better preamp ic than 4580/5532?

braincell · Post by **braincell** » Wed Jun 18, 2008 3:18 pm

You are so smug Astro

.

Post by **garyb** » Wed Jun 18, 2008 3:33 pm

Immanuel wrote:
garyb wrote:in class A one device handles top and bottom of the waveform. in class B and AB, one device has the top(push) and the other the bottom(pull). this is more efficient(louder with less power required), but not as "musical" sounding.
Gary, this is wrong. What you are describing is single ended or unballanced design versus push/pull or ballanced design.

Class A is about consuming full power all the time. You can say, that the PSU feeds the cirquit with full power all the time, where as in the other designs, the cirquit has to draw the needed amount of power out of the PSU.

yes, what you are saying is also true. neither are exact descriptions. never the less, class A or single ended designs handle the entire waveform. push-pull designs have output devices in pairs with each half of the pair handling half the waveform.

http://www.duncanamps.com/technical/ampclasses.html

http://www.pcmag.com/encyclopedia_term/ ... 350,00.asp

Cochise · Post by **Cochise** » Wed Jun 18, 2008 3:36 pm

Immanuel wrote:Class A is about consuming full power all the time. You can say, that the PSU feeds the cirquit with full power all the time, where as in the other designs, the cirquit has to draw the needed amount of power out of the PSU.

Sorry again for my OT attitude, but this reminds me SSB

braincell · Post by **braincell** » Wed Jun 18, 2008 7:00 pm

Why is OT such a sin? These topics are starting points.

the19thbear · Post by **the19thbear** » Wed Jun 18, 2008 11:06 pm

sooo just to get back on topic.... i guess the LM4562 is a good substitute??

i appreciate all the talk about tubes! i like them as well... but hey... they just wont fint into an ic socket! dont ask me why

any other suggestions?

Post by **garyb** » Thu Jun 19, 2008 1:11 am

tubes and transistors fill the same function. the classes apply regardless of tube or transistor.

the LM4562 is a high quality op amp. the difference will be subtle. soon, you'll need to upgrade caps and resistors too....

braincell · Post by **braincell** » Fri Jun 20, 2008 6:05 am

I found that clearly some brands of tubes sound much better than other brands. I don't think you can say that about transistors. When you say transistors can sound like tubes, it is a general statement. Which tubes do they sound like? I am not buying it. Let's just say that in theory transistors can sound good and some do. Maybe it is a matter of taste as well.

Immanuel · Post by **Immanuel** » Fri Jun 20, 2008 6:23 am

garyb wrote:yes, what you are saying is also true. neither are exact descriptions. never the less, class A or single ended designs handle the entire waveform. push-pull designs have output devices in pairs with each half of the pair handling half the waveform.

Gary - as I see it, you are still off. Class A does not have to be single ended. Try to find a high end mic pre which is not both class a and push/pull (ballanced). Also, single ended does not have to be class A.

Cochise · Post by **Cochise** » Fri Jun 20, 2008 6:47 am

Apart from tonal qualities, as I've already outlined, with tubes the different knee introducing into saturation state allows for sound settings having only high dynamic peaks been saturated. that's not easy to achieve using transistors.

... I've found out TL072 is JFet based...

About the 4562, as far as i can get from data sheets: it has the same pin layout of 4580, has similar THD, looks like it has more gain...

Cochise · Post by **Cochise** » Fri Jun 20, 2008 6:59 am

braincell wrote:I found that clearly some brands of tubes sound much better than other brands.

Afaik, tubes are hand made. Tubes of the same brand sound different.

astroman · Post by **astroman** » Fri Jun 20, 2008 8:14 am

braincell wrote:I found that clearly some brands of tubes sound much better than other brands. I don't think you can say that about transistors. When you say transistors can sound like tubes, it is a general statement. Which tubes do they sound like? I am not buying it. Let's just say that in theory transistors can sound good and some do. Maybe it is a matter of taste as well.

it's a matter of fact that neither transistors nor tubes do sound at all
what sounds is the device, built from active and passive elements according to a specific design.
for some sounds someone wants it transparent and crystal clear, for other sounds another one prefers a muddy tone or even a disharmonic distortion.

A tube based circuit design is as good or bad as a semiconductor one by default, but tubes have the visual mystery advantage (and of course the vintage touch), though Germanium transistors recently seem to catch up a bit...
Most of that stuff is just marketing blurb anyway, as has been mentioned already.

My request for another circuit design than the (so-called) 'usual' 4580/5532/TL72/TL82 layout was based on the impression that for a very specific application there are better ways - whatever they may be based on.
I didn't have a look into the Avalon U5 or the Tecamp Puma bass amp, but these units have exactly that extra definition I miss.

And for those swearing on tubes I suggest to listen particularily close to the latter amp. You won't trust your ears that it's a tubeless design, once you start turning that 'Character' dial to the right...

cheers, Tom

Cochise · Post by **Cochise** » Fri Jun 20, 2008 8:37 am

Cochise wrote: About the 4562, as far as i can get from data sheets: it has the same pin layout of 4580, has similar THD, looks like it has more gain...

And it has similar very linear response through audio frequency range...

Cochise · Post by **Cochise** » Fri Jun 20, 2008 4:53 pm

Some time ago I was reading about good OpAmps from Analog Devices....

Post by **garyb** » Fri Jun 20, 2008 9:56 pm

Immanuel wrote:
garyb wrote:yes, what you are saying is also true. neither are exact descriptions. never the less, class A or single ended designs handle the entire waveform. push-pull designs have output devices in pairs with each half of the pair handling half the waveform.
Gary - as I see it, you are still off. Class A does not have to be single ended. Try to find a high end mic pre which is not both class a and push/pull (ballanced). Also, single ended does not have to be class A.

find me a class A amp that IS push/pull. balanced is not push/pull. balanced has the ground isolated from the audio positive and negative signals. class A can be balanced or unbalanced on it's input. push/pull is class B or it's variants(AB, H etc.) single-ended refers to the fact that the whole waveform is handled but each output device. only one is required for the entire waveform with class A. push/pull requires pairs of devices. when one is on the other is off and vice versa, each handling half the waveform.

from the duncan link posted earlier:

If we now superimpose a signal on the grid voltage, the anode current will vary up and down in sypathy with the grid voltage, hence the "Out" waveform.

As the title suggests, this is "Class A". The distinguishing feature of class A is that the valve is conducting current at all times. Note the the "Out" current never drops down to the zero line at any time.

Some output stages are class A (such as the Vox AC-30), and all preamp sections are class A. If you want to check out a circuit diagram with a class A output stage, you can download the circuit of my Blues-112 combo. Note that you will need Adobe Acrobat installed to make sense of it!

OK, that's class A out of the way. What about class B? In the diagram on the right, we have set the bias point to where the valve has almost stopped conducting.

Note that the input signal is a lot larger now in order to drive the valve hard enough. Also, the output current is only for half of the waveform.

To make any use of this, we have to have a "push-pull" output stage which employs two valves (or two banks of valves) so that each side amplifies each half of the waveform. While the first output valve provides the output current as shown on the right, the second valve fills in the gap which follows it.

astroman · Post by **astroman** » Sat Jun 21, 2008 3:58 am

Cochise wrote:Some time ago I was reading about good OpAmps from Analog Devices....

the SSM 2019 (mentioned in the quote about the XITE preamps) is by Analog Devices

enumeratus wrote:
Strattosphere wrote: ...Hopefully they'll use something like Burr Brown INA137s or THAT 1512 chips for the preamps.
Stratt
Good guess - the XITE preamps actually have SSM 2019 input amplifiers.

cheers, Tom