freestompboxes.org

Hi everybody!
There is a local boutique amplifiers dealer in Barcelona that has this nice little amp!
It's a 1W amplifier formed by x2 12AT7 and x2 6AK6 on the power amp... It include a 2 band EQ, gain control... loop fx or preamp output with a TRS...
and sounds pretty good for the width of this lil monster.

I found the gut shots of the entire amplifier building process and I guess if there is anybody that can help me since I'm not so good at this...
here is the sample, I tried in a store and yes, the clean of this amp is brutal!
[youtube][/youtube]

I will try to figure out and get the schematic but if someone in the forum can help me we could try to get a good schematic to clone this little beast, the other 1W tube amplifiers doesn't look/sound this good :p and with all those features!

https://dl.dropbox.com/u/1416648/DIY/Ro ... om-one.zip

thank you all!

I built a 6ak6 based power amp, but push pull and it outputs around 3w. One 6ak6 will give 1w, don't know why he runs them that inefficiently.

www.diy-fever.com/amps/3w-tube-power-amp/

bancika wrote:I built a 6ak6 based power amp, but push pull and it outputs around 3w. One 6ak6 will give 1w, don't know why he runs them that inefficiently.

http://www.diy-fever.com/amps/3w-tube-power-amp/

I guess that this amp is made to run Output tubes "hot" with master at max volume look at the demos, 3W maybe gives too much volume for homeroom playing amplifier...
I just know that this sounds pretty good and the tone its so sweet.. Or maybe it really isn't 1W and they are selling with less nominal Wattage… Room One sounds better than Room Three hahahaha

Ok guys, I'm working on this


I'm copying from the pictures the turret layout and then it will be easier to trace the schematic, so time to time

Hi!

Just did some editing for you. I guess those elko´s in parallel with the 1k5 (99,9 % it´s 2 cathode preamp-stages) may be anything between 1uf and 22uF...

Hey! thank you man! I was planning to put the values later but this is a great help, it makes my job easier
I'll be updating this untill I finish! Thanks for your help!

a bit more progress:


It's almost finished, now lacks the most difficult wires to see and few easy ones

Ok I don't know why I can not edit the previous post as an update but here I go.
It seems to be finished now the three ? marks of the Speaker outputs seems that they need to be soldered directly into OT transformer which is a Hammond 125B
For the power output, it should be calculated the voltage ratios this amp needs and then put specs here…

And I didn't draw the power switch but its easy and obvious :p I'll draw it later.

Something else! can someone help me drawing the schematic of this thing I don't have a lot of practise with schematic drawing…

One more thing, I don't know the pot values too… but this is pretty standard or easy to find, isn't it?

thanks!

Ok fellas, nobody is looking at this thread… but I'm still working on it!
here is the complete schematic!
https://dl.dropbox.com/u/1416648/DIY/Ro ... %20One.pdf

I think its correct, I revised it, and my turret layout seems to be ok too… If anybody can re-revise it to confirm that I'll be so happy, 4 or more eyes can see more than 2

I'm not sure at all about the ground plan of this amplifier… it has a CT on the transformer, probably something like 165-0-165 or less I have to do the calculations (the max recommended voltage for 6AK6 is 185) and then another separate ground to the 2nd cap that goes to speaker and OT transformer, and then the 2 last filter caps are grounded together from pots to preamp... If somebody can put some light, on why is that?

and that's all, after a final revision I'll start planning my build!

ah, and thanks to Bancika who gave me some help at schematic drawing because it was so messed up at first…

And something else, I still have to figure out what's the real pot. values and those 2 capacitors, I don't know at all their values, those teoric values should work and can I can buy few different values to test them... again, asking for some help

For my 6ak6 based amp I used 135VAC (under load, some 12% more with no load) secondary. Rectified it gives right about 185V.
165VAC would be way too much

diafebus wrote:Ok I don't know why I can not edit the previous post as an update but here I go.

There is a time limit for editing, a few minutes IIRC.

Ok fellas, nobody is looking at this thread… but I'm still working on it!

Don't be too sure that nobody is looking, and thanks for posting and all your hard work and effort.

bancika wrote:For my 6ak6 based amp I used 135VAC (under load, some 12% more with no load) secondary. Rectified it gives right about 185V.
165VAC would be way too much

Yes, sorry I did the calculations before and 135Vac should be fine, at 200mA? for the heaters I though something between 1A and 1,2A to have more margin
And what do you think about pot values?

deltafred wrote:Don't be too sure that nobody is looking, and thanks for posting and all your hard work and effort.

I hope so :p btw as I take informations from forums, I like to share my work too, this is how those comunities works

diafebus wrote: I hope so

918 views for an 11 post fairly new thread is pretty good I would have said.

200mA is too much, but it won't hurt apart from the fact that voltages could be slightly higher (5-10%) under smaller load. I used 110mA secondary which is good for approx 70mA after rectification. That should be more than enough. I don't remember exactly, but those two tubes shouldn't pull more than 35-40mA.
For heaters you're ok with 1A, that leaves 100mA to spare.

bancika wrote:200mA is too much, but it won't hurt apart from the fact that voltages could be slightly higher (5-10%) under smaller load. I used 110mA secondary which is good for approx 70mA after rectification. That should be more than enough. I don't remember exactly, but those two tubes shouldn't pull more than 35-40mA.
For heaters you're ok with 1A, that leaves 100mA to spare.

but 110mA for two 6AK6 then remains the 2 12AT7, is 110mA safe enough? I mean there is not just 2 poweramp tubes here, I know the preamp tubes doesn't require much current for the plates but is to be sure that will be enough, maybe something like 120-140mA would be more adjusted… don't know I don't have much experience with calculating PT ratings.

And what do you think about pot values? 1M maybe is too much and it would work with 500k for volume and gain, what I could say is gain and volume seem to be the same value because they have the same code written on it's back, and the same happens with bass and treble pot, but maybe it's just a coincidence

thanks anyway the next week I expect to order everything.

Guys I have to ask to the moderators to close this thread, since I've recieved an email from MPF owner asking and I think he is right, is not a big company and I have to respect their rights, so please can you delete this topic?

I'm so sorry I had this misunderstood with those people.


thanks for your patience and participation!! And sorry for all inconveniences!

(ALL LINKS ARE DOWN FROM NOW)