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Cyclone

Inverted variations on a clone?

Part 1: Pre-Work and Housing

Last modified: 30-Apr-2004

 

Finished Cyclone amp in black

Introduction

A while ago I was contacted by Jerry who wanted to build a Gainclone for himself. Jerry was (more than) capable of making the housing himself but did not feel comfortable with designing and building the electronics for the clone. He therefore suggested to join forces and make a gainclone that resembles the original to a fair extend but would be built from the ground up.

Jerry would do the mechanical design and construction for two Gainclones and I would help with the electronics, suggestions for component layout and the tuning of the gainclone.

Assuming that just like the original Gaincard we would be able to give all components their place in the small box, we had to start with the housing of the Gaincard and the Power Humpty and all electronics would have to wait until we had these partly finished.

Boxes

Recently I visited Jerry where he showed me the results so far. He had been working over weekends and I must say I was very much impressed with the results. But there was something else as well: I never had seen the original gaincard and so far I assumed that it's "small size" would be in the same order of my GeenKloon boxes. I was so wrong.


The two boxes made by Jerry are made of solid aluminum and the front and back plate joining the two tubes (1 for each channel) are made of 10mm thick aluminum. The aluminum pipes are 4mm thick, and we may have to use an aluminum construction inside to mount the chip on (cooling).

But more important: They are beautiful but soooo smalllll. Hmmm, this is gonna cost me more time than expected to make sure that everything fits in these two small boxes. There are a few things we therefore have to worry about:

After we decided on what we wanted to be on the backplate, I left it to Jerry to decide on the first issue and find a solution for the lack of space on the back panel. PowerCon connectors and similar solutions for connecting the V-/0/V+ power supply wires are far too large and do not leave enough space to connect the speaker wires to the amp. Maybe the best solution is to hard-connect the power supply wires to the amp and use a nice connector on the power supply side instead (The Power Humpty is soooo much larger, there is more space there to use fancy connectors).

Design of an Inverted GainClone

Well, let's talk about the electronics for a moment. This project is a variation on the GeenKloon project. Whilst the GeenKloon was built on the non-inverted topology, the Cyclone gainclone will be based on the inverted design.


The inverted configuration is said to be even better sounding, so therefore I'm very much interested in hearing an inverted clone. If we suppose a gain which is equal to the gain of my GeenKloon 20x (26dB) then the following formulas describe the amp.
Gain = (R2/R1) = 200,000/10,000=20 times, which equals 26dB.

The best value for R3 can be determined using the following formula:
R3 = (R1*R2)/(R1+R2) which equals 9.5kOhm.

In order to preserve low frequencies the value for capacitor C1 must be chosen sufficiently high. 2.2uF may be on the low side, 4.7uF is used more often.

Design Considerations

Although everybody tries to stick to the idea of less-is-more of the original GainCard, there are areas where we are deliberately changing things from the original such as:

Well, we're close to starting the actual construction. More on page 2 ...

references

  1. TNT Audio review of the original Gaincard (Geoff Husband)
  2. TNT 2nd Review by Werner Ogiers

 

 



 

 

© Maarten@Platenspeler.com, Feb 2003, 2006