Dumbleator Voltages?

[Charlie Wilson]

Sorry, I know this has been discussed many times in the past but a couple questions/observations. I just finished Dumbleator #3 and here are my voltages:
Pin 1-- 243.3 vdc
Pin 3--24.32 vdc
Pin 6--213.2 vdc
So my voltages are a bit on the low side. I have been told that the 30vdv on pin 3 is the most important target voltage but it seems to me my plates should be higher. If I tack a 10k resistor across the 15k B+ dropping resistor I can get fairly close to the target voltages. Is this what guys are doing? Has anyone built a Dumbleator using Brandon's transformers(I know that was a long time ago) or a Heyboer R2-C reproduction and hit the schematic voltages? I say this because I noticed something on the box of an original Triad R2-C. The primary is 115 vac. At a modern 120 vac line voltage, this puts the unloaded secondary at about 140 vac. Heyboer must have wound my transformer(and the original Brandon ones) with a 120 vac primary and 135 vac secondary. Actually I know this because at 115vac I get 130 vac. With the voltage doubler, this would account for being about 10 v low. I guess I need to call Heyboer and tweek the specs of my transformer.
CW

[talbany]

CW
I usually use the 1st dropper (15K) tweak my plates. Then adjust the cathode gnd resistor (27K) to get me around 27-32 V.Your going to get some swing there by swapping out different tubes. I shoot for exactly 30V and give myself +-5% in either direction.
BTW.Just checked my R2-C was a little high so I had to use a 22K there to get me 260 on the plates..If this is a problem Brandon is a sweetheart just give him a shout out I am sure he would get back but am not sure if there is anything else you can do to tweak that X-formers voltages
Hope this helps!

Tony

[Charlie Wilson]

Well I called Heyboer and my suspicions were correct. Their RC-2 is 135vac at 120vac. So the voltages will always be low with a 15k dropping resistors. Tony, the only reason I mentioned Brandon was originally when I had Heyboer make me the transformer, I asked them to make the same one they made for Brandon. So I lowered my dropping resistor down to 4K7 and now have 255vdc on pin 1. I put a 220k and 36k in parallel for the cathode follower resistor I have 29.5Vdc on pin 3. Pin 6 is still a little low at 216vdc but the Loop sounds great. It really makes a difference getting the voltages were they should be. I believe you that Brandon is a great guy, but next time I think I just have to give Heyboer the proper specs before they make the transformer.
CW

[talbany]

Ahh OK.. I just checked and my RC-2 primary is spec @120 pri. I kind of had to fight that one to get it lower.It is the best sounding D-lator I have built to date using the voltages you just posted.Plenty of headroom loud and proud with lots of 2nd order.BTW. This one is loaded with the older 220P Di-Films (Paper-Mylar) to my ears the best sounding cap to ever grace a Dumble circuit
Oh. Did you end up using the CTS's or did you go with Alpha's
Have fun with your new loop

Tony

[erwin_ve]

Thanks CW and Tony, I got curious on the voltages in my Dlators (got 2).
My percolator (Tony!)1 had old style Cathode Follower (1k5 and 10k) with 15,5v on pin3.
My dumblelator clone had the 1k8 and 27k with 33v on pin3. I change the latter to 24k and has 30v on pin 3 now.
I made a reamping track and recorded both Dlators using my amp and condenser mic.
Differences are very subtle keeping in mind that both Dlators have different tubes.
Overall the old style has more compression going on and a little more low end.
The other one is a little bit more open on pick attack and harmonics.

[talbany]

Erwin
Thanks for posting your results!. I hear the same thing!. The results are subtle but are there. Btw I doubt anyone would hear +-5V in either direction. Maybe if you are Eric Johnson

Tony