Dialing in your plate voltage and tubes (NON HRM)

[tonejunkie]

I am beginning the process of dialing in a Non HRM 100 watt in a Funk chassis. When I try different tubes the plate voltage can swing by up to 15V or more so for example with one tube I may get 193 on CL1 and with another I may get 178.

1) Now is the change in tone I am getting between these two tubes more a function of the change in plate voltage or the tube itself?

2) Also if you are tweaking your dropping string to get certain plate voltages and you say want to use a tube that pulls down your plate voltage to below a certain value you think your should have (lets say 190 on CL1) should you change your dropping string to listen to that tube at the that voltage?

3) It seems that the new production JJ are the most popular tubes to use with this amp and I seem to only want to use those in the overdrive, what's my problem? OK no need to answer this one, I know its subjective.

4) When do you know that your done playing with plate voltage and tubes and move on to the circuit tweaks.

Now for specifics, I currently have the following

CL1 188 (Tung Sol Reissue 12AX7)
CL2 193

OD1 195 (JJ ECC83S)
OD2 200

PI 275 (EH 12AX7)
B+ 445

Bias 41ma (Short bottle TAD 6L6)

I did some work last night and I think I like the results, but I would like to be able to take it to a gig and listen then come back with some tonal desires (yes I have them too) and be able to tweak away.

[tonejunkie]

PICS YEAH

[Structo]

Very nice build!

I'm not sure I can help on the voltage/tone thing. I noticed too the voltage swings using different tubes. But not as much as you did.

The consensus on the preamp voltages is V1 190-200v, V2 200-205v and the PI 290-295v

[Blindog]

Nice clean build!. Now the fun begins..

My 2 cents, stick with the base ODS-101 non HRM dropping string for now, and try different tubes until you get what you are after. Otherwise you may end up chasing your tail. I went through a half dozen or so until I found the ones that gave good balance and dropped (or raised) the plates where I wanted them.

That being said, I dont think you will get your PI up to around 300V by changing tubes. Try lowering your first resistor in the string. Also, I like a long plate tube in the PI, JJ ECC803S or Sovtek 12AX7LPS are a couple I've had good results with.

Oh, and don't forget to adjust your PI trimmer to about 5-6 volts higher on the input side of the PI. This will help dial in the "bloom". You may have to go through a couple different tubes if you can't dial it in.

Have fun!

Mark

[dogears]

Yech.... .05 midcap and 150 slope. Oops, I think you have the bass cap on the edge and it is a .01....

Also, what size are your bias feeds? They look half value in the pic.

Also, the plates and cathodes of V1 and V2?

Are your OD1 and OD2 caps backwards?? The .005 is on the second stage and yours is on the first.

[talbany]

Now is the change in tone I am getting between these two tubes more a function of the change in plate voltage or the tube itself?

Both.. Every tube has it's own unique sonic signature due to it's design or plate structure, plate impedance, materials used etc..This stays pretty balanced w/same manufacturer 12ax to 12ax..the X factor comes from the tubes current draw which has an effect on the tubes bias..Since in most cases no 2 tubes draw the exact amount of current...current effects voltage....voltage effects bias.. bias effects tone..The differences can be subtle to drastic...IMHO both are equally important..

15v is a pretty wide swing although not out of the question..I've had some pretty large swings going from older tubes (pulls) to newer ones..If you try to shoot for 190 V1 and keep the swing between 10v or so in each direction you should be able to find the magic tube.. Hope this helps

Tony

[tonejunkie]

The EQ section is the skyline (Layout is obviously wrong thanks Scott). I do not have the LFB in CL2.
CL1 220k/3k3 w/ 4.7uf
CL2 150k/2k2 w/ 4.7uf
OD1 220k/3k3 w/4.7uf (.01 coupling)(layouts wrong again?)
OD2 150k/2k2 w/ 5uf (.005 coupling)(layouts wrong again?)
My snubbers are 330pf,

Dogears I don't know what bias feed are.

I'm in Seattle this weekend for two private gigs (first corporate gigs of year) so I will not be able to work on this amp till I get home on Monday.

[Structo]

The EQ section is the skyline (Layout is obviously wrong thanks Scott). I do not have the LFB in CL2.
CL1 220k/3k3 w/ 4.7uf
CL2 150k/2k2 w/ 4.7uf
OD1 220k/3k3 w/4.4uf (.01 coupling)(layouts wrong again?)
OD2 150k/2k2 w/ 5uf (.005 coupling)(layouts wrong again?)
My snubbers are 330pf,

Dogears I don't know what bias feed are.

I'm in Seattle this weekend for two private gigs (first corporate gigs of year) so I will not be able to work on this amp till I get home on Monday.

In your photo, the orange drop on the far left is the mid cap.
It should be either .01 or .05.
If .01uF you should use a 250K mid pot. (I think)

The bias feed resistors are the two at the far right that reside between the two big .1uF couplers, the pair that feed the bias.
Looks like you have 10K, should be 220K.

Double check your tone stack cap values and placement.

[tonejunkie]

Ok, the bias feeds are 200k, not 100k or 10k (I can see that you cant see the red on that set of resistors in the pic). 200k is the value I have on the ODS 101 Non Hrm schematic, and in terms of the layout the bass cap is on the far left and the mid cap is to the right of that. The bass cap is a .1 and the mid cap is a .01 to a 250k pot. Also, my .01 coupling cap from OD1 is much smaller than the .005 cap going form OD2 (they are both 6PS) I don't know why that is. Is my circuit correct? I think it is :-I Thanks for the input guys!

[tonejunkie]

I had to order some resistors to get my PI in the right range. I will comment on the results when they get here. Thanks for the help guys!

[Structo]

Also, my .01 coupling cap from OD1 is much smaller than the .005 cap going form OD2 (they are both 6PS) I don't know why that is. Is my circuit correct? I think it is :-I Thanks for the input guys!

I use SBE 6PS 600v orange drops and my .005uF is smaller in physical size than the .01uF.

Although those schematics are ok, I think that most of the guys building the modern ODS amps follow #124 so that may be the reason you have differing values.
Hey, as long as you are happy with the tone, that's all that matters.

JJ tubes always seem a bit dark to me. If I had a real bright amp I would try them but in the several amps I have I may use one in the PI or D'lator but not in V1 or V2.
Right now I have a vintage Raytheon in V1 and V2 (Baldwin pulls) and an EHX in V3.
RCA Blackplate 6L6GC's for power.

I think it may be a combo of both the plate voltage, preamp tube bias and square area of the plate that changes tone between tubes.

Have you built a Dumbleator yet? They really do compliment the amps.

Talking about cap sizes, when I bought some F & T filter caps for my D'lator, the 30uF caps are bigger than the 47uF, both 500v.

[tjauernig]

That's a really nice looking build. As far as dialing it in, I know there's all sorts of advice floating out here, and some is really good. But, don't worry about voltages as much as the tone you hear. 10-20 volts on a preamp plate does not matter as much as you might think, unless your actual playing is that consistent. Case in point, Dogears played one of my amps at a NAMM show 2 years ago. It sounded great, it had the "chirp", the "bloom", the whole deal. The guys from Blackstone Cherry came in and the amp still sounded great. But the difference was that with those 2 guys, the amp was now a metal machine. I did not intend for it to do that, but it did when they played it. And, those guys have toured with them for the last 2 years. It still makes me laugh when I think of that. I've had other guys play my stuff, and it made me wonder if it was broken. It wasn't, it was just the way they play.

All that being said, adjust within acceptable parameters for the circuit. But use your ears, you'll hear it when it's right.

[dogears]

Who was that Las Vegas cat that was watching? I had fun in that nice soundproof room!

Case in point, Dogears played one of my amps at a NAMM show 2 years ago. It sounded great, it had the "chirp", the "bloom", the whole deal.

[Structo]

I think it just goes to show how versatile these amps can be.
And of course the old argument that tone is in the hands.

[talbany]

That's a really nice looking build. As far as dialing it in, I know there's all sorts of advice floating out here, and some is really good. But, don't worry about voltages as much as the tone you hear. 10-20 volts on a preamp plate does not matter as much as you might think, unless your actual playing is that consistent. Case in point, Dogears played one of my amps at a NAMM show 2 years ago. It sounded great, it had the "chirp", the "bloom", the whole deal. The guys from Blackstone Cherry came in and the amp still sounded great. But the difference was that with those 2 guys, the amp was now a metal machine. I did not intend for it to do that, but it did when they played it. And, those guys have toured with them for the last 2 years. It still makes me laugh when I think of that. I've had other guys play my stuff, and it made me wonder if it was broken. It wasn't, it was just the way they play.

All that being said, adjust within acceptable parameters for the circuit. But use your ears, you'll hear it when it's right.

Yeah.. I kinda see your point and kinda not.. Sure you can get a 10-12v swing with a tube change and how you set it up guitars and FINGERS are no doubt the X-Factor..
When I first finished my 70's amp voltages V1 in the 200 volt range.. I though I would play with the dropping string a bit and for grins drop it to 175-180 area 20v and that was it the missing link..Perfect..It's in the breakup..Maybe it was this amp or maybe just me but I noticed a big difference.... There you go someone else's opinion!! FWIW..

Tony