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Messages - joecool85

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1
Amplifier Discussion / Re: Help with Gallien-Krueger 200GT guitar amp
« on: February 28, 2019, 11:22:07 AM »
I have worked on this GK 200GT for a little too long and believe the 1976 "boat anchor" output transformer is bad. Rather than searching for a replacement, I would  like to replace the whole power amp board with a chip amp, either class AB or D. The problem I have, if it is actually a problem?, is that the preamp section which I like a lot, except for the "Current Limiter" pot, has a negative -8.7 vdc signal wire to the power amp board. Is that too much voltage and needing to be changed to a positive voltage before using a chip amp power board? I believe the preamp is working correctly but I am not sure because the schemo is hard for me to read and not sure if the signal from R85, the reverse 10k pot called "Current Limiter" is showing a negative voltage feed to the power amp? Review of the Owner's Manual shows that the Current Limiter function is to change the power output of the amp (I would just as soon remove it). Would anyone care to look at this and offer suggestions?  thanks

There shouldn't be any DC going to the power amp on the signal line.  If there is, something is wrong upstream.

2
Amplifier Discussion / Re: Trace Elliot Tramp 40w more gain in preamp mod?
« on: February 27, 2019, 03:18:49 PM »
I used a OD808 clone as a boost (with volume full and drive at min)

maybe if I stack another OD, like de OCD, or another mid or high gain, as boost too.
It could help to distort de amp?

thanks for replay! :tu:

Try winding up the drive on that OD808, I think you will be pleasantly surprised what it sounds like.

3
Amplifier Discussion / Re: Power transformer questions
« on: February 22, 2019, 02:09:23 PM »
I'd like to build a power amp somewhere in the range of 30-100 Watts running an 8 ohm cab. When it comes to building a +/- dual rail power supply, I am thinking I will need a center tapped secondary on the transformer.. (or is dual secondary coils better?? if so why?)

Does this transformer seem adequate? Under powered? Overkill??
What would be the maximum wattage amp one could safely build using this transformer?
https://www.digikey.ca/products/en?keywords=166M72

What models of transformers are others using for their power supplies, and what sort of wattages are they achieving??

I havn't messed around with transformers at all since a few labs 15+ years ago in college..  Know enough to not get myself killed, but don't want to waste a ton of money on the wrong transformers either..

I like to have 2x the VA rating as compared to the wattage at RMS.  IE, for your situation you would need a 60-200VA transformer.  The one you linked should be fine.  In this case, other than size and price, there isn't a problem with going larger.

4
The Newcomer's Forum / Re: Gear Suggestions
« on: January 15, 2019, 10:44:16 AM »
I suggest getting a Weller WLC100 station.  They are fantastic, reliable, inexpensive units and are used commercially in labs all around.  Typically they sell for $40 USD or so.  Regarding multimeter, I suggest a digital multimeter (referred to as a DMM).  I don't care for the "auto sensing" type, I like to adjust myself.  Brand isn't super important.  The one I use is a Craftsman because Sears had one on hand years ago and it fit the bill.  Higher end brands like Klein and Fluke are great if you can afford it, but not necessary.  Here is the cheap Craftsman I used for almost everything: https://www.amazon.com/Craftsman-34-82141-Digital-Multimeter-Functions/dp/B000X5TSUA

$20 and it gets the job done very well.

Past that the next thing I recommend is a "third hand" type of gizmo.  I use mine regularly and it's a real help.  You can get them all over the internet from very basic to very fancy.  I use this $5 one: http://smallbear-electronics.mybigcommerce.com/third-hand/

A silicone soldering matte is something I have been considering as it would keep my station clean.  I have one at work that I use mostly for keeping screws in place while tearing down laptops and such.  For $14, it's well worth it: https://www.amazon.com/SEASWAL-Soldering-Resistant-Electronics-Workbench/dp/B075F3C6J3

EDIT:
I forgot to add, make sure to get quality lead solder (I like Kester 60/40 in 0.031") and also some desoldering braid (sometimes called desoldering wick).  Thicker solder is harder to work with and mostly unnecessary for the small joints you will be working on.  I use leaded because it flows so well and withstands the test of time.  I do have lead free silver solder, and it works, but requires more heat and doesn't flow as cleanly.

Good luck!

5
Amplifier Discussion / Re: Happy New Year!
« on: January 10, 2019, 08:51:19 AM »
I'm glad to hear you are enjoying the site !  :tu:

6
Amplifier Discussion / Re: Hotone Nano Amp Heads
« on: January 08, 2019, 12:38:25 PM »
In which case they may sound a bit like my diy tda2003 amp so probably not worth my buying one. Looking for something to feed my diy 1x12 cab. At rhe moment I'm using various pedals with my diy amps and happy with that for now. I also play a lapsteel BTW.

Sent from my SM-G935F using Tapatalk

Just because they use a TDA2003 does not mean it will sound anything like your amp at all.  By definition, chip amps do not color the sound.  The "sound" of the amp is defined by the preamp.

7
Amplifier Discussion / Re: Grounding techniques
« on: January 02, 2019, 09:39:21 AM »
If you are having noise issues with the amplifier, I would look into why.

The power pack itself may be the issue, noise wise.

I agree, most likely it is the power pack that is causing the noise.  Sometimes this can be filtered by adding power caps inside the amp.

8
Amplifier Discussion / Re: Grounding techniques
« on: December 31, 2018, 08:19:23 AM »
I am using a power supply with no ground so that no mains voltage gets to my amp. Any suggestions on how to add a ground wire to cut noise?

Sent from my SM-G935F using Tapatalk

Using a ground will not introduce mains voltage to your amp, so I am unsure what the concern is here.

9
Amplifier Discussion / Re: NO soldering wireless guitar amp project.
« on: November 12, 2017, 07:59:12 AM »
Nice job!  I've always wanted to do this but never took the time.  I think you may be the first to talk about this on here, thanks for sharing!

10
Tubes and Hybrids / Re: fender bassbreaker 45
« on: September 13, 2017, 08:16:14 PM »
wondering if anyone has any documentation/schematics on this amp?

everything works and ive got a solid swing coming from the PI to the power tube grids -

but the output section is not happening - im getting normal plate voltage but ZERO screen voltage and -3VDC or so grid voltage - problem is this amp has a pretty complex thing going on with the variable output and mosfet control B+ (or whatever it is!) -

i know schematics are hard to find for these - anyone have thoughts on a similar circuit i could use for reference?

Did this amp just recently come out?  It must be under warranty.  If so, contact Fender.  If not, you'd still need to contact Fender lol.  Good luck either way!

11
The Newcomer's Forum / Re: Modding a Honeytone Amp INTO a vocal pedal
« on: August 01, 2017, 07:35:13 AM »
DonĀ“t connect the headphone jack to the XLR connector.
In fact, remove that XLR to avoid confusion (as in: "WTF? ... I plug this into the mixer and it does not sound")

Make/buy a headphone plug to regular guitar plug cable and send headphone out to a mixer "Line Input" or if more than 20/25 meters away, ask Soundman for a "Direct box" .

That said, I guess you are inserting too much and worse: contradicting elements in your sound, I guess I know what sound are you trying to achieve and you will not.

Want a *real*  lo-fi sound? : plug your vocal microphone into a small cheesy amplifier, even the Honey Tone might do, put amp inside a closed case or if recording at home,in another room, a bathroom is perfect because of the natural reverb, and pick it with a microphone.

The *acoustic*  element is a large part of that sound.

Or use just the tube preamp, drive it hard so it becomes gritty, send it straigt to mixer, and there cut all bass, all high treble and increase some nasty mid-high frequency, think 2000 or 2500Hz .... instant Lo Fi  ;)

If yu want a boxy sound increase around 300/400 Hz.

Juan is right, you aren't going to get a lo-fi sound doing what you are talking about.  Even the cheapest of amps will pass through reasonable sound when taking the speaker out of the mix.  You need to mic that little speaker to get the sound you are looking for.  I love the idea of a closed case "amp box" to do this in.  Then you can set it up wherever you like.  Many times this is called an "isolation box."

12
Schematics and Layouts / Fender Frontman 25 DSP FM25DSP schematic
« on: July 12, 2017, 01:17:43 PM »
Fender doesn't have this file on their site anymore, and I just had to track it down (thanks archive.org).  So I figured I'd share it here.

13
Tubes and Hybrids / Re: New amp day! Silvertone 1481
« on: June 19, 2017, 06:05:50 AM »
Thanks Enzo,

Yes, I should do more checking.... however...

I'm embarrassed to admit.... "I" may be the cause of the failed transformer.

You see, I drilled a hole for the secondary wires to go inside the chassis so I could install the speaker jack.

Foolishly I did this with the transformer still bolted in place... do you see where this is going....

That's right, the tiny pilot drill I used, punched through the chassis and nicked the winding's.  :grr

I then of course, removed the Tx and made the hole big enough to install a grommet for the wires.

Then inspected the Tx carefully with a magnifying glass and did not see any real damage, but the drill bit did go a small ways into the winding.

Fairly sure I screwed it up.
Bummer. However I feel for you. I did a similar thing where I was putting a heat shield back onto my wife's car. I had to drill a hole for the rivet and it was to go into the spare tire housing...I didn't remove the tire first. Made for a funny moment at the tire shop when I told them I drilled the tire LOL.

Sent from my XT1055 using Tapatalk


14
Amplifier Discussion / Re: My K-20X
« on: June 10, 2017, 02:20:50 PM »
Hi Joe, Hope you don't mind me putting this here.

Thought we could compare our K-20 amps.
I opened it up to install a speaker jack and was mildly surprised at the differences to yours.

Mine was made 1993, which probably accounts for the differences.
Any idea what year yours is?

The layout and circuit board are obviously different.
Mine has the line out on the front panel and a fuse holder on back.

I was hoping to find the same circuit board as yours with the un-populated areas for the reverb.

Oh well, I'll just use a reverb pedal.

A minor feature I like is the slanted speaker baffle.

Cheers!

Edit; looks like it would be easy to make the drive switch, foot switchable.  :)
Yours is a K-20, mine is a K-20X. Almost identical circuit, but there are differences especially in the PCB. I'm not sure of the year on mine because it isn't stamped. But I bought it around 2000.

Sent from my XT1055 using Tapatalk


15
Tubes and Hybrids / Re: NAD!
« on: June 08, 2017, 02:03:29 PM »
Ummm, yes this is the area of the forum for tube amps.

I guess this forum doesn't get much traffic from tube amp folks.

Oh well, mods please feel free to move this thread as you see fit.
I guess it would have been better in players corner.

You are correct, this is where this post belongs - no worries!  :tu:

Also, neat amp!

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