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Messages - Jazz P Bass

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1
Amplifier Discussion / Re: Krell amplifier repair
« on: October 29, 2020, 11:25:47 AM »
That is an odd if not interesting amplifier circuit.

Each polarity side is basically a mirror image.

Cute 'bias mute' circuit.

2
Amplifier Discussion / Re: Tech 21 Power Engine 60 input hum
« on: October 29, 2020, 12:59:22 AM »
Thanks for winding it down.

3
Amplifier Discussion / Re: Champion Amp Kit help needed.
« on: October 15, 2020, 11:58:21 AM »
You need to figure out where the distortion is coming from.
From the datasheet the power amplifier has an input sensitivity of 125 mv at a rail voltage of 9-12Vdc.
That is o/k for a typical guitar signal.
The preamp is a different animal.
Input sensitivity is rated at 5 mv @ 9-12Vdc power supply.
A guitar signal will overload that input.
I would go with the datasheet suggestion of adding a 10K control to limit the input signal.

"Features:
• Operating voltage range: 4 - 13.5VDC
• Music power: 3W @ 9 - 12V
• Frequency Response: -2.5dB @ 20Hz, -0.2dB @ 20kHz
• Gain: 34dB for Amplifier, up to 58dB with pre-amplifier
• Input Sensitivity for Amplifier only: 52mV RMS @ 5V, 125mV RMS @ 9 - 12V
• Input Sensitivity for Amplifier & Pre-amplifier: 2mV RMS @ 5V, 5mV RMS @ 9 - 12V
• Quiescent current: 2mA (Pre-amplifier) + 30-60mA (Amplifier)
• Standby current: 2mA (Pre-amplifier) + 1-10uA (Amplifier)

Note: Optional 10kohm potentiometer for external volume control use RP-7610"

4
Amplifier Discussion / Re: Help with Crate CR112 Tonestack
« on: October 04, 2020, 01:33:27 AM »
The Cannabis Rex speaker is a fine speaker.
I have thrown them in Fender Deluxe amps and they sing!

5
Amplifier Discussion / Re: Peavey VSS-20 amplifier with chorus noise problem
« on: October 01, 2020, 02:24:06 AM »
I find it odd that you have 'less noise' at the ground connection of U8 & U9.
There should be 'nothing' there.

6
Tubes and Hybrids / Re: Vox vt120+ combo schematic needed
« on: September 30, 2020, 11:31:14 AM »
The amp uses a surface mount TAS5615 Class D output IC.
As both of those blown capacitors are on each output rail, it is hard to see why both of them blew up.
Unless the output IC went belly up & cooked them at a high frequency.

7
Amplifier Discussion / Re: Peak dissipation in class B output stage
« on: September 28, 2020, 05:02:18 PM »
The output transistors that you picked are way overkill for the amp that you are designing.
Yeah, they will work.
But still.
Way over the top.

8
Amplifier Discussion / Re: Peavey VSS-20 amplifier with chorus noise problem
« on: September 27, 2020, 10:13:08 PM »
Have you checked the 'digital +9vdc supply'?
It should be pretty free of any ripple voltage (Vac).

9
Amplifier Discussion / Re: Peak dissipation in class B output stage
« on: September 22, 2020, 11:43:35 AM »
I would build a tried & true amplifier.
Attached is a simple low power amplifier.
Tube Works TD 742.
Build it.
Study it.
Blow it up.  :lmao:

10
The Newcomer's Forum / Re: Roland JC-120 with weak reverb
« on: September 19, 2020, 12:45:40 AM »
A TA-7200 P 10 watt power amplifier is used to drive the reverb pan.
It appears to be a 1.1 Vac output signal on the schematic.
Measure it and see what you have.

11
Schematics and Layouts / Re: G-K Gallien-Krueger MB112 ICEpower
« on: August 29, 2020, 11:57:36 AM »
ICE Power schematics have never been released as far as I know.

12
Tubes and Hybrids / Re: Blackstar HT5 noisy Clean channel
« on: August 16, 2020, 01:19:15 PM »
I have attached the input circuit diagram.
The signal branches off of IC2A to the Clean and the Crunch channel.
Either of those is selected by jfets. (Clean/ Fet1: Crunch/ Fet2)
You will need to track down where in the Clean circuit the signal is failing.


13
Guitar News / Re: Quilter OverDrive 202 - palm sized amp with rock concert sound
« on: August 13, 2020, 01:14:32 AM »
" switchmode amplifier, PWM (pulse width modulated) amplifier and Class-D amplifier"

14
Amplifier Discussion / Re: peavey musician series 400
« on: August 08, 2020, 01:09:50 AM »
!!!"  DISCONNECT any speaker"!!!

15
The Newcomer's Forum / Re: FX loop noise
« on: August 06, 2020, 11:43:38 AM »
Try the guitar into the Zoom & then go into the FX Return jack.
This will tell if it is a Send circuit issue or a Return circuit issue.
Be aware that you may have to adjust the gain on some of the Zoom presets.

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