Interesting voltage drops

[DaveBo32]

The D-lite sounds a little steril. So I decided to check my voltages which were high roughly V1a=208,V1b=216,V2a=218,V2b=227. I've been battling this for a while, I actually have a new OT coming soon.
I started to try a couple of different 12ax7 to see if the amp would sound any warmer. Finally the amp is sounding better..great. I checked the voltages again roughly 198, 209, 210, 224. What the.@#$. I started palying some more, the amp started sounding steril again. I check the voltages sure enough they were high again(changing the tubes didn't solve it). Interesting...then I heard it..click..that damn electric radiator I bought to keep my garage warm. When the heater turns on, its drawing so much current and starts knocking my voltages down on my D-lite, which in return is making my amp sound better..HA. That's it I'm bringing my heater where ever I jam. Is the pwr supply used in the ODS-101 regulated better?

[mlp-mx6]

You don't have any power supply regulation in that amp that I am aware of. It is totally that the xfmr is converting the incoming voltage per the turns ratio.

I would suggest that you measure the wall voltage based on what you expect the "normal" voltage to be, and adjust your dropping string in your amp based on that.

[odourboy]

Last one first - no - none of these supplies are regulated and they are all slave to the whims of our power grid.

Seconds, I think your electric radiator did you a favor! (Quickly helping to diagnose the source of your sterile tone). It sounds like it's time to look into playiing with the PS string to see if you can get the V1 and V2 plate voltages down a bit. Might be easiest to start by reducing the FET (electric radiator) simulator resistor at the end of the chain by a bit and see what happens. You might aligator clip a high value R in parallel and tinker with the values until you get it where you want it.

[dogears]

Raise the 1st B+ dropping resistor to a 2.2K to 3.3K.

Lower the FET simulation resistor to a 150K to 180K.

[DaveBo32]

I started to mess the PS, I need to pick up a few resistor values. So what are the "ideal" dumble voltages. Is it CL 200,210 OD 210,225?

[Bob-I]

I started to mess the PS, I need to pick up a few resistor values. So what are the "ideal" dumble voltages. Is it CL 200,210 OD 210,225?

Give or take a few volts, yep. I'd say 225 is getting a tad high, shoot for closer to 200 all around.

[DaveBo32]

I started to mess the PS, I need to pick up a few resistor values. So what are the "ideal" dumble voltages. Is it CL 200,210 OD 210,225?

Give or take a few volts, yep. I'd say 225 is getting a tad high, shoot for closer to 200 all around.

Bob,
So my voltages should all (v1a, v1b, v2a, v2b) 200V? I thought they should be an increase of 10V between stages(v1a-v1b) and (v2a-v2b). Looks like I'll be busy. What should the phase inverter be?

[Bob-I]

Bob,
So my voltages should all (v1a, v1b, v2a, v2b) 200V? I thought they should be an increase of 10V between stages(v1a-v1b) and (v2a-v2b). Looks like I'll be busy. What should the phase inverter be?

Of course you can nail that, but go for as close as you can without going ape over it. As you can hear already, it's pretty obvious when it's off.

Don't know about the PI off hand.

[DaveBo32]

Raise the 1st B+ dropping resistor to a 2.2K to 3.3K.

Lower the FET simulation resistor to a 150K to 180K.

Embarassing Question,
Where on the Dlite is the FET resistor? I'm still learning this stuff.

[odourboy]

Embarassing Question,
Where on the Dlite is the FET resistor? I'm still learning this stuff.

Not a D-lite owner here, but from the schematics and layouts I've seen, it's a 220K 3W fellow located at the top (front of the amp) of the row of 4 22uF electrolytic caps on your PS board. One end should be connected to ground, the other is your B+5

If you clip on a 1M in parallel with it, you'll damn near bang on 180K. Using a 470K will put you at 150K total. (just as a test)

[DaveBo32]

Thanks, That was the resistor I thought was the FET res. When dogears said 150k, I started questioning it. I try some experimenting tonight when I get home. Thanks again guys..

[odourboy]

Thanks, That was the resistor I thought was the FET res. When dogears said 150k, I started questioning it. I try some experimenting tonight when I get home. Thanks again guys..

You just haven't got the hang of NJ 'shortspeak' yet (I'm still working on it myself! ). He's was saying:

Raise the 1st B+ dropping resistor {from a 1K} to a 2.2K to 3.3K {range}.

Lower the FET simulation resistor {from a 220K} to a 150K to 180K {range}.

[DaveBo32]

Well, I installed my new OT and added a 1M res. in parallel with the 220k FET res. What a night and day difference. I can't believe how much the sound has improved. Its to late for me to crank it up, I'll have to wait until tomorrow. Adding the 1M to the FET improved my voltages.

My new voltages: Input VAC 116.3 6V6 @ 20mA
V1a = 200.7
V1b = 211.7
V2a = 211.7
V2b = 220.2
V3a = 337.9
V3b = 323.2
B+1 = 457
B+2 = 453
B+3 = 446
B+4 = 329.3
B+5 = 323.5

Are these voltages correct? Should I leave them alone?

[Bob-I]

Excellent. Every little tweak helps, that's why there is NO perfect Dumble schematic. You need to let the amp speak to you and answer it.

[dogears]

Add 1K to the 1st dropping, as I suggested. It will get even better, I bet.