Search found 170 matches

by george giblet
29 Jun 2020, 10:13
Forum: Amplifiers
Topic: How to improve tube amplifier tone by changing one part
Replies: 101
Views: 5262

Re: How to improve tube amplifier tone by changing one part

Google "speaker cable burn in" if you want to see crazy :D
I remember HiFi people saying they could hear the improvement in sound quality when a line filter was placed on the mains side.
by george giblet
23 Jun 2020, 06:51
Forum: Amplifiers
Topic: How to improve tube amplifier tone by changing one part
Replies: 101
Views: 5262

Re: How to improve tube amplifier tone by changing one part

I found this video. I could hear a difference but it *really* helps to listen with decent headphones and listen at a relatively high level. I can't comment on how the experiment was carried out. You would need the amp pots to be totally untouched, as well as the whole recording chain - no level adju...
by george giblet
20 Jun 2020, 08:12
Forum: Amplifiers
Topic: How to improve tube amplifier tone by changing one part
Replies: 101
Views: 5262

Re: How to improve tube amplifier tone by changing one part

I'd be measuring the value of the two caps with a cap meter; 10% difference in capacitance could come across as subtle change in tone. Another thing is leakage. Leakage can change the bias point. I'd only start thinking there was a difference after checking at least that much. Nonetheless I'm happy ...
by george giblet
18 Jun 2020, 03:12
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Aguilar - Agro Bass Overdrive
Replies: 12
Views: 710

Re: Aguilar - Agro Bass Overdrive

Why not trace it as is. It doesn't look like a lot of useful stuff is under the goop, if any. After tracing you will have a few wires/tracks entering the goop. From the surrounding circuit you can guess what might be in there. (Maybe compare against Chicago Mike's schem. However, it looks different ...
by george giblet
14 Jun 2020, 06:45
Forum: Electric Guitar Rewiring
Topic: EMG DG20 (SPC and EXG) schematics etc.
Replies: 58
Views: 50303

Re: EMG DG20 (SPC and EXG) schematics etc.

For the LF442: You can change the 1N914 diode on the power to a lower drop Schottky (choose a type with a low drop as they aren't always the same) to get a little less drop. You can save 0.6V drop by removing the series diode altogether and instead using a *reverse* 1N4004 etc. *across* the power ra...
by george giblet
07 Apr 2020, 00:58
Forum: Modern Stompbox Effects (1975 - ...)
Topic: MXR M288 Bass Octave Deluxe [gut shots, tracing]
Replies: 11
Views: 2030

Re: MXR M288 Bass Octave Deluxe [gut shots, tracing]

I have traced almost the whole thing. Or at least the important part.
Good work man!

The last time I looked at it I was checking some stuff around the rectifier/detector.
Can't remember the details though.
by george giblet
28 Feb 2020, 07:02
Forum: Amplifiers
Topic: using a 18volt transformer
Replies: 19
Views: 1275

Re: using a 18volt transformer

Do you have the 1 ohm resistor and 0.22uF capacitor on the output of the LM1875?
They help prevent oscillation. They aren't optional you should have them.

Look at the LM1875 datasheet.
by george giblet
23 Jan 2020, 09:31
Forum: Electric Guitar Rewiring
Topic: Southbeach Bass Preamp (2-band)
Replies: 5
Views: 5800

Re: Southbeach Bass Preamp (2-band)

It's the Nordstrand 2-band preamp.
The 3-band is also on this forum but under a different section.
Nord translates to North ; change to South
Strand translates to Beach.
:slap:
by george giblet
23 Oct 2019, 08:17
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Xotic - Soul Driven [schematic]
Replies: 11
Views: 2882

Re: Xotic - Soul Driven [schematic]

Sorry I accidentally hit submit and I can't edit. 1) My clone based on the above schematic definitely does not have too much bass - it's pretty modest over the full range of the knob and doesn't sound like much more than 6dB of gain across the range. This is purely anecdotal though and should not be...
by george giblet
23 Oct 2019, 08:13
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Xotic - Soul Driven [schematic]
Replies: 11
Views: 2882

Re: Xotic - Soul Driven [schematic]

Here's a gallery of another set of tracing photos - https://imgur.com/a/KjWJTjn Excellent thanks. From those pics I can see the underside of the board. There's not a lot going on under there which reduces down the number of possibilities by a large factor. There's +V power rail running under the di...
by george giblet
19 Oct 2019, 06:56
Forum: Modern Stompbox Effects (1975 - ...)
Topic: Xotic - Soul Driven [schematic]
Replies: 11
Views: 2882

Re: Xotic - Soul Driven [schematic]

I'm not convince the bass switches are correct. I've built a number of post bass-boost circuits like that and with a 18k+15k+10k in series the bass boost is enormous. The Boss BD-2 only has 6.8k. The specs say Flat (0dB), +2.4dB,+3.6dB, +6.0dB. At first I thought 0dB could be when the feedback resis...
by george giblet
17 Oct 2019, 00:53
Forum: Electric Guitar Rewiring
Topic: EMG DG20 (SPC and EXG) schematics etc.
Replies: 58
Views: 50303

Re: EMG DG20 (SPC and EXG) schematics etc.

On the 'Bass Boost' op amp is the feedback resistor (in parallel wth 2n2) 4.99 or 499 ?
499k makes a lot more sense based on the relative values of Bass and Treble boost.

4.99k would make the bass circuit fairly benign. Even 49.9k would only produce a small amount of bass lift.
by george giblet
15 Oct 2019, 08:18
Forum: Amplifiers
Topic: the right diode bridge ampere
Replies: 16
Views: 2793

Re: the right diode bridge ampere

can i mount the body of the diode bridge to the chassis of the amp?? can i put a screw on the middle hole of it and mount it to the amplifier chassis??
No problem, a lot of people do that.
by george giblet
14 Oct 2019, 23:24
Forum: Amplifiers
Topic: the right diode bridge ampere
Replies: 16
Views: 2793

Re: the right diode bridge ampere

if i put it right it will work sir???the whole power supply?? i compute the voltage after the big capacitor is 21 volts going to the power amp am i right ?? Yes it should work. You might get a bit more voltage, say 22V at no load. At no load the transformer output will be a little higher than 15V r...
by george giblet
14 Oct 2019, 07:36
Forum: Amplifiers
Topic: the right diode bridge ampere
Replies: 16
Views: 2793

Re: the right diode bridge ampere

please check my new diagram below if it will work on my mg15 marshall amplifier power section or if my amp will work normally or gonna blow up Wired exactly like you have drawn it - it will blow up! Notice there a "+" terminal. The terminal is pointing in a different direction to all the other term...
by george giblet
13 Oct 2019, 04:19
Forum: Boutique Stompboxes dissected...
Topic: Nordstrand - 3b preamp [traced]
Replies: 37
Views: 5990

Re: Nordstrand - 3b preamp [traced]

There is a mistake in the schematic, nothing bad, pin 5(+) of ic4b don't have to be connected to pin 1 from ic3a but to pin 3 of ic3a, because it need to be at vcc/2. What you have said here is correct. When I traced over the 3-band, the opamp + inputs on the bass, mid and treble sections all conne...
by george giblet
13 Oct 2019, 00:27
Forum: Modern Stompbox Effects (1975 - ...)
Topic: MXR M87 Bass Compressor Demo
Replies: 20
Views: 12070

Re: MXR M87 Bass Compressor Demo

yep make sense george, i was sratching my head on this input topology, not making any sense , i was thinking about some sort of common base circuit, :D , silly me ,great link george , i will redraw and resume the work , thanks again Those SMD parts drive you crazy when you can't ID the part. Too ma...
by george giblet
12 Oct 2019, 03:02
Forum: Modern Stompbox Effects (1975 - ...)
Topic: MXR M87 Bass Compressor Demo
Replies: 20
Views: 12070

Re: MXR M87 Bass Compressor Demo

also, whats going on with this varicap on input? d17 and d18, https://pt.wikipedia.org/wiki/Varicap thats new to me , its some form of Witchery ? :0) , ok going back to work It's not a varicap, it's a tranzorb, https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode They are used to prote...
by george giblet
12 Oct 2019, 01:06
Forum: Modern Stompbox Effects (1975 - ...)
Topic: MXR M87 Bass Compressor Demo
Replies: 20
Views: 12070

Re: MXR M87 Bass Compressor Demo

OK I think the issue is GY is really 6Y. Then it all makes sense since they are the same JFETs use on the M78!

https://www.newark.com/on-semiconductor ... dp/67R1327
by george giblet
12 Oct 2019, 00:39
Forum: Modern Stompbox Effects (1975 - ...)
Topic: MXR M87 Bass Compressor Demo
Replies: 20
Views: 12070

Re: MXR M87 Bass Compressor Demo

So for example in your schematic the collectors of Q19, Q21, Q22 all connect together and go to a cap. This looks like the gates of the P-channel JFETs in my M78 schematic. The source of each of those goes to ground which matches with the bases of in you schematic going to ground. So I suspect if yo...