The bottom plates are not for sale somewhere and were made by Mick on a one-off basis.
look for a heatsink with about the same dimensions as the acrylic bottom plate ( or slightly larger) and use that (probably cool looking too). Or find/buy a square piece of aluminum of about the same thickness (or slichtly thicker) and size of the acrylic base plate and file the edges nice and round (not easy to get this right I reckon)
hello everybody, my name is Cyril i am from France and with a friend we have some problem with an Indeed Amp G2. The cause of the problem: during a bias adjustment, i have touched the heat sink of the amp and i have made a short-circuit (big flash). The amp is over. i have changed one LM317 and one IRF630, the amp still not responding. in details , the heating filament doesn't run. I don't now where i can test the amp for seeing where is the problem.
Hi There is nothing wrong with the pot. Mine came with an 6n11 tube. I had the same problem. I changed the tube with an 6922 jan philips made in the 70's. No noise from the pot. The 6922 needs less current than the standard one Indeed is using (Chinese made). If you want to keep the tube that came with the amp, in order to save money, try to adjust the bias a little bit higher. My amp was not adjusted at all, it had 10.47V left channel & 14.96V right channel. Indeed says that 11.5V is fine, i succeeded great results with 12.8V per channel. When you do the adjustment you will have to be patient, the two channels interact , which means adjusting left will affect right channel also.
The 2 channels interact because at 13V the LM317's are not in their linear range, they simply do not work as they are supposed to at that voltage. They do not work symmetrical in this case and are introducing the crosstalk and distortion. Even that distortion (measurably very high and a-symmetric) is missed by many owners and trained ears alike, I must admit. The optimal range for a stock indeed is 15.5V to 16V which was also confirmed to be correct by Pink Floyd (Mike) when adjusting 'by ear'.
A 'hidden' problem this causes, doesn't seem very appearant when doing the (static) adjustments. Once 'stabilised' the amp appears to work correctly/stable with 12V bias voltage.
However, as soon as the amp does what it is supposed to do (amplify AC signals and not being run static) the bias adjustment changes continuously dependent on musical content (voltage swing) and is literally all over the place degrading performance MEASURABLY during play. This is quite considerable, yet not very audible for most people.
after the heater mod there is no interaction anymore and is dynamically as stable as statically as the LM's are always in their minimum range. Distortion is measurably (even considerable) lower in this case. The audibility of this improvement depends on the listener I suppose.
How much the pot 'scratches' depends on the grid leakage current of the tube (an aspect of the triode). This is dependent on the emission, gain and physical construction of the tube.
Hi, just 2 questions. Do you have any reasonable explanation why in some tubes (like 6922) bias does not go more than 14.7V . Whatever adjustment I do it cannot go more than that value . Tubes are NOS & test very strong on my tube tester. For the money paid, I'm pretty satisfied with this little amp, it drives my BeyerDynamic DT250 with ease, these headphones are 80ohm , do i need to modify the output resistor to make them sound better ?
In order to accommodate better tubes (those with higher than average emission) you can change 2 things. a: the cathode pots (increase in value) b: increase the current of the anode current source.
a: will give you a wider range but with a small adjustment the bias voltage may vary a lot. This can be 'improved' by mounting small multi-turn pots.
b: this will allow the better tubes to be adjusted properly but the lesser tubes (and 12AU7 e.t.c.) may not adjust properly anymore as the 'range' one can adjust in is not increased but only 'shifted'.
I have never heard the DT250 but the graphs predict the sound won't change much with a lower or higher output resistance. a matter of trying I guess.
Hi I was tempted to test the 8audio board so i did. I used 5Watt wirewound resistors & top quality capacitors. I put IRL510 instead of IRF510 & bias is 13.5V as mentioned somewhere in this forum. The good thing is that the amp works great, it needs about 20 minutes to get stabilized bias measurements & they are much more precise if you use a 5k pot instead of 1k. The only weird thing is this : Only the IRL510 from the right channel gets hot (but you can touch it without getting burned). Left channel IRL510 & 317 regulators are running cool. Is this considered to be normal
FINALLY !! i fount it ! - its the solder joint of the pot wiper, it didnt wet well so the connection to pin3 was open it probably put too much load on the pot and shorted it too and also on the circuit. i replaced the pot and resolder and its working ok
so in conclusion a few things i learned and might help other noobs trying this mods: get a good solder iron and desoldering pump this thick pcb is not easy to solder and desolder with cheap equipment on the other hand its really hard to break it and it can stand many mistakes also desoldering braid and some extra flux (i use goot) ALWAYS check for continuity !
i replaced the cheap pots with precision, one turn pots the same size and it make a difference: first its much easier to bias the voltage, second the distortion on low vol now gone and third the leds (mainly the blue) does not flicker a bit and actually they lit very bright now also getting 5-10 good quality pots from ebay is a good idea since they cost just 1$ and if one of them accidentally opens you can always replace them
lastly MANY thanks to solderdude who manage this forum and help me a lot (and was very patient for my troubles) you rock! thanks
You where right . One of resistors although it states 35ohm it wasn't. I changed it with another one & now everything is normal. Is 13.6V bias ok (i'm using IRL510 - LM317 - cc88 tube), or should i go a little bit higher ? Thanks for your helpful advice. Vassilis
Quick question about replacing the MOSFET's in the Indeed amp. When installing the new IRF510 MOSFET, do I need to add some more thermal grease (a.k.a. thermal compound)? Or will the heatsinks transfer enough heat even without adding more thermal grease?
I recommend using IRL510 instead of IRF510. IRL will give 50% more output power (than IRF) and lower distortion and an even wider bandwidth.
Also I can highly recommend you use insulation kits (plastic ring and silicone spacer) to mount the MOSFET's This prevents the 24V being present on the heatsinks. With silicone insulators you don't need heatsink compound (thremal grease).
Some have destroyed valuable sources by accident while touching the center RCA pin to the heatsink.
Without silicone (or when using Mica spacers/insulators heatsink compound is recommended. The thinner the layer the better.
put a tiny amount on the MOSFET and wipe it flat/off with something like a creditcard. VERY little is required. Using a lot of this stuff so iy ouzes out will give worse thermal coupling.
I also fitted the IRL510 to my indeed & done all the mods, cathode caps, better heat resistant capacitors etc.... Congratulations to the members here. It is a completely different amp now & much more dynamic .
By the way 13.5volt must be measured at pin 1 & 6 of the tube anode , am I correct ? Not the (+) of the output capacitor.