Search found 138 matches

by teemuk
14 Sep 2020, 08:33
Forum: DIY Stompbox designs
Topic: Guitar Distortion Pedal, Popular Electronics, September 1999
Replies: 4
Views: 474

Re: Guitar Distortion Pedal, Popular Electronics, September 1999

10K input impedance, no low-pass after clipping, output "ground" referenced to half-supply bias, etc.

Next please.
by teemuk
03 Sep 2020, 09:54
Forum: Amplifiers
Topic: Peavey amp
Replies: 33
Views: 1906

Re: Peavey amp

The "Supersaturation" generation of Peavey amps didn't generally have any notch EQ after the tonestack - except for the effects of current feedback in power amp that emphasizes high and low end response. The Bottom/Body/Punch tone controls (featured in later amps) provided level response with contro...
by teemuk
01 Sep 2020, 10:56
Forum: Amplifiers
Topic: Peavey amp
Replies: 33
Views: 1906

Re: Peavey amp

Jmpj48 wrote: 31 Aug 2020, 17:20 Why would they make a amp with no tone stack on the gain channel. And don’t even put a fx loop in it.
It's one of the cheaper models so to reduce cost they cut down features. You get what you pay for.
by teemuk
31 Aug 2020, 10:47
Forum: Amplifiers
Topic: Peavey amp
Replies: 33
Views: 1906

Re: Peavey amp

Consult the manual. It probably says tone controls are inoperational on gain channel (that's "feature" of several Peavey amps of the era, sometimes implemented to a "Thick" switch). Yes, as explained the tone stack is bypassed with signal path that swamps impedance of tone controls. Later "Supersatu...
by teemuk
07 Jul 2020, 07:14
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Victory Electronics - Sizzle Tone
Replies: 5
Views: 746

Re: Victory Electronics - Sizzle Tone

I agree. I also recognise seeing this font type in several different places, such as album covers. It's probably some fairly "common" type. Someone with graphic design background could probably tell exactly what it is. E.g. Electro-harmonix logo uses font called "Skjall" but it is different than thi...
by teemuk
18 Oct 2018, 15:25
Forum: DIY Stompbox designs
Topic: Friedman BE-100 JFET emu
Replies: 33
Views: 11510

Re: Friedman BE-100 JFET emu

These things are never going to nail the tone of the original tube design because a JFET simply isn't a "drop in" substitute for a 12AX7 triode tube. Key elements that create "tone" of a circuit are overdrive characteristics and "voicing". These JFET "emulation" circuits can somewhat mimick the "voi...
by teemuk
06 Feb 2018, 15:44
Forum: Amplifiers
Topic: Funky distortion circuit on this fender 'super twin' amp
Replies: 31
Views: 13440

Re: Funky distortion circuit on this fender 'super twin' amp

Zombie thread resurrected I see... :D Yes, this is definitely a weird circuit since cathode follower likely isn't a first choice when you want to produce "tube distortion". This one "brickwall" clips very asymmetrically and very "hard", with abrupt clipping onset. Aside the signal asymmetry it is pr...
by teemuk
06 Feb 2018, 14:58
Forum: Amplifiers
Topic: Strange Phase Inverter in Geloso tube amps?
Replies: 7
Views: 2836

Re: Strange Phase Inverter in Geloso tube amps?

Yes, nothing but a generic "cathodyne" phase inverter there. ...And overall the setup is pretty generic too: Since cathodyne does not have voltage gain (only insertion losses) there is a common cathode amp input stage for voltage amplification. The same stage also receives negative voltage feedback ...
by teemuk
19 Aug 2017, 07:59
Forum: Amplifiers
Topic: Seymour Duncan - Powerstage
Replies: 3
Views: 1901

Re: Seymour duncan Powerstage

Seems like they jumped the bandwagon of "micro" amp products. Everyone seems to have one now. What comes to overall compactness, keep in mind that these "pedal" -type amps often tend to require an external power supply unit, which is about equal in size and weight with the actual amp unit, and then ...
by teemuk
12 May 2017, 17:19
Forum: DIY Stompbox designs
Topic: Speaker and Cab simulators
Replies: 122
Views: 67639

Re: Speaker and Cab simulators

You're right about what a speaker sim actually does, it's "just a filter" and I wish there was a simple (stomp)box with a filter inside that was modelled after a really good sounding example of one of those digital cab impulses. The virtue od digital signal processing (like "impulse response" proce...
by teemuk
13 Nov 2016, 10:05
Forum: Amplifiers
Topic: PEARCE G2R schematic - channel 1, what's happening here?
Replies: 2
Views: 1865

Re: PEARCE G2R schematic - channel 1, what's happening here?

For "modern" high-gain designs it is customary to attenuate / filter out majority of lower frequency signal content in order to decrease intermodulation distortion. Yes, many modern high gain design have a significant gain peak around lower mid-range frequencies, e.g. 1 kHz. Yes, it sounds rather hi...
by teemuk
30 Apr 2016, 09:43
Forum: DIY Stompbox designs
Topic: Digital components in analog circuits?
Replies: 5
Views: 3397

Re: Digital components in analog circuits?

Concerning "digital potentiometers"... They are actually somewhat broad product category with different types of arrangements for control and different types of arrangements for attenuation. Most complex "digital potentiometers" actually run the signal through Analog-Digital-Analog -conversion proce...
by teemuk
30 Apr 2016, 09:15
Forum: DIY Stompbox designs
Topic: Digital components in analog circuits?
Replies: 5
Views: 3397

Re: Digital components in analog circuits?

You may not always need a "digital potentiometer" if you can substitute it with OTA, LDR, FET or multiplexer IC. All can be used for various purposes of "gain controlling", whether frequency-selectively or at full bandwidth, and you can generate an analog control signal to them with digital solution...
by teemuk
20 Aug 2015, 16:38
Forum: Amplifiers
Topic: Add Three Prong Cord to Japanese SS Amp?
Replies: 4
Views: 2086

Re: Add Three Prong Cord to Japanese SS Amp?

mictester wrote:Of course if you drive this thing hard, it'll be a big germanium fuzz box!
Pignose in a much bigger box is what I'd say...
by teemuk
07 Aug 2015, 15:19
Forum: Amplifiers
Topic: Add Three Prong Cord to Japanese SS Amp?
Replies: 4
Views: 2086

Re: Add Three Prong Cord to Japanese SS Amp?

Yes, replace with a 3-prong coord, and yes add fuse. Preferably on both mains and secondary side.

---

On a completely another topic though, I wonder what could be built to the "unused sections" of the circuit board. :hmmm:
by teemuk
12 Jul 2015, 11:37
Forum: Davidoff Library
Topic: LAST VALVE SOUND SIMULATOR
Replies: 11
Views: 13097

Re: LAST VALVE SOUND SIMULATOR

Someone may have more understanding of these things but to me that is just a fancy name for a tone control and frankly a tone control with only 3 or 4 dB of boost or cut is not something that would bother to build. Heck,,even an average parq Eq would make a bigger impression I have to agree. Consid...
by teemuk
21 Jun 2015, 19:10
Forum: Amplifiers
Topic: Fender - Vibrolux Reverb Boost (Late 70's)
Replies: 3
Views: 2327

Re: Late 70's Vibrolux Reverb Boost

Oh, the infamous "pull master"... It's an overdrive feature implemented to some of their amp models (ca. early 1970's), which employed driver stage of the spring reverb as additional signal booster (a traditional Fender preamp didn't have enough gain for overdrive). Here's a similar "factory" schema...
by teemuk
29 May 2015, 16:11
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: BK Butler - Tube Driver [schematic]
Replies: 69
Views: 70038

Re: BK Butler - Tube Driver [schematic]

...oh, forgot to mention, quoted as being a feature that actually makes the distortion more tweakable and versatile. http://music-electronics-forum.com/attachments/30544d1410787181-tube-works-rt-902-real-tube-rack.jpg http://music-electronics-forum.com/attachments/30544d1410787181-tube-works-rt-902-...
by teemuk
29 May 2015, 16:07
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: BK Butler - Tube Driver [schematic]
Replies: 69
Views: 70038

Re: BK Butler - Tube Driver [schematic]

tictac wrote:Does anyone know about the "Bias Control" that's available as a new feature?
In older TubeWorks units (e.g RT-902 Real Tube Rack) the "Bias" control was simply a potentiometer wired as variable cathode resistor.
by teemuk
11 Apr 2015, 09:18
Forum: DIY Stompbox designs
Topic: selenium diodes for clipping?
Replies: 7
Views: 3676

Re: selenium diodes for clipping?

http://oi57.tinypic.com/30dl4hx.jpg Note how the selenium characteristic curve is less "steep". This is due to its higher series resistance. Putting series resistance to ordinary silicon diode will change its characteristics towards similar direction. The "knee" from reverse bias to "effective" for...