100K non-HRM plate voltages

[pine]

I have just switched my 50 watt non-HRM #124-style amp over to 100K plates on V1 only; I think the voltages are a little high and wanted to ask your opinions and or recommendations. This amp has an OD entrance mod and a treble bleed, a .047 mid cap and a 100KA mid pot. There is a 150K FET simulator resistor which actually measures out at around 130K.
V1a=208, 1.6
V1b=209, 1.6
V2a=207, 1.8
V2b=213, 1.7
V3a=315, 61
V3b=309, 61
6L6=476, bias at 40mv
PT1=363
PT2=364

As you can see V1 is now higher than V2 and V3 is over 300 volts

The cleans are more blackface sounding, but not as sparkling as I had hoped and seem to lack depth, for want of a better word. OD bass is a little farty on low E chord. I could probably go to a 100K FET simulator resistor but I don't think I want to go lower than that on that component. What should I do?

[dogears]

How is it based on #124? Nothing seems to be similar..... Different plates, different cap size, different tonestack, etc....

Fwiw, I like around 185v on the preamp. Adjust the string. Raise the first resistor as high as 8.2K if needed. Move up from 2.2K to maybe 4.7k at first.

Also, I'd lower that bias to 32ma or so. Cleans up the bass issue.

[pine]

Thank you for the reply, It started out as a 124 style, and after browsing the forum a bit I changed a few things.

[glasman]

You have a pretty high primary DC at 476 with the tubes at idle.

I would suggest raising the value of the first resistor in your dropping string. Not sure what you are using, but I would start by doubling it's value. I have found that replacing the 3K (pretty common value) with a 7.5K in the first dropping position makes a world of difference. I have done this on every Ceriatone I have worked on and the owners were amazed.

Of course that is only my opinion.

Gary

[glasman]

oops. Sorry Scott, I did not see your response.

Gary

[pine]

My thanks to both of you guys; Gary, this is in fact a Ceriatone that I only use a Strat or 335 through, I am primarily playing blues and soul, so you can see why I was going for a blackface clean, but I love the Dumble OD sound as well. I'm using a Weber Ceramic Blue Dog speaker that seems to sound pretty good in the 1X12 combo.

[pine]

I'm thinking my 100K plates on V1 experiment is not a shining testament to my admittedly small stash of know-how. By changing the dropping string, I was able to get the plate voltages close to what my forum browsing tells me is ideal for 100K amps, (204 on V1a, plate voltage on power tubes 472, etc.). But the cleans are now piercingly bright even with the presence off. I tried changing the presence cap to .47uF, and that enabled the amp to get bright enough to cut through steel (the dog gave me the old "how could you betray me like this" look and left the room) but still the clean side of amp is way out of line with the blackface tones I wanted. The OD side, when the level is turned up, gives me this horrible hash on the bass strings when strumming a chord (girlfriend left the house, I cannot print what she was muttering). V1 is an NOS GE 5751, V2 is an NOS Fisher (Telefunken), and the PI is a Mullard 12AX7. BIas set at 33mv. I put a pair of 33uF caps in parallel with the power supply filter caps to try to tighten up the bass. I did change the resistor before the ratio pot from 180K to 150K, could this be the source of my woes?

[dogears]

You must raise the bypass caps up to at least 10uf, or even 22uf when going to 100K plate loads. On the clean side. Do this and then report back about the brightness.

Also, put back in the 12AX7. 5751 will probably be brighter due to lower gain factor having less impact on miller effect.

I'm thinking my 100K plates on V1 experiment is not a shining testament to my admittedly small stash of know-how. By changing the dropping string, I was able to get the plate voltages close to what my forum browsing tells me is ideal for 100K amps, (204 on V1a, plate voltage on power tubes 472, etc.). But the cleans are now piercingly bright even with the presence off. I tried changing the presence cap to .47uF, and that enabled the amp to get bright enough to cut through steel (the dog gave me the old "how could you betray me like this" look and left the room) but still the clean side of amp is way out of line with the blackface tones I wanted. The OD side, when the level is turned up, gives me this horrible hash on the bass strings when strumming a chord (girlfriend left the house, I cannot print what she was muttering). V1 is an NOS GE 5751, V2 is an NOS Fisher (Telefunken), and the PI is a Mullard 12AX7. BIas set at 33mv. I put a pair of 33uF caps in parallel with the power supply filter caps to try to tighten up the bass. I did change the resistor before the ratio pot from 180K to 150K, could this be the source of my woes?