Is the Dynalo still a good choice? - Page 2

I don't think the concern of 11x gain was noise floor, I think it was that there would be a very small usable range of the volume with sensitive cans. That being said, the output level of your source should be a key consideration when choosing gain as well. A source that puts out 1 Vrms with an amp with gain of 11x is about the same as a source that puts out 4 Vrms with an amp with gain of 3x.

Cool, I use the gamma2 as my source as well. My beta 22 has a gain of 5, and it gets more than loud enough with senn hd600 and lcd2s. I wouldn't recommend doing any higher than 5x if you want to have reasonable volume control, and if you don't plan to get less efficient headphones you probably want to go for something around 2x.

 

BTW, Vrms is root mean square voltage. It is calculated by taking the integral of a signal squared over a certain period of time, dividing by the time interval, and taking the square root of that result. For practical purposes you can generally assume the rms value to be the maximum voltage level divided by the square root of 2. So from this you can see that the peak output of the gamma2 would be 2 volts, giving it a Vrms of 1.4 volts.

5x is pretty much the max for reasonable volume travel with Grados.

What kind of horrible things will have to be endured with a gain of x11 and Grado's?

What happens if said user upgrades to a higher impedance headphone?

Why was the Dynalo designed with a 20K pot in mind, and a gain of x11 times?

Is 5x ok with music that's brick walled? or rather more music with dynamic range?

 

This has to be somewhat confusing to someone? Namely the 3rd question.

 

Cheers

No idea why it was originally designed with an 11x gain. 5x should be fine with most music, though you may not get a huge volume travel with high sensitivity headphones. Nothing horrible would be endured, but you would only be able to turn the knob like 5% to get loud volume.

That would be the post I was talking about, It doesn't make much sense. I'll find out sometime (tomorrow maybe), my Dynalo amp board is completely stuffed, and all that's left is the PSU to be completed.

 

What pot are you referring to?

1: You (generally) attenuate a LOT which puts you in a poorly matched section of the pot, and IME screws with frequency response a bit. Higher gain results in more noise due to funky resistor effects, bummer. The only advantage is that the volume control is WAY down, like you are holding back a more powerful amp - purely psychological. 

 

2: The word of the lord passed down in the headphone chapter of the audio bible that you need gain of 11 to run anything more than 75ohms will have to be broken then. Obviously Im making a cheap joke. The lord did not come down and give us this rule, a human being (who like all human beings is prone to errors, and unlike many human beings listens loud as hell with 600ohm headphones) pawned it off on us - the rule may even predate people listening to headphones for hifi! gain of 10 was VERY popular for preamps, despite the fact that power amps have been running with 1v input sensativity since the 60's or earlier. Anyways, Despite what the easy to follow rule tells us, high impedance headphones generally run just fine on amps with voltage gain in the 1-4 ranges. Try it! Some people MAY top it out, but then gain of 11 is only a little more than 3 (if you max out an amp with gain of 3 easily, 11 is not even enough!). If the volume knob NEVER gets within 1/3 of the max you have more gain than you need - save yourself some resistor noise, and reduce the gain.

 

3: Why a 20K pot? If Im not mistaken Kevin Gilmore had a Penny + Gilles 20K pot "just sitting around" waiting for an application... Good enough reason to use a $250 pot for me. 

 

Many MFR's make 20-25K audio pots, its just that nobody uses them*. EVER. P+G is awesome so they can do anything they want.

 

* another rule given us by the good lord in the general section of the audio bible is that the only values of potentiometer to use as attenuators are 10K, 50K, and 100K. Values below 10K, or between those 3 values must never be used as an attenuator least you be smitten. In all seriousness, 20K is a sweet value: Its a LITTLE bit more than 10K (twice as much!) which buys you an extra octave of bass in cap coupled sources, but not so high impedance as to cause undue noise. 50&100K ohm pots have much more inherent noise which coupled with the trend for too much gain gets you nothing but too much noise * too much gain! values lower than 10K (1K,2K,5K are common) are SWEEEET because they have VERY low noise, but may prove too difficult for some sources to drive well, and forget it with cap coupled sources. 

 

Quote:

EVERYTHING was designed for 11X gain back then. 

 

poosticks... the quote in a quote thing didnt work. Just immagine the part you quoted just before the part I quoted is there. 

 

Everyone talks about gain without consideration of the source voltage level, ASSUMING that the user has a "standard" 2v source. Some people have high output 4 or 10v sources, others have a very low 0.25v. With a 4 or 10v source you need NO gain to run almost anything - just a good stiff buffer that can handle the heat. With a 0.25v source you actually need gain to run 300 ohm headphones!

I don't know if someone has already reacted to this but i'm going to answer anyway ; you can not use a sigma 11 with a dynalo unless you add a ground channel, which is complicated. Actually I am not sure if Kevin Gilmore ever considered a ground channel for any of his amp. In short you need to use a bipolar power supply such as the sigma22 with a dynalo.

 

To respond to the original question, I have a dynalo and it is indeed a great amp, you can not go wrong with it ! I lowered the gain too but I don't remember how much...

 

Again I think it has been said (that won't prevent me from repeating ) if you have a high gain, you need to use the potentiometer in a "region" where the two channels are not matched well at all (especialy with a cheap pot). A low gain allows you to turn it up a bit which "compensates" the differences of volume between the right and left channels.

Edit : Nikongod said : "You (generally) attenuate a LOT which puts you in a poorly matched section of the pot" It is exactly what I was trying to say.

 

Edited by bidoux - 5/14/11 at 1:24am

Actually if you go back a few posts I pointed out the same thing:

 

The OP said he will be using a gamma2, aka a 1.4V source, so I suggested a gain somewhere between 2 and 5. 

 

The rest of your points are excellent.

 

As someone who has had severe pot imbalance issues in the past, I can attest to Nikongod's statements about it putting you in a bad section of the pot. The solution to this would seem to be a stepper, which generally has no channel imbalance, but you're still attenuating a huge amount, and that can lead to two problems with steppers.

A resistor with a 5% tolerance will be much less accurate at higher resistance values than lower ones. (That said, if your stepper uses 5% resistors, you've got bigger problems in store...)
The bigger problem is that your steps will probably be HUGE! Splitting 11x gain into equal chunks means that you have very little precise control over volume.

The moral of the story is to not overdo the gain, in the end. I've built every single one of my amps with gains of 5 or less, and hardly ever had an issue with 2V or lower unbalanced sources. (Nearly all of my sources have been 2V/6dBV.)
Edited by revolink24 - 5/14/11 at 9:24am

Check out the "Stackofhay edits", It has the information you need, and more!

 

Could I get away with lowering R16 value to ~5K and still keep the 10pF compensation cap?