• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Photo Gallery

Jane: " ... the diodes (1N4004) that elevate the 7812 output voltage from 12V to 12.6V ..."

FYI: this is a common practice in solar cell power regulation = uA 7812 with "lifting diodes" to push the ground leg up ~~ 0.6 VDC. However, there are two diodes installed on the "ground" leg, one forward biased and one reverse biased (forward & reversed in parallel). It turns out that on power up and shut down and occasionally during "heavy" power demand, the 78XX series does want to source and/or sink a small current in the other direction from the ground plane. An added (reversed, parallel) diode is a good idea for audio use as it will add to the noise rejection component of the regulator. Check it out ...

/\ ... \/

:smash:
 
There is just one rectifier at service. The other one is for display/maintain symmetry. The E80CC was chosen due to linearity. In the beginning I was considering 12AT7 (with local feedback), but I found E80CC to be better and more linear -- at least on the paper. And I think it's sexier with "high-heeled" tubes. ;) The drawback is availability and price.
The OTL don’t sound much, it’s quite transparent. At normal listening level the distortion is less than 0.1% second harmonic which adds very little colour to the sound...

Jan E Veiset
 
Disabled Account
Joined 2004
6v6 PP

Just finished.
 

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Dyna ST-70 Clone or BB-70

Here's a pic of my best sounding home built amp so far, the Big Boy Model BB-70. The On/Off switch fried already, so I had to bypass it. Instead of using a face plate, I applied decals directly on the aluminum. It looks kinda bad, but it does the job. I think I'm going to order a plate at BNP Lasers for about $50.

~~~Johnny~~~
 

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Octal based Marantz 7C line amp

Hi,

This is my project finished during the X'mas holiday.

I am using 12SL7 for the first 2 amplification stage and 12J5 for the buffer. All coupling capacitors are Mundorf Supreme Silver-in-Oil.

It sound very good which matches the Marantx 7 I built using TFK 12AX7 for amplifier and Brimar 12AU7 as buffer. This one employs all Jensen Copper-in-Oil for signal path.

73
Johnny
 

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I've finished this prototype yesterday, going to try it today on concert:

6p3samp2.gif


The prototype for this prorotype was Altec Lansing 1569A, I like their direct coupled phase splitter for the stability on low end when deep feedback is applied.
Mine uses 6p3s and 6n1p tubes. Initially I wanted 6n2p in input but gave up the idea because of stability issue on high end (too much gain). However, with different layout it would work fine.
Transformers are from ADA guitar amps. Measured maximal sinusoidal output on each channel is about 80 Watt.
 
FastEddy said:
Wavebourn: Noticing the multi-band EQ ... is that your "pre-amp"/ front end for this fine looking Amp ??

This thing sits between mixer pult and amp to equalize flat everything from microphones to speakers. It has "FBQ" feature, LED indicator on each band control, so when feedback causes oscillation on some frequency it is visible in which band this frequency is, so step by step frequency response can be corrected before the concert. On the picture FBQ is off so all LEDs are on.
 
Wavebourn: " ... when feedback causes oscillation on some frequency it is visible in which band this frequency is, so step by step frequency response can be corrected before the concert. ..."

This is SOP for older stage hands, roadies ... ==>> A tried and true method and the best way to "equalize the venue" without resorting to lab quality equipment & measurements. Works best during final sound check with the crowd just beginning to fill the arena.

:cool:
 
FastEddy said:
Wavebourn: " ... when feedback causes oscillation on some frequency it is visible in which band this frequency is, so step by step frequency response can be corrected before the concert. ..."

This is SOP for older stage hands, roadies ... ==>> A tried and true method and the best way to "equalize the venue" without resorting to lab quality equipment & measurements. Works best during final sound check with the crowd just beginning to fill the arena.

:cool:

However, a crowd adds some damping factor, but anyway resonant frequencies almost stay the same. ;)