ODS rebuild

[Ampnos1]

I recently (over the holidays) rebuilt my ODS style amp and what a difference it made! My first build, which I did last year was not a good sounding amp at all! It was harsh and very bright sounding until I built a lator for it and that made a huge improvement. I couldn’t let it go how bad it sounded without the lator so I decided to do a rebuild and see if I could make and improvements. My first build had modern orange drop film/foil coupling caps a mix of carbon film and carbon comp resistors.

I decided to rebuild with NOS orange drops and draloric resistors and kept everything else the same. The amp is now very smooth/mellow and not at all harsh or bright even when pushed and the lator is no longer needed.

So for the experts, could these few component changes have made that big of a difference because the amp is truly night and day sounding now?

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[martin manning]

Can you describe the Modern vs NOS Orange drops? 6PS vs. 715 or 716P? The PP caps are brighter due to the dielectric type, so perhaps your D'lator was taking the edge off the high frequencies. Any chance you did a better job of soldering and lead routing on the rebuild? It looks nice in the photos. Bottom line is a lot of things have changed.

[Ampnos1]

The original caps were 6PS replaced with NOS 6PS and yes a lot of components was changed so maybe just a combination of all. But soldering on the fist build was just as good. I pride myself on soldering for fear of cold solder joints and trying to back track errors

[desertmouth90]

Ive heard many people say that the correct Orange drops are 6ps and the other give such a harsh tone and that the resistors dont make much difference.

Only going from what ive heard, but you made a sounds choice!

I am currently looking for a 240v transformer for a Dumbleator clone.

[Raoul Duke]

Looks very tidy. Great job

[ijedouglas]

Ive heard many people say that the correct Orange drops are 6ps and the other give such a harsh tone and that the resistors dont make much difference.

Only going from what ive heard, but you made a sounds choice!

I am currently looking for a 240v transformer for a Dumbleator clone.

I would have to disagree on the resistors not making any difference, they definitely do. Every single part of the amp that touches the signal chain (pretty much EVERYTHING) makes a difference. To focus on a single piece of the puzzle is IMHO myopic.

[martin manning]

Many people have tried to sort this out. Here's a test I hadn't seen before using Champ and Deluxe amps for the comparison tests. It does not include old vs. new Orange Drops, but it does include PP OD 715's and a variety of PET caps. Get your headphones out and see if there is any noticeable difference.

https://www.youtube.com/watch?v=0RdgkxoSS34&t=15s

DAW phase flipping was tried as a method to detect differences, and some were seen, but that method was found to be unrepeatable. Even larger differences were observed when the same cap configuration was compared against itself.

IMO the biggest change that was made here was getting rid of the CC resistors, lowering noise content and variation of resistances from the target values.

[Ampnos1]

Martin, I would agree that the CC’s were a big part of the problem. I measured the ones I pulled yesterday before I tossed them just out of curiosity and they all read higher values. A few were so far out of spec I have not doubt they specifically contributed to the harsh sound.