For non-availability reasons there is 1k5/22u at the cathode of the recovery. Bright at send is 550p/270p, bright at recovery is 270p/120p.
Voltages on the supply nodes (15k and 100k supply resistors) with an EH 12AX7 are around 260V and 360V.
The fourth pot replaces the 220k grid resistor at the recovery with variable 10k-220k (a severe case of GMS....gear modification syndrome I guess). At first tests with an EH 12AX7 at bedroom levels the increase in brightness when turning down to 10k is clearly noticeably but subtle. So a switch likely would be OK.
With the 200p cables from and to my 80s non-HRM style amp at bedroom level I actually prefered it with the brightness pot all up.
No tests at real levels so far......
Do you have any recommendations for the tube?
Peace,
Markus
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What's that relay function (bypass perhaps?) and same question for that extra pot...
Thanks
The relay completely bypasses the whole thing. Can be switched with a foot switch. Therefore the 5th jack.
The 4th pot was planned as some kind of tone control to fine tune the treble content of the D'lator. Gary mentioned in an old thread that the 220k can be lowered to increase the treble content of the D'lator.
The influence of the pot on the treble content is clearly weaker than for the bright switches.
Will have to wait for tests at resonable levels to hear whether the pot is really useful.
Mark I found with my D'lator that the cables to and from the loop were very critical to the brightness or lack of when using the loop.
I tried using a couple cheap cables I had laying around and it made the amp sound muffled.
I use two 6 inch pedal cables to and from the amp and loop.
I ordered some Gotham cable from Redco and made two 15ft cables with nice Neutrik plugs.
Dramatic difference in tone and now I don't have to use the bright switches.
So the pf/ft is very noticeable with the D'lator. If your amp already leans towards being dark you need low pf cable.
The cables I built are 70pf each according to my DVM.
I do however have my amp modded to the way Tony had posted so that the bright switch on the amp has three positions.
Down is off, middle is on and up is on in clean and off in OD.
I had to install a third relay to trip the bright cap off when OD is on.
Oh and by the way, to my ears different tubes did not change the tone much but what I did notice was the different voltages each tube would drop.
Try to pick a tube that will give you around 30 volts on the cathode of the cathode follower.
thanks a lot for sharing your observations
When I checked the frequency response of the D'lator itself and found that it is actually pretty flat "edit: with the grid resistor of the recovery stage at 10k" it came to my mind that the cables to and from the loop would probably influence the high end more than the loop itself. Glad you observed this in reality.
From my limited knowledge this also makes sense. The output impedance of the amp's send with an 1M master pot is pretty high, the output impedance of the D'lator itself with the 250k already lower. For the send of the D'lator it should be even lower since it is a cathode follower. Therefore the cable capacity should matter most from the amp to the D'lator.
Please correct me if I'm wrong.
Will check the voltage at the cathode's followers cathode now.....
Peace,
Markus
Last edited by markusw on Thu Apr 29, 2010 6:14 pm, edited 1 time in total.
For the send of the D'lator it should be even lower since it is a cathode follower. Therefore the cable capacity should matter most from the amp to the D'lator.
Please correct me if I'm wrong.
That is correct!!.. Although you still have some loading from the 250k pot..
Will check the voltage at the cathode's followers cathode now.....
Shoot for 30v
Tony
" The psychics on my bench is the same as Dumble'"
Alright
An EH 12AX7 measures 28,3V at the cathode of the follower and 240V at the anode of the recovery. A JJ ECC83S measures 29,7V and 229V,
a Holland Philips 12AX7 30,5V and 231V.
Since Tom mentioned that the tube itself doesn't seem to be that critical I probably will keep the Philips for something else.
What do you think?
Thanks Tony, will stay with the JJ.
According to http://www.tube-classics.de/TC/Tubes/Va ... /ECC83.htm the Philips should be from 1959 - 1962.
A friend of mine got a whole box of them from his father. He was so generous to give me a couple of them.
In V2 they sound fantastic btw. I also measured a couple of them in V1 (100k/100k plates). In contrast to new tubes nearly all of them seemed to be balanced regarding their plate voltages. Seems they knew how to make tubes at that time
Last edited by markusw on Fri Mar 26, 2010 10:47 pm, edited 1 time in total.
Hey good find.. Quite a few original Traynors came Phillips/Mullard loaded Pre and OPT 34's X-3's I believe.. I had a perfectly matched quad I pulled off a Traynor I bought.. Killer sounding set I loaded in a Non HRM that went to constantly touring act. I told him get a good flight case keep the amp in the buss'es hold not in the trailor.. 2 weeks later.. Hey Tony my amp is blowing fuses!!.. wasted that quad FLUSH!!... Good Luck!!
Tony
" The psychics on my bench is the same as Dumble'"
MMMmmmmm, vintage tubes. I like to find the best I can and use it in V1, then for V2 (OD) I like a bit higher gain which the later generation Chinese 12ax7's usually sound pretty good to me.
