Br777
Headphoneus Supremus
- Joined
- Feb 2, 2010
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Just want to say i owned this amp at one time and loved it. Glad to see its getting a "revival" so more people can experience its greatness
I have built with socketed caps. Wasn't really worth the trouble, as most of the interesting caps will need some creative lead work to get in the amp comfortably, making the sips hard to use with the previous designs spacing. Might be different with the new lead spacing.
Give it a try and let us know?
The Soniccaps are a slam dunk, but even the stock wimas perform admirably i'n this design.
At one end we have some reports of some IEM users hearing hiss & having little usable volume pot range, and at the other end reports of its e12 circuit tripping for very loud/heavy bass passages. For example, 96 dB sensitivity 32R & 250R DT880s receive good reports, where (stock 100R R18s) CTH driving 600R DT880s at loud/high levels begins to distort & if driven further can cause its e12 to trip (a good thing - its doing its job if clipping is present or LV supply wavers).
The R18 resistors were introduced early on in CTH development as a way to contour/shift its wide performance swath within the Bell curve discussed above. I believe we suggest R18 values from 0R -> 150R, with the default 100R being best with the majority of cans. However, if you wish to target the high-sensitivity/low-impedance end consider 150R, the low-sensitivity/high-impedance end consider shorting the positions.
Quote:
Thanks -- I will skip the SIPs for C4. I plan on shoe horning some Obligatto Film Cap 0.22uF / 630V from Parts Connexion as I'm also getting my tube socket from them. Since they are Canadian it should hopefully be easier / cheaper shipping then Sonic Gen II's (despite the slam dunk) for me.
The Ob's are BIG, it's not impossible, but I had to fly them on long leads.
Argh, I can't insert pictures!
> What's the deal with the heater currents with regards to 150mA/300mA? Does that mean you can safely run a given tube at both 12v and 6v?
The 9-pin mini tube spec for the CTH includes 3 heater-related pins; pins 4, 5 & 9. The usual/series heater voltage & draw (using pins 4 & 5) is what we consider here NOT a tube's parallel heater voltage & draw (its pin 4-> 9 & 5->9 parallel specs are ignored as CTH has no electrical connection for the heater centertap pin #9). So 12.6v (series) heated tubes (e.g. 12au7) use CTH's 12.6v position, 6.3v (series) heated tubes (e.g. 6922) its 6.3v position.
The max (series) heater draw we recommend for CTH is 600ma, unless a heatsink is fitted it LM2595 & its coils up-spec'd beyond the BoM spec 800ma rating.
> I'm using the RK27 pot for my volume control and every time I touch it I hear a buzz.
Since your pot is mounted to a plastic panel, you need to ground your pot, in CTH to its IG which = its SG. Easy on RK27 - you loosen one of its back screws & run a jumper from it to the IG pins/connection on the pot.
> Also, I do hear a slight hum/buzz with some headphones and some tubes. You can't hear it when music is playing. I was under the impression that the 470uF C3H would take care of this.
We believe the old heater "buzz" problem was solved in early 2009 with re-specing C3H to 330u, and we now raised this to 470u as an extra measure. We know your 1st build has had its problems & repairs, but maybe this is a case ground problem. You must assure your case is grounded, e.g. running a wire from SG to a contact screw in the case.
Bottom line is assure your pot & case are grounded to IG/SG and double-check they are using an ohmmeter (measuring to either RCA-in jack ground). This should solve it.