Feed my frankenstein!

Folsom · « **on:** 17 Jan 2006, 12:02 pm »

Once an old Rotel receiver... now a dedicated amplifier with nothing but volume

The entire bass/trebel/balace/loudness/tape monitor board was removed.

All signal wires have been replaced with Cat5.

Cat5 runs directly from RCA jacks to volume pot/shunt network, and then it goes directly to the amplification circuitry.

Volume pot changed to shunt operation.

Headphone jack was removed and amplified signal was run directly from fuses to speaker cable jack terminals.

I think I am ready for my 3875 kit

(This was practice for soldering)

Folsom · « **Reply #1 on:** 18 Jan 2006, 12:59 am »

mjosef · « **Reply #2 on:** 18 Jan 2006, 01:50 am »

Are you using a 'phone camera'?

Bill Baker · « **Reply #3 on:** 18 Jan 2006, 03:09 am »

I think those are 300 watt Hologen bulbs?

Anyway, how does it sound? Any noises or wierd things going on? Any audio DIY project is a good project. As long as you can putthings together after taking them apart (and they work again) you are ready for the next step.

Gordy · « **Reply #4 on:** 18 Jan 2006, 04:41 am »

Quote from: Response Audio

I think those are 300 watt Hologen bulbs?

You can grow tomatos with that amp

Folsom · « **Reply #5 on:** 18 Jan 2006, 08:22 am »

They are little fuse lights..... Yeah they are intense to look at with the clear bulb and exposed filament. It is kind of cool to see the filament glowing though.

There are NO weird noises. It sounds better then it ever did before. I have been using Devils and Dust as a sort of reference FLAC compilation to compare my changes with. I have from the beginning of modding it and before twisting my cables, started with not being able to properly understand parts of the song "Reno" to full understanding. There is no question of what any one is saying in any song now that I have played. Every thing has improved.

The one thing I am not happy about is my left channel (was right but I guess I switched the pot's channels, but not the signal to any thing, right is right left is left) does not respond at super low volumes. It is just some thing that is wrong with the Pot to begin with.

All in all every thing is improved, it is still not going to match my Chip amp with Blackgates and gold connectors that I have on order for my Christmas present... However for some thing I found in the garage, at this point of a zero dollar investment and my $20 a piece total investment with Tangband 871's, two crappy speaker wires, and a mini to RCA, it is completely worth using for computer speakers.

I doubt any one on here would really be impressed with it… I wish I had some thing like a T amp or of the sorts to compare it with (I think it would outclass T amps now). I never thought this old thing would go so far. If you saw the inside you would not guess it really puts out true 20wRMS a channel. You would also not believe it works well. This was made back in the day of hand soldering; it looks far from a current circuit board. My one complaint is the soldered in tuning device that is impossible to get out. I removed all the excess wires I could find, especially the tuning ones to keep down any induced outside interference. All of the Cat5’s by channel are twisted together so that should help as well. There is only about a 4x2 section of the amplifier actually functioning at all now, excluding the large capacitors and transformer.

I might put in some ratshack gold plated RCA jacks I have…. The RCA jacks on this are cheaper than cheap. Any one got an idea for some speaker wire terminals I can find in my own house?! I hate the little press to open, insert cable, and let go things. Perhaps there is some thing on the amplifier I can use…. I also really want to remove the fuses that go to the speakers. I fear they are there for really good reason though, but there are fuses on the circuit board. I got a feeling the base amplification circuit in this is the same used in the more expensive Rotels of it’s time. The original unit was over two hundred dollars in the late seventies I believe.

Overall the increased clarity by reducing all signal paths and components, the fuller very easy to understand sound is what I am happy about.

For free if this allows me to hear differences in characteristics of music and simple sound descriptions that we hear in more expensive stuff, to a much lesser extent, it is doing well as a solder project.

Oh wait if I turn volume up 100% with no signal I get a small hum…. That could be from the RCA’s running over power cords or the lights inside. The hum does not appear until after 80-90% volume, so I can live with that.

Folsom · « **Reply #6 on:** 18 Jan 2006, 08:23 am »

Cellphone camera, who, what, me?

Folsom · « **Reply #7 on:** 18 Jan 2006, 08:54 am »

Screw it I am making some 9259 speaker cables... This will help too. I have 9259 and later will probably get some 89259 for real RCA's and speaker wire for my chip amp.

Folsom · « **Reply #8 on:** 18 Jan 2006, 11:23 am »

Wow even 9259 is impressive! Talk about a whole new level of transparency..... I am almost uncomfortable with this much transparency. This is just weird! Like what the hell weird! This is totally beyond weird!

I am not sure I like it yet. I feel creeped out.

Folsom · « **Reply #9 on:** 18 Jan 2006, 11:37 am »

I think twisting them might of been a mistake. I have lost place of the voice of the singer. It sounds like it is in my head.

Folsom · « **Reply #10 on:** 18 Jan 2006, 12:54 pm »

Ok lesson well learned never criss cross coaxial speaker wire......

Folsom · « **Reply #11 on:** 18 Jan 2006, 01:23 pm »

Under further review...

I can totally understand why 89259/9259 is considered better then most entry level wire for any thing. This stuff is amazing.

I also know why it is so important to have 89259.... The 8 stands for a different grade of outside and inside insulation.... This is important considering the inside insulation will melt when ever you do any thing.... I used a fair amount of electrical tape. If I where to do my speaker cables EXACTLY like JR's I would need 89259 just because of the heat resistance so I could solder with out the crap melting, to keep structure. I however have an idea how to improve on JR's design significantly..... I just have to figure out how to do it, what to use to do it.

I am highly compelled to dig into my amplifier and put in the ratshack gold plated RCA plugs, and put in some sort of new speaker cable jack some things.... Hell even some thing that accepts some crimpable/solder spades I have laying around would be good.

Occam · « **Reply #12 on:** 18 Jan 2006, 02:34 pm »

Quote from: Destroyer of Smiles.

....There are NO weird noises ...

Its not a real DIY project unless there are some weird noises, at least initially

Congrats!

Gordy · « **Reply #13 on:** 18 Jan 2006, 03:35 pm »

If you're looking for free, or next to free, speaker connectors you could try using brass bolts. You'll need 4 nuts and two nylon/insulating washers per connector. The two 'middle' nuts would be used to fasten the insulating washers and bolts to the chassis and the other two (one inside, one outside) to fasten your wires. Ugly, but much better than the steel connectors you've got there now... and a small dab of silicon rubber would help prevent the bolts from moving and contacting the chassis from the side...

Folsom · « **Reply #14 on:** 18 Jan 2006, 11:18 pm »

I will look in the garage to see what I can find, I know I will find some thing better.

9259, again, wow, I had no idea my cheap ass bestbuy monster cable stranded copper wire was one of the biggest bottle necks in the entire little computer desk setup! However it sure would of been nice to have 89259 for easier soldering and construction, I need more electrical tape haha.

Folsom · « **Reply #15 on:** 20 Jan 2006, 10:37 am »

Well I took a ratshack Mini to RCA and turned it into a 9259 cable... Unfortunately the soldering iron I am using is a little fat tipped.... and ratshack stuff melts easy so all the connectors are not as straight as before. It is still a massive improvement in dynamics as well as predicted revealing.

Perhaps I will make the first purchase of a mini, and two RCA ends to go with the better cable. Yeah I know it is a waste of money but I need some thing to listen to music with until I finish the 3875 and pre-amplifier. Also I might be making a subwoofer to with the TB's. Actually it will be three TB's but that is hardly the point!

Folsom · « **Reply #16 on:** 20 Jan 2006, 10:49 am »

Quote from: Occam

Quote from: Destroyer of Smiles.
....There are NO weird noises ...

Its not a real DIY project unless there are some weird noises, at least initially
Congrats!

I rewired the inside of the amplifier some more! I ended up with one failing connection so I would get feed through with out turning up the volume knob. I fixed it..... Stupid tiny Cat5!

Folsom · « **Reply #17 on:** 21 Jan 2006, 05:10 am »

Well I replaced the old speaker jacks, the crappy snap spring ones with some copper covered in silver bars that have a box that tightens down onto the wire via a screw that pressed on the top of the bar to pull the box up.... They are pretty snazy for just being some terminal things that where left over.

Oh yeah the sound? Copper sure conducts better then brass or steel! Impressed with a more full body sound. One less bottleneck!