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A Very Compact Hybrid Amp - Page 124

post #1846 of 2213
I'm looking for a project and this looks like a good option. The board looks very cramped but I like a challenge, and my CK²III build was perfect first time so why not! Just got a couple of questions before I ask about shipping costs which hopefully someone can answer

First as this amp has a tube in it it should not be turned on/off too often? This is closely related to the second - how hot does it run? The vented case looks a bit scary to have on all the time in the summer... no air con in the uk

Last (and possibly most important!) most of my listening is through K340's which are notoriously hard to drive - how will the CTH cope?

Thanks for any thoughts
post #1847 of 2213
Thread Starter 
suicidal_orange, welcome to the cth.

I think that wiatrob has some kits available at spruce canyon labs if you want to go that route. Boards are available from Cavalli Audio (me).

It's ok to turn the amp on and off as much as you like. Tubes are designed for this and, although it is better to leave the heaters on continuously, there are other drawbacks to this. In addition, unlike other compact tube hybrids, this amp will take a very large variety of 6.3 and 12.6 volt tubes, many of them in current production. So you won't have any problems finding tubes for it.

If you get the kit and case from spruce canyon, there will be sufficient ventilation even in the heat of summer.

I can't answer #3, but perhaps another owner of the amp can.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #1848 of 2213
Quote:
Originally Posted by suicidal_orange View Post
I'm looking for a project and this looks like a good option.
Go for it, its a fantastic little amp.

Its not a difficult build as long as you are careful, read through the build instructions a few times before you start to familiarize yourself with the build and double check each component before you solder it in. Pay particular attention to the tombstoned diodes and transistors and you should not have any problems.

While the amp does run hot it is well within the limits of the components and the amp is not big enough to act as a room heater! There is a slight improvement in SQ to my ears after the amp has had an hour or so to warm up so on a weekend it stays on, during the week I just turn it on when I get a chance for a listen.

Can't help on the K340 question either, but it does fine with all the headphones I have tried including a pair of Yamaha HP-1 orthos which also have a reputation as hard to drive. I can tell you it will be a great match for your Woodied Grados though.

Since receiving my Grado HF-2s this has become my favourite combo by far.
post #1849 of 2213
Very impressive thread. Thanks to all of their input.
post #1850 of 2213
Quote:
Originally Posted by runeight View Post
suicidal_orange, welcome to the cth.

I think that wiatrob has some kits available at spruce canyon labs if you want to go that route. Boards are available from Cavalli Audio (me).
Indeed, there are kits available. I am no longer supplying bare PCBS, these will be available from Runeight...
post #1851 of 2213
Quote:
Originally Posted by runeight View Post
Boards are available from Cavalli Audio (me).
How does anyone order these and will you be supplying boards direct for any of your other designs?
post #1852 of 2213
Quote:
Originally Posted by Forte View Post
Go for it, its a fantastic little amp.
Its not a difficult build as long as you are careful, read through the build instructions a few times before you start to familiarize yourself with the build and double check each component before you solder it in. Pay particular attention to the tombstoned diodes and transistors and you should not have any problems.
While the amp does run hot it is well within the limits of the components and the amp is not big enough to act as a room heater! There is a slight improvement in SQ to my ears after the amp has had an hour or so to warm up so on a weekend it stays on, during the week I just turn it on when I get a chance for a listen.
< snip>
Since receiving my Grado HF-2s this has become my favourite combo by far.
I'd like to echo Forte's thoughts here w/a few embellishments of my own:
  • Dead on WRT building. Review CTH site info well & print scaled-up copies of images & left few cols of excel BoM. For me a tedious but useful step was sorting the kit resistors & taping them to their rows in the enlarged BoM. Watch polarized cap orientation too (long lead is +). I'll post a couple more closeups of a populated PCB when its ready. Once you get past the resistors think its smooth sailing
  • WRT heat, you have to have a couple Nelson Pass amp designs around to know what heat is As said, and across many builds, we've no heat-related issues (esp. since Q1P re-spec a while back). Mount comps low & w/a bit of wiggle room near 24V reg & you'll be fine.
OT: Forte - Seeing another post of yours it seems you & I will end up w/B22 & HF-2s as well. From the NY meet, opinion was it would take critical listening in a quiet environment w/A/Bing to pick out any compromise WRT my budget B22 build. Guess that's a testament to the B22 design. And HF-2 mated very well w/CTH & B22. So far, after 1 day w/HF-2s, I'm finding the better mastered material is rendered very accurately w/relentlessly revealing B22 (great), so of course poorer mixes/mastering shows through as well (not as great). CTH w/good tube choice seems to somewhat mask the objectionable aspects of less-then-ideal recordings as one would expect (from an amp w/a tube in it). So its nice to have both types of designs in one's arsenal
post #1853 of 2213
Thanks for all the opinions, I'll not be discouraged that the build isn't hard as it will probably be attempted during the Christmas break so a stress free build will be good

I was worried about it being a room heater if it needed that much ventilation, it doesn't ever get really hot enough in the UK to think it would damage itself just that I like things cool (I'm still wearing a t-shirt out and some days it's not reaching 50°F - some call me mad ) but summer cannot be used as an excuse to stop listening. I'll just turn it off lots and have an excuse to buy spare tubes just waiting for them to die

Now to sort out the ordering - wiatrob will have an e-mail shortly!
post #1854 of 2213
Quote:
Originally Posted by suicidal_orange View Post
I was worried about it being a room heater if it needed that much ventilation, it doesn't ever get really hot enough in the UK to think it would damage itself just that I like things cool (I'm still wearing a t-shirt out and some days it's not reaching 50°F - some call me mad ) but summer cannot be used as an excuse to stop listening. I'll just turn it off lots and have an excuse to buy spare tubes just waiting for them to die

Now to sort out the ordering - wiatrob will have an e-mail shortly!
Don't worry about the temps, it's the first week of summer here and the temp hit 100°F yesterday and its going to get a lot hotter before long. My build has the solid top with just a few small vent holes and copes just fine with being left on.

If you haven't already ordered consider the Sonicap upgrade, well worth the cost.
post #1855 of 2213
I've just read a reply to my semi order, no stock of Sonicaps but I've been offered some Russian paper in oils which wiatrob says are 90% of the Sonicaps so I'll probably go with them. It's a nice cheap upgrade, I'm not one to turn that down. Or should I try and source them elsewhere? Which caps are they anyway? I'm not good at understanding schematics to work out the values
post #1856 of 2213
Thread Starter 
They are C4L and C4R. These are the primary audio coupling caps between the tube stage and the transistor buffer. Of all the places in the amp where cap upgrades are possible this is the only one that really makes sense and will have an audio impact.

Please let us know how you do.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #1857 of 2213
See the CTH Tube & Tweak thread for discussion of those (de)coupling caps. As the only capacitors in the primary signal path they do have an influence on the sound, tho less so than the choice of tube. In fact, the "voicing" of the amp is accomplished though a combo of tube/coupling cap choice with the tube the much larger part of the equation.

You can spend 60 cents -> 60 dollars or more on the 0.22uf coupling cap & more $$ may not mean more to your liking. From what I've read those green Russian PIOs may give a slightly more mellow presentation than the std or WIMA caps & I'll be finding out for myself w/this next build. I think I'll go w/Bill's green PIOs because the CTH does not lack detail & they might make it a bit more "tubey" for fun.

Some more reading for you. Don't stress on this tho

Edit: I guess I'm too wordy as someone else beat me to it. Again.
post #1858 of 2213
I've read a lot about signal path capacitors from playing with iMods, and more money = better (all the way to V-Caps...) but I've not tried many in the middle. At 0.22uf it seems size may be the limiting factor instead of budget, but I'm only on page two of the tweaks thread so will keep reading before making a decision.

Thanks again for the help

EDIT - Just read in the tweaks thread that the CTH handles a K1000 so my K340's should be fine
post #1859 of 2213
I DO have Obliagto Gold .22s, and (Yikes!) Russian Teflons already leaded for the CTH. No way you can fit them in the case - same with the more esoteric film caps because of their higher voltage.

As implied above - spend your money on Tubes, I have stock Wimas in my proto that I've never felt the need to change.
post #1860 of 2213
I'm with Bill on this. Save your $$$ for tubes. A nice Bugle Boy or something like that will be money well spent. ( not to dissuade you, but...)
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