DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 18 Nov 2018, 03:57

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 64 posts ]  Go to page 1, 2, 3, 4, 5 ... 7  Next
Author Message
PostPosted: 08 Jan 2009, 08:13 
Offline
User avatar

Joined: 04 Sep 2008, 09:35
Posts: 179
Location: Menton, France
another quick Q. When i received the lm3886 kit, i did a quick check and noticed that an optional piece (the Ci) feedback cap, was only delivered for one pcb and not two. i know i can build the kit by omitting this cap, but is it better to include it? taking into account that either it gets forwarded to me or i have to source it myself.

cheers


Top
 Profile  
 
PostPosted: 08 Jan 2009, 13:38 
Offline
Editor
User avatar

Joined: 28 May 2008, 21:53
Posts: 4571
Location: Winnipeg, CANADA
Hi Sabs, here is my LM3886 Chipamp / Gainclone that I built from a chipamp.com kit. I did not use the optional feedback capacitor. There are a couple things to note. If you are getting DC offset, the feedback capacitor will likely lower DC offset by quite a bit. But it does have effects on the frequency response. I went without it and DC offset was acceptable so I left it out.

_________________
[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


Top
 Profile  
 
PostPosted: 08 Jan 2009, 16:10 
Offline
User avatar

Joined: 04 Sep 2008, 09:35
Posts: 179
Location: Menton, France
Yo Gio,

i think i'm gonna do like you because mainly i don't want to sacrifice the lm's freq response. if it's an issue i'll just add them and replace the R3. thats the wonder of DIY!


Top
 Profile  
 
PostPosted: 17 Jan 2009, 08:59 
Offline
User avatar

Joined: 04 Sep 2008, 09:35
Posts: 179
Location: Menton, France
Hi guys, splitting my time between this and the tube amp.

Just a thing whilst mounting the power supply board for the chipamp. do i need to add the two contact terminals for the AC or is it easier to solder the wires direct? I only ask cause on the instructions it says to do then last, but with the transistor diodes in the way it look a bit tight?


Top
 Profile  
 
PostPosted: 17 Jan 2009, 12:37 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 20:12
Posts: 972
Location: Houston, TX
Well both ways are easy. What I would consider is will you ever remove this power supply to work on it or use it elsewhere or to use a different supply in its place..?..
I would say dont solder direct. Using faston connectors or terminal blocks is a better long term solution. Thats my opinion. Heating up those wires to remove them can take time and leave your board a bit messy as well as sometimes lifting a trace which is just no fun.
Have not used that board but I have a real tight fit getting my Fastons on my amps power board as well. I use needle nose pliers to remove and apply them.
Ri

_________________
DIY Lightspeed Passive Attenuator


Top
 Profile  
 
PostPosted: 18 Jan 2009, 13:35 
Offline
User avatar

Joined: 04 Sep 2008, 09:35
Posts: 179
Location: Menton, France
So got a bit of time in to day, a,d started to build the two kits for the amp. The jaycar phono preamp and the chipamp.....er..... chipamp!
both have been a pip so far, i took riguys advice and added the terminals, just in case later i want to upgrade. the chip amps and power supply are all finished. and the jay car is midway. here is a photo so far. A lot will know the score but here they are again for the cheap seats......
Attachment:
P1180028.jpg

So the preamp will have the most adjustments. i am replacing all stock components to others i have sourced. I have decided they will both be housed in the same case so the signal will be in through the preamp with the output connecting directly to the chipamp inputs, both will have ac from the same transformer.
I have decided to leave the pot on the preamp and wire this to the rear side of the case, this way i can control the gain directly from the preamp and have a decent strength source for the amp.

i'm still searching for a ideal sized case but aim to have everything ready so when i have found it it will be a quick mounting job.
More later.........


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.



Top
 Profile  
 
PostPosted: 20 Jan 2009, 23:27 
Offline

Joined: 07 Jan 2009, 00:42
Posts: 20
Just started my LM3886 amp as well. Putting the 12AX7 pre-amp on hold till I can get a break with school work and can get parts sourced and can get a buddy from back home's help (he knows high voltage tube stuff better than I do).

Ordered 4 amp PCBs and 4 chips, 2 channels of which were part of the stereo kit. The other 2 I'm leaving up for experimentation, testing different caps and what not.

Other than the transformer (ordered a 25V 300VA from Antek on monday, I'm driving a 8Ohm load) all the parts are in, and my case is going to the shop next week to get its back panel drilled.

Pic of the amps with the heat sinks strapped to them with spring-metal clips I sourced them from a dead amp I had laying around. Oh and the 15$ butter-stick of an EMI filter I found :mrgreen: .
Attachment:
amp3886.jpg

Still need a pre-amp for the whole thing, thinking of going PassLabs B1, but they seem to be sold out right now online, so I may try my hand at experimenting with an op-amp and voltage controlled attenuator setup (have some old dbx VCAs I pulled from a 1982 DAC of some sort).


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.



Top
 Profile  
 
PostPosted: 21 Jan 2009, 00:17 
Offline
Editor
User avatar

Joined: 28 May 2008, 21:53
Posts: 4571
Location: Winnipeg, CANADA
Here is an idea for the attenuator: Lightspeed Attenuator - A passive attenuator. 2 resistors !

_________________
[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


Top
 Profile  
 
PostPosted: 21 Jan 2009, 02:30 
Offline

Joined: 07 Jan 2009, 00:42
Posts: 20
gmilitano wrote:

Yup, I read that as well, unfortunately the day after i placed my mouser order :P.

I bread-boarded one of the VCAs using the application notes that I can find. Seems the only people who make/made this chip is/was THAT Corp. The part is dbx2150A, but there's no info on it other than a cross-reffed datasheet for the THAT2150A. I'm gonna bring it into the lab and see what it does as I don't have a +/-15V source in my apartment. If all goes well (and i don't release the magic smoke trapped from 1984), I'll see about spinning a board and giving it a more thorough evaluation and I'll post some more info in a new thread.


Top
 Profile  
 
PostPosted: 21 Jan 2009, 07:39 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 20:12
Posts: 972
Location: Houston, TX
I posted that attenuator Gio mentioned. Just to throw my 2 cents out there and not to threadjack I wanted to say it is awesome and would work great with your chipamps. All reports come back that is sounds better than any other passive preamp and that it beats most actives in ABX shootouts.
Ri

_________________
DIY Lightspeed Passive Attenuator


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 64 posts ]  Go to page 1, 2, 3, 4, 5 ... 7  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Google Adsense [Bot] and 9 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy