I am glad you brought this thread back up Rudolf. I now have time to work on my projects and I am making two chassis for this amp. One for the power supply and one for the signal side.
I have the room and like the looks of aluminum oil can caps. Does anyone know if the 6800uf caps can be found in oil cans??? I just like the looks of those sticking up out of the chassis.
I have the room and like the looks of aluminum oil can caps. Does anyone know if the 6800uf caps can be found in oil cans??? I just like the looks of those sticking up out of the chassis.
Hi,
I also would like to begin to build this beautiful project of Tim ... maybe updated with 4 tubes per channel.
I was doing some calculations on the fly, and I think, just like that, the power transformers are slightly undersized. I have pretty much a given (if i am not wrong) that the power supply is common to both channels. Especially in the section of the heaters of 6C33C.
What do you think about that?
Thank you,
Michele
I also would like to begin to build this beautiful project of Tim ... maybe updated with 4 tubes per channel.
I was doing some calculations on the fly, and I think, just like that, the power transformers are slightly undersized. I have pretty much a given (if i am not wrong) that the power supply is common to both channels. Especially in the section of the heaters of 6C33C.
What do you think about that?
Thank you,
Michele
Attachments
Hi,
I have built 2 amps using the Tim mellow design. One using 6C33c's and the other 6C41's, both written up on this site. Both have woked excellently for the past 3 years with no problems - until now! I,m writing this as my experience may be of some use to others should their Amp. have similar problems in the future. The symptom was that one of the 6C41's would overheat - glowing red, obviously drawing too much current - this had the effect of severely loading the positive 150v rail, reducing it to around 45v. The negative rail rose to around 255v. First thoughts were that the glowing valve was the cause of the fault, but it proved not to be. The problem with fault finding on this design is that because it uses direct coupling between stages, normal methods are difficult to use due to only having a short time to measure votages before damage occurs (or fuses blow!) Isolating a suspected stage is therefore difficult. After carefully 'cold' checking all likely (high value resistances) and finding nothing wrong, the EF86 driver's were changed - this, thankfully, cured the problem. Sometimes a substitution pay's off!
Regards,
David.
I have built 2 amps using the Tim mellow design. One using 6C33c's and the other 6C41's, both written up on this site. Both have woked excellently for the past 3 years with no problems - until now! I,m writing this as my experience may be of some use to others should their Amp. have similar problems in the future. The symptom was that one of the 6C41's would overheat - glowing red, obviously drawing too much current - this had the effect of severely loading the positive 150v rail, reducing it to around 45v. The negative rail rose to around 255v. First thoughts were that the glowing valve was the cause of the fault, but it proved not to be. The problem with fault finding on this design is that because it uses direct coupling between stages, normal methods are difficult to use due to only having a short time to measure votages before damage occurs (or fuses blow!) Isolating a suspected stage is therefore difficult. After carefully 'cold' checking all likely (high value resistances) and finding nothing wrong, the EF86 driver's were changed - this, thankfully, cured the problem. Sometimes a substitution pay's off!
Regards,
David.
It is indeed a weak point in the otherwise excellent design, I think, that if ever something goes wrong with one of the EF86 drivers, causing it to lose conduction, then the 100K resistor from grid to anode on the corresponding 6C33C output tube will drive it into heavy conduction. I couldn't see any way to build in a safeguard against this, without radically changing the entire circuit, so I've just made myself stop worrying about it...until now.
Chris
Hi Chris, As I see it, the only downside to an exceptionally well thought out (and very noval design!) I still never leave the room without switching off though!
ATB,
David.
(and to Flanagan, the close tolerance of the 4.7M resistors is critical, get the best possible for added long term stability)
ATB,
David.
(and to Flanagan, the close tolerance of the 4.7M resistors is critical, get the best possible for added long term stability)
Hi, probably a am a little late on that chat, but I have just started a new project OTL-ESL 63, taking in account Tim's otl design as it is and my ESL'63. My intention is to swich the primary trafo of the 63 from 8 ohms(16+16 paralel is original) to 32 ohns, puting the two coils in series. More than that, as there is room on the input trafo I think to duplicate the primary and all together to go to 64 ohms. Am I crazy? (now I am gatherin the components, including 4 trafo from an desasenbled esl 63 to be modified. what do you think about?
Hi,
thanks for the advice, for shure I' ll try the easyest way first (916+16=32 ohms)
Do you think I shall make any adjustments to bias or else passing from 8 to 32 ohms ?
By the way there are no news about "desperateaudio" or the ather guy regarding their OTL project, any impresions, anything at all? Are they still listening this one or abandoned...?
thanks for the advice, for shure I' ll try the easyest way first (916+16=32 ohms)
Do you think I shall make any adjustments to bias or else passing from 8 to 32 ohms ?
By the way there are no news about "desperateaudio" or the ather guy regarding their OTL project, any impresions, anything at all? Are they still listening this one or abandoned...?
I went back and found I was the eleventh to post, and it brought home to me that I built mine more than 5 years ago; I had been thinking it was "just a couple of years ago." Tempus fugit...
Anyway, I have been using mine on an almost daily basis since I built it, and it has given me essentially no trouble in all that time. I am very satisfied with its performance in all respects.
Chris