1954 DIY Tube Amp

[DaveInVA]

Back in 1954 my Dad worked for Halldorson Transformers and soon after worked for Grommes where he eventually was General Manager. When transformer companies came out with new audio transformers they would sometimes offer a sample schematic showing its use and sometimes even offer a kit. Stancor did this also. So in 1954 my Dad designed this "HiFi 20" to showcase their new line and they were going to offer it in kit form. I am not sure if these ever made it that far but I have all the documentation including the Bill of Materials (both handwritten and official), my Dads notes on its design, the mechanical drawings for the chassis and even a Nov 1954 receipt from Newark Electronics for some of the parts. But best of all I have the actual prototype. It was my first amp ever as a kid. Mono of course. I always thought it would be cool to build a 2nd one for stereo. I haven't done so as yet but here are some pics of the original:

http://www.braveknight.com/images/HiFi20BK.jpg
http://www.braveknight.com/images/HiFi20FR1.jpg
http://www.braveknight.com/images/HiFi20UN1.jpg
http://www.braveknight.com/images/HiFi20Sch.jpg

And some misc things attached..

Dave

[ke4mcl]

thats really cool man! i love seeing old tech history like that. you should recap it and put it to use. a nice mono amp with a good corner speaker is sweet for playing 50's jazz.

[Flick]

I love it!

[DaveInVA]

thats really cool man! i love seeing old tech history like that. you should recap it and put it to use. a nice mono amp with a good corner speaker is sweet for playing 50's jazz.

http://www.braveknight.com/images/Scott331B.jpg

And I have the perfect unit to drive it with - the 1954 Scott 331-B mono am/fm tuner preamp my Dad bought to use with it. I wish I still had the squeaker he had that I used as a kid. Was an art deco gold and brown large ported cabinet with an old 12" Jensen Coaxial from that same period, but the cabinet was older. I will have to find something similar to use. I still have his Garrard RC80B Vinyl grinder also:

http://www.braveknight.com/images/RC80.jpg

I can have my almost complete original first hifi system.


Dave

[vinyldavid]

*hearts*

You have the coolest shtuff. I'll be getting a single Karlson cabinet, driver unknown and want to put together a mono system sometime...I have a Heathkit AJ-30 mono tuner, a Russco CueMaster with Empire 98 arm as the TT, an Ampex AG-440B as the R2R, a Hafler DH-200 with one channel blown as the power....I just need a preamp.

[StereoGaryo]

Nice.
Looks like a pair of 5881's for the finals.
Sweet sounding tube.

[DaveInVA]

Nice.
Looks like a pair of 5881's for the finals.
Sweet sounding tube.

Yes they are still the original Tung Sol 5881's and they still test strong.

Dave

[stereorob]

http://www.braveknight.com/images/Scott331B.jpg

And I have the perfect unit to drive it with - the 1954 Scott 331-B mono am/fm tuner preamp my Dad bought to use with it. I wish I still had the squeaker he had that I used as a kid. Was an art deco gold and brown large ported cabinet with an old 12" Jensen Coaxial from that same period, but the cabinet was older. I will have to find something similar to use. I still have his Garrard RC80B Vinyl grinder also:

http://www.braveknight.com/images/RC80.jpg

I can have my almost complete original first hifi system.


Dave

dude, seriously, you have one of the most impressive collection of unique stereo gear ive ever seen. everytime i read one of your threads, i get a rapid heartbeat! ive been looking for a tube scott tuner/pre or receiver with the gold face and twin racing dials like that for 15+ years. absolutly beautiful beautiful stuff! and that one of a kind tube amp is out of this world! *bigthumbup*

[dey93254]

Dave,

You wouldn't happen to have the parts list to this amp as well would you? I think I would love to build a pair (for stereo) of these to run as a final amp.

[DaveInVA]

Yes I do. I have all the paperwork. I'm not sure if this ever went into any production but all the paperwork including parts lists, chassis mechanical drawings, parts prices etc. My Dad kept it all. Its a wonderful sounding amp. I'd love to build a stereo pair myself as it would be hard to make an exact copy of the one existing version.
I'll try scanning the parts lists and see if they are readable. Otherwise I will make up a parts list and post it here.

Dave

[DaveInVA]

Here are scans of his original parts list. There is another parts list done professional as a "Bill of Materials" for production but its over several pages. There is also a page that shows parts comparisons to other "Williamson" style amps of the day so they could prove they were not plagiarizing another companies design. I guess they had to cover their butts. Lastly is his actual frequency response measurements.
If you want to keep it all octal subbing a 6sn7 for each 12AU7 should work fine.

http://www.braveknight.com/images/Sch2.jpg
http://www.braveknight.com/images/PL1.jpg
http://www.braveknight.com/images/PL2.jpg
http://www.braveknight.com/images/PL3.jpg
http://www.braveknight.com/images/PL4.jpg

Here is another version dated the same day:

http://www.braveknight.com/images/HiFi20Sch.jpg
http://www.braveknight.com/images/PL5.jpg

They look basically the same.




Dave

[vinyldavid]

*eyepop*

Those measurements are stellar! I need to build a pair of those someday...

[DaveInVA]

*eyepop*

Those measurements are stellar! I need to build a pair of those someday...

Shows how good those stock transformers were back then. Its also "Ultralinear" with screen taps and that likely helps also.

The trick is going to be to find transformers that good or find some original ones somewhere as they may come up from time to time.


Dave

[DaveInVA]

Here are the specs for the output transformer:

model H4103 | pri. imped. 7400 | + or - 1db 10-100,000 Cps | 40watts max |100Ma max pri. DC/half | $22.50 (in 1954)

Thats $189.58 in todays money so it would have been a high end tranny for sure.


Dave

[DaveInVA]

The C5029 Choke specs:

4 HY, 100 ohm DC, 175 MA DC $6.30 (1954)

Dave

[DaveInVA]

P9316 Power Transformer specs:

375-0-375 150 ma, 5V 3A, 6.3 CT, 4.5A, $12.85 (1954)


Dave

[dey93254]

Once I get the parts together I will post pics of the build. Thanks dave

[DaveInVA]

Once I get the parts together I will post pics of the build. Thanks dave

Cool, let me know what you find to use for the output tranny. The power tranny and choke should be no problem.

Dave

[vinyldavid]

My local amp builder suggested this:

These will work for two mono amps
http://www.edcorusa.com/p/439/cxpp50-ms-6_6k

http://www.edcorusa.com/p/783/cxc100-5h-200ma
http://www.edcorusa.com/p/589/xpwr002_120


Use this power transformer for stereo with solidstate rectification , or mono for solidstate rectification .
http://www.antekinc.com/details.php?p=731
http://www.antekinc.com/pdf/CA-xxx.pdf

Need for the cover is optional , can be mounted under chassis if the chassis is 3 inch tall

Good source of caps & chassis
http://angela.com/electrolyticcapacitorsbyjjnichiconandjensen.aspx

Choke for stereo amp

http://angela.com/hammondchoke193p.aspx

A rough estimate of quailty parts is $600 to $700

[DaveInVA]

I've dealt with Angela and Edcor many times and always had good results. Not many new transformers seem to have the 100khz bandwidth the Halldorson ones did. Also going to 6.6k from 7.4k will give you slightly more power but also a little more distortion. That was always a trade off to decide where to go. It probably wont be much higher distortion but I figure my Dad had a reason for choosing that one as they also had a 6.6k version then also. The original amp sounds wonderful and I always wanted to built either a stereo version or 2 mono blocks. I used the heck out of it as a kid and my Dad used it previously and it never once broke and still has all the original parts. The Edcor would probably be the best choice without spending a ton of money. Hammond makes an output with those specs also but I've had mixed luck with them and wouldn't take the chance with something like this.

vinyldavid - what did your amp builder think of the design?

Dave

[vinyldavid]

I'm not sure where to get better transformers....I have no idea who makes good transformers these days.

If I can find a suitable pair of output transformers, I'm going to try and get the suitable PSU iron on the cheap. Maybe some organ amps or something to go on after someone else pulls the tx's.

The amp builder said it was very similar to the Eico HF-20 and 22...makes me wish I hadn't gotten rid of my HF-20. Otherwise he didn't give much of an opinion.

A friend of mine took a look at the schematic and thought it was a good simple design that measured extremely well, and if I end up building them he wants to hear them (he doesn't like tube amps for HiFi as a rule).

[ke4mcl]

hammond actually makes decent iron for their hifi line.

[DaveInVA]

That Halldorson output would be $189 in todays money and it specs at 10-100k in their catalog and in real life use measures even better in some respects. So it was definitely a high end tranny then. I guess you could always put that in an ebay search and hope a couple of originals turn up.
I have used Edcors before though and they will probably sound just fine. They only list theirs from 20-20k -/+ 1 db though it may do better in real life...


Dave

[DaveInVA]

It's a Williamson topology which was the flavor of the day through much of the 50's because of its low parts count and decent specs made hifi affordable to more people. Thats why my Dad made that chart comparing components with some of the already available ones on the market to prove the design wasn't an outright copy of someone elses.


Dave

[vinyldavid]

I've never actually heard of Halldorson before this thread....unfortunately there's none related on eBay. They obviously are incredible iron.

[DaveInVA]

I'm not sure where to get better transformers....I have no idea who makes good transformers these days.

If I can find a suitable pair of output transformers, I'm going to try and get the suitable PSU iron on the cheap. Maybe some organ amps or something to go on after someone else pulls the tx's.

The amp builder said it was very similar to the Eico HF-20 and 22...makes me wish I hadn't gotten rid of my HF-20. Otherwise he didn't give much of an opinion.

A friend of mine took a look at the schematic and thought it was a good simple design that measured extremely well, and if I end up building them he wants to hear them (he doesn't like tube amps for HiFi as a rule).

The hf 20 & 22 are lower power and dont have the cathode bias balancing to adjust for a symmetrical waveform but also being a Williamson layout is similar yes.

Dave

[DaveInVA]

I've never actually heard of Halldorson before this thread....unfortunately there's none related on eBay. They obviously are incredible iron.

Gramer - Halldorson was a competitor of Stancor, Chicago transformer etc. My Dad worked for them after WWII and ended up at Grommes later.

Here is one of their catalogs online:

http://www.tubebooks.org/file_downloads/halldorson.pdf


Dave

[vinyldavid]

I did not verify the builder's claims...just blatantly reposed his response after being linked to this thread. Hopefully someday I can make a pair.

The builder does know what he's doing...he built the best amps I've ever heard-beating a Marantz 8B, TOTl Audio Research, McIntosh MC2500, 2301, 1.2kW, and everything else I've ever heard.

[DaveInVA]

I did not verify his claims...just blatantly reposed his response after being linked to this thread. Hopefully someday I can make a pair.

He was right in that they are similar in design mostly due to them both using the Williamson layout.

Dave

[DaveInVA]

http://www.braveknight.com/dave/images/DadHalldorsoncr.jpg

Here is my Dad (on the left) at one of Halldorsons show booths probably McCormack Place Chicago...


Dave

[ke4mcl]

here ya go david..
http://www.hammondmfg.com/1608.htm

i would go with the 1650f. the high plate resistance will result in less power but the 5881's will last longer. quality vintage 5881's aren't cheap.

[DaveInVA]

here ya go david..
http://www.hammondmfg.com/1608.htm

i would go with the 1650f. the high plate resistance will result in less power but the 5881's will last longer. quality vintage 5881's aren't cheap.

I've used a lot of Hammond iron and have had mixed results. I mentioned using something closer to the original spec of 7.4k also because you will also get lower distortion though a lower impedance may get a little more power it will also have a little more distortion and like you said may shorten the life of the tubes. Because the prototype amp has lasted so long and with no repairs needed and still has original tubes seems to say everything is operating in its safe zones and not being pushed to the max (or beyond) like some amp designers did in order to get more power etc.

Dave

[DaveInVA]

If you find yourself a pair of these they will work fine:

http://www.ebay.com/itm/ACROSOUND-MODEL-TO-300-ULTRA-LINEAR-TUBE-OUTPUT-TRANSFORMER-W-TAPPED-PRIMARY-/180826136184?pt=Vintage_Electronics_R2&hash=item2a1a13de78#ht_500wt_1200

Yes they are a little low at 6.6k but they are excellent quality well respected trannies....The TO-300 is fairly easy to find as it was used in lots of old GriefKit stuff.


Dave

[DaveInVA]

Just an update. I just looked over the actual amp and compared it to the 2 schematics I posted. It most closely matches the one with only 4 coupling caps. I guess after doing the first circuit he redid the second to simplify the circuit somewhat as it does have fewer parts. Both are dated from the same day. The only difference I can find is that it doesn't have the input coupling cap as shown in the simplified schematic. Otherwise seems the same.


Dave

[DaveInVA]

Here is the Acrosound catalog with specs and sample Williamson amp circuits showing family similarities to this type of amp. This company was one of Halldorsons competitors of course.


http://www.clarisonus.com/Archives/Trans/Acro55.pdf


Dave

[DaveInVA]

I've pretty much decided to build a stereo pair. I may make a stereo chassis as it will be a little cheaper to build then 2 monoblocks though having a separate power supply for each channel can be a big plus. I am going to see if I can get the chassis pro made by a friend of a friend of mine that has a CNC machine and makes custom stuff.
Not sure what transformers I want to use yet. I like the Arcosound iron because it will probably be the easiest old iron to find and they have a good rep. They do spec them for 5881 tubes in their catalog but they are 6.6k and not 7.4k so will likely have slightly higher distortion. They also seem to have a lower power bandwidth than the Halldorson iron so they may not sound as nice played loud. In the meantime I will research other old and new transformers for better fits. I did find a higher power 3.6k tranny so you could use 4 outputs (2 in parallel) for more power but I think I want to keep it more to original spec.


Dave