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I'm looking at the trinity layout and I was wondering why you ground the elctrolytics with the power transformer instead of grounding them to the star ground by the inputs?

I've always thought you grounded the PT seperately from the board.

Thanks,

Scott

You'll find different amps with totally different grounding schemes, and they'll all work. It's just something you learn to accept.

The power supply electrolytics (bank of six of them) are grounded separately from the pre-amp, low level signal side. This keeps the two hi / lo level signal grounds separate.

My first attempt, tied them all together, in a star configuration and it was not as quiet.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

it all comes down to experience. thanks for the layout.

The e-caps represent high current grounds. You want to keep the high current grounds separate from the low current grounds for lowest noise. That means you ground the power transformer center taps, the filter caps, and the power tube cathodes to one ground point (high current) and the preamp grounds to another ground point (low current) to keep them from competing with one another.

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--s2
www.s2amps.com
www.category5amps.com

Speaking of noise, do you find the carbon comp resistors to be noisier than the carbon film ones? I'm trying to decide which to use. I want this amp to be very quiet for recording purposes.

CC are noisier than MF. If you want you can sub MF in the pre-amp. You can do this now, or after you listen to it because subs are easy to do on a board like you have.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Where is the mojo coming from that seems to be attached to CC resistors? I was measuring one yesterday, and I heated it up and watched the value change rather dramatically.

I built a Tweed Pro and used carbon film resistors, no carbon comp, and it has tone to the gills. Quiet as hell too.

I've got a bunch of carbon film resistors. I'll screw around with the new lightning, maybe changing one at a time to see if there really is anything to the CC mojo.

Carbon comps should be used in the preamp, if you want their mojo. if you build an amp properly the comp resistors will be fine. Heater wiring and grounding will cause hundreds times more noise than a comp resistor.
I have built all my amps w comps and they have a little more softness and smoothness to me.

Good luck.

T

I think the biggest issue with Carbon Comps is that they drift over time and at different tempuratures. Carbon film sound pretty much the same in the preamp to me and don't have the drift problems.

Metal films seem to have a slightly wider frequency response that I like in some amps and don't in others. In a Fender style amp where you play mostly clean the metal films seem a little more detailed. However, I find them less mid focussed and I like in a Marshall style amp.

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Richard Johnson
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Playing an insturment doesn't make you a musician, listening does

I once used CCs exclusively for the magic mojo juice they supposedly supply. Eventually I discovered 1W CFs from Xicon. They seem to sound just as good and are noticably quieter (and cheaper). They are now my staple.

I can hear a difference betwen CC and MF and CF and MF but not between CC and CF. My money is on CF.

To put this into perspective, I have one of those crazy sets of ears which can hear everything. I actually agree with EJ when he sez Duracell sounds better than Energizer...

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--s2
www.s2amps.com
www.category5amps.com

RG Keen has some info that might help explain most of your concerns
http://www.geofex.com/

On that note, I recently discovered that by using high speed grounding rules as per Howard Johnson's book High-Speed Digital System Design: A Handbook of Interconnect Theory and Design Practices ISBN: 0471360902
works VERY well, even in lo-speed designs like guitar amps. There is also a JPL proprietary spacecraft packaging manual, JPL D-8208 REV I and Electrical Grounding Architecture for Unmanned Spacecraft NASA HBK 4001 that actually utilizes most of H Johnson's prctices (published a few years after JPL's docs). Thge there's Henry Ott's practices which H Johnson and JPL both get and acknowledge as resources.
This may seem over the top, and obviously, a lot of shoddy layouts actually work, but if you want insurance.......

Then there's the aspect of waveform development that is NOT freq dependent, risetime. And if you look at how resistors are made, you might find things to consider when choosing resistors, CC or otherwise, for 'MOJO'.
All this to say......what were you asking about?

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the bastard son of Jack Parsons
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