What (budget) power amp to buld

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What (budget) power amp to buld

Postby Trackhappy » Wed Jan 13, 2016 11:25 pm

Hi all,
I have been in electronics for a long time, and just lately got a hankering to build a valve amp. I don't have an amp at home, so it would be useful. I'd like to make it look nice in the lounge, maybe some nice timber bits for accent. I have been looking around at various choices and decided the following:
1. I don't have the experience to modify a design so it must be a proven design.
2. I don't want massive power, minimum 10, up to 40 watts maybe per channel (although I'll nooo complain if I can get more for a good price).
3. I have the skills to build it and fault find it if necessary (and healthy respect for bitey amps).
4. I have mechanical skills to make or modify a chassis.
5. I have a limited budget, but don't want to skimp on important stuff.
6. I am in Australia.
7. I'd like the bigger size tubes just to look impressive.
8. Decent speakers will follow if I get the amp right.

I was looking at the ST70 and a host of others, then came across Pete's "Engineers Amp". This one appeals to me as proven, relatively simple, and a good starter project. The PCB looks great, (shame that the Aussie dollar does a nasty on it and postage adds insult to injury) and I may well order it shortly unless I get any comments convincing me otherwise. My main concern are the output tranny's. Does anybody know of a source of suitable iron in Australia? Hammond are available over here, what are the equivalent in Hammond?
Any other comments or local sources, I'd be happy to hear.

Thanks,
Glenn.
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Re: What (budget) power amp to buld

Postby soundbrigade » Sun Jan 17, 2016 1:44 pm

Australia ... well, that's gonna be tough. Once you let go of that rope you Aussies hold on to you will fall off the planet .... ;)

Seriously, I, myslef is build the Currawong from Silicon Chip. Building it because it was cheap and simple but I have some doubts when it comes to some kind of sonic result.

IF I was to go for a somewhat beefier amplifier, I'd look at tubes like EL84 for a small beef or EL34 for a bigger beef or KT88 for yet a bigger beef, where EL34 would be an optimal choice. In this case we start at 12WW up to 30-50W, depending on tubes and construction.
When it comes to cheap tubes, I'd have a look at Russian GU50, but as there aen't too many proven designs, the EL34 is the better choice.

I read this page about cheap output transformers: http://www.ozvalveamps.org/optrans.htm

When talking about proven designs, check Erik Andersson's site. All the schematics are showing commerscal available tube amps: http://www.erikasson.se/schemor.php.
The Audio Innovation 800 is a good one, but there are tons of good designs for EL34 out there.
Magnus

"It is always more difficult to fight against faith than against knowledge."
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Re: What (budget) power amp to buld

Postby Trackhappy » Sun Jan 17, 2016 5:01 pm

Thanks for the response.
The links look interesting, especially the cheap transformers. I think on balance the Engineers Amp suits my budget, skills and performance. I am not really into changing designs at this stage so I will stick to the stated transformers or direct equivalents. I will just have to get the necessary dollars aside and place an order on Edcor and Pete I guess. Until I have that under my belt, not much else can happen.

Thanks for the great forum by the way. Very interesting and helpful.
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Re: What (budget) power amp to buld

Postby Gingertube » Mon Jan 18, 2016 11:27 pm

G'day from Oz

For others reference - Pete's Engineers Amp.
http://www.pmillett.com/DCPP.htm

Has a good rep from people who have built it. Getting suitable Compactron Tubes may be an issue here in Oz.

I have not heard a Currawong but as a hobbiest tube amp designer/builder (and Electronic Design Eng in the day job) there were issues with the design I did'nt like, particularly the phase splitter. What bothered me most was that the design "faults" were basic and easy to correct. Well easy to correct before the PCB was laid out anyway.

I may have some "stuff" on my shelf in Adelaide which may be of interest to you if you don't want to build from scratch.
1) An old Jap "STAR30" push pull 6GW8 Integrated Stereo Amp with a Solid State MM phono preamp in it, a few dings and scratches on the case. I could let you have cheapish. Put it on the shelf 2 years ago when it stopped working. Prior to that I'd used it as the workshop sound system in the day job. Available as is or fixed. Can supply some spare 6GW8 (ECL86) as they are getting hard to find.
2) A VERY Impressive looking TRIO brand Integrated Amp with one blown output tranny, push pull EL84, sitting on my shelf with a pair of Hammond 1608 Output Trannies waiting for me to fix it. I intended to replace both output trannies to keep them the same and rebuild the power amp section to my Baby Huey design. This would be a MUCH more complicated undertaking although less so if repaired to existing circuit. Gold Anodized case, fancy balance meter on the front panel etc.
Probably not suitable since I already have taken apart.
3) TOO EXPENSIVE??? A pair of VDV70/100 Monoblocks, the 100W version. Quad of EL34 each channel monoblock, Plitron Torroidal Power and Output Trannies. A few stray extra holes in one of the chassis. Small ammount of work to set them back to work. I pinched the Winged C Svet EL34s for some guitar amps but could drop some JJ's in them.
4) A bit daggy and not real cheap - My Baby Huey Prototype, Push Pull EL84 with Hammond 1608 Output Trannies. Working, Lovely sound. Dagy coz being the prototype it had a heap of mods before final circuit and in fact started life as a Morgan Jones Bevois Valley.

Also if you deside to build from scratch I may have suitable power and output trannies on my shelf (depending on what you decide to build).

P.M. me if any of this is of interest.

Cheers,
Ian

Soundbrigade "Australia ... well, that's gonna be tough. Once you let go of that rope you Aussies hold on to you will fall off the planet .... " - Don't worry, the earth sucks.
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Re: What (budget) power amp to buld

Postby Trackhappy » Mon Jan 18, 2016 11:49 pm

Thanks Ian, PM sent.

At this stage I am happy to look at all options. Fussy not, repairs don't mind, chassis damage is fine, I intend to put a flashy wooden case around it anyway. Modifications only if they are proven ones as at this stage I don't have the necessary knowledge and experience to make design changes.
Jap sounds like a nice project to start.
TRIO sounds nice, but doubt I could afford it.
Monoblocks, sounds like a fun project.
Baby Huey, prefer something to fix or build.

Cheers,
Glenn.
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Re: What (budget) power amp to buld

Postby Trackhappy » Tue Jan 19, 2016 5:48 pm

Had a look at the Baby Huey thread, that is a possibility if you have a couple of tranny's and I can afford them. Is there a preferred/stable version I can look at? I wanted to use "big tubes" just for visual appearance, but maybe I should start with these.
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Re: What (budget) power amp to buld

Postby Trackhappy » Tue Jan 19, 2016 8:41 pm

Anyone tried these cheapies?
http://www.ebay.com.au/itm/Bugera-6L6GC ... SwFqJWnnQn

Based on the link provided by Soundbrigade, would those and these:

http://www.altronics.com.au/p/m1130-40w ... ansformer/

Be a usable combination for a 6L6 Clementine?
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Re: What (budget) power amp to buld

Postby Trackhappy » Thu Jan 21, 2016 2:33 am

After some more research I figure the 100 volt line transfers M1120 suit push pull, probably not single ended. I think that they will suit the ST-35, albeit not perfect. I am not quite sure about the UL tap percentage, which looks like it may be 40% not 25%. There are articles online saying they will work ok. At their price, I'll have a go and eventually replace them with something better.
So, ST35 it is. With the US dollar so strong, I'll skip the PCB from Triode and point to point it. I won't make a final chassis until I am happy with the whole thing.
Now to find a 240V tranny and start buying bits..... surreptitiously ;)
Maybe I'll mount it inside my Dalek p[
Cheers,
Glenn.
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