[regal]

Quote:

Originally Posted by AffeX /img/forum/go_quote.gif . In my opinion AMB does this part slightly better documenting builds on his website, and maybe avoiding the same 'stupid' questions over and over in here. .

AMB has a store and sells his amp boards, Alex comes up with designs and they are so downright good that folks make them work. The heaters aren't any more complicated than any triode amp. Just use a tread or two with a case mounted heatsink .

 

[AffeX]

@regal: Yeah, I recon the difference between the two. You really don't need to defend Alex, as I don't intend to attack him cause I have the deepest respect for his work and his contribution to this community - all services free of charge.
But having 'someone' to sum up all the valuable info would still be great, but of course if I only had the knowledge I could do it myself.

To someone like me, that has not had any previous experience with tubes and triode amps, this is just new stuff. I have found myself reading a whole lot of pages here, without really finding the answers I needed to plan my own build or maybe just failing to see it among all other info and build pics.

 

[regal]

Just study Pmillets DC heater page and adapt a tread (tangent website) to it. Makes perfect low cost DC heaters, use a case mounted heatsink. Use the Hammond 8.5V 2A transformer from Digikey. Wire the heaters in parallel.

 

[dBel84]

Quote:

Originally Posted by AffeX /img/forum/go_quote.gif But having 'someone' to sum up all the valuable info would still be great, but of course if I only had the knowledge I could do it myself.

Have you read the info on his website? If you have and it still doesn't make sense then I would recommend that you take a step back and rethink your plan. This amp might not be the best to build "blind" ; either do more reading so that you know what you are doing or find someone locally to help you.

..dB

 

[ujamerstand]

A quick question from the curious, a protection circuit such as the epsilon12 is recommended to zero the DC offset at start up; to change the start up delay to the amount of time that is similar in Millett hybrids, one could simply change the values of R11 and C7 to values to let's say, 1M ohms and 470uF? Should C6 be changed as well?

 

[regal]

Quote:

Originally Posted by dBel84 /img/forum/go_quote.gif Have you read the info on his website? If you have and it still doesn't make sense then I would recommend that you take a step back and rethink your plan. This amp might not be the best to build "blind" ; either do more reading so that you know what you are doing or find someone locally to help you. ..dB

I agree with dB here, you don't want to end up with a fustrating mess. Start with the SOHAII, its pretty easy if you can understand the heatsink mounting/isolation concept.

 

[AffeX]

@regal and dBel84
I see what you mean and I appreciate your concern. I can see that EHHA might not be as much a beginners build as the SOHA, but I'm determined on the EHHA, and I'll just have to read more and investigate further until I know what I'm dealing with. But I thank you both for help and hints and hope you will be just as helpful further on.
I also appreciate dBel84's view on choice of tubes, as I almost had the impression from this thread, that 6H30dp would be the only tube worth listening to and prices on these tubes almost put me off. Now I go for 100% standard build as provided in the kits from Jeff Rossel. And to be honest this has made it all a little simpler.

 

[les_garten]

Quote:

Originally Posted by dBel84 /img/forum/go_quote.gif Tube choices:: I have Sachu's EHHA on loan at the moment and I couldn't understand why it sounded lifeless. On a whim I pulled out the Russian 6H30 supertubes and replaced them with a set of amperex 6GM8's - a night and day transformation. I know many folk have reported fantastic things with the 6H30, but my personal experience has not been a positive one with these tubes in this amp. With the 6GM8s the amp shines, has great levels of microdetail and all the slam I could ever want. I am suggesting that new builders keep this in mind and recommend a fair try of the 6GM8 for which this amp was designed. The 6H30 are not only significantly more expensive but need high current heater supplies too. ( 6GM8's are however becoming more pricey themselves. ) ..dB

Hey!
Was there anything positive with the 6H30's?

 

[dBel84]

They are moar SEXY ..dB

 

[ujamerstand]

Quote:

Originally Posted by ujamerstand /img/forum/go_quote.gif A quick question from the curious, a protection circuit such as the epsilon12 is recommended to zero the DC offset at start up; to change the start up delay to the amount of time that is similar in Millett hybrids, one could simply change the values of R11 and C7 to values to let's say, 1M ohms and 470uF? Should C6 be changed as well?

Any takers? How did you guys implement your delays?

 

[AffeX]

Can't guide you there, ujamerstand.
I'm planning to implement epsilon12 as is - no tweaks.

 

[AffeX]

I'm planning this NT-LN 250.30-6 (250VA/2x30v/2x6V) shielded audio torroid from THEL for my balanced EHHA build.
My idea is to use 2x30V as is for the s22 psu, and from same torroid connect the 2x6V in series to provide 12V for this power regulator a dual LT1063 power regulator, suggested by Ferrari for powering tube heaters. I will connect the two sides of this power regulator in parallel to the 12V, and set output to 6,3V.

Any comments on this would be most welcome.
In particular I'd like to know, if it affects sound quality to pull both amp power and heater power from same torroid?

 

[ujamerstand]

I think if you want to use the epsilon12 circuit you must use the values in modified versions of it. Such as the millett minimax. The higher values in R11 (1M) and C7 (470uF) helps to lengthen the delay at startup to around 47 seconds. The default delay time is apparently three seconds, so your headphones would still see the much of the DC offset after the delay (remember the tubes needs 30 seconds or so to heat up.) And I found out that apparently smaller values at C6 (47uF) helps to get the mute function at shutdown faster; So I'm using those values instead.

As for the trafos, I'm thinking along the same line as you are, using a 15V trafos for the heaters, and down regulate it with DC regulators. I don't know if that's going to affect the sound, you might want to try out different configuration to see which one is best.

 

[dBel84]

Quote:

Originally Posted by ujamerstand /img/forum/go_quote.gif A quick question from the curious, a protection circuit such as the epsilon12 is recommended to zero the DC offset at start up; to change the start up delay to the amount of time that is similar in Millett hybrids, one could simply change the values of R11 and C7 to values to let's say, 1M ohms and 470uF? Should C6 be changed as well? .... Any takers? How did you guys implement your delays?

Well there is a fundamental misunderstanding of what the e12 does in this instance. The DC offset is zeroed by the active EHHA circuitry. The e12 merely acts to monitor this offset and switches the output if the offset is greater than 60mV iirc. Hence at power up and shut down the transients are larger and thus the e12 will protect the headphones in these circumstances. If for some reason the amp fails, the offset will ramp up and the e12 will once again protect the headphones.

The Millett Max, minimax etc do not implement a true e12 circuit in the that it does not "sense" the output for dc offset , it is more of a timer for start up and shut down. The questions you ask are not relevant if you use AMB's e12 .

..dB

 

[AffeX]

Quote:

Originally Posted by ujamerstand /img/forum/go_quote.gif I think if you want to use the epsilon12 circuit you must use the values in modified versions of it. Such as the millett minimax. The higher values in R11 (1M) and C7 (470uF) helps to lengthen the delay at startup to around 47 seconds. The default delay time is apparently three seconds, so your headphones would still see the much of the DC offset after the delay (remember the tubes needs 30 seconds or so to heat up.) And I found out that apparently smaller values at C6 (47uF) helps to get the mute function at shutdown faster; So I'm using those values instead.

I see it this way: epsilon12 is not a delay to allow tubes to preheat, but as smeggy just explained it, just to protect headphones for a short period of time after the amp is turned on.
So first I turn on main power for the tube heater psu. Then either manually or after a timed delay of 30-60 seconds I turn on s22 and as the epsilon12 is powered from the 30V main rails like the amp, the epsilon turns on at the same moment protecting the headphones with the 3 seconds delay.
For timed startup delay, have a look at this delay as mentioned earlier in his thread.