I have recently been checking out some pictures of Robbens amp settings and have noticed several things of interest
First are his in input Vol is set rather low usually around 4 or sometimes noon
2 and most strange is his Bass control is usually set around 7
This to me seems rather high for a high plate skyliner while using Humbucking Pups...
Thinking back I remember seeing his Bass control set almost at Max the last time I saw him play (@ Birchmere)
ON my 102 (Feedback City amp) w/ Dlator and while using my Less Paul (Bridge around 7K) the amp is rather boomey but I dont remember Robbens tone as being too bass heavy..
I wonder if his Bass control has been modified from the usual 500kA james config..
Just something I thought was a little strange on both accounts..
Tony
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Last edited by talbany on Fri May 17, 2013 7:58 pm, edited 1 time in total.
" The psychics on my bench is the same as Dumble'"
The louder you turn up an amp the more bass you get. Maybe in order to keep the preamp sounding full and lively with that slightly lower preamp volume setting (as you noted) he compensates by turning the bass up.
I always find the quieter I have an amp the more EQ I have to dial in ie. push the EQ knobs up higher.
Apparently, as measured the bass pot was 400KA, not 500KA. I've seen a bunch of nice looking vintage CTS pots with a 10% taper that measured really low, maybe his is one such specimen? And as for the Volume control, if that one has a 30%, that setting might not be so low after all.
Cheers,
Gil
talbany wrote:I have recently been checking out some pictures of Robbens amp settings and have noticed several things of interest
First are his in input Vol is set rather low usually around 4 or sometimes noon
2 and most strange is his Bass control is usually set around 7
This to me seems rather high for a high plate skyliner while using Humbucking Pups...
Thinking back I remember seeing his Bass control set almost at Max the last time I saw him play (@ Birchmere)
ON my 102 (Feedback City amp) w/ Dlator and while using my Less Paul (Bridge around 7K) the amp is rather boomey but I dont remember Robbens tone as being too bass heavy..
I wonder if his Bass control has been modified from the usual 500kA james config..
Just something I thought was a little strange on both accounts..
ayan wrote:Apparently, as measured the bass pot was 400KA, not 500KA. I've seen a bunch of nice looking vintage CTS pots with a 10% taper that measured really low, maybe his is one such specimen? And as for the Volume control, if that one has a 30%, that setting might not be so low after all.
Cheers,
Gil
talbany wrote:I have recently been checking out some pictures of Robbens amp settings and have noticed several things of interest
First are his in input Vol is set rather low usually around 4 or sometimes noon
2 and most strange is his Bass control is usually set around 7
This to me seems rather high for a high plate skyliner while using Humbucking Pups...
Thinking back I remember seeing his Bass control set almost at Max the last time I saw him play (@ Birchmere)
ON my 102 (Feedback City amp) w/ Dlator and while using my Less Paul (Bridge around 7K) the amp is rather boomey but I dont remember Robbens tone as being too bass heavy..
I wonder if his Bass control has been modified from the usual 500kA james config..
Just something I thought was a little strange on both accounts..
Tony
Gil
Thanks for that..I didn't know the Bass pot in 102 was 400k
My 102 has CTS both around 30% and with the Vol on 4 and the Bass set at 7 reads 192k (to ground) at the entrance to V1b (before the grid resistor) As I turn the bass control up it actually increases the resistance..
This is the number I wish I could see on 102 since he always seems to be able to get that harmonically rich breakup on the clean side with the input set fairly low...
The input vol being a bit out of tollerance I would expect but even with the bass pot at 400kA stll to me set at 7 would still be a bit bass heavy..
Maybe Robben would loan me the amp for some measurements..
That amp has something going on!!
Tony
" The psychics on my bench is the same as Dumble'"
ayan wrote:Apparently, as measured the bass pot was 400KA, not 500KA. I've seen a bunch of nice looking vintage CTS pots with a 10% taper that measured really low, maybe his is one such specimen? And as for the Volume control, if that one has a 30%, that setting might not be so low after all.
Do we have any way of knowing if the good folks who are measuring these amps' parts is doing so in-circuit or out of circuit? Seems to me measuring the bass pot in-circuit would most likely give false low reading.
If you look at the 102 schematics posted here, that's where the 400K for the bass pot is measured. I have no idea whether the measurement was done in circuit or not.
Cheers,
Gil
talbany wrote:
ayan wrote:Apparently, as measured the bass pot was 400KA, not 500KA. I've seen a bunch of nice looking vintage CTS pots with a 10% taper that measured really low, maybe his is one such specimen? And as for the Volume control, if that one has a 30%, that setting might not be so low after all.
Cheers,
Gil
talbany wrote:I have recently been checking out some pictures of Robbens amp settings and have noticed several things of interest
First are his in input Vol is set rather low usually around 4 or sometimes noon
2 and most strange is his Bass control is usually set around 7
This to me seems rather high for a high plate skyliner while using Humbucking Pups...
Thinking back I remember seeing his Bass control set almost at Max the last time I saw him play (@ Birchmere)
ON my 102 (Feedback City amp) w/ Dlator and while using my Less Paul (Bridge around 7K) the amp is rather boomey but I dont remember Robbens tone as being too bass heavy..
I wonder if his Bass control has been modified from the usual 500kA james config..
Just something I thought was a little strange on both accounts..
Tony
Gil
Thanks for that..I didn't know the Bass pot in 102 was 400k
My 102 has CTS both around 30% and with the Vol on 4 and the Bass set at 7 reads 192k (to ground) at the entrance to V1b (before the grid resistor) As I turn the bass control up it actually increases the resistance..
This is the number I wish I could see on 102 since he always seems to be able to get that harmonically rich breakup on the clean side with the input set fairly low...
The input vol being a bit out of tollerance I would expect but even with the bass pot at 400kA stll to me set at 7 would still be a bit bass heavy..
Maybe Robben would loan me the amp for some measurements..
That amp has something going on!!
Perhaps a combination of all the above:
30% Vol pot that's but reads 35%, very gainy 12ax7 in V1, K resistors 5% under, Plate resistors 5% over. Could easily add up to 10-20% more in gain.
As mentioned with bass pot, could be a little funky. I built an amp that had all the tork between 1-4 on the bass pot, thought the pot was lin swapped it for another 500k log, same result, checked wiring and components many times, swapped again and gave up. Put it down to that's how this circuit wants to work so be it.
Could be tubes as well. A friend scored some NOS Russian military 6L6s a few years ago, nice looking well built tubes, tried them in my amp and hated them, hardly any bass. All mids and highs lacking too much bottom end.
Add Speakers as well into the mix, some are darker some brighter.
Just my .02
