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A Very Compact Hybrid Amp - Page 90

post #1336 of 2213
inductors with more current capacity, whether or not to increase C1H and C2H is still not clear. wiatrob has one, I will be modding mine soon as well.
post #1337 of 2213
I am going to try increase c1h and c2h just to see if i can iron out that last bit of noise.
post #1338 of 2213
I'm wondering why I haven't seen a CTH in the bom case with mini jack input and 1/4" output. It seems like there's plenty of room on the front for this.
post #1339 of 2213
Quote:
Originally Posted by rds View Post
I'm wondering why I haven't seen a CTH in the bom case with mini jack input and 1/4" output. It seems like there's plenty of room on the front for this.
heh..you must have missed mine then...

I have RCA inputs and a 1/4" Neutrik jack in the small BOM case.



post #1340 of 2213
I'm surprised the RCAs aren't hitting ICH. But it looks like you have no fuse or heater switch. I want to have fuse, power switch, heater switch, 1/4" and mini jack. I'd prefer the mini jack or even RCAs on the back but it seems impossible even to jam a mini jack on the back panel.
post #1341 of 2213
Quote:
Originally Posted by rds View Post
I'm surprised the RCAs aren't hitting ICH. But it looks like you have no fuse or heater switch. I want to have fuse, power switch, heater switch, 1/4" and mini jack. I'd prefer the mini jack or even RCAs on the back but it seems impossible even to jam a mini jack on the back panel.
I will be adding the power switch later. The ICH is slightly bent forwards towards the front of the amp to make space for the RCAs. There is however no space for a fuse in the back with the RCAs..

I could have moved the RCAs to the front or put a mini in the front for the input and then put a fuse in the back but I didn't.
post #1342 of 2213
Quote:
Originally Posted by zkool448 View Post
Typical Canadian....
Nah.. we send in the JTF2
post #1343 of 2213
So is someone doing a miniGB for C3H? If so, I'd like to get in on it too..
post #1344 of 2213
My little contribution to this project. This was drawn for the Spruce Canyon labs kit in particular (for the fuse and switch placement), but the greyed out areas apply to all standard builds in the (small) bom case.
I'm calling this a prototype because I haven't had a chance to use it yet, but I'm pretty sure everything is right.
I'll post a link to the pdf shortly.



PS I know on Cavalli Audio the center of the AC jack is shown as 18mm, but my measurements don't agree.

Download
the pdf here
post #1345 of 2213
Quote:
Originally Posted by wiatrob View Post
Holland, did you get any temp measurements on the switch reg?
Did the upgrades, using a 470uF/35V C3H, 220uF/10V C1H & C2H, and the 2 inductors. The muriata is a bit too tall for my build, had to find space underneath. I think the digikey 1A version of the stock coil may fit better.

No noise, BTW, with IEMs (Crossroads Mylarone x3), using a 120R resistor right on the jack, not in R18 (didn't feel like changing it on my proto build). Didn't make it straight wire, too lazy. :P

Anyhow, on my build with the rear open to measure the switcher directly (it has a small heatsink on it and under the PCB) it is @ 65C, idling. Tube is fully out of the case using a socket saver. With the rear fully enclosed, and measuring temperatures inside the case, it's 55C.
post #1346 of 2213
Quote:
Originally Posted by MrSlim View Post
So is someone doing a miniGB for C3H? If so, I'd like to get in on it too..
Looks like Bill may be offering his full kit customers a way to get C3H replacement for free, and some of them may take him up on it. His support of the CTH kits & his customers is extraordinary. At this rate they could wind up expecting greeting cards at holidays & their birthdays from him as well

My thinking is that the heating circuit designer & those on the proto PCB teams (aka "the guilty") could just just pay Bill his cost plus a buck or 2 for his troubles as one way to get the replacement. Once a cap is IDed and confirmed & if he orders enough in some future order.

But as DIYers, although we don't like admitting it, we are only one step away from another parts order at any point in time, so that's another way to go
post #1347 of 2213
Quote:
Originally Posted by adamus View Post
boxed up and the hum is gone. tiniest bit of white noise but no annoying distant wasp. I believe we have cracked it
Quote:
Originally Posted by adamus View Post
I am going to try increase c1h and c2h just to see if i can iron out that last bit of noise.
adamus - Unless you are working to support tubes w/heater draw > 4W, my wordy research suggests heater circuit tweaks beyond raising C3H to 330uf may not be fruitful. So would be curious to hear your findings.

Keep in mind that very, very low level hiss/white noise (sometimes detectable when music is not playing) is unavoidable w/the CTH's class A discrete RS+OB AFAIR. R18 output resistors of 68R -> 150R serve to suppress this hiss & provide better vol pot control.

One thing that would be great is if someone w/sensitive cans could confirm my findings that raising C3H to 330uf, in support of std CTH tubes w/heater draw < 4W, is comparable to/not easily distinguishable from CTH w/heater circuit disabled & battery heater:
  1. pulling D1H & D3H and *carefully* pulling L1H (watch out for unraveling or loss of coil attachment)
  2. running wires connected to tube pins #4 & #5 external to the case.
  3. creating a 6V pack out of 4 "D" cells tapped & soldered in series
  4. connect neg/- of 6V pack to wire connected to pin #5, positive pin #4
Box things up & try any "noisy" 6.3V heated tubes you have (in an EMI quiet area).
post #1348 of 2213
Nice suggestions CF - I'll look for a 330uF coil at the electronics store tody.

AFA C3H is concerned I have already made the GB. Caps will be here Tuesday. Nicihicon low impedance, 10x20mm I'll do a test install and then they will be available, per my previous post.

I'm providing these free to those who got kits. Nux has agreed to redistribute Down Under, as he has a set of perf tops on the way.


If anyone would like to do so for Canada, that'd be swell.

I'll handle US postage.

EDIT: If anyone else needs some - please ping me. I'd be happy to send them on for cost + shipping...
post #1349 of 2213
all,

I got slightly board, and needed an excuse to try my new soldering iron out so i messed around with different caps in c1h and c2h.

no change. scoping around, the remaining noise is mainly from the buffers.

However, i do still notice slightly noise on the 24v rail when a tube is plugged in. much much reduced from before but its still there.

overall i am now very happy with this amp, its a solid little performer and a refreshing change to the bijou. Switching between two very different sound signitures is good fun.
post #1350 of 2213

low impedance cap for C3H preferred but not required

To my surprise I found a std 470uf 35v 10mm dia X 16mm H cap in my stash. Pulled C3H in my orig CTH in std BoM case & was able to fit the 470uf in its place. Now no hum whatsoever in that CTH either.

So I've updated my C3H revision guide. Again. Message is if you've any 270uf -> 470uf 35V+ cap that fits it should do the trick.
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