|
Post by Koolind on Oct 21, 2010 17:57:49 GMT
Mounting the parts i ran into a problem; i only recieved 4x A1015 transistors, so i'm missing 2 Will any A1015 be fine, or are there any quality differences between the different brands? Apparently not all of them are marked the same. Is it only the "A1015" that is important, or does the "GR8G" a specific model-type? EDIT: Nevermind ! For some reason they were just mis-placed by myself apparently Hopefully i will stop hiding parts from myself later on
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 21, 2010 19:43:27 GMT
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 21, 2010 19:58:29 GMT
Mounting the parts i ran into a problem; i only recieved 4x A1015 transistors, so i'm missing 2 Will any A1015 be fine, or are there any quality differences between the different brands? Apparently not all of them are marked the same. Is it only the "A1015" that is important, or does the "GR8G" a specific model-type? EDIT: Nevermind ! For some reason they were just mis-placed by myself apparently Hopefully i will stop hiding parts from myself later on Yes, the little buggers sometimes fall out of the plastic bag onto the carpet, only to be found next time you vacuum the carpet ! The GR in the designation indicates the HFE (gain) range of that type of transistor, so would have been important for best results. Alex
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 21, 2010 20:10:11 GMT
hi Alex how's it going any ideas for a nice regulated psu for this amp would be MOST welcome. pushing it i bit further into class A as Frans suggested earlier may an interesting idea also. not sure that the heat sinks are gonna be up to the task but that needs to be found out i guess. (can always put bigger ones in ) anyhow just fishing take care
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 21, 2010 20:30:19 GMT
hi Alex how's it going any ideas for a nice regulated psu for this amp would be MOST welcome. pushing it i bit further into class A as Frans suggested earlier may an interesting idea also. not sure that the heat sinks are gonna be up to the task but that needs to be found out i guess. (can always put bigger ones in ) anyhow just fishing take care Hi Shaun I would suggest getting rid of those 2R2 PSU resistors as Frans has suggested, or at least a tenfold reduction. Alex PM sent.
|
|
|
Post by Koolind on Oct 21, 2010 20:40:35 GMT
One thing i havent understood yet; Why does the four power transistors need heatsinking, when the four identical ones in front of them does not? I suppose that they serve different purposes? Or is it more in the lines of a two stage amplification, where the last set is taking the heavy load?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 21, 2010 20:50:41 GMT
The four need heatsinking because these transistors are the Class A output stage and need to deliver the current to the headphones. They have about 90mA running through it so with about 28V across them each dissipates (in other words converts to heat) 2.5 watts. the other ones before that only have to supply current to the base of the cooled transistor. These having a gain of about 20x the current in the uncooled stage does not need to be that high. The current in these transistors is only about 12mA with 28V on it these only dissipate 0.3W and do not need much cooling as they themselves have big enough surface to cool themselves.
|
|
|
Post by Koolind on Oct 21, 2010 21:11:50 GMT
The four need heatsinking because these transistors are the Class A output stage and need to deliver the current to the headphones. They have about 90mA running through it so with about 28V across them each dissipates (in other words converts to heat) 2.5 watts. the other ones before that only have to supply current to the base of the cooled transistor. These having a gain of about 20x the current in the uncooled stage does not need to be that high. The current in these transistors is only about 12mA with 28V on it these only dissipate 0.3W and do not need much cooling as they themselves have big enough surface to cool themselves. Oh ok.. So my logic was actually somewhat right Thank you for the explanation!
|
|
|
Post by dicky on Oct 22, 2010 19:53:36 GMT
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 22, 2010 20:09:50 GMT
Let me know what drills you need dinky, well done, yours turned out better than mine, which needs a bit of tweaking, then hopefully it will be ready to go as my enclosure is finished and lonely.
|
|
|
Post by dicky on Oct 22, 2010 20:39:19 GMT
Thanks heliharris, and thanks for the offer, but I'll probably be able to borrow some from a friend - I'm just putting it off. I don't like drilling metal - I never get a nice round hole. I'm not sure what drills I'll need yet. I need to drill the base for the feet, transformer, earth and the pcb mounts, and the front panel for the pot extension rod bush - this is the one that I think will be tricky. I need to get some 15mm pcb stand-offs, do you know where I can get them on 'tinternet? I'd like brass ones and all I can find are plastic. Are you using one of the boxes that match the Panda kit, or have you used something else? Regards, Richard
|
|
|
Post by PinkFloyd on Oct 22, 2010 21:44:02 GMT
Well done Richard, that looks very well put together indeed To save you drilling all these holes it may be easier for you to order the pre-drilled Panda enclosure? Yes, it is £50 shipped, but will save you a lot of hassle in the long run and will look very good into the bargain. Mike.
|
|
|
Post by dicky on Oct 23, 2010 4:55:09 GMT
Thanks Mike, I'd be up for that. Do you have any enclosures yet, or are you waiting to see how much interest there is? I'd like a black fascia, if possible. (And maybe some other odds and ends.)
|
|
|
Post by PinkFloyd on Oct 24, 2010 20:06:37 GMT
Thanks Mike, I'd be up for that. Do you have any enclosures yet, or are you waiting to see how much interest there is? I'd like a black fascia, if possible. (And maybe some other odds and ends.) The enclosure situation is something I really don't want to get into. I can get 10 of them shipped to me for $542 USD (£345 GBP) so that works out at £34.50 per enclosure. £15 cheaper than getting one shipped direct from China to your doorstep BUT, remember this........ I will then have to pay postage / packing / time to ship the enclosures out on top of this so £34.50 per unit is not a viable proposition as far as I'm concerned. Somebody, somewhere, would save a "couple" of quid but I'd be lugging enclosures into my post office, queuing up and almost certainly "losing" out of the deal so, nope.... it's a lot better to order these direct from the ebay guy OR from Hifidiynet. The Hifidiynet enclosure is $69 (£44 GBP) but that doesn't include shipping. I am pretty confident I can get the enclosure price down for members here but you will have to PM me for a code to enter when ordering from Hifidiynet..... I will negotiate this tomorrow and see what I can them down to "shipped" price I will let you all know. Mike.
|
|
|
Post by PinkFloyd on Oct 24, 2010 20:13:10 GMT
The Hifidiynet enclosure also comes with the coupling kit so it's an even better buy than the ebay one. I'll see what I can do with regards to price and hope I can get a fair bit of discount for registered members
|
|
|
Post by PinkFloyd on Oct 24, 2010 20:43:03 GMT
Just to let you guys know.... I have adjusted the gain on Panda 1 and 2 to +6db and I much prefer the action of the pot now.... more "oomph" and, I don't know why but, I believe it also sounds slightly better! It's a BITCH removing the two 300 ohm resistors from the through hole plated board so if you are going to try this I suggest you solder on an additional 300 ohm resistor on the underside of the board and this will give you the 150ohm you need. 300 + 300 = 150 connected in parallel. Here's where they are: Just flip the board over and solder another 300 ohm resistor on the underside.... a standard 0.25W metal film type will be fine.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 24, 2010 20:57:16 GMT
Is the amp as supplied fixed at the original gain, Mike? For orchestral music which tends to be recorded at a lower level, there was just enough to push the K701 to a satisfying level. I would guess a gain of 2 in comparison to my Neco at 3. Now the gain is doubled it'll be fine. Boy do I miss good quality listening and it's only been 2 days! Presumeably the noise floor stays low too?
|
|
|
Post by PinkFloyd on Oct 24, 2010 21:57:19 GMT
Is the amp as supplied fixed at the original gain, Mike? For orchestral music which tends to be recorded at a lower level, there was just enough to push the K701 to a satisfying level. I would guess a gain of 2 in comparison to my Neco at 3. Now the gain is doubled it'll be fine. Boy do I miss good quality listening and it's only been 2 days! Presumeably the noise floor stays low too? It has been increased by 6db... you WILL notice a difference Mike. Edit: What noise floor?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 24, 2010 22:08:49 GMT
Whoops. Sorry. Tiny screen and drink! That's massive!
|
|
|
Post by PinkFloyd on Oct 24, 2010 22:22:28 GMT
Whoops. Sorry. Tiny screen and drink! That's massive! It's just right with a wide range of 'phones..... don't worry
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 24, 2010 23:26:32 GMT
Further improve the PSU area, and you will hear the noise floor. Of the recordings !
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 25, 2010 7:08:06 GMT
I often do Alex. It'x amazing how noixy some microphones are. The Panda is inky black between tracls and you can easily hear the knob twiddlers ob recordings. On the Mahler recording you keep hearing the conductor's clothes rustling. Any clearer and it will sound like he has a mac on! I'll have to find recordings with naked conductors with the Panda up louder.
|
|
|
Post by dicky on Oct 25, 2010 7:24:54 GMT
Sorry, Mike. I thought you were intending to supply enclosures - just my assumption when I saw you offering the Panda kits - my mistake. I'd really like a black fascia - I'll hold off until they're available on t'internet - he only has silver at the moment.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 25, 2010 7:32:46 GMT
I often do Alex. It'x amazing how noixy some microphones are. The Panda is inky black between tracls and you can easily hear the knob twiddlers ob recordings. On the Mahler recording you keep hearing the conductor's clothes rustling. Any clearer and it will sound like he has a mac on! I'll have to find recordings with naked conductors with the Panda up louder. Ian How would you like even more low level detail, as well as some more natural warmth from your Mahler ? Perhaps after you return from Germany ? Alex
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 25, 2010 9:08:30 GMT
Not half Alex. Listeng on this crappy system I'm usung here painfully points out just how good those files are; especially put through the Panda. God I miss home. Talking to you guys on this is like whispering through a keyhole. Especially bad when evryone around you speaks a different language. I keep thinking they're talking about me. Someone asked me for an 'artogroof' which Was funny.
|
|