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GregVDS  HeadWizer Joined: Oct. 25, 2005 |  Message [#200] posted on: 11-20-2006 03:47 AM CST (US).   |  |  Ok, to all of you who requested a buffer board, please, can you check to the marketplace if your status is ok with what you asked? Many thanks, All the best, |
gewa HeadWizer Joined: Sep. 22, 2006 | Message [#201] posted on: 11-20-2006 04:00 AM CST (US). | | Greg I'l take one of those Intersil boards. Regards [Edited by gewa on 11-20-2006 at 05:22 AM.] |
| GregVDS HeadWizer Joined: Oct. 25, 2005 | Message [#202] posted on: 11-20-2006 05:59 AM CST (US). | | Ok Gewa, you go for the Intersil. I added you on the marketplace. All the best, GregVDS |
| rreynol Member Joined: Oct. 13, 2005 | Message [#203] posted on: 11-20-2006 06:12 AM CST (US). | | I'll take the other intersil board Greg. Thanks. |
tomb Headphone Council Joined: Mar. 1, 2006 | Message [#204] posted on: 11-20-2006 07:11 AM CST (US). | | Digi, Thanks for your suggestion on the heat sink. I'm using the Hammond, so will probably opt for the side bolting. That way, I can save the heat sinks for the 12V regulators - since all these buffers may require it. About your buffers - do you have any measurements of offset or current capability?
  Based on earlier discussions, DC offset may be a huge issue without an opamp. The suggested Diamond Buffer designs include an opamp operating as a DC servo. For example, here is Runeight's earlier design in the SOHA design threads: According to someone who may have tried it, offset could still be an issue even with this design. However, your buffer board appears to be a straightforward DB, without opamp or DC servo. So, I am curious - how is the offset controlled? Your board looks interesting, especially since you are actually offering kits. I am also curious about the Class AB operation vs. other buffers you are considering (as listed on your web page), and how they may compare to the excellent work that dBel, Gewa, and especially Greg have done with the monolithics. Thanks in advance for your answers! [Edited by tomb on 11-21-2006 at 02:49 PM.] Attachment: C2314.gif |
| GregVDS HeadWizer Joined: Oct. 25, 2005 | Message [#205] posted on: 11-20-2006 02:00 PM CST (US). | | for the six amongst you, please check on the marketplace for your status. All the best, GregVDS |
digi01 HeadWize Fanatic Joined: Dec. 3, 2002 | Message [#206] posted on: 11-21-2006 01:51 AM CST (US). | | to tomb, Yeah I know soha is a open loop design. For mine assemblied the buffer works fine with.I have not check dc offset.I think the current capability is 10ma approx per channel.I am still working on classA buffer. For solid buffer or boost IC configuration.unregulated supply was recommended,VR1 VR2 can be bypassed with 2~5ohm 2W resistors. P.S. Zang |
| gewa HeadWizer Joined: Sep. 22, 2006 | Message [#207] posted on: 11-21-2006 02:13 PM CST (US). | | My PortaPro arrived today  Because GregVDS mentioned in post #190 that the voltage regulators got kinda hot with the bufferstack and the dual op-amps I already took some precautions and mounted a small heatsink to them. It's not big but at least they can get rid of the heat a little better. Regards Attachment: C2315.jpg |
| GregVDS HeadWizer Joined: Oct. 25, 2005 | Message [#208] posted on: 11-21-2006 02:19 PM CST (US). | | Gewa, check the marketplace What did you use to insulate the LM's from the heatsink? And when I said hot, I meant REALLY hot (more than the heater LM337, much more). I still look for a way to insulate my LM's from the bottom of the box. (If they need to be, what is connected electrically to the heatsinks of the LM78 and 79?) If it's ground, perfect, if it's not... All the best, [Edited by GregVDS on 11-21-2006 at 02:21 PM.] |
| gewa HeadWizer Joined: Sep. 22, 2006 | Message [#209] posted on: 11-21-2006 02:19 PM CST (US). | | From another angle. GregVDS
Just your ordinary, everyday run of the mill mica insulator and plastic flanged bushing. Regards [Edited by gewa on 11-21-2006 at 02:23 PM.] Attachment: C2316.jpg |
| GregVDS HeadWizer Joined: Oct. 25, 2005 | Message [#210] posted on: 11-21-2006 02:22 PM CST (US). | | You still have a big hole to drill, no?  All the best, |
| gewa HeadWizer Joined: Sep. 22, 2006 | Message [#211] posted on: 11-21-2006 02:33 PM CST (US). | |
Yes, but I'm gonna put something special in it!
Wel, according to the datasheets for the LM78XX it is GND but for the LM79XX it's Vin!!!! Regards |
| dBel84 HeadWize Fanatic Joined: May 5, 2006 | Message [#212] posted on: 11-21-2006 02:56 PM CST (US). | | Yes , the 79xx has to be isolated - I isolated both similar to Gewa but I merely bent a normal TO-220 heatsink in half to clear the headroom. It still gets hot . Before I added them, the top of the chassis would heat up which I am sure was not healthy for the regs in general..dB |
| gewa HeadWizer Joined: Sep. 22, 2006 | Message [#213] posted on: 11-22-2006 12:22 PM CST (US). | | GregVDS Boards arrived today! That's the quickest mail delivery I know of to this point in time (1 day), must have been a pigeon on steroids Regards |
| GregVDS HeadWizer Joined: Oct. 25, 2005 | Message [#214] posted on: 11-22-2006 02:41 PM CST (US). | | GEWA: Yep, I was frightened too the first time I saw the real thing, we're on the brink of smt here . I'm sad the board is too long to enter the case, thats a disapointment. Couldn't you shift the buffer board toward the tube with curved legs (I mean some kind of z form (right side schematic)), or angle the board so as it can enter the case (left side schematic)?My explanations coming with board are clear enough? Anyway, I'm really happy the delivery was that quick for you. I expect FERRARI will receive his quite soon too, and hope to have good news from the States during next week. All the best, [Edited by GregVDS on 11-22-2006 at 02:47 PM.] Attachment: C2321.jpg |
| gewa HeadWizer Joined: Sep. 22, 2006 | Message [#215] posted on: 11-22-2006 04:39 PM CST (US). | | GregVDS
Don't worry mate, I will make it fit with some minor surgery
At first glance everything looks well explained, thank's for that. Am I correct that the ground isn't monitored by your Epsilon version? I'm taking AMB's schematic as reference and there both the two GND path's as well as the L and R signal path's are connected via 10K resistors to the TL081. Don't know whether this is necessary or not, just asking. Regards |
| GregVDS HeadWizer Joined: Oct. 25, 2005 | Message [#216] posted on: 11-23-2006 02:45 AM CST (US). | | GEWA: That's exact, I don't monitor the ground channel. I think there is no need to monitor it in the SOHA for it is not an active ground. Look at AMB epsilon12 webpage, I think the SOHA falls in the category of two active channels and passive ground, for which AMB says to only connect live of left and right channels and bypass the epsilon12 for ground. You would monitor ground in an active ground amp, such as AMB's M³ or Tangent's PIMETA (not sure). The Epsilon12 has two ground pads (G1 and G2) for the David Gillmore amps and others where you have two active ground channels to monitor. I hope this is of some help. All the best, |
| gewa HeadWizer Joined: Sep. 22, 2006 | Message [#217] posted on: 11-23-2006 05:48 AM CST (US). | | Thanks Greg. This reminds me again that I have to learn to read stuff thoroughly before starting to ask questions  Regards [Edited by gewa on 11-23-2006 at 07:00 AM.] |
| GregVDS HeadWizer Joined: Oct. 25, 2005 | Message [#218] posted on: 11-23-2006 06:38 AM CST (US). | | No no, I'm absolutely identical, when I don't know something, I first ask, and then sometimes, realize I could have searched and found by myself. Ok, let's say we're somehow lazy , but that's really not a problem, we're all here to ask and answer.Let me know how things go, All the best, |
| gewa HeadWizer Joined: Sep. 22, 2006 | Message [#219] posted on: 11-23-2006 07:46 AM CST (US). | |
It's not because I don't pay attention to some details that I'm lazy! Although, there must be some truth in it because I get that remark from my wife from time to time Regards |
vixr HeadWize Fanatic Joined: Sep. 17, 2005 | Message [#220] posted on: 11-23-2006 08:03 PM CST (US). | | Please ask questions... Its helps to alert others to the issues. I for one have trouble understanding the techspeak of datasheets and schematics... Simple questions and plain answers are best. |
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