Anyone ever build a amp for their Home stereo system

[lego4040]

I'm interested in building a amplifier for my home stereo and was hoping some one here has. I don't need earth shaking power, just something to warm the sound up and help the receiver out. I watched a cool video on the making of a Macintosh and was blown away. Any info would be well appreciated

[Ken Moon]

There are DIY audio forums out there somewhere.

And there are several nice stereo power amps you can build using EL34s or 6L6s. Preamp kits and info are out there too.

I built a Dynaco ST-70 clone kit years ago and sold it. It was just like building a guitar amp kit.

Triode Electronics makes a Dyna Clone kit that looks pretty nice for a reasonable price. Might want to look for reviews of that one.

St-70 kits go for about $800, and there are so many that you should find some reviews before buying.

Sometimes you can find a nice old tube power amp on FleaBay "for parts".

Or you can roll the dice and buy a Chinese clone.

I would definitely suggest against making 300B monoblocks. Those tubes are way overpriced:

[lego4040]

Triode I know of and have been on their site. I've bought from them too The dynaco's look nice and from the sounds I've heard from the ST35&70 That seems like a good starting point. Ill browse fleabay as well. I have a drummer friend with a really good vintage japanese tube receiver and amp that is he says he wants to part with for free. He just cant seem to give it up every time we get together tho

[SILVERGUN]

Here's a cheap kit that I had remembered seeing over at AES...
https://www.tubesandmore.com/products/K-502

But take a look how simple
1- PT, 2- OTs, handful of Rs and Cs, small board and a couple jacks.

Might make a cool little project to use those clues and throw something together....
After all, it's just 2 little characterless tube amps running in parallel.  .....no tonestack, phase inverter, reverb, OD channel, silly input jack wiring, etc... to worry about

[DummyLoad]

dynaco MKIII driver board coupled to two pair of KT88 with a hammond 1650W OT and the compliment PT. 


--pete

[lego4040]

Wow thats cheap for a 8 watt stereo amp, I will do some reasearch. Maybe Ill hook my stereo's left channel to Sluckeys AC15 and the right to Dougs Stout   

[kagliostro]

Only one idea

http://www.mcmlv.org/Archive/HiFi/HeathkitW5M.pdf

http://www.mcmlv.org/Archive/HiFi/HeathkitW3AM.pdf

http://www.mcmlv.org/Archive/HiFi/HeathkitW3M.pdf



K

[lego4040]

I had a heathkit years ago, didn't work. Before I got into this hobby

[shooter]

I did a custom build and used the M7 preamp board  http://www.analogmetric.com/
I moded it for guitar but plugged it into a SS amp before I moded it and she sounded nice into a pair of 8" audio Nirvana speakers.  Also did a SE quad el84 with a 6sn7 driver and used that for over a year as my home HI-FI.

[lego4040]

Nice stuff there as well, any specific tube choices? I see builds using 12ax7/6L6 and 6ns7/KT88's. I've never heard or used the last two and that seems appealing. 10 watts per channel seems enough

[lego4040]

Pete I've been looking at those dynaco's. My Dad used to got to those Ham Radio flea markets and see all these amps and tubes all over

[lego4040]

http://pages.ebay.com/link/?nav=item.view&alt=web&id=381020639546 here is one

[DummyLoad]

http://pages.ebay.com/link/?nav=item.view&alt=web&id=381020639546 here is one

looks like it's in good condition and that the tubes are still OK. are you going to bid on it?


--pete   

[lego4040]

Yeah I was thinking so, I need to look at my receiver manual. My Pioneer VSX-D814 doesn't seem to have a line out and in for a amp or EQ. Yes it looks like it's in Great condition

[DummyLoad]

yes it does.


http://s3.amazonaws.com/everystockphoto/fspid20/95/92/4/vsxd814-pioneer-receiver-95924-o.jpg


use the white colored outputs - front L and front R - you should be able to disable the internal amp in setup: the outputs in the white are to connect to an external multi-channel amp(s).


see page 24.


http://www.pioneerelectronics.com/pio/pe/images/portal/cit_11221/93198953Operating%20Instruction%20VSX-D914-K.pdf


--pete

[lego4040]

  you did what I did. I downloaded the PDF and went to page 24. I found some nice kits on www.siliconray.com out of china. I have a extra Hammond PT 290CAX, 4 EL84's, a 12au7 and 12ax7 laying around. Just need 2 hifi grade OTs and a schematic, layout or board from one of the sites that'll work with the tubes I have

[drew]

That's a Tweed Champ-type PT, according to the internet.  Not enough oomph for a 4xEL84 amplifier, is it?

[lego4040]

Compared to the PT used for the ST35 from DYNACO it is no match for power. Their PT puts out about 200-300ma and has two seperate 6.3 heater taps. It's nice only having to wire a amp with only one volume pot and nothing else. Since this will be a future project I'll have time to scrounge for parts and $$

[Ed_Chambley]

Compared to the PT used for the ST35 from DYNACO it is no match for power. Their PT puts out about 200-300ma and has two seperate 6.3 heater taps. It's nice only having to wire a amp with only one volume pot and nothing else. Since this will be a future project I'll have time to scrounge for parts and $$

I have 3 Dynaco ST70's and 2 more "parts" chassis.  For my use the ST70's are overkill and I have been considering replacing them.  Right now they are Left, Right and Center.  I have a Yamaha stereo receiver running the rear.  Everything is together and rather difficult to maintain.  Don't get me wrong, it sounds great, but it does take up a lot of room.


I get most tube stereo from old consoles.  A while back I found an old Zenith console for $25 with 2 EL84 that has a great sound, just not much power.  Recently I found a Stromburg Carlson with 4, EL84.  Nice white chassis and just dusty.  It was $35 and I made a wooden stand for it and it looks nice.  I prefer the look of the Dynaco's with KT88's and even EL34.  The big tubes just look cool, but for an inexpensive tube home stereo the Stromburg Carlson I found is really nice.

[lego4040]

I would glady take any advice and what models and name brands to look at/ for. The one on eBay I posted is getting Lots of bids already. I can search my local papers here too

[Ed_Chambley]

I would glady take any advice and what models and name brands to look at/ for. The one on eBay I posted is getting Lots of bids already. I can search my local papers here too

I find the best deals at Antique/Flea market places.  Once the amp is removed from the console and put on ebay the price goes from $25 to $250.  There are lots of good ones, but to get a big tube you will be looking at components like Dynaco.  Any of the old tube consoles sound really good, or least the amps do.  There is not a lot of difference in consumer grade from this period.

[P Batty]

The Dynacos are a good choice if you can find one cheap. There is a big Dynaco culture with upgrades, mods, etc.. readily available (except for those pesky 7199 tubes.) I got one in a home-made console at the Thrift store for $5.  I upgraded the caps and turned it for $300 with several buyers interested. The layout makes it easy to work on and they sound great. Even if the driver board is bad, the transformers are worth $$ and a great starting point for a home built.

[lego4040]

I joined DIYtube.com forum to get started and there is lots of good info there. Hopefully those Chaps are as nice as you guys here. The Dynaco St35 is really nice and a good starting point. I found this site here http://www.parksaudiollc.com/st35.htmlwhich is the owners from diy audio. It has the pcb version of the dynaco and it reminded me of all the effect pedal boards I still have stacked up to build. My brother gave me a really nice old school Onkyo TX-4500 recently as well

[lego4040]

Man there so many choices for SE EL84 stereo amps, low watts and incredible sounding. One German guy basically made one based on the 5F1 and it was incredible. Now with that in mind I was looking at Hoffmans GA-5 PVC build and wondering if that would work? Value changes of coarse but it would let me spend here and also pick up parts needed to finish the Stout. I've seen SE stereo amps with one 12AX7 and some with two. I would use one, left side of amp would use 1st half of tube and right side the other half of it. Why waist  half a tube

[lego4040]

While I wait for some money to make my purchases to finish the stout and probably the parts for the dynaco st35(board from Parks Audio and Edcor trannies) I started on a stereo my brother gave me, a Onkyo TX-4500 From 1977. I cleaned it up, blew dust out and hit pots with cleaner.  holy crap does this sound nice. It's got a wormer sound then my Pionneer D814

[Blind Lemon]

Check out Tubelab.com I built one of his Simple Single Ended and a pair of near field speakers for my office. One 12AT7 and 2 EL34s and a little bit of sand.


It is sweet, but only about 6-7 watts, good for a small room.


BL

[lego4040]

Tubelab is a nice site there. I ordered from Edcor tonight. I got my PT and two OT's for 107$ with Shipping

[lego4040]

Been busy and haven't done much but my board came in and it's sweet candy apply purple. Here is main board schematic, C9&10 are 470uf not 100 as shown

[lego4040]

Progress

[lego4040]

I have to go back and look at the AC 15 thread of mine. Some one asked me about the wood I just used here, to make a plate for the vox. I got some more. It could've been over at BYOC

[lego4040]

Wow this was quick to solder up since I didn't have to wire point to poiNt. Snubber caps on bottom across each main. Hopefully I'll have trannies soon, 6-8 week build time from Edcor and this is week 3. I'll tell you this, you fellows here lot nicer and quicker w responses. That hifi world is a little uppity. The creator of these is nice and responsive but no one else. Maybe We can start a non guitar amp section here

[HotBluePlates]

Looking good!

Does the board vendor have any tips/tricks for verifying you have everything soldered in the right spot?

Once upon a time, I had a job at a p.c. board manufacturer. There was a special test conducted on finished boards before a final function check & burn-in. I'll spare you some of the details, but a computer made tests of resistance, capacitance and inductance at various points on the board to attempt to identify missing or wrong parts, and solder bridges or opens. Sometimes you can measure various test points to get a quick verification of probable-right parts placement throughout the board before firing it up.

[lego4040]

These boards are verified and silk screened. It's a paint by numbers board, literally. The forum has lots of info and lots of builds and tricks/mods. Not a lot of forum conversation like here. You tube has some of his builds operating and they are sweet sounding. My next step is a diy 4.5" and horn speaker

[lego4040]

Here is the website http://parksaudiollc.com

[lego4040]

Edcor shipped my trannies today, 4 weeks to build instead of the quoted 6-8

[lego4040]

Chassis top has board connected with tube holes. Transformers in tomorrow

[lego4040]

Progress

[lego4040]

The Iron Has Come

[lego4040]

I been away dealing w work and family issues but I'd like to wish every a Happy Holiday. I finally finished my stereo amp but have to find out what this high pitch squeal is coming from. It does play when I hook my iPhone mp3 to it. I will upload small video to my YouTube and post link here. Thanks for all your help guys

[lego4040]

Here is the YouTube linkhttp://youtu.be/py6u11u9Bqs

[terminalgs]

sounds like feedback. sources for feedback might be NFB loop or power supply caps.
 
do you have a schematic?


Does it squeal in both left and right channels?

[HotBluePlates]

sounds like feedback. sources for feedback might be NFB loop ...

I agree. I did the exact same thing in my last amp build; managed to connect a negative feedback loop in the wrong polarity, made a full-power oscillator.

Your schematic in Reply #27 shows NFB returning to R9 & R10 (one for each channel), but doesn't show where those came from. I assume they're from the output transformer secondary. If that's correct, swap either the primary leads or the secondary leads of the OT to turn the positive feedback into negative feedback. Pick either the primary or secondary wires depending on which is the easiest to access and swap.

Let us know if that swap doesn't fix it.

[lego4040]

Here is the rest if that schematic hook up. I got a email from this amp support web saying the Same thing about the NFB's. I will look into it but I got a weird reading on the NFB's resistors 9&10. On the board when I checked them they give me a reading of 123ohm and when I lift a leg off board I get correct 1.2k? I'm taking reading right at resistors coming out of body too

[sluckey]

Just swap the two secondary leads on both OTs.

[HotBluePlates]

Just swap the two secondary leads on both OTs.

Yes. Do what Sluckey (and me, and customer support) is saying.

...I got a weird reading on the NFB's resistors 9&10. On the board when I checked them they give me a reading of 123ohm and when I lift a leg off board I get correct 1.2k? I'm taking reading right at resistors coming out of body too

Non-issue.

Look at the schematics (it's a pain, because there are 2 sheets with relevant info): If you put your meter leads on the legs of the 1.2kΩ series feedback resistor, there is more than 1 path from one lead to the other. First path is straight through the 1.2kΩ resistor.

Second path is through the 100Ω shunt feedback resistor to ground; the other lead ultimately connects to the speaker jack and another 40Ω total to ground. So this path is 140Ω total resistance.

Both paths are in parallel; when you put your meter leads on the 1.2kΩ resistor, electricity travels through both paths. 1.2kΩ || 140Ω = [(1200Ω * 140Ω)/(1200Ω + 140Ω)] = 125Ω. Throw in some resistance variation due to normal part tolerances, and you have your measured 123Ω.


("1.2kΩ || 140Ω" is read as "1.2kΩ in parallel with 140Ω")

[lego4040]

Here is one reply from the creator of these systems about my problem. [A] and are just the cathode bias test points for the EL84s. I've moved them around from the previous revision. I changed the heater center tap hook up from [A] to just because it is closer to the edge of the PCB and further away from electrolytics (less chance of a soldering iron melt job on a cap). So either [A] or is fine for the 6.3VAC center tap - it doesn't matter.

lego4040, that sounds like a typical reversed NFB oscillation as Ed points out. First just disconnect the feedback (disconnect connection at J8). Then retest for oscillation. It that fixes it, swap the wires at your Edcor OPTs (8 ohm and GND) and reconnect J8 and retest. If it is still there, possibly we damaged C9 or C10 by shorting HV to the cap with the 12AX7.

Shannon

[lego4040]

  reversed leads fixed and it is a sweet sounding amp so far. Thanks for the help guys. Will keep posted