Here are the voltages of my new HRM. Do these seem in line?
V1 189.5, 197
V2 201.5, 203
V3 262, 261
Dumbleator 192, 293
6L6's
466V @ 45ma
The pics of the amp is in a thread titled started a ODS.
The pic below is the dumbleator I built using the torodial transformer and power supply configuration in the Hoffman preamp pedal. It was put in a 17x4x3 hammond box connected to a faceplate for rack mounting.
There is also a MP3 attached but I did it in 10 minutes and I accidentally turned the suck knob to high. I like the clean tone (I play in a funk band) but the OD is a little buzzy. The guitar is a Strat with Lindy Fralins. This is my main guiitar so I will have to tune the amp to it. Any suggestions?[/list]
You do not have the required permissions to view the files attached to this post.
Last edited by tonejunkie on Tue Dec 19, 2006 7:24 am, edited 1 time in total.
Good Start - Let the tweaking begin! First thing I would do is get the CL and OD stages about 10Volts higher and see what that does to the sound. If you're using the 150K resistor to simulate the FET try raising it to 200K that should give you the rise in plate voltage. If not you would have to mess with the dropping string or adjust the Cathode resistor value (not recommended on the first stage). 196 to 204 on CL1 seems to be the magic number IMHO.
Last edited by heisthl on Tue Dec 19, 2006 3:37 pm, edited 1 time in total.
I replaced the 150k fet simulator resistor with a 250k (200k brought me to 192 on CL1). This brought the voltages to:
202, 211, 220, 227, 315, 295
I thought the bias was ok but it did sound better when I brought it down to 40ma around 60% max dissipation.
I played the amp at sub bedroom level (wife is sleeping) but I think it did help some. I will play it in the afternoon at a good volume to see what I think.
Are the voltages in the dumbleator OK (1st post) and are the new voltages on the OD tube OK (seem high but I want some input). Thanks for the help guys. TJ
I would think the dumbleator is good - I think the ideal is 300 and 200 but the voltages you posted still give plenty of headroom. The change from 150k to 200k to 250k is not very linear according to your readings -what did 220K give you? Make sure to play for 30 minutes before checking voltages - set the volume on 0 before measuring. These amps sound better after 20 minutes or so - don't know why?
dogears wrote:I'd say the bias a way high. Try 36ma or so......
??? At 466V doesn't that work out to 70%? Should the bias be colder than that?
That is 21w pretty hot for a 30W tube and usually not needed but 70% is fine if you belive the rated max specs of 30W for a 6L6GC. 6L6 can be biased much colder and still not have crossover distortion, also if you are really using a 5881 I would say it is too hot
I am using svetlana 6L6GC for this amp I they are now biased at 40ma @ 462V. Also the new voltages after playing for an hour are:
202, 207, 216, 226, 311, 297
I know I want to finalize the voltages to the correct range before we begin tweaking. What do think.
I am again happy with the clean tone but the overdrive is a little harsh. I play lightly anyway but there is a harshness or brittleness to the notebloom when I get to about a medium light pick attack. I would like to smooth out the OD. Maybee I'm getting ahead of myself.
The settings I am currently using are:
Vol 2
OD 10
Level 3
Master 1
Presence 11
HRM
Bass 11
Mid 12
Treb 10
Also the values I am using are exactly what is on Normsters HRM with loop layout but with the loop in a external dubleator format. I will post a clip on friday.
Also, what are your HRM settings? Too much mids causes harshness. Why don't you post your HRM settings here. Maybe someone can volunteer their settings. I'll say that if you have the controls as high as you have them, assuming the numbers you posted are settings, I don't doubt the tone sucks. Try less than 1/2 on all settings.
Try raising that first volume (Dumble called it Gain I think) to about 11:00. Adjust the trim so that these settings give you a nice smooth breakup, not a hi-gain type of sound.
Not to hijack your thread but....I've been playing with the scope a bit. On the OD side OD1 only distorts the top half of the since wave, then of course it inverts it. OD2 distorts the top half, which is now the undistorted side after the sine is inverted.
I think the goal of the trim and gain settings should be to distort that sine wave evenly on both sides. You can then control the amount of overdrive with the first gain control. I've noticed that if you distort the 2 sides unevenly you'll end up with either a pretty muddy tone or a pretty harsh tone. These amps really seem to benefit from symmetry where Marshall style amps seem to only distort 1/2 of the sine wave.
I like the clean tone (I play in a funk band) but the OD is a little buzzy. The guitar is a Strat with Lindy Fralins. This is my main guiitar so I will have to tune the amp to it. Any suggestions?[/list]
