[dgardner]

I must get at least one PM a week asking me about the the various incarnations of DIY Gilmore Amps. Perhaps this thread can keep the explanation in circulation.

First of all, I had nothing to do with the crazy names.

Dynalo = The Original Gilmore Dynamic Amp. Since Kevin Gilmore designed it to cranks his Grados, people think is only suited for only low impedance headphones. Wrong. It drives nearly every headphone 32-600 ohms quite well. It remains the least expensive and easiest to build so I guess it is the "low end" of the product family.

Dynahi = The higher power and newer Gilmore Amp. Since Kevin boasted it as being great for the "high volume nuts", and good for the especially inefficient K-1000's, everyone assumed it was for high impedance phones and called it the Dynahi. Or perhaps the high power level helped the name along.

Dynamid = don't forget about the bridged version of the Original Gilmore Dynamic. People considered this to be "the reference amp" for a while so its proper place in the pecking order must be "the middle", and therefore it was called the dynamid. Stupid name.

Dynamite (a.k.a. Dynamight) - Oh, and don't forget, if you are insane, you can create a balanced dynahi, which is affectionately know as the dynamite. Without dumbing the gain down, it melts things. I built one. It's cool.

EDIT:
Dynazilla - The fictional name given the yet-to-be-realized concept of building a dynahi amp with a big enough output stage and large enough power supply to power 8 ohm speakers.

 

[robzy]

Quote:

Originally Posted by dgardner the bridged version of the Original Gilmore Dynamic.

First silly question of the thread:

Does this mean balanced?

(And thanks a lot for the post, will hopefully weed out confusion)

Rob.

 

[Glod]

Thanks! Very interesting info. I like history in general and explanations in particular

 

[Icy006]

Great thread.

To expand on the Dynalo thing: I like to think of it such that Gilmore didn't design it for Grados or low impedence in general. Rather, he designed it to address the common shortcomings of other amps in handling low impedence loads.

If I may use examples from the DIY community: Why can't a CMoy drive Grados (or much of anything) with authority? Because it's using a single packaged op-amp (not discrete logic op-amp) to gain voltage AND source current. The packaged ones can't handle this very well on their own.

Stepping up a level to the PIMETA, now the packaged op-amp is handling voltage gain and there are dedicated packaged current buffers (BUF634) to off-load current sourcing strains. My Grado SR-325s reward me with better low-end thump, and a generally less strained sound.

So up another step to PPAv2, and what do we see? Still have packaged op-amps gaining voltage, but now the current sourcing section is done via a Diamond Buffer. This is discrete logic.

Stepping up each one of these levels, it's generally agreed that it just plain sounds better. In particular, going from PIMETA's BUF634s to PPAv2's discrete buffers should make your Grados sound better. Granted, this is a hashed example, as these amps don't use strikingly different designs.

So what's even better than this? If you apply Gilmore's Rules of Proper Audio Design (TM): "3. Ultra high open loop gain: REAL, REAL BAD!!! That basically means anything with an opamp in it." So, he whipped up a spiffy discrete design that addresses not only low impedence load issues, but a variety of potential audio evils.

This should result in an amp that handles ANYTHING with authority. In addition, the fact that more often than not it will spank the other guy for low impedence loads is just a bonus

 

[pabbi1]

Dynatoob?

 

[jar]

Where do the gilmore based commercial amps fall in relation? Specifically the Headamp Gilmore Lite and GS-1, but info on any other commercially built KG designs is also appreciated.

 

[philodox]

Gilmore Lite and GS-1 are both dynalo.

...I thought it was 'Dynamight'. Ooops.

My next Gilmore is probably going to be a balanced mig2. Just because nobody else has it.

 

[grawk]

Surprised no one has made a balanced bama slamma

 

[dip16amp]

The balanced amps come in a couple of versions also.

The orignal Gilmore dynamic amp has a balanced bridge option which added an inverted output stage to each channel. That amp has two input stages and four output stages. The balanced bridge amp only needs an unbalanced source. Two outputs are connected to the left side of the headphone and the other two are connected to the right side. It has twice the voltage swing, twice the slew rate, and four times the total power.

A fully balanced amp will have four input stages and four output stages as four separate channels. That is how the balanced dynahi is built and how some of the balanced dynalo amps are built. But it requires a balanced source to drive all four channels.

 

[dip16amp]

The Headamp gilmore reference is a fully balanced dynalo. Have not seen any commercially built gilmore balanced bridge amps.

 

[philodox]

Quote:

Originally Posted by grawk Surprised no one has made a balanced bama slamma.

Can anyone compare the new bamaslama [from a design perspective] to the minimig or the mig2? I've always thought the mig2 would be my next amp, but that is mainly from a 'grunt, more power' perspective and the fact that it draws half a kilowatt.

 

[Illah]

Yeah the Dynalo/Gilmore Lite/etc. aren't just for low-z cans. The Gilmore Lite is praised again and again for the HD6x0 series - I can verify that it drives them VERY well.

So would people on here then say that the Dynalo/Gilmore Lite/etc. is better than an opamp design like the PPA? Also what's the advantage of a Dynamid if the source isn't balanced - does it basically just act like a dual-mono amp?

--Illah

 

[Illah]

Bump - I'm curious to know the advanatages/disadvantages of the Dynamid

I'm in need of another amp and am very happy with my Dynalo so maybe this one would be the ticket. About how much would a decently configured Dynamid cost?

Thanks,

--Illah

 

[Tim D]

Bridged basically means 2x the voltage using 2x the amp parts (thus you could be looking at 2x the cost). You basically get more power at the cost of adding slightly more noise/distortion. If your listening preferences and phones actually ever clipped before you'll end up with less distortion actually with the bridged amp. With Senns I'd find that pretty unlikely however. In a sentence, a bridged amp is just 'more of the same', and I would explore other more different venues, but that is just IMO and not really DIY discussion. I'm sure someone can chime in with a Tim Allen grunt and explain why you could possibly want more power however for Senns.

I have a stereo amp that can go into 'bridged' mode. However with my speakers it is utterly pointless, and would cost me the price of buying another stereo amp that operates in bridged mode (so again 2x the cost). If I upgraded stereo amps, I could however switch the old one to bridged mode and have it happily power a subwoofer however.

 

[Garbz]

Well i'm going to utterly disagree with Tim. Sorry in advance for the confusion.

Firstly back to robzy who we left behind. Balanced is a different method of transmitting a signal (or power for that matter). Instead of having an active signal referenced to a ground you have an active signal referenced to an inverted referenced signal. I.e. 4 active outputs on your amps instead of 2 active + ground. The benefits of this is that any common mode noise picked up along the cable lengths is cancelled out when the signal is fed into transducers or into a differential amp. This makes it ideal if you have long cable runs.

A balanced Dynamid is esentially a 4 channel amp. It's not fair to simply say that each channel has twice the power that's only mentioning half the benefits. Balanced configs offer similar benfits to say 3 channel designs in that it keeps high current returns from the powersupply. But it also keeps both channels entirely separate reducing crosstalk, and it has the noise cancelling benefits above.

Switching from single ended to balanced made a world of difference at home for me, and my dynamid is nearly finished. Even if you take things by Tim's opinion you still have insane ammounts of power which is good. Twice the power + twice the slew = better sound all around. I personally say (and lots of reviewers do to check the reviews on this forum) say the Dynamid sounds far better then the Dynalo, and apparently the difference is even more apparent for Sennheisers then for Grados.

I've seen people run 700watt amps through 120watt speakers. You can never have too much clean power.

/Edit: Mind you unless you have a balanced source you either need to make the balacned design, feed the output of one channel into an inverter, use a DRV134 or similar balanced line driver, or some fat transformers (my fav) to get the signal balanced. There's been LOTs of discussion on balancing signals here recently just search around.