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mg16 29th November 2001 04:33 AM

I am collecting parts to do the diy project published in glass audio magazine 1995. "Single ended Glory" by Eric Barbour. After reading reviews and posts concerning 45 tube amps, I am certain that they have the qualitys I am looking for. I own modded Klipsch Lascalas,(104 db/1w), so the 2watt output should be sufficient for my medium to small listening room.
Has anyone built this project? In the article, Mr. Barbour says that expensive single ended opt's are unnecessary, as the 25 ma. drawn by each tube won't saturate a decent 30 watt push pull opt.
He says any unit of 30 watts with 4 to 6kohm plate to plate resistance will be fine. He used the iron from a Sansui receiver,(1000a), and could discern little difference when he subbed in a friends Audio Note single ended opt.
I see transformers rated at 5kohm primary at various parts suppliers. Is 5kohm primary the same as 5kohm plate to plate?
I have built many projects, but this is my first tube amp.
It seems simple, won't be that expensive, and should sound great by all accounts. I am now using 2a3 monoblocks.
I understand the dangers involved in tube high voltage and feel secure enough to build it. Any help appreciated.

GRollins 29th November 2001 04:45 AM

Yes, a 5k transformer primary is the load presented to the plate(s). For optimum power transfer it should match the plate impedance, but a little bit one way or the other will not hurt.


45drive45 12th December 2001 07:21 AM

I am not familiar with the exact circuit that you are refering to but Ihave built and am using a 45 tube amp. Driver tube is 5842 and uses a 1:2 interstage.
The #45 sounds wonderful! Better than a 2A3 that I also built and definitely better than the PP34 that I built. I am not using any exotic parts and it definitely sounds better than my SE2A3 which I spent much more on due to the expensive resistors etc.

mg16 13th December 2001 04:42 AM

to 45drive45
Thanks for the info!
Can you reccomend some good,( and affordable), output transformers for the 45 amp. What output iron did you use for your 45? I would like to use something a little better than the Hammond 125se for $28.00 each, but less expensive than the Magnequest exo-45 which is very expensive but supposedly fantastic with 45's. Something under $200.00 per pair?

45drive45 18th December 2001 09:18 AM

For the opt I am using a rebuilt WE iron from Japan. It looks horrendous ! haha. Here in Singapore there are a few diy folks who have use Lundahl OPT with great success. Its not very expensive but obviously it depends if you have easy access to it. Personnaly I have used Lundahl and it sounds good and not THAT expensive. Over here its about S$195 or about US$110 each. Only thing about the Lundahl its not potted so its really ugly displaying unless you can get a nice cover for it. In all my new amp, I try to place everything under the chassis and only leave the tubes on top..sometimes a capacitor or two! Decided to go with a minimalist style on the outside but under the chassis its loaded. The main reason was to hide those ugly Lundahl OPT and Interstage and Power Trans.
Have fun building

siu sin man tho 30th March 2003 07:15 PM

2 Attachment(s)
I use 417a to push 45 already.
later use 6C45 interstage to puch 45.

Joel 30th March 2003 09:15 PM

Re: to 45drive45

Originally posted by mg16
I would like to use something a little better than the Hammond 125se...
Why is that? Have you listened to one? They sound quite good actually - don't let the price tag fool you.

SHiFTY 30th March 2003 10:42 PM

Another vote for the 125ESE :) I am using a pair of them and they aren't half bad... They are quite big physically too... Freq response is apparently 20:20K flat at 1 watt....

The-Planet 31st March 2003 01:03 AM

45 output transformer
I've built this circuit several times. The Hammond 125ESE and 125E are both good sounding within their modest price range, but have significant limitations in bass. If you really hope to get the best from a 45, spend a bit more on the iron.

If you really need to keep under $200/pair, look into the Hammond 1628SE or One Electron UBT-2

If you can swing a bit more, the Electraprint BE5KB ($260/pair) is a great choice - very sweet sounding. At a bit higher price the Magnequest DS-050 ($360/pair) are also very very nice.

siu sin man tho 31st March 2003 08:36 AM

2 Attachment(s)
this is the finish outlook of my 417a push 45 se amp.
I use tango iso xe20s c-core output.
I can choose 3.5K or 5K to change the sound quality.
I use this amp to push my 1970's klipish la scala.
1970's still use alnico magnet.
also I use this amp to push my AER too.



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