Search found 143 matches

by teemuk
04 Apr 2021, 07:25
Forum: Amplifiers
Topic: Valveste 8080 copy EXPERIMENTAL tube gain stage mod
Replies: 19
Views: 5259

Re: Valveste 8080 copy EXPERIMENTAL tube gain stage mod

Did you try removing the feedback? Cathode bypassing and changing plate resistor have lesser effects when the stage gain is largely determined by negative feedback loop: 1uF bypass makes open loop gain higher at higher frequencies but does not alter closed loop gain much. 100k to 220k plate load inc...
by teemuk
01 Apr 2021, 13:22
Forum: Amplifiers
Topic: Valveste 8080 copy EXPERIMENTAL tube gain stage mod
Replies: 19
Views: 5259

Re: Valveste 8080 copy EXPERIMENTAL tube gain stage mod

You could also experiment with just removing the global negative feedback loop around tube stages of the original design. It's what keeps the gain so low that the stages run clean with the given input signal range (limited by clipping LEDs). The solid state input stages are also already introducing ...
by teemuk
01 Apr 2021, 12:57
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: MusicMan Phasor
Replies: 9
Views: 4545

Re: MusicMan Phasor

Peavey introduced the VTX series around the same time so it's difficult to say who copied who. Both likely took the design from some electronics journal of the days. As a side note, Peavey also added a solid-state tube amp emulation circuit to their version of the circuit so that this tube amp would...
by teemuk
09 Nov 2020, 09:22
Forum: Amplifiers
Topic: Requesting Laney Klipp circuit analysis.
Replies: 6
Views: 2664

Re: Requesting Laney Klipp circuit analysis.

It's a basic differential amplifier circuit (yes, similar to LTP phase splitters) sans negative feedback, very low impedance plate load and (very importantly) with only 80VDC plate supply to lower headroom and clipping threshold. Because two opposite-phase outputs are not needed (like in a phase spl...
by teemuk
19 Oct 2020, 15:07
Forum: Amplifiers
Topic: amp differences
Replies: 5
Views: 2528

Re: amp differences

You could compare circuit diagrams of, say, those Mesa and Fender amps and see plenty of differences in them. Those differences are largely the answer to your questions of "what" and "how".
by teemuk
14 Sep 2020, 08:33
Forum: Printed/Published Online Designs
Topic: Guitar Distortion Pedal, Popular Electronics, September 1999
Replies: 4
Views: 4282

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: 7906

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 w...
by teemuk
01 Sep 2020, 10:56
Forum: Amplifiers
Topic: Peavey amp
Replies: 33
Views: 7906

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: 7906

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 contro...
by teemuk
07 Jul 2020, 07:14
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Victory Electronics - Sizzle Tone
Replies: 5
Views: 2114

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 i...
by teemuk
18 Oct 2018, 15:25
Forum: DIY Projects
Topic: Friedman BE-100 JFET emu [documentation]
Replies: 33
Views: 17911

Re: Friedman BE-100 JFET emu [documentation]

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&quo...
by teemuk
06 Feb 2018, 15:44
Forum: Amplifiers
Topic: Funky distortion circuit on this fender 'super twin' amp
Replies: 31
Views: 18297

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...
by teemuk
06 Feb 2018, 14:58
Forum: Amplifiers
Topic: Strange Phase Inverter in Geloso tube amps?
Replies: 7
Views: 4681

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...
by teemuk
19 Aug 2017, 07:59
Forum: Amplifiers
Topic: Seymour Duncan - Powerstage
Replies: 3
Views: 2768

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...
by teemuk
12 May 2017, 17:19
Forum: Printed/Published Online Designs
Topic: Speaker and Cab simulators
Replies: 122
Views: 84275

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 ...
by teemuk
13 Nov 2016, 10:05
Forum: Amplifiers
Topic: PEARCE G2R schematic - channel 1, what's happening here?
Replies: 2
Views: 2955

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...
by teemuk
30 Apr 2016, 09:43
Forum: Multi-Effects
Topic: Digital components in analog circuits?
Replies: 5
Views: 6452

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-Anal...
by teemuk
30 Apr 2016, 09:15
Forum: Multi-Effects
Topic: Digital components in analog circuits?
Replies: 5
Views: 6452

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 w...
by teemuk
20 Aug 2015, 16:38
Forum: Amplifiers
Topic: Add Three Prong Cord to Japanese SS Amp?
Replies: 4
Views: 2919

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: 2919

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.

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On a completely another topic though, I wonder what could be built to the "unused sections" of the circuit board. :hmmm: