[sharkz]

Does anyone have any opinions of a CTH with Grados? I have read nothing but good things about these amps with Fostexes, but I listen to Grados a good amount too and I am wondering if there is any synergy there as well?

 

[schwallman]

 
Quote:

Does anyone currently have a finished CTH for sale? Looking to pick one up now to power my Grados and Fostexes. Please PM me if you are willing to sell one. Thanks.

 I have a pair of 325s that sing nicely with the CTH.

 

[sharkz]

I am admittedly not the most knowledgeable in electronics, so can anyone tell me if this amp has any DC filtering caps in the input? I will be running a DAC where the DC coupling caps have been bypassed and I want to make sure I won't be passing (or amplifying) and of the DC signal through to my headphones.
 
Sorry if this is a stupid question.

 

[cfcubed]

CTH does not have input blocking caps: http://www.cavalliaudio.com/diy/cth/main.php?page=schematics/ipschematic
But the design prevents harmful DC offset from making it from CTH input through to its output (headphones) due to its interstage C4 caps & integrated/modded e12: http://www.amb.org/audio/epsilon12/
 
However it is advisable to check the output of source devices for DC in any event as it could/would cause troubles down the line.  A symptom of possible DC at input for CTH could be temperamental e12 relay latch/lock.  One CTH owner had this & we tracked it down to DC on the CTH's input from a CD transport connected to it.

 

[sharkz]

Thanks for the information cfcubed. I actually took delivery of one of your built CTH's yesterday. I am loving it with my modded Fostexes so far.

 

[blaken]

I am almost done with my original CTH. It has been shelved for almost 2 years due to moving and a new baby. I was hoping someone had an idea for a replacement multi colored LED for under the tube. I am red/green color blind so the provided one wont work. I haven't been able to find a red/blue that fits or is the right voltage. Another option is red/yellow. Green/Yellow wouldn't work for me.

My other option is to mount two very small LEDs on the front panel and just know that the top one is 12v and the bottom is 6v but I would still like one under the tube. Is there somewhere I could tap into for constant power for an LED?

Sorry I have never worked on anything near this complicated and don't want to mess it up.

 

[cfcubed]

I guess if you cannot find a dual LED with the colors you need you may need to go that 2-LED-in-front-panel route.  You could use 2 different color LEDs that you can differentiate and/or that stacked upper (green?/latched) - lower (red?/not latched) arrangement. 
Based on CTH e12 lights here: http://www.cavalliaudio.com/diy/cth/main.php?page=schematics/e12schematic
 
But you know the above & this still leaves out the tube LED you desire.  LEDs like about 5V IIRC & if you'd like to avoid loading one side of the rail splitter & not the other you could wire in an appropriate LED + resistor to each (- / virt gnd, virt gnd / +) but you'd have to locate PCB spots to tack in feed wires & we all know this board is tight.   I'd be tempted to try wiring the extra tube LED in parallel w/the green/latched LED & see what happens.  It may disturb the balance of the CTH e12 LED circuit, e.g. you may need play around with its resistor values or BC327 for BC560 or something. 
If its not quick n easy I'd skip the tube LED, turn down the lights & enjoy the heater glow  And the sound.  Assuming all is working of course

 

[Tribbs]

I to have the Grado 325s and can wield a soldering iron.
I am hoping to find a CTH printed circuit board.
 
If anyone has a spare CTH PCB laying around please contact me.
 
Unfortunately I'm late to the game. Any chance of another PCB group buy?
 
 

 

[theledman]

Quote:

I to have the Grado 325s and can wield a soldering iron.
I am hoping to find a CTH printed circuit board.
 
If anyone has a spare CTH PCB laying around please contact me.
 
Unfortunately I'm late to the game. Any chance of another PCB group buy?

Echo that. I'd like to get a board as well.

 

[frank2908]

ditto, I would love to buy one, but unfortunately I live in Vietnam now. In case a group buy is not possible, what is necessary to get it custom made? Can I show the image in the first page to the custom pcb printing shop or do I need something else, like a Gerber file ( just googled it, I have no idea what it is ). Please help

 

[cfcubed]

Not a good idea & not productive to try to reproduce the CTH PCB.  Instead let me ping runeight & see if he'd get PCBs fab'd and what level of interest that might take.  With someone conducting the GB of course.  Note there is always hassle re-sourcing parts for this tiny amp (in particular the coils, LM2595 & CRDs).

 

[Paul Clark]

I am good for at least two PCBs.
 
Have those parts always been a hassle to source?

 

[cfcubed]

Kind of, esp the CRDs in the spec'd values.  Haven't checked around for the latest BoM parts myself lately, but its something that should be done prior to committing to boards I'd think.  Seems its always taken two parts orders, e.g. Digikey & Mouser.
 
Pinged runeight & he says he's game to make a PCB run if someone else handled everything else (e.g. the GB - $$ collection & shipping). 
I'm considering stepping up & conducting the PCB GB (otherwise it should be a known, reliable entity around here)
Quote:

I am good for at least two PCBs.
Have those parts always been a hassle to source?

 

 

[Magedark]

How much would it be per board? I'd be up for one board, provided we can figure out the part sourcing as well.

 

[Paul Clark]

Quote:

Originally Posted by cfcubed /img/forum/go_quote.gif
 
Pinged runeight & he says he's game to make a PCB run if someone else handled everything else (e.g. the GB - $$ collection & shipping). 
I'm considering stepping up & conducting the PCB GB (otherwise it should be a known, reliable entity around here)
 

 
Once it is decided, will there be another seperate "group buy" thread started?
 
Ref > http://www.head-fi.org/t/536098/closed-group-buy-for-cth-compact-tube-hybrid-pcb