I picked up an AC powered RA-1 on Audiogon which was rated a 9/10.  The pictures looked ok and there was no mention that the unit had been altered.  I received the amp and it wasn't packed properly so the AC adapter prongs left some gouges on the face of the amp.  Upon inspecting the amp, I...

I picked up a Creek OHB-11 headphone amplifier a couple months ago.  I used it at work with Senn 280's and it sounded pretty decent.   Then I saw how easy they are to mod.  I used Nichicon audio capacitors for the output (470uF), feeback loop (47uF), and op amp supply pins (47uF).  The main PS...

I'm currently using an RA-1 with my GS1000i headphones and would like some opinions regarding the HPA-1.    From what I have gathered, generally, the HPA-1 has "less grain" than the RA-1.   From pictures I have seen of both amps, the HPA-1 appears to be better built even though it...

i'm working on yet another amplifier and it has bad output transistors. the pair consist of one D1705 and one B1154. these parts cross into NTE36 and NTE2306 respectively. the datasheets for these parts list the NTE37 and NTE2305 as the complement. should i stick with the original parts or...

i'm looking for a couple of relacement pots for an amplifier. the markings on them are: M 50K C and M 10K A the 50K unit is a dual pot and the 10K is single. they are about 3/8" square with a threaded plastic bushing and short shaft. i don't have a hard copy of any mouser of digikey catalogs...

i'm having the hardest time finding the datasheets for the following parts: 70039ab 70720fb 70710fb i think they are made by philips semiconductor. please help. thanks

I'm thinking of building this amp but I'm wondering...what is the purpose of C5 and R4 in this circuit? Can they be removed?

after reading much about the toshiba DVD players and how good they sound i decided to try some mods on my old sony dvd unit. the first thing i did was to remove the opamp (njr4558) and replace it with an opa2227. the old opamp was fairly difficult to remove because it had been tacked in place...

this has nothing to do with amps, but i just wanted to share the good news. i just finished taking my LAST FINAL EXAM! i graduate on saturday! now i will have more time to build amps and stuff.

i'm building a szekeres amp and i have some questions concerning the power supply. i plan on using an 18V transformer and regulating the voltage down to 12VDC. is the drop in voltage too much for a 7812 1.5A regulator? i have two 2700uf 35VDC caps before the regulator and a 2200uf 35VDC...

i'm in the process of building another amp. i plan on biasing the opamps into class a and then buffering them. very similar to the PIMETA with different component values and such. i'll be using an opa2132 and buffering it with buf634's. for biasing, i will use the 2 jfet method with the...

i'm working on buiding the szekeres mosfet amp and i have a couple of questions. 1) i'll be using a dual 8 volt supply to power the circuit. to add gain, i can use an opamp based circuit before the buffer, correct? 2) i added trim pots to the mosfet buffer to get rid of the output cap...

Where are all you guys getting the ALPS and panasonic potentiometers? (and knobs too). i have looked thru my digikey and mouser catalogs and i just don't see any. thanks

I started building a power supply with a 10-0-10 center tapped transformer. when i measured the actual output without a load it was 11-0-11 VAC. i built a bridge rectifier and added some caps (1100uf). when i tested the DC output of the rectifier and caps it was +/-15V. how can that be? will the...

i broke apart an old hp deskjet power supply and found that it's just a transformer with dual secondaries. 120VAC in and 10x2VAC out @ 2 amps. i was planning on using it in a power supply for a mains powered ra1 clone and ph1 clone. is using this transformer overkill since both designs are op...

i built my first CMOY a couple of months ago. the sound was crappy, but i was using a TL082 from the ratshack and some cheapo 5 dollar sony headphones. i have since taken the amp apart and reused some of the components to build me a CMOY amp with RA1 values to drive a set of grado 125's with the...

Hello, I have been reading Headfi posts for quite some time, but I just recently joined. Anyway, how do I post pictures of my DIY amps? Are there any sites that will host photos? I have built a CMOY and a CMOY/RA1 type amp. I still have some parts left over to build a couple more, but work and...