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A Very Compact Hybrid Amp - Page 104

post #1546 of 2213
what value of output resistor are you guys using for grados?
post #1547 of 2213
Quote:
Originally Posted by keyid View Post
what value of output resistor are you guys using for grados?
No grados here anymore, but I've settled on 100R R18s... Think some are up to 150R or so. Of course this depends on the cans used, source driving level/db and mu/gain of the tube(s) used. E.g. 1/4 vol for 8416 = about 1/3 vol for the 12au7 I pulled this morning, so 8416's mu/gain must be higher...
post #1548 of 2213
100Rs here too - I'll double check next time I get this case open.
post #1549 of 2213
what resistors do you guys recommend for R18s if someone plans to use the amp with an AKG K701. I don't have the K701 to test out different ressitors..appreciate any input on this.
post #1550 of 2213
100R works great for me with the k701s. I still don't get the knob to 12 o'clock, even with a very quiet source.

Seems like 100R is just a good all around choice. Works very well for my rs-1, k701, hd650, and gs-1000i.

With 100R the amp still seems to have more gain than would ever be necessary for any of the above phones, but increasing the output resistance over 100R probably isn't a great idea performance-wise.

Also, 3 flavors of CTH
post #1551 of 2213
This is really an interesting amp, will most likely be my first tube build, followed by Bijou or EHHA. Thanks for all the info
post #1552 of 2213
I tried alot of resistor values from none to 150 using kwame and also like 100 best with senns, but for my new grados I hope to get end of the month im thinking of lowering them. Yes im also itching to build another amp either Bijou, Soha2, EHHA or b22 so many choices.
post #1553 of 2213
Quote:
Originally Posted by cfcubed View Post
BTW Bill & I may soon have something more exciting to replace your fuse holder with We'll see...
hmmm... is it something to do with R3H ?
post #1554 of 2213
Quote:
Originally Posted by rds View Post
hmmm... is it something to do with R3H ?
Oui. And as Bill said if it comes about it'll be in the Tweaks thread...
post #1555 of 2213

Need help

Hi gent,

As you can see, I'm newest on Head-Fi
Well, I just finished my CTH, and it worked at frist time. I can't give at this moment a serious appreciation about the sound, cause I have't had time to taste others tubes than the one from wiatrob (PS thank for the Caps). It just sound amazing.

However I've a little trouble concerning my PSU. As it was very hard to find a 220V/24VAC wallwart in Europe I'm using a 25VA/24V toroidal tranformer cased on a same little BoM case with a troggle switch. But when I switch off the power, I have a sorte of "CLOCK" on the can. I"ll appreciate your help to avoid it.

Thank's
post #1556 of 2213
Quote:
Originally Posted by Hawdah View Post
. But when I switch off the power, I have a sorte of "CLOCK" on the can. I"ll appreciate your help to avoid it.
A pretty good, short click in the phones at power-off is normal for this design and nothing to worry about.

As for most amps w/tubes in them, a pulse happens at power-off & you are hearing the very start of that before the CTH's e12 kicks & releases the relay. I think I measured something like 100mv at the output for a fraction of a second when this happens (not enough to damage headphones).
This is far less voltage & for much shorter duration than many kinds of headamps that do not have the protection the e12 provides.
I just take the phones off my head just prior to power-off.
post #1557 of 2213
Quote:
Originally Posted by cfcubed View Post
A pretty good, short click in the phones at power-off is normal for this design and nothing to worry about.

(not enough to damage headphones).

That's exactly what I wanted to hear.

Many thanks
post #1558 of 2213
OK it is finally time. Looks like a rainy weekend, it's father's day, and my new solder station arrived last night, all the signs that point to me not having to do any yard work, etc. and being able to spend a little me time. I am going to build the CTH kit that has been calling me for a few weeks now. I am very excited to say the least. I will be sure to post my progress.

Also, I will need the cap that was changed a few weeks back, if anyone has a spare I would be happy to pay, it would help me avoid a Mouser order that I know I can't afford!
post #1559 of 2213
You can try a local electronics shop and/or a surplus shop. Single caps are pretty cheap.
post #1560 of 2213
Quote:
Originally Posted by holland View Post
You can try a local electronics shop and/or a surplus shop. Single caps are pretty cheap.
Only thing local to me is Rat Shack...
Thanks, though, I think I have one on the hook.
For me Mouser is kinda like those warehouse stores, you can save money by shopping there but it always cost more cause you can't help buying more stuff!
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