DIY something like iMPAMP??

[nkko]

Does anyone know where i can found similar DIY project with complete schematic to build?

Thanks for any help!!!

 

[nkko]

sorry here is a link impamp

and can someone suggest me a pair of good speakers thet would play nice with that kind of amp.

i need it mainly for my ipod and laptop pc.

 

[pinkmouse]

That is so sweet! 🙂

I would go for something like the new Jordan JXR6 drivers to match that.

 

[andrei]

I designed a small 6SN7-6BX7 push-pull amp using commodity parts - see schematics. Three tubes, single PCB construction, solid state HT rectifier, toroidal output transformers. Not as compact as iMPAMP, but a little bit beefier at 5W/channel.

 

[andrei]

PCBs are already laid out and manufactured - they are 4x5.5 inches, double side, solder mask over silver-plated copper. I just need build a prototype and test it 🙂.

 

[andrei]

I've taken a look at the iMPAMP web page - it's a cute design. Here is my reverse-engineering summary:

Amplifier topology is a single stage push-pull using 6021W sub-mini tube. That tube has 0.7W anode dissipation rating, which means that it runs in Class B to get 1W output. Bias for PP pair is done with a single blue LED. External 12V/1A PSU feeds two 6021 heaters in series, and HT is stepped up inside by a pair of AMVECO 70000K 1.6W toroids connected in reverse. Rectifier is obviously solid state. The only thing which is not quite clear is how phase splitting is done in a front-end...

 

[Peter M.]

Cool amp!😎

Fostex FE207E has a high sensitivity, 95db/W you`ll need it with just a one watt amp.

5902 subminiature pentode has a max anode dissipation of 4W, could make a cool little single ended 1W spud-amp...
Oh no, I got a couple of them in my drawer, juuuuust what I needed now, another project...🙄
😀

Regards,
Peter

 

[Peter M.]

http://www.roehrentechnik.de/html/kolibri.html

http://www.jogis-roehrenbude.de/Leserbriefe/Hermann-Mini-Amp/Hermann-Mini.htm

 

[Peter M.]

http://mapage.noos.fr/dom.mafrand/schematics.htm

http://amps.zugster.net/projects/subminiature/gallery.html

 

[userguide]

Andrei,

You're right !

Here what I found to complete the reverse-engineering of the ImpAmp:

Two OP275 phase-splitter like this circuit (see pic)

(Personnaly I prefered the DRV134 for phase splitting)

Transformer: Fender W022913 (125A10B)
PART# 022913
MOUNTING 2 13/16"
HEIGHT 2"
LENGTH 2 5/16"
WIDTH 2"
WATTS 12
PRIMARY 8500 CT
SEC 8

So nothing missing to build a ImpAmp clone !?

Let's build the YinYamp !

 

[andrei]

Opamp phase splitter? It figures...

I would use OPA1632/THS4130 instead of OP275. But of course, autoformer is way cooler 🙂.

 

[DigitalJunkie]

I built a small 1Wpc SE 60FX5 headphone amp. 1 tube per channel!
It sounded pretty good after some tweaking,but all the 60FX5 tubes I could find were pretty microphonic. 🙄 I dunno if they're all like that,or if it was just the ones I got.
I'm sure there are similar tubes you could use that might be better in that respect.
The schematic I based the amp on was from an RCA sheet,I think it was used as an X-tal-pickup phono amp ?

Might make a sweet little guitar amp,that won't wake the neighborhood. 🙂

 

[userguide]

Yeap !

OPA1632 is a good candidate for balanced input too.

Z.Vex choose OP275 for his tiny amp !!!

Look this picture that I found on Zvex forum - september 2005 (increased and corrected with photoshop)

Who says reverse-engineering ? 😉

 

[userguide]

original picture of OP275

Bottom view...

 

[userguide]

top view...

 

[userguide]

autoformer is way cooler...

Andrei,

Your 6SN7-6BX7 push-pull amp design in this thread is really cool !

a tiny Tamura MET-09 in autoformer mode at input !Y!E!A!H!

Could you suggest me a turn ratio for the toroidal output transformer ?

I have some Amveco 62070 in my parts bin but I don't have an inductance meter to mesure it for ~ 64mH ?

I want to test and listen this great idea. 🙂

 

[andrei]

Thanks! Now I'll have to build this thing to see if it works 🙂.

Actually, I designed for Amveco 62070 (parallel secondaries) as output transformer. I measured one with LCR meter, and the measured values looked really good. Leakage inductance is small, so high frequency extension is not going to be a problem, which was a concern since it is never documented for power transformers (you could guess the primary inductance from idle current spec). I can look up the exact numbers if you are interested.

 

[userguide]

6SN7-6BX7 push-pull amp design

Hi Andrei,

I've some 7v + 7v toroid from Amveco to try with your design.

If the primary impedance will be the ratio squared x the secondary impedance.
Ratio: 115 / 7 = 16.5
Primary impedance: 16.5 x 16.5 x 8 = 2178 ohm (seem to be OK with this low Rp TV triode)

Next I've to found some 6BX7GT and I'll be ready to test it...

Sylvain

 

[andrei]

2kOhm load is too low for 6BX7GTB. You'll have to parallel the secondaries, and use primaries in series. That will give you 115+115:8.4 turn ratio (8.4 is no-load volatage output of 62070), for the reflected impedance of 6kOhm for 8Ohm load.

 

[zachary vex]

wow, you guys are a trip! 8^) remember that the OP275 opamps are mounted on a daughter board and there are components underneath them as well. there are no capacitors in the audio path (all DC-coupled) except two tiny ones in the negative feedback loop of the input to deter RF oscillation. good luck! 8^)