Search found 577 matches

by little eddy
Sun Jan 13, 2019 9:21 pm
Forum: Buying and Selling
Topic: Wanted Oscilloscope or Advice
Replies: 6
Views: 114

Wanted Oscilloscope or Advice

Looking to buy an oscilloscope to help with my testing and fault finding. Does anyone have one they were looking to sell? I see a few USB ones (particularly Hantek) but there are doubts as to whether some/all of them work with Windows 10. Advice and/or recommendations would be appreciated. Thanks, M...
by little eddy
Sun Jan 06, 2019 4:19 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

Might have found the issue - a noisy laptop supply! Will try and get another to test my theory but if not, although a lot more work have the parts for a CRC supply. Just one question. I was looking at an F5 power supply schematic and it has a CL-60 thermistor between 0V and the chassis ground. Was g...
by little eddy
Wed Dec 26, 2018 7:24 pm
Forum: Speakers
Topic: Speaker Surround Replacement
Replies: 3
Views: 165

Re: Speaker Surround Replacement

Success.

About 4 hours for the pair.

It took a bit longer to remove/replace the dust caps but that allowed the shims to be fitted around the driver coil that held it steady while gluing the new surrounds.
by little eddy
Tue Dec 18, 2018 8:53 pm
Forum: Speakers
Topic: Speaker Surround Replacement
Replies: 3
Views: 165

Speaker Surround Replacement

Just bought a pair of new woofer surrounds for my Dad's ailing AR-MST speakers: https://www.ebay.co.uk/itm/ACOUSTIC-RESEARCH-AR-MST-OTHER-MODELS-8-IN-WOOFER-SURROUND-KIT/191446196897?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 ar-mst.jpg I was going to recommend he sells them but they...
by little eddy
Tue Dec 11, 2018 5:17 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

I've been struggling with one channel of this amp, (the other channel works fine). I have 2 inputs. When using 'In 1' wired directly across the 50k load resistor (taking the bias voltage to the pre transformer output), the audio sounds fine. But when I wire to 'In 2' via the dc decoupling cap, there...
by little eddy
Fri Sep 21, 2018 12:56 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

Well unsurprisingly there are a few niggles with this amp but will just try to focus on one point at a time. Looking at the pcb schematic below, when I wire 'directly' from my pre-amp transformer output across load resistor R3, there is a hum that is not there when I connect to the normal input term...
by little eddy
Thu Sep 13, 2018 3:29 pm
Forum: Buying and Selling
Topic: Wanted: 6SN7 Tubes.
Replies: 10
Views: 920

Re: Wanted: 6SN7 Tubes.

I tried a lot with used in my Rocky amp. Ended up using Kenrad VT-231 with 'black' glass (but can't believe the prices currently on e-bay). I also tried I think some Russian 6H8C if I'm not mistaken. I didn't like them but they may suit. I probably have a fair number of different ones if you want to...
by little eddy
Fri Aug 17, 2018 9:12 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

Steady at 1.7A.
18-08-17 Mofo small IMG_20180817_204044837.jpg
Next the other channel and then it's time to have a listen.

If it's any good, this is a remarkably easy Class A amp to build.
by little eddy
Thu Jul 26, 2018 5:46 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

Could be a silly question (as often they are from me), but in the MoFo schematic and pcb, why is there a 200k grounding resistor proposed before the signal dc-blocking capacitor, that for ac is effectively in parallel to the 50k load resistor? I'm considering leaving this out unless I'm missing some...
by little eddy
Sat Jul 21, 2018 10:32 am
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

One of my questions is about the 50k 'load resistor'. Will the Niobium output stage see this as a load? The attached probably closer resembles a valve inter stage fixed bias arrangement? 18-07-21 MoFo Simple.jpg Don't know why but I'm thinking about a dc voltage developed across R3 (if there is any ...
by little eddy
Fri Jul 20, 2018 10:09 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

ed wrote:
Fri Jul 20, 2018 9:23 pm
mmmm...I'm scratching my head on this one..

how are you setting the bias on this?
Bias is set by P1 and R4. There will be continuity through the Niobium secondary winding connected to the RCA socket.
by little eddy
Fri Jul 20, 2018 9:12 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

So here's my attempt at a simplified input, designed to match the Niobium transformer 'non-grounded' output.
18-07-20 MoFo Simple.jpg
Any comments would be appreciated.
by little eddy
Fri Jul 20, 2018 12:04 am
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

A question regarding the dc blocking capacitor C1. My Niobium pre has an 'isolated' transformer output in that it is connected directly to the RCAs and not connected to 0V in the pre Can I bypass the input cap C1 within the MoFo, and connect the input either directly across R3, or from the top of R3...
by little eddy
Thu Jul 19, 2018 8:55 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

Re: MoFo

This could be a really compact design for the initial build, even smaller if the pc psus were off-board.
Initial layout small.jpg
by little eddy
Wed Jul 18, 2018 10:28 pm
Forum: Solid State
Topic: MoFo
Replies: 17
Views: 2544

MoFo

With the LM3886/F4 on hold, primarily because of no availability of the now almost obsolete complementary JFETs needed for most of the Pass amp builds, it is time to embark on a different SS amp build prompted by Ed's Lateral FET build and his reference to the MoFo thread. I also think Ray may have ...