More detail mistakes

[steveneddy]

OK - you read about one stupid mistake today - let's keep the party going.

The amp? My "own design". Part Bassman, JTM45 and some Trainwreck stuff in there. The best ideas I have come across - so I threw them all in one big basket and went to work.

But - during the build I made a few small mistakes that could have cost me an amp - and made the amp under powered.

Number one was the previous post where I had the speaker ohm selector switch wired backwards - 4-8-16 wired 16-8-4 - made the amp sound funny and not very loud.

I'm glad I caught it - but THAT wasn't the reason it wasn't very loud in my opinion.

SO - all day checking the schematic and build notes - measuring voltages several times over - doing math until it hurt - what was the deal?

The amp sounded good - nice and clean - but it wasn't loud enough. It is a 6L6 powered amp - should loud and punchy - I know how they are supposed to sound - I've built enough of them.

Check, check, check - test, test, test - conclusion? Well - F*** it - I'll just rebuild the entire pre-amp section - I had the tone stack after V2 - so I decided that it wasn't working that way - so I spent the day moving the tone stack after V1 - and cascading V2 for a small amount of drive.

The amp has a pre-volume and a master volume between V2 and the PI - I thought my design had the pre-volume in the wrong spot - I was wondering about the value of the pre and post volume pots. Everything was crossing my mind.

Almost to the end - stay with me.

So I finally get everything rewired as neatly as possible - I'm running a new shielded cable to the Master Volume when I look really close at the shielded cable that was there already - and what did I see?

I am using Belden inside of my amps - and I was aware of the Mogami inner conductive shield - but I never thought about it with the Belden cable.

I removed the cable the looked at it closely and you could see where the inner conductive shield - not the shield wire - was touching the inner signal wire - well not the wire itself - but the volume pot connection when the wire was uninstalled and bent just a little.

So today I found a wiring mistake on the OT - the amp got a preamp rewire job - and I found another dumb mistake and repaired it.

NOW the amp sounds right - loud and punchy - the Master and pre volume pots work now. Tone stack works like it's supposed to.

Case in point - especially for me - pay attention and know what kind of shielded wire you are using. And pay attention.

Now that I found that faulty shielded cable install I want to put the amp back the other way to too how it will sound. Aw - maybe next one. This one rocks!