minimum wage. Of course that wasn't what the company charged the client if a panel came back for repair, although to be fair they did have other expenses.

 

These guys are interpreting wiring diagrams, building PCB and veroboard circuits, boxing subcircuits and assembling them to panels, mounting gauges and switches, cutting, drilling and building support frameworks and safety isolation barriers, printing logos and legends in addition to selecting appropriate wire gauges and insulations and wiring breakers neatly with cable-tied coiled strain relief and individual shrink-wrap wire IDs.

 

I'm trying not to be unfair here. Was I happy working there? No.

 

I'm not saying that people running audio companies should be paying their employees subsistence wages. $65 an hour is not just paying somebody's wages tho', it probably includes a healthy profit that the wage slave doesn't see, and it's far too much for an individual to charge for their labour when doing assembly work, anywhere in the world.

 

w

post #65 of 106
Thread Starter 

That's all down to the current economic situation, and the pendulum will swing back eventually. Back in the 'good old days'', several of my former workmates from Brisbane set up camp in London where they were earning 30 quid an hour cutting code - at the time, the pound was close to 3 Aussie dollars and it seemed a fantastical amount to those of us who stayed home. We all know how that panned out (others chose Dubai and Dublin - aaah, hindsight) - my point is that its all supply and demand. I would prefer Bottlehead to build my amp than run the risk of electrocuting myself, but that's just me - the important part is the fact that they give us a choice. I would expect that paying them $65 an hour means I get some sort of guarantee on the build and a certain level of competency is expected for that kind of money - they should be able to assemble an amp in considerably less time than it would take me.  wink.gif

post #66 of 106
Quote:
Originally Posted by estreeter View Post

That's all down to the current economic situation, and the pendulum will swing back eventually.

 

What? You mean the $65 is artificially low, but it'll recover to a higher price when the economy recovers?

 

The whole point is that it's got very little to do with supply and demand, it's all about charging what the market will bear.

 

What the market will bear is being unduly influenced by advertising, ignorance and tacit cartel pricing. They charge what they think they can get away with.

 

There are 2 distinct markets. The market supplied by largely by Chinese producers is controlled by competition and supply and demand and is evaluated by purchasers on the basis of  performance and value for money.

 

The market supplied by western boutique suppliers is driven by illusory concepts amounting to little more than fashion and exclusivity. Exclusivity and conspicuous consumption are sides of the same coin. Conspicuous consumption is driven by the idea that having more money to spend than someone else makes you intrinsically superior to them and excites envy.

 

The product of the boutique suppliers is ostensibly technology, but it's not founded on the basis of performance. In reality the 2 markets bear the same relationship as the clothes sold on the high street and the high fashion clothes exhibited on the catwalk and bought by filmstars and footballers wives, the main difference being that the customers for boutique hi-fi are primarily men.

 

I don't care that you spend your money on fashion. I do care that you appear to be unaware of and unwilling to admit to it. I do understand why you are unwilling to admit to spending money to validate your superiority, however. It's not something I'd be proud of.

 

w

post #67 of 106
You need to take some economics classes. Supply and Demand still governs the market dynamics of people buying for fashion as opposed to utility.
Edited by Skylab - 9/8/12 at 7:06am
post #68 of 106
Thread Starter 

Uh-oh - I sense that we are in for more lengthy paragraphs and extensive use of bolding. I guess that's just how things are done at the Harvard Department of Economics.  wink.gif

 

Back on earth, about the only thing I've taken away from this thread is that I need to audition everything, regardless of parts cost or design topology, and leave the debate to the electrical engineers and economists. 

 

http://www.economics.harvard.edu/

post #69 of 106

Yeah, like diamonds are in short supply, and the market isn't manipulated. None so blind as those who will not see...

 

Something like this, I thought.

 

 

 

'course the gain is nothing to write home about.

 

 

And the distortion is abysmal, or merely brilliant depending on how you look at it, considering it's tubes. biggrin.gif

 

w

post #70 of 106
Quote:
Originally Posted by wakibaki View Post

Yeah, like diamonds are in short supply, and the market isn't manipulated. None so blind as those who will not see...

 

Something like this, I thought.

 

 

 

'course the gain is nothing to write home about.

 

 

And the distortion is abysmal, or merely brilliant depending on how you look at it, considering it's tubes. biggrin.gif

 

w

 

I dont think that 10uf is enough to bypass the cathode on an output tube, especially when you bias the tube with a CCS. What does the bandwidth look like? 

 

Your power supply sucks. I like active (even when made with SS parts) regulators as much as the next guy, but one cap and nothing more between the rectifier and the output stage is hopelessly inadequate for an SET amp. Add CDC, CLC, or another active regulator stage - or ideally a couple. 

 

I also think your feedback arrangement will cause you headaches. SET transformers dont generally work well with feedback taken from the secondary. You may have success with feedback from the primary (oops, the transformer is hard up in the signal path outside the feedback loop, and quality matters again) or if you get a SET transformer with a "tertiary" winding specifically for feedback (Sowter makes one for headphones, sorry about your wallet). 

 

I don't care that it runs in the simulator. 

 

For someone who said this was an easy project you have a lot going against you already. 

post #71 of 106
Quote:
Originally Posted by nikongod View Post

 

I dont think that 10uf is enough to bypass the cathode on an output tube, especially when you bias the tube with a CCS. What does the bandwidth look like? 

 

Especially when you bias the the cathode with a CCS? What does a CCS feature? Very high impedance.

 

I don't think, given the stupidity of this observation, that I'll bother giving much credence to your other objections which are obviously based on the premise that 'these grapes are sour anyway'.

 

w

post #72 of 106
Regardless, your cap is still off by about an order of magnitude.
post #73 of 106
Quote:
Originally Posted by wakibaki View Post

Especially when you bias the the cathode with a CCS? What does a CCS feature? Very high impedance.

 

I don't think, given the stupidity of this observation, that I'll bother giving much credence to your other objections which are obviously based on the premise that 'these grapes are sour anyway'.

 

w

 

Indeed, very high impedance.  

It is very unconventional to have a high impedance looking out of the cathode in a common cathode stage. If that is what you wanted to try why bypass the CCS at all?

 

Since you did try to bypass the cathode/CCS it is reasonable to assume that you were looking for a more conventional low impedance looking out of the cathode but with only 10uf there you didn't really find it.

 

Using a CCS to bias the cathode is different than using a resistor. With a resistor you have the benefit that the resistor is in parallel with the cap which slows the roll off of the cap, if only slightly. With the CCS you have nothing but the cap.

post #74 of 106

I think this is a bit simplistic, and really begs the question, i.e., which items are priced based on 'what the market will bear' vs the others - the high end audio stuff i say is....

Besides,  seems to me that 'what the market will bear' is another way of saying supply and demand.  There are market forces described by Veblen, where 'snob appeal' plays a role, but it takes some independent argument to specify which goods those are.

Quote:
Originally Posted by wakibaki View Post

 

What? You mean the $65 is artificially low, but it'll recover to a higher price when the economy recovers?

 

The whole point is that it's got very little to do with supply and demand, it's all about charging what the market will bear.

 

What the market will bear is being unduly influenced by advertising, ignorance and tacit cartel pricing. They charge what they think they can get away with.

 

There are 2 distinct markets. The market supplied by largely by Chinese producers is controlled by competition and supply and demand and is evaluated by purchasers on the basis of  performance and value for money.

 

The market supplied by western boutique suppliers is driven by illusory concepts amounting to little more than fashion and exclusivity. Exclusivity and conspicuous consumption are sides of the same coin. Conspicuous consumption is driven by the idea that having more money to spend than someone else makes you intrinsically superior to them and excites envy.

 

The product of the boutique suppliers is ostensibly technology, but it's not founded on the basis of performance. In reality the 2 markets bear the same relationship as the clothes sold on the high street and the high fashion clothes exhibited on the catwalk and bought by filmstars and footballers wives, the main difference being that the customers for boutique hi-fi are primarily men.

 

I don't care that you spend your money on fashion. I do care that you appear to be unaware of and unwilling to admit to it. I do understand why you are unwilling to admit to spending money to validate your superiority, however. It's not something I'd be proud of.

 

w


Edited by fzman - 9/24/12 at 8:24am
post #75 of 106
I don't mind the CCS there. It should actually lower distortion. I have used a similar construction. I would use a better CCS than a LM317, but whatever. So long as it does not oscillate it will be OK. However, I would connect the other end of the cap to B+ rather than ground to take better advantage of the CCS.

The thing to keep in mind is that the CCS impedance is in parallel with (Ra + ra)/(mu + 1) which will govern the cap size here.
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