[dgardner]

I would like to assemble the group's opinion on what things would make the Kevin Gilmore dynahi an easier and more attractive project for the do-it-yourself crowd. Right now, the build complexity seems to be more the issue than the total cost. This amp is not cheap to make, but is certainly worth the effort IMHO. Maybe some things can be done to get more people to complete this project successfully. Lots of PCBs have been sold in the two groups buys, but it seems like relatively few of those people have completed the project. Nothing against the builders and peddlers of completed units. This is a DIY discussion.

 

[skyskraper]

the reason my dynahi is only in part collection phase is due to time and money. m3 done. dynalo almost done. dynahi next

im sure a lot of other are like me in that the boards are for the future when one gets bored or has a few more projects under their belt

 

[rellik]

tangent style build guide

Edit: mabe stickying the transistor matching guide would be helpful as well

 

[kilkil]

The dynahi is my first amp. I just decided it doesn't cost that much more than a ppa, which is what I was thinking of making. The actual populating the boards is not hard, assuming you can solder and drill holes in an angle iron. I think if someone created step by step directions and description of what each part does in the circuit that a lot more people would see it as an easier project. I looked through all the dynahi threads I could find to understand what I understand about the dynahi now, which is quite a bit of reading. Having to order parts from 5+ different places plus going to home depot a few times is a little bit of a put off. This also requires matching of parts which can be a little scary to people, it requires an acceptable multimeter.

 

[n_maher]

I'll throw in my 0.02 as a relatively new amp builder.

My basic concern with the Gilmore amps is the relative lack of documentation on the actual build process. At least I haven't been able to find much. And to be honest I'm not sure that is a bad thing. From what I've read the Dynahi is an amp that shouldn't be taken lightly or attempted without a fair amount of actual electronics knowledge. The ability to solder and match resistors is simply not enough.

If there were a site like Tangent's that spelled out the steps involved in building a Dynahi/mid/lo I'm sure that you would find more people trying to build them. But it seems to me that the consequences of building one without some pretty detailed instructions could be horrible for your headphones. For me, I bought a Dynalo board with the intentions of building one after I've completed several more projects which will hopefully continue to teach me about the circuits that I'm building. In actuality it may not be any harder to build than my M3, but it sure looks that way to the newb in me. The cost factor for parts is also a bit of a scare with the upper Gilmore projects. I can't see myself ever spending $500 to $1000 on parts for am amp, which seems to be what people are doing with hi/mite versions.

Hope that helps you in some way and thanks again for running a great group buy on the Dynalo boards.

Nate

 

[bg4533]

I have gotten over most of these now. The Dynalo will also help me make a step to the Dynahi.

Here is what has held me off (both building and non building reasons):
1. The case work and heatsinking is difficult. Drilling all of the holes for is a lot of work. A drill press or at least nice hand drill is needed.

2. I still don't understand transistors. I like to know how things work before I tackle them. I understand most of the opamp designs around here.

3. Matching the transistors and other parts is very important. Without understanding transistors and their interactions this is confusing. It is also important to match resistors. A lot of people around here don't have good enough multimeters.

4. I don't know how this amp is going to sound and I can't really change the sound. With opamp based designs I had an idea of what my next amp would sound like. I knew my PPA with OPA627s would sound similar to Pimeta with the same opamps. I also can change the opamps and get a different sound if I am not happy. I have heard very differing opinions of the Gilmore amps. Some say they are bright. Some say they are very full and warm. Who knows if I will like my very expensive and involving amp.

5. The Dynahi is a large and hot amp. I don't have a ton of space and my room is already hot. My amp sits about 3 feet from me at my computer. I dont want to be any warmer.

6. There have not been as many builders around here. There is more to go wrong and it will be harder to fix my problem if there is one.

7. It is an expensive amp. Having to order from a ton of places doesn't help this. Nor does having to buy a ton of extra transistors to match.

Solutions:
1. Angle brackets like Dgardner had made would help a lot.

2. Put together something that explains transistors and gilmore amps to beginners. Most people here have at least built Cmoys. Have comparisons to opamp based designs.

3. The ability to buy already matched transistors. At least the expensive ones.

6. This should eventually fix itself once things get going.

-----

I might add more to this list as I think of things.

I am currently working on 2 Dynalos. The first is a basic one with Elpac PSU. The second is a higher end one with Dynalo PSU and other better parts. If I like the Dynalos enough I will proceed with the Dynahi.

 

[SnoopyRocks]

Here's a short list of what I would like to see

1. consolidated information (most important)
2. part list with supplier part numbers and alternatives (all parts! - there should be no need to look up any part numbers for a typical build - even resistors, pot, jacks, wire)
3. circuit description (this is about building an opamp, not using one)
4. step by step build guide (including which parts need to be matched and how to match them)
5. trouble-shooting guide
6. simplified heatsinking and casework - something that doesn't require a machine shop

As a side note, I'd like to say thanks Dan for organizing the group buys and doing the pcb layout. I recall you mentioning that you are a digital guy. (I'll forgive that transgression because of your work here.

) You have this analog guy's approval. I especially like the propper gound plane on the rev3 dynalo. (I haven't seen the others.) Nice work.

 

[phobus]

another vote for heatsinks and casework!

 

[Pars]

I have several sets of boards, but have just barely started getting some of the parts for one. I echo some of the concerns already voiced in that:

1) The Dynahi is an expensive amp to build. It requires alot of parts, parts matching, and the mechanicals of the heatsinking are somewhat daunting if you don't have access to proper tools, etc.

2) Troubleshooting could be difficult, as there is alot of interaction between parts and stages.

Because of the individuality of casework, I'm not sure how much standardized brackets, etc. would help, unless you were willing to live with a particular style of case/heatsinking, etc.

Some random responses:

Quote:

Originally Posted by bg4533 3. The ability to buy already matched transistors. At least the expensive ones.

Borbely Audio in Germany sells matched sets for a 50% premium.
Quote:

Originally Posted by SnoopyRocks *consolidated information (most important) *part list with supplier part numbers and alternatives (all parts! - there should be no need to look up any part numbers for a typical build - even resistors, pot, jacks, wire) *circuit description (this is about building an opamp, not using one) *step by step build guide (including which parts need to be matched and how to match them) *trouble-shooting guide *simplified heatsinking and casework - something that doesn't require a machine shop

Dan has done some of this already, with his well laid-out site. There are some parts lists floating around (probably on Dan's site as well) that are about as concise as its going to get, IMO. A step-by-step build guide? Dunno, maybe a possibility. Dan already has a couple of diagrams showing the realationship of the transistors (at least on his Dynalo board, thought there was one for the Dynahi as well). A writeup on matching would be a welcome addition. For troubleshooting, even a basic voltage listing of what you should see at certain points in the circuit would probably be helpful for many.

Thanks to Dan for all the work and group buys that he has done, as well.

Chris

 

[aerius]

The fact is the Dynahi is NOT a beginner's project, there's just no way around that. It's not something like a CMOY or PIMETA that one can just slap together and easily understand and troubleshoot if things don't work. While it's entirely possible that one can just slap the parts on the board and have it work, the problem is what if it doesn't work? That's when you need the experience & knowledge to troubleshoot things, and that experience & knowledge, IMO, is going to be very hard to put into a neat easy guide.

I think a lot of people got in over their heads when they bought the boards, figuring that given a PCB it would simply be a matter of sticking in the parts. It's a bit more involved than that.

My advice? Build and understand the Dynalo first. Same basic principle, much cheaper parts, and no heatsinks to worry about.

 

[dgardner]

Quote:

Originally Posted by aerius The fact is the Dynahi is NOT a beginner's project, there's just no way around that. It's not something like a CMOY or PIMETA that one can just slap together and easily understand and troubleshoot if things don't work. While it's entirely possible that one can just slap the parts on the board and have it work, the problem is what if it doesn't work? That's when you need the experience & knowledge to troubleshoot things, and that experience & knowledge, IMO, is going to be very hard to put into a neat easy guide. I think a lot of people got in over their heads when they bought the boards, figuring that given a PCB it would simply be a matter of sticking in the parts. It's a bit more involved than that. My advice? Build and understand the Dynalo first. Same basic principle, much cheaper parts, and no heatsinks to worry about.

Very true. I agree that this is not for beginners and that the dynalo can be a great place to learn without getting into the larger mechanical challenges. The dynahi is already too expensive for many members. But for those who have lost their minds (like me) and don't think $500-$1000 is out-of-whack for a primo headphone amp, there ought to be an easier road with a more rewarding outcome.

My Dynahi DIY Complaint List (so far):

The Good:
1 - Kevin Gilmore gave us something very nice to work with. (Thank you Kevin)

2 - Readily available amp PCBs via group buy. (Thank you MisterX!)
3 - Readily available PSU board via group buy. (Thank you MisterX!)

The Bad: (or should I say, areas for improvement)
1 - PSU transformers were never really spec'ed out and the sources typically had long leadtimes. PSU circuit does not handle oversized secondary voltages very well. Large dropout voltages make the unit on the thermal-hairy-edge in the dynahi application. I had to re-build mine once already.
2 - The whole heatsink bracket concept is so-so, and it's fabrication is out-of-the-question for a lot of users. A really nice and affordable custom engineered component is almost a necessity.
3 - Incomplete (at best) level of documentation about the theory of operation. A few dozen people or more are up to speed, but many are clueless.
4 - Casework options have serious constraints. You have lots of heat. You must vent the box or attempt to get the heatsinks incorporated into one of the outside walls, where the cool are resides. The box cannot be made really small and pretty to look at. It will never ever be portable. The amp boards run hotter than the PSU if you select the tranformer right, but its parts run hot too.
5 - No one willing to make the matched transistors readily available. Yet. (I don't think Borbely stocks all these parts)

The Ugly: (or should I say, the visually uninspiring)
1 - Dynahi amp circuit is a wonderfully symetrical design, but the layout does not have anywhere near the maximum visual impact that could be made.
2 - The PSU board is nothing special to look at, but the circuit is nice, simple, and easily configured for other applications. Lead bending operations required to lay the parts down flat are truly scary, especially on $15-20 power op-amps. Off-the-shelf transformers, possibly PCB mount toroids, might might make this circuit board something more turnkey for DIY'ers.
3 - Let's cut to the chase. This amp and PSU should be a thing of absolute beauty to look at. Right now it is not. We should find a way to change that.

 

[Magsy]

Just how many watts of heat does this thing disapate in a standard unbalanced config? Does anyone know?

 

[Edwood]

I am rather obsessive about documenting step by step pics when I build things.

So I will try to make a nice pictorial guide for people to follow. Perhaps we can consolidate a nice pictorial step by step guide from start to finish when there is a nice completed one.

So for me the most daunting task is matching transistors.
#1. How to make a proper breadboard matching station.
#2. What specific values to look for.
#3. What matching ranges are "good enough" and "best without wastful overkill".

I have a good deal of shop experience, so the casework does not really bother me. But I no longer have access to a full shop and mill, so I have to do almost everything by hand. I do have a small bending brake, which most people do not, but I will try to show a guide of how to bend sheet metal with basic hand tools. Same with drilling holes with only a hand drill.

-Ed

 

[dgardner]

Quote:

Originally Posted by Magsy Just how many watts of heat does this thing disapate in a standard unbalanced config? Does anyone know?

At 60ma bias for each output transistor, a stereo unbalanced amp dissipates roughly 28 watts total. At 80ma bias for each output transistor, a stereo unbalanced amp dissipates roughly 37 watts total. Lowering the supply rails slighty and making sure the output stage bias doesn't get too high, both help limit the total heat. The bias can be controlled in a number of simple ways by slightly changing certain resistors.

These power numbers don't include power supply heat.

 

[rellik]

Quote:

Originally Posted by Edwood So for me the most daunting task is matching transistors. #1. How to make a proper breadboard matching station. #2. What specific values to look for. #3. What matching ranges are "good enough" and "best without wastful overkill".

i second that