Jump to content
Why become a member? ×

Building a 100W Valve amp - undecided on name as of yet!


umph
 Share

Recommended Posts

Right as some of you may know i'm a total amp nerd and i've been planning to start building amps etc. for a long time now. Basically been putting off finalizing things though because i've never been quite happy with the design and i've yet to think of a good name and design a logo for it. Think i've got to a stage where i'm happy with the design though!

Specs so far on the head.

Low / high gain inputs (read active / passive)

5 controls (depth / gain / bass / treble / master)

Depth controls the bass roll off frequency - great for tightening things up

Gain control is spread over 2 gain stages, making it pretty easy to dail in just the right amount of grind.

Preamp heaters ran off seperate 12.6v dc supply, to keep things low noise.

Speakon outs for 4 / 8 / 16 ohms.

600 ohm balanced, post OT transformer balanced line out (subject to tweaking till i find what sounds best)

Running this one with a pair of kt88's in tetrode mode so it should be good for 100 - 120 watts.

Totally over speced power supply, to avoid sag and keep the massive low end.

Transformers hand wound in nottingham to HIFI quality.

There are probably some things i've left out so feel free to ask me.

Here are some shots of the very slow progress, although you can expect to see more happening soon!



chassis lay out before drilling.


everything drilled and fixed in.



start of wiring, looks bit of a mess atm but should be alot better once everythings tidied up!

Edited by umph
Link to comment
Share on other sites

[quote name='Pentode' timestamp='1327961305' post='1519686']
That's looking very promising.

Gotta love that iron!

How about calling it the 'Hernia 100'?
[/quote]

Haha, it's not that heavy, it's still an easy one handed lift at this stage. The iron is awesome though, flat down to 20Hz, which is pretty brutal.

No idea about pricing yet, i'll have to work it out after i've found someone who can do me faceplates / enclosures.

Edit, yeah the roost is coming down with me on friday for some doom.

Edited by umph
Link to comment
Share on other sites

[quote name='Beer of the Bass' timestamp='1327965020' post='1519781']
Looks well thought out! I'm curious about the tone stack - is it based on a James/Baxandall type or something else?
[/quote]

tis the james stack centred around 600Hz. i may still change it for an active bax though

Link to comment
Share on other sites

[quote name='MoonBassAlpha' timestamp='1328052370' post='1521214']
Aren't the laminations in the transformers traditionally mounted at 90 degrees to each other? I'm sure I've seen it/read it somewhere.
I think it's meant to cut down mutually induced hum. Or something. I may have just dreamt it though...
[/quote]

No your right. I was taught that as well. Dunno how much difference it makes in practice, but of the top of my head I cant think olf any commercial amps that didnt do it. Usually with the Choke at 90 degrees to the trannies as well.

Looks nice though.

Link to comment
Share on other sites

[quote name='S9_S12_Bass' timestamp='1328043167' post='1520912']
Is looking good, have you taken this out of another amp or put bits and pieces together? Either way it looks good. How did you get the depth to work in terms of selecting the frequency?
[/quote]

nah it's all parts i've got lying around. Depth control is just an rc filter so wasn't to hard to work out. Simple but effective.

Link to comment
Share on other sites

[quote name='SebCarr' timestamp='1328092320' post='1521545']
Cool project. Valve rectifier? What pream tubes? Why 12.6v heaters? Some serious voltages to get KT88s singing. ~600v on the plates? Eek!
[/quote]

Nah keeping it SS The extra bases are there if i fancy turning it into a 200W. 12.6v heaters use half the current and thus produce less noise, although it doesn't make to much difference with dc.

in regards to transformers, theres enough seperation for it not to cause an issue, only really matters if you have them right next to each other. Having one facing the other direction would mean more noise due to the magnetic field messing with the valves.

Link to comment
Share on other sites

[quote name='SebCarr' timestamp='1328097200' post='1521649']
SS rectifier makes sense if you're going for no sag.

12.6v shouldn't make any difference with DC if it's properly regulated and filtered, but can't hurt I guess as a little ripple will probably creep through.
[/quote]

Yeah the preamp heaters are all in series so it's easier to run them at 12.6v to.

Link to comment
Share on other sites

[quote name='umph' timestamp='1328095047' post='1521607']
Nah keeping it SS The extra bases are there if i fancy turning it into a 200W. 12.6v heaters use half the current and thus produce less noise, although it doesn't make to much difference with dc.

in regards to transformers, theres enough seperation for it not to cause an issue, only really matters if you have them right next to each other. Having one facing the other direction would mean more noise due to the magnetic field messing with the valves.
[/quote]

Bit unconventional having trannies at opposite ends, used to seeing them close and the signal path going from one end of the chassis to the other. Still, whatever works for you.

Looks a nice job . Were the transformers and chassis easy to come across ? I've never seen any advertised anywhere.

Link to comment
Share on other sites

[quote name='BRANCINI' timestamp='1328121017' post='1522205']
Bit unconventional having trannies at opposite ends, used to seeing them close and the signal path going from one end of the chassis to the other. Still, whatever works for you.

Looks a nice job . Were the transformers and chassis easy to come across ? I've never seen any advertised anywhere.
[/quote]

Look at an amp thats not a marshall or a fender, they're pretty much all laid out like how i've got it. Chassis was ebay and i drilled it all out myself and transformers were from a chap i know

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...