sachu
Headphoneus Supremus
- Joined
- Oct 29, 2006
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I just ordered a coupleof the hammonds that were on the BOM. Should do fine IMO.
The board is designed for that..so figured might as well. The two hammonds work out a hair cheaper than a single toroid. And i think i'll take a hammond over an Antek any day.
Yes, it is reasonable. But, I haven't got a clue if you will like the amp under those conditions.
To get there with R13/R14 at 10k you need R11 at 3k9. Then my guess is that C2/C3 should be increased to 33p or even 47p to keep the amp stable.
There is no good answer I'm afraid because it will just be a matter of degree. It may also be that you will not notice high NFB or even like it better. I just don't know.
Generally, with my amps I try to use minimum NFB possible for the given design because this, especially in hybrids, tends to let the tube's sound come through. Too much NFB seems to wash it out.
But I must admit that I haven't personally done a systematic set of listening tests with socketed resistors to create a progression of SQ changes that can be mapped against resistor changes.
Your resistor combination won't require cap changes.
Let's talk DC offset at power on.
I have been measuring it whenever I turn the amp on as well as doing some extra power cycles to get a better idea of how it behaves.
In general, most of the time it spikes somewhere between 1.25V and 1.5V. I have gotten one or two samples as high as 1.7V and *might* have seen as high as 1.9V, but, that might have been operator error, so, I am throwing it out. Like I said, most of the time it is between 1.25 and 1.5V. As for settling time, the amp is in double digit millivolt readings within 3 to 5 seconds upon power on. I would say offset is within single millivolt range in well under ten seconds.
So, tough call on the need for the epsilon 12 circuit. One could always double switch the transformers (separate switches for heater and rail power supplies as mentioned in earlier posts) or just wait a minute before plugging in the phones. I am probably going to build a couple of the epsilon 12 boards and use them just to be safe (and because I kind of want to build them).
Good data. I don't know if the settling time would actually improve if the tube was hot. This would depend on a number of factors in the way the rails come up, what charge is left in big capacitors, etc.
This in itself would be an interesting experiment. For anyone with lots of spare time.