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Messages - pelanj

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Tubes and Hybrids / Hybrid tube amps work!
« on: June 05, 2009, 03:30:20 PM »
I have bought a miniature tube buffer after being inspired by this youtube video: http://www.youtube.com/watch?v=YsRhIFJzFug&feature=channel_page

It is built around a 6Z1P miniature pentode with wire leads. The pentode is connected as a cathode follower. This little thing is quite magical - before the amp for clean or distorted sounds, or in the effect loop of a ss preamp (Marshall 9004). It gives a nice tubey feeling to the tone. So I strongly believe, a great hybrid tube amp can be built. If a mixed mode feedback power amp is used along with a muti-stage distortion preamp, then it needs just a preamp tube in the signal path to get satisfying guitar tones for the hi-gain stuff and maybe for other uses as well.

A Marshall Valvestate has these features, but it fails in the distortion-generating stage - there are loads of distortion pedals that can do distortion much better.

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Tubes and Hybrids / Re: frankenstein idea
« on: June 05, 2009, 03:09:05 PM »
You can do that, but you have to run the power amp into an appropriate load (eg. 8ohm resistor) and then make a voltage divider to bring the signal to the right level. The same approach worked for me with a 15 tube head.

3
Hello, I have recently tried one trick with small speakers, that really helped the distorted tone. I have used a 2nd order lowpass as found in HiFi speaker crossovers with the rolloff frequency around 4-5 kHz. That really takes away the buzziness assiciated with small speakers which have a wider frequency response that usual guitar speakers. I wonder why this is not very often used in small practice combos. It sounded more natural to me than using a line level lowpass. Maybe it is due to reduced damping and also it can smooth out power amp clipping in Ruby sized amps.

4
Amplifier Discussion / Little travel combo with fuzz/distortion
« on: March 30, 2009, 05:43:20 PM »
Here are a few pictures from my newest build - http://kremator.rajce.idnes.cz/Kombo_se_zkreslenim/

Nothing really fancy, just a combination of this chipamp - http://www.redcircuits.com/Page96.htm and Bazz Fuss DeLuxe - http://www.home-wrecker.com/bazz.html (without the series inductor). There is a bypass for the Fuss and very little cap tweaking (I used what I found:) ). All built into a plastic home theater center speaker. There is a resistor in series with the external speaker output to simulate low damping factor. Although the Bazz Fuss is a little limited in tone options, it is nice to have around for practicing. I usually use it with various distortion pedals for more "metal" sound. All powered from a 9V battery or an external AC/DC adaptor - currently a 5V Motorola phone charger.

One notable feature that makes this maybe interesting is the low pass filter for the internal speaker - an ordinary second order lowpass (as in hifi loudspeaker crossovers) formed by 330 uH inductor and 3u3 capacitor. The corner frequency is around 4500 Hz for a 6 ohm loudspeaker. I think it provides a nice approximation of a larger (12") speaker. I even think of building one into my old Marshall MS-2 as the small speaker inside sounds crappy with distortion - the MS2 itself sound surprisingly well with a 2x12" box.

The good thing about this chipamp is that it is sufficiently loud for practice even with 3 volts. I am planning to buld one into one of the left surround speakers with a volume knob and a low pass filter to make a small warm-up amp to take anywhere.

And for the very brave ones, here is some noodling with the amp using an Ibanez MikroGRG and a Logitech headset microphone with various settings and low pass on-off:

http://www.edisk.cz/stahnout-soubor/87773/kombo3.mp3_1.02MB.html
http://www.edisk.cz/stahnout-soubor/47885/KomboTest1.mp3_2.63MB.html
http://www.edisk.cz/stahnout-soubor/05097/kombotest2.mp3_2.84MB.html

Just enter the bot protection code to the window below it and press "stahnout soubor".

5
Hello,
in my view, a well designed power supply does not get any benefits from a well designed isolation transformer of any kind. The only benefit is interrupting possible ground loops.

6
Amplifier Discussion / Re: Mesa Boogie Dual Rectifier backup ss amp
« on: March 15, 2009, 11:28:04 AM »
Just a small point - not only push-pull pentodes, but single ended pentodes/triodes provide the tube feel as well (all the small tube combos out there). I think an ECL86 or ECC81 power amp should be sufficient and hope to try out soon.

The Dr.Boogey pedal looks nice - I might try one later as I have a bunch of distortion pedals with quite nice sound if used with a tube amp.

7
Amplifier Discussion / Re: Ultra Class A Superdrive Power Amp
« on: March 12, 2009, 09:13:15 AM »
By the way, I have recently finished a TDA7233 based chipamp (datasheet circuit with small changes). I have built in into a plastic home cinema surround speaker to get a sort of combo amp. The surround has a 3inch fullranger, so the heavy distortion sounds from a pedal sound like nordic-black-metal-hive-of-bees. But it works really well with SansAmp GT2 and Digitech's pedals with speaker emulated outputs.

I hope I can get some opamps and transistors to test the ideas from the previous post soon.

In the Teemu's book i have found a circuit, where an op-amp had a cathode follower in the feedback loop. If this was combined with the class B output stage with BD139/BD140 (corrected by the feedback) and some current feedback as well, it could make a nice small practice amp with "tube harmonics".

8
Amplifier Discussion / Re: Mesa Boogie Dual Rectifier backup ss amp
« on: March 12, 2009, 08:58:25 AM »
That is very nice and informative post, Phil. Your setup is kind of similar to my test setup with non-dedicated
components. I used a small and kind of cheap 15W custom built head with a resistor ("giant distortion pedal"
) and a DI-box (level shifting), then to a ss combo. The tube amp amp I used had a big flaw. It had a great tone but at a too low or too high sound level - this setup allowed me to have any of the nice tones at any volume. Later I moved on to more conventional amps (JCM800 2204, Engl Fireball and now Mesa Boogie Dual Rec.), but I still keep this concept in mind and now I am getting really close to a perfect "bedroom" or recording amp.
I already have the parts for my dummy load and 10-30 W ss power amp but I am still waiting for my low wattage amp being built. I prefer to get all the parts together before I start.

Now I have an idea of a "universal" sound rig. Programmable preamp, a programmable EQ, tube power amp, a relatively small PA amp in a rack, connected with MIDI. There are some amps/preamps close to it, but quite large tube power amps are used, when it is not necessary.

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Amplifier Discussion / Re: Ultra Class A Superdrive Power Amp
« on: March 10, 2009, 06:52:21 PM »
I have found another one - but it seems a little strange to me - as drawn, the quiescent current would flow through the speaker winding. Is does not seem to me as a good idea... http://scitoys.com/scitoys/scitoys/computers/solderless/amplifier.html

In my quest for a low volume guitar amp, I will maybe try out something like this - http://www.google.com/patents?id=eh8yAAAAEBAJ - is that a good idea? :)

10
Amplifier Discussion / Ultra Class A Superdrive Power Amp
« on: March 09, 2009, 11:55:13 AM »
Anyone tried that (http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html)? I tried it today on a breadboard with a 230 / 12 V transformer (15 V no load), which gives twice as much load to the transistor.

The power is really minimal and the amp overdrives very easily and when played clean it is even less loud. Right now I cannot think of any reason why should it be preferred over a LM386 (or similar) based chipamp...but kind of fun to put together with minimal effort.  8)

11
Amplifier Discussion / Re: Mesa Boogie Dual Rectifier backup ss amp
« on: March 07, 2009, 05:53:33 PM »
Phatt, transconductance as I understand says, what plate current corresponds to grid voltage, kind of "amplification factor". That is nice setup you have, I am also very slowly heading towards something very similar. I have a 15W higain tube amp to play with, but I have to finish the reamping stuff.

J M Fahey, do you think that speaker load is essential? Could it be something like Weber mass - coneless speaker. Or a speaker completely enclosed in a box not to produce any noise.

My first idea was to get a ss amp with a good distortion tone (Randall, maybe) and use its preamp as tone generator, then "reamping" in the FX loop and use it's poweramp to drive speakers. I think this is a valid approach using the same principles as you both described. Anyway, thanks for helping me with sorting my thoughts:)

12
Amplifier Discussion / Re: Mesa Boogie Dual Rectifier backup ss amp
« on: March 04, 2009, 02:42:54 AM »
Hello Phil,
I have read through amptone many times and I am quite familirar with the concepts. I tried to describe what is my tone and what have I have already done to achieve it. As a summary, I am searching for an amp that could stand next to a DR and not being ashamed or even drowned by it. With a possibility of future installing soft limiting circuit (maybe even a small tube power amp into fx loop). And something smaller for home to power my other 2x12 with less severe requirements.

I would love to build one competely myself, however just adding to and existing and working design is less time consuming and could provide the same results.

13
Amplifier Discussion / Mesa Boogie Dual Rectifier backup ss amp
« on: March 03, 2009, 07:46:49 PM »
Hello all,
since a few years, I use a M/B DR (two channel) as my main amp, having a EL84 equipped .50 Caliber as a backup (both rackmount). I would like to present my view on the "tube sound" with regard to modern metal tones. Then, based on this, I would like to find a currently manufactured (or easy to get in Europe) ss backup amp for the DR, good enough to use at rehearsals where the other guitarist stil uses a DR. And after that, one smaller one for my "bedroom" practice.

My main tone is the Red channel, Orange being cloned to modern set for more "midrangey" sound with a delay. As the speaker box, I use something very similar to M/B vertical half-back 2x12 equipped with EVM12L clones from Eminence, lower chamber is ported in the Thiele style. I also sometimes use one half of ADA SplitStack Vintage (bright position), the other half is in my bedroom for practice. Sometimes a standard 4x12 with V30 Celestions. My main guitar is a Gibson LP Studio. When I am using the Caliber with the same box and guitar at rehearsal volume, I think I can hear the compression (be-it poweramp or not) and the amp is pushed almost to its limit. I do not have this feeling at all with the DR's 6L6 poweramp. So I guess I am not a fan of heavily compressed power amp tones, however that "tube power amp" sound is something I can really distinguish from a ss amp. I wonder what it is.

Before getting the DR, I was experimenting a lot and I have found the following - for my tones/application, a tube preamp is not necessary, a well designed solid state ANALOG (no POD, Digitech RP) preamp (a nice exampe - Rocktron ProGAP)/distortion box (but not for example MT-2) can do it fine. However, I have always found a tube power amp in the signal chain as madatory. Either being a pure 50/50 style rack power amp (properly biased 6L6's slightly preferred in the same amp to EL34's) or a "reamping" system, where a low power all tube head (even any preamp into its FX loop) was run into a load and later amplfied by a 2x12 guitar combo's poweramp (Behringer GMX212 to be specific). Between the tube head and the combo, a splitter was inserted to form a parallel FX loop changeable to a WET-DRY stereo arrangement with this particular combination. A Boss Turbo Distortion with an old Marshall 1959 (not sure about the exact type, maybe even modified) could be tweaked to a very heavy yet articulate sound. A Fender SuperChamp XD, being digital, with it's tube power amp sounded also quite convincing.

I currently own two pedals worth mentioning - a Tech21 GT2 and Digitech Death Metal, both quite usable with a fullrange powered speaker for practice. Both have this thickness and sweetness at low volume, never tried them really loud.

I have read through teemuk's great book to realiye a few things. What I need is probably an ss amp with a convinceable hi-gain sound that cuts through, around 100W (or more to have some headroom) preferably mixed mode feedback power amp and a serial FX loop. The FX loop is needed, because to be as satisfied with the tone/feeling as possible, I would like to implement most probably some kind of a switchable soft limiting device, either tube or not, to substitute the tube poweramp (in a quick experiment, a compressor stompbox could be set to sound quite convincing. In my view,a gain cascading preamp is highy preferable - if a Boss OD was run into a Boss DS, the total sound reminded "tube sound" better than each of them alone.

I would like the amp to be as light and small as possible (Crate PowerBlock does not work). I am looking at the RX or RG series Randalls. I remember once playing an RG150G3 next to a RH50T (all tube). While the RG had a kind of more versatile distortion, it failed in the "tubeyness" at the first few tones. Unfortunately, that is some time ago and it was only a few minutes. I used to have then the RH for some time, so i know the sounds quite well and I have long forgotten how the RG played. Are there any readily available alternatives?

As for the practice amp - basicly there is nothing better as 12" speaker, even at low volumes. Those 8inch speakers sound like c..p with anything but clean sound. I have modified my old MS-2 with an speaker out instead of headphone out (with either 10 or 100 ohm series resistance for attenuation) - and it works quite well with one half of the SplitStack - with everything on full. But I miss post-distorion tone controls. Now, here is the problem. The smaller the amp is, the less controls it has (and no speaker out as well - modifying is easy but voids the warranty). I do not need more than 2 W of power for clean tones and much less for distorted. I need only slightly higher volume than the MS-2 with a 100 ohm series resistor to a 8ohm box - that gives power of around 10 mW. That means any common combo amp could be fine, I would prefer a head instead. One that comes in mind is the MG15 microstack, but it is not sould without the (IMHO) useles speaker boxes. The other possibility is a modified small combo.

So, do any of you have experience of playing such a small amp/combo with a proper speaker? Which could be fine for me?

And, at the end, please select from amps/combos available at www.thomann.de or www.musik-produktiv.de, as any other would be probably hard to get at my place. Thanks for reading my monstrous post and I am open to suggestions and debate:)

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