On a side note:
I know I am involved in a private joke, and I have no problem helping out with that, but I sincerely hope I am ok asking about Ceriatone products.
No Worries.. Thanks for playing along
Glad I could help and good luck with the amp!!
Tony
" The psychics on my bench is the same as Dumble'"
rogb wrote:Anyone here fiddled with the PI of a AB763 Deluxe type build and BM'd the PI?
I was thinking to have a go on mine next week if I have the parts in stock?
Yes, that's basically an Ultraphonix Showman, AB763 front end with a BM PI.
One thing on these types of changes, don't expect your amp to "sound" any different when you first turn it on, it won't. It will "feel" different and it may take you a while to get used to it and understand what the changes are really doing to the amp. Take your time and really get to the know the amp before you make the changes, and of course afterwards. All of the sonic qualities that Tony mentions he can hear come from many years of tuning, tweaking and listening to develop his ear. It took me quite a while before I could hear the differences and relate them back to circuit changes. Some guys can probably pick things up a lot quicker, but if you don't hear any change right away, don't just give up on it, live with it for a while. I mention this here because these PI changes fall into that category, very subtle especially at lower volumes.
Great I will give it a try Bill. thanks. I have been Jonesing for a UP type build for some time now.
Any other tips?
I have Mid pots on this build already, and I think I know the resistor changes to get the BM configuration.
I have the channels separated on this so the Vibrato is stock (and I love it) and the Normal channel is the one I do my experimental modding on.
I think (and hope) it will take the PI changes well.
Maybe go to 12AX7 instead of AT as the PI tube?
I can relate to that Bill. I didn't realize some of the changes I did to my 5f6a was in the direction of the UOP until a couple of good TAG members clued me in.
I really like what I hear, so smooth, definition and just plain more enjoyable to play and listen to. I still haven't done the preamp changes that match the UOP my changes were close but not quite there, but since I didn't know what changes to make, I feel I did pretty darn good about how close I did come, considering knowing nothing about UOP.
wjdunham wrote:
One thing on these types of changes, don't expect your amp to "sound" any different when you first turn it on, it won't. It will "feel" different and it may take you a while to get used to it and understand what the changes are really doing to the amp. Take your time and really get to the know the amp before you make the changes, and of course afterwards. All of the sonic qualities that Tony mentions he can hear come from many years of tuning, tweaking and listening to develop his ear. It took me quite a while before I could hear the differences and relate them back to circuit changes. Some guys can probably pick things up a lot quicker, but if you don't hear any change right away, don't just give up on it, live with it for a while. I mention this here because these PI changes fall into that category, very subtle especially at lower volumes.
"Give it time to grow on you". Once again some solid insight from you Bill.
I'm glad to hear that the BM mod won't be a drastic change in sound, as I am just looking to tweak a little bit to get to the sound that is in my head. I am also intrigued by what the change in "feel" might be like as that connection with my amp is what makes a great gig. This seems to echo what Tony said about "touch sensitivity" but after your post I feel less apprehensive as you have stated that the tone diff will be subtle. This is my fav amp that I have ever owned as far as the "user experience", with a blonde fender vibro-king at stage volume being the second place.
On a side note:
I am starting to realize that some of you guys are actually amp manufacturers and quite well known and reputable as well. I would like to let you guys know that give of your time and knowledge so freely, I am truly grateful.
The fact that you guys enjoy what you do so much that you are here to share knowledge and create that enjoyable experience for others is inspirational.
I think the 0.1 to 0.02u coupling cap change is by far the biggest difference. The effects of the resistor changes in the tail will be largely obscured by the PI trimmer adjustment, and the 47p across the plates will only affect the very high frequencies.
martin manning wrote:I think the 0.1 to 0.02u coupling cap change is by far the biggest difference. The effects of the resistor changes in the tail will be largely obscured by the PI trimmer adjustment, and the 47p across the plates will only affect the very high frequencies.
Ok, easy enough to try the caps out and see. Thanks Martin.
rogb wrote:Great I will give it a try Bill. thanks. I have been Jonesing for a UP type build for some time now.
Any other tips?
I have Mid pots on this build already, and I think I know the resistor changes to get the BM configuration.
I have the channels separated on this so the Vibrato is stock (and I love it) and the Normal channel is the one I do my experimental modding on.
I think (and hope) it will take the PI changes well.
Maybe go to 12AX7 instead of AT as the PI tube?
I should have mentioned this - most definitely switch the PI to a 12AX7, another thing the real UP's all have. The extra gain is essential for the ultra rich harmonic content that gets generated by the PI in this configuration. I really like the long plate tubes here, JJ ECC803 are what I use in all the amps for the Phase Inverter. Don't like them as much in the preamp, but work well in the PI, just a bit smoother IMO.
Make sure to scope all your coupling caps and orient them appropriately (lots of info here on the forum about that). Use 470K mix resistors in stead of 220K, adds just a bit more HF rolloff which I feel helps.
One of my favorite configurations these days is a 25W 2x6V6 with a BM PI and a Classic tone stack (.05 mid cap, 100K slope) and a 300pF or 250pF treble cap. The 6V6 power amp with the BM PI is a blues machine
rogb wrote:Great I will give it a try Bill. thanks. I have been Jonesing for a UP type build for some time now.
Any other tips?
I have Mid pots on this build already, and I think I know the resistor changes to get the BM configuration.
I have the channels separated on this so the Vibrato is stock (and I love it) and the Normal channel is the one I do my experimental modding on.
I think (and hope) it will take the PI changes well.
Maybe go to 12AX7 instead of AT as the PI tube?
I should have mentioned this - most definitely switch the PI to a 12AX7, another thing the real UP's all have. The extra gain is essential for the ultra rich harmonic content that gets generated by the PI in this configuration. I really like the long plate tubes here, JJ ECC803 are what I use in all the amps for the Phase Inverter. Don't like them as much in the preamp, but work well in the PI, just a bit smoother IMO.
Make sure to scope all your coupling caps and orient them appropriately (lots of info here on the forum about that). Use 470K mix resistors in stead of 220K, adds just a bit more HF rolloff which I feel helps.
One of my favorite configurations these days is a 25W 2x6V6 with a BM PI and a Classic tone stack (.05 mid cap, 100K slope) and a 300pF or 250pF treble cap. The 6V6 power amp with the BM PI is a blues machine
Thanks Bill, that is really helpful. I am halfway there as the Deluxe is configured in this way already. The 220K you mentioned are the channel coupling mixers, right?
The Normal channel of this amp has switchable LNFB and Deep too. The amp has switchable NFB as well. PPIMV too which is one of the most useful mods for tailoring your overall levels to a room.
I have a bunch of tubes, a few LP 12AX7s, I think I have a JJ803. I like to use a balanced Sovtex LPS sometimes.
I have been trying to gather information on the UP for a while now.
I wouldn't have believed changing a few parts could transform an amp like that!
Single notes feedback at will as do chords, but you can clean up with a turn on the volume pot.
It really has got that UP feel now, if you crank it with the 339, it's well into Marshall/dimed Tweed territory.
With the Strat, it definitely has an EJ vibe going.
I haven't even tried it with delay and reverb yet.
Amazing!
The Vib channel has more gain now, as you might expect with all the PI changes, but a touch on the guitar volume gets it really clean again.
Very versatile with an ABY box changing channels.
