Building a DIY poweramp - Build complete - w/ live recording

    Quote from greenblob

    Thanks. Yeah, I was going to record something but realized there wasn't a whole lot of point. It just sounds like a really good, transparent poweramp!


    If I remember, next time I'm jamming with the drummer and bass player I'll get some audio/video to try and demonstrate it's substantial available volume in a band situation.

    ... I would really like to check that out

    Quote from ibanez270

    Looks great man. I keep blowing fuses :)
    Did you connect only one side of the power supply? I only have 3 taps coming off my tranny center is ground. I can't figure out the power supply AC1 and AC2 ?


    The power supply connections are a bit vague. Had me scratching my head for second as well. You need to connect both sides (all 4 terminals are used)
    If your transformer is the correct type you should have dual outputs (or be center tapped making two hot wires and a common center) Eg. With the three wires you should get voltage between one wire and the center tap. Then voltage from the other wire to the center tap. Basically like have two transformers sharing the same center.


    I dont believe the center should have continuity to ground.


    Sorry if I'm stating stuff you know, just trying make sure the transformer is the correct type.


    The power supply board is basically 2 identical circuits on one board. The pair of AC1 terminals powers one half, and the AC2 pair is for the other half.
    So one of the hot wires would go to one of the AC1 terminals, and the center tap (common wire) would go to the other AC1. As it sounds like your using a center tapped transformer you will need to use the same common wire as the neutral for the AC2 set. So wire a jumper from the common on the AC1 set to one of the AC2 pair. The second AC2 is for the send hot wire from the transformer.
    Does that make sense? Easy to do but tough to explain it seems!


    Here is a full dual secondary schematic:
    [Blocked Image: http://www.chipamp.com/images/ps-rev3-sch.gif]



    And heres a center tapped 3 wire. (ignore the "?".. i borrowed the picture).
    The AC1 H and AC1 N (and AC2 H, AC2 N) are the board terminals you are concerned with.
    [Blocked Image: http://www.thenoodleincident.com/inflight_correction/image/sherman_CT_mystery.gif]



    Hope that clears it up. Good luck! :thumbup:

    Thanks,I have it hooked up like the second pic. That works and I have a blue LED.
    Jumper is the center tap.


    When I connect the amp I here a hum and if I leave it on to long the fuse blows.


    I have the pics up on diyaudio. Hope they can help.
    I may have to buy a tranny like yours. I wish I could find one like the Ambrosi transformer. Been looking all over and can't find it.:(


    Thanks for your help.

    The amplifier board looks good. All the wiring connections look good. Looks like there may be a possible short between the 3rd and 4th leg (from the left of pic) on the main chip (solder ball on top of board)? Probably not but check that.


    Does the fuse only blow after some time with the speaker connected?


    I'd check the power board 1 more time.


    Did you check both sides of the power board outputs earlier? The LED only indicates one side is correct. If not:


    Disconnect the 4 wires going to the amp board.
    On the power board, check for DC voltage on V+ to PG+. Should be a positive voltage.
    V- to PG- should be a negative voltage.


    I was in communication with Viabcroce trying to find a transformer as found in the Ambrosi. Although he was massively helpful, all he could really tell me was they were sourced from Italy. I found this which might be similar to what they use. They sure look close: http://www.parts-express.com/5…er-center-tapped--129-084
    The transformer I used is very proven though so I played it safe.


    The DIY audio forum guys will fix you up and that is a much more suitable forum for troubleshooting.


    I'm sure you'll have it rockin in no time.

    Hi there!
    Really great job!
    Hope, you hae a lot of fun with it!!!
    I used to build also several small low power (tube) stomp boxes and have no experience with high power stuff...
    My question is: do you really need the transfromer for IC based amplifiers?


    A second question: does anyone has experience with the magnum power amp?
    http://www.thomann.de/de/elect…x_44_magnum_power_amp.htm
    A small amplifier in stom box format - seems to be perfect for the kemper... What will be the drawbacks here?

    I had considered the 44Magnum as my first option. But thought later on that a slightly more powerful, retrofit power amp would do a better job, so got in touch with Andrea Ambrosi and... the rest is history :)


    The drawbacks of the 44Magnum that were a deal breaker for me: it is external, so one more box to carry; it needs to be powered independently; it requires more cables which would go in my way; it's one more device to carry, connect, power; if you want to use two cabs you need a special cable; it is meant for guitar, and the last part of the volume's stroke drives the power amp to distortion, while I wanted a completely linear and transparent amp.


    :)

    Quote from rdwilson

    ... I would really like to check that out


    Heres a jam recording from our practice room using the KPA and poweramp into a 2x12 THD cabinet.


    Live jam with poweramp


    Heaps of volume. Plenty more on tap. Was only at about 65% on the output. Recorded with a simple handheld stereo field recorder placed in the middle of the room, with it angled towards the guitar cab. Room volume was very balanced.

    Quote from greenblob

    Heres a jam recording from our practice room using the KPA and poweramp into a 2x12 THD cabinet.


    Live jam with poweramp


    Heaps of volume. Plenty more on tap. Was only at about 65% on the output. Recorded with a simple handheld stereo field recorder placed in the middle of the room, with it angled towards the guitar cab. Room volume was very balanced.


    Sounds really good man. What profile are you using?


    I took your advice and used a toroidal transformer and it went together very easy. It is loud we have practice tomorrow so I'll know how it sounds then.
    I also built a 2x12 cab with green tolex,looks awesome. Anyway thanks for your help.

    Cool. Glad you got yours up and running. Through a 2x12 you should have enough volume to do just about anything.
    The profile was one of MBrit's from his second pack. I think its called Little Walter 22 or something similar. A great pack if you haven't already checked them out. The outrageous over the top delays are an eventide timefactor in the kpa loop.