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dgardner  HeadWizer Joined: Sep. 27, 2004 |  Message [#1] posted on: 12-26-2005 09:24 AM CST (US).   |  |  The purpose of this thread is to discuss the assembly, construction, and debug of the Kevin Gilmore Dynahi Amplifier Board. This board is currently available via a group buy here. I will post more details and links in the next few days.  [Edited by dgardner on 01-17-2006 at 02:56 PM.] |
| DigiPete Member Joined: Oct. 12, 2005 | Message [#2] posted on: 01-12-2006 08:55 AM CST (US). | | Dan, How hot can the power output transistors safely get on the Dynahi board. I popped my Dynamite case open yesterday http://www6.head...3&postcount=877 and the transistor case temperature was a toasty 65°C |
| dgardner HeadWizer Joined: Sep. 27, 2004 | Message [#3] posted on: 01-12-2006 10:53 AM CST (US). | | That's not too bad. Junction temp will be several degrees C higher, but looks like nowhere near maximum ratings. Check the voltage across one of the 20 ohm emitter resistors. Caluclate the current. Double it since the resistors are in parallel pairs. If operating properly, the output current at idle should fall into the 65-75mA range per transistor. If you are up the 80's, some downward adjustment might be worth considering. How big is the heatsink? |
| DigiPete Member Joined: Oct. 12, 2005 | Message [#4] posted on: 01-12-2006 08:04 PM CST (US). | | Hi Dan, I am drawing about 70-72ma per transistor once at operating temp. The heat sink is 3/16" thick angle aluminum with two HS-TWS heatsinks from surplus sales. You can see it on the link I provided to my head-fi post. Thanks [Edited by DigiPete on 01-12-2006 at 08:16 PM.] |
| dgardner HeadWizer Joined: Sep. 27, 2004 | Message [#5] posted on: 01-13-2006 08:10 PM CST (US). | | Looks like everything is great. No one said this baby runs cool.  [Edited by dgardner on 01-13-2006 at 08:11 PM.] |
| DigiPete Member Joined: Oct. 12, 2005 | Message [#6] posted on: 01-14-2006 12:44 AM CST (US). | | Grounding question for Dynamite? Should I isolate the input jacks(grounds) and power supply grounds from the chassis, since there are now two power supplies with potentially a difference in voltage between the two? [Edited by DigiPete on 01-14-2006 at 11:33 PM.] |
Snoopy Member Joined: Aug. 5, 2005 | Message [#7] posted on: 01-14-2006 06:41 PM CST (US). | | Here are some pages that I found helpful / interesting. It is far from thorough or complete, but some more information to think about nonetheless. I presume everyone has already gone through Dan's site. Build Discussions:
Heatsinks / Cooling: |
| DigiPete Member Joined: Oct. 12, 2005 | Message [#8] posted on: 01-16-2006 08:16 PM CST (US). | |
You said it! I finally built the other two boards for the balanced unit and put them into the case (both running I need to mod the case a bit to extend the vent slots over the heatsinks, this should help a bit. Pulling 75ma per transistor. [Edited by DigiPete on 01-16-2006 at 08:18 PM.] |
| Snoopy Member Joined: Aug. 5, 2005 | Message [#9] posted on: 01-16-2006 09:56 PM CST (US). | | Heat Sinks / Cooling: The notion of making an angle brack for the heatsinks doesn't really appeal to me. Besides it's better to have a direct connection to the heatsink. I came accross some another company ThermaFlo that has a lot more options, compared to what I've seen in the old threads on the other site. Thermaflo has a lot more options available than surplus sales. ThermaFlo's site claims that they will do small quanties, but prices are not listed and I haven't called to find out. Here are a few models that seem appropriate to me: These seem adequate and a cleaner solution...but I haven't built a Dynahi so I don't really know. What do you guys think? |
Pars HeadWizer Joined: Nov. 12, 2003 | Message [#10] posted on: 01-16-2006 10:47 PM CST (US). | | No comment on the sinks you ID'd (not qualified and haven't really looked into it). However, Thermaflo were the first sinks that Kevin Gilmore used. See this, specifically post #28. There is also some discussion of Thermaflo in another thread "over there"... simple search on Thermaflo. Can't remember exactly why a group buy or something didn't occur on these... probably the cost and the availability of the Surplus Sales units pacified everyone into going that route. I'd agree with you on the angle bracket, etc. as not being the best solution, especially the bending of the leads on these devices. BTW, bryan may have some extras on the COnrad sinks, so I'd PM him or email him if I were you (and you think these are adequate). Chris |
| DigiPete Member Joined: Oct. 12, 2005 | Message [#11] posted on: 01-17-2006 08:19 PM CST (US). | | From my experience: Bending the leads is a snap, and with some 1/8" thick sheet aluminum you can scribe a line on it near the edge, put the transistor leads against the line, and presto, perfectly bent leads for all 16 transistors. The hardest part I found was machining the angle bracket and precisely drilling the holes for the transistor mounting bolts. Also, the angle bracket is a substantial heatsink in itself, and I used thermal compound to connect the surplus heatsinks to the bracket, so there is hardly any loss in heat transfer. The other heatsinks by thermaflo just offer a different configuration/geometry, but no better performance per se. Pick whatever works for you |
Steinchen HeadWizer Joined: Oct. 12, 2005 | Message [#12] posted on: 01-28-2006 06:41 AM CST (US). | | finally, after some delays, I finished my Dynahi. Due to the limited and simple tools I own casework has been hard this time. total front rear inside boards The heatsinks (0.45K/W) are a little oversized, it takes about 30min for the amp to warm up, but that's better than running too hot. I'm absolutely stunned by this amp. I expected it to sound similar to my Dynalos but the Dynahi is even far better. It has an amazing clearity, detail and soundstage. Everything is well defined, tight and under full control. Last but not least I got an amp that is capable of seriously driving my K1000. And the Ultrasone HFI-700 really shine now. I am seriously exited. Thanks to Kevin Gilmore for sharing this excellent design and to Dan Gardner for the boards. Special greetings to ble0t, thank you for the kit |
| dgardner HeadWizer Joined: Sep. 27, 2004 | Message [#13] posted on: 01-28-2006 10:43 AM CST (US). | | Nice work! I love the clean front and back panels. What can you tell us about the case? It's the perfect size. |
n_maher HeadWize Fanatic Joined: Dec. 15, 2004 | Message [#14] posted on: 01-28-2006 02:07 PM CST (US). | | It's pictures like these that get me downright excited to give buidling this amp a try. I'm starting to gather parts and components now but given my fricken work schedule (2 days off so far this year) I don't expect to be starting in earnest before June  .Nate |
| Steinchen HeadWizer Joined: Oct. 12, 2005 | Message [#15] posted on: 01-29-2006 03:40 AM CST (US). | |
I got the case from http://www.schuro.de/preisl-gehaeuse.htm Basically it's a 19" rack case, 2 units heigh, designed with small power amps in mind. It measures 45x33x8 cm (18x13x3 inches). Weight of the finished amp is 7.6Kg [Edited by Steinchen on 01-29-2006 at 03:41 AM.] |
vixr HeadWize Fanatic Joined: Sep. 17, 2005 | Message [#16] posted on: 02-09-2006 10:38 AM CST (US). | | WOW... steinchen, that amp is simply beautiful. you are an artist. thanks for the look |
amb Headphone Council Joined: Apr. 1, 2004 | Message [#17] posted on: 02-19-2006 07:37 AM CST (US). | | I have finished building my Dynahi. The casework of my build follows the same theme as my other headphone amps, except this time it's bigger and bolder with the group-buy Conrad MF30-75 heatsinks serving as the side panels. Separate cases house the amplifier and power supply. I'll post a photos here. Further details and more photos are at my Dynahi page. I am not sure about the brushed aluminum volume knob yet, and might switch to a matte black knob instead (to match my other amps).
[Edited by amb on 02-19-2006 at 07:38 AM.] |
| dgardner HeadWizer Joined: Sep. 27, 2004 | Message [#18] posted on: 02-19-2006 10:08 AM CST (US). | | AMB- Absolutely gorgeous as expected! |
| Pars HeadWizer Joined: Nov. 12, 2003 | Message [#19] posted on: 02-19-2006 01:28 PM CST (US). | | Very nice Amb... front/rear plates are acrylic? Nice design to the case. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#20] posted on: 02-19-2006 02:28 PM CST (US). | |
Yes, the front and back are 3/8" thick acrylic. It was clear, but I painted the outside face with Krylon "Fusion" spray paint for plastic (black), and then a couple of coats of Krylon Matt Finish transparent spray to give the desired surface finish. The edges are sanded to give a "frosted" translucent look. This is the same for all the headphone amps I've built so far, including my M³, Millett Hybrid, modified SDS Labs and STEPS. Here is a pic of the amp with the front and rear panel attached (but unpainted yet to test fitment).
[Edited by amb on 02-19-2006 at 02:43 PM.] Attachment: C1397.jpg |
| Pars HeadWizer Joined: Nov. 12, 2003 | Message [#21] posted on: 02-19-2006 05:58 PM CST (US). | | I saw on that "other" forum that you use Tap Plastics. Do they do all the cutting/machining, etc. or do they just supply the plastic? I don't know if we have anything like that around Chicago... I had a hard enough time just finding a place to get scrap pieces of plexiglass/lucite, etc. from (without paying $40 a sheet for it). But I always liked some of the plastic cases, such as yours and those ones that doobooloo used to do. |
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