Kofi Annan in: "Open for Suggestion"

[Kofi Annan]

OK gang, it's been a while since I exposed my unconscionable ignorance with you, but I'm still reeling from the completion of the Seven Pound Mono Amp and haven't had time for responses, let alone new posts. But a mighty wind is blowin' at the Annan compound, and you know what that means....

So, some time ago, I started to compile parts for Thorsten's Monkey DRD, but given the completion of the aforementioned project, I will need to redeploy said accumulated parts to a new project.

And that's where you come in.

So, I have the following:

* a pair of 500V transformers wound by the world-famous SET fanatic and and overall curmudgeon, Jack Eliano

* A set of 1.5A filament chokes, also wound by the aforementioned barnacle

* A pair of 274B rectifiers (Valve Art, nothing fancy)

* Four D3A pentodes (to be used as driver tubes for the 300b DRD); datasheet here

* Several motor run caps, suitable for PSU smoothing

* Loads of poopy diapers and puke towels

So, the story is, I need some suggestions. I'd like to stay single ended and I wouldn't rule out a 2A3, KT88 (maybe Mikael's) or even a 300b if the price is right on the remaining parts. I have a set of Bottlehead Paramours that I like quite a bit, but I'd like to beat these with the new project.

Would you help a brother out? Wouldja?

Kofi

[BHD]

My first suggestion would be to build the amp you intended to, since you've already shelled out the long green for custom wound iron. The difference in cost between the amp you originally intended to build and any you might build at this point isn't going to be all that much anyway.

My other suggestion would be to sell the parts in the market place and use the money to buy diapers and formula...

[kevinkr]

Seems like the 300B DRD would still be a good idea with the D3A..

Just need some opts and a pair of exo-01 chokes to get it off the ground..

Transcendar makes some very nice 3K output transformers usually selling on eBay for about $120 a pair. I designed a 2A3 amplifier around this iron last year and was more than pleased with the end results. George (Tubelab) has built a bunch of 300B amps using the same iron with good results as well.

Edit:
The seller's eBay ID is ggaet.. Nothing currently listed for sale, but if interested I'd shoot him an email.

Link to most recent auction:
http://cgi.ebay.com/Pair-3K-Audio-Ou...QQcmdZViewItem

[Kofi Annan]

My first suggestion would be to build the amp you intended to, since you've already shelled out the long green for custom wound iron. The difference in cost between the amp you originally intended to build and any you might build at this point isn't going to be all that much anyway.

My other suggestion would be to sell the parts in the market place and use the money to buy diapers and formula...

Good advice on both fronts.

Just need some opts and a pair of exo-01 chokes to get it off the ground..

OK-- so the EXO-01 choke from Magnequest is a 100H job, while the Lundahl LL1667, which is what Thorsen has in his DRD schematic, is listed at 270H. With a disparity this great, I'm guessing it would not make a good substitution, but you know, I'm probably wrong about this...

[b]Transcendar makes some very nice 3K output transformers usually selling on eBay for about $120 a pair. I designed a 2A3 amplifier around this iron last year and was more than pleased with the end results. George (Tubelab) has built a bunch of 300B amps using the same iron with good results as well.[/]b

Wow. I wish I could use these, but again, the schematic calls for a 5.5K OPT. See the design below.

If these components could make for a direct substitution, then I'd gladly do it! So..... can they?

Kofi

[dsavitsk]

Originally posted by Kofi Annan
OK-- so the EXO-01 choke from Magnequest is a 100H job, while the Lundahl LL1667, which is what Thorsen has in his DRD schematic, is listed at 270H. With a disparity this great, I'm guessing it would not make a good substitution, but you know, I'm probably wrong about this...

I would think 100H would be fine, but you could also just use the Lundahl part.

Originally posted by Kofi Annan
Wow. I wish I could use these, but again, the schematic calls for a 5.5K OPT. See the design below.

3.3K is pretty standard for the 300B. The 5.5K will rob some output power, which, if you don't want the extra power, maybe a 2A3 is in order instead. Might be a bit cheaper to build.

[Kofi Annan]

I would think 100H would be fine, but you could also just use the Lundahl part.

Thanks!

3.3K is pretty standard for the 300B. The 5.5K will rob some output power, which, if you don't want the extra power, maybe a 2A3 is in order instead. Might be a bit cheaper to build.

Good point. I have 96dB Fostex 206Es in a BLH, so I don't need tons of power.

I also found some James Transformers that I think would suit the project nicely and not break the bank. They are rated at 120mA of DC current and the schematic calls for 80mA, but I would have thought this would be rated at AC, not DC.

What's the verdict on the Jameseseses? Can I use 'em?

Kofi

[dsavitsk]

The James transformers are quite nice, and quite a bargain.

The DC rating is what they need to be under to keep from saturating. The AC rating would, I suppose, corresponds to total output power. But, DC is what you are interested in.

[Jaap]

Only make a SEamp if your speakers have no X-over.

I spent years making se-amps while my religion forbid me to make PPamps. The best I made was a D3a (or E810F: sounds the same) triode strapped into tribute interstage into 300B (TJ meshplate) into vanderveen (Amplimo or Plitron) 3K OPT. Has seperate PSU for driver and powertube, build as monoblocks (8 chokes and 4 powertransformers, 2 x GZ37 tuberectifiers).
I spent weeks in bed with heavy pains for that amp because my back was more or less tore apart while I tried to lift a part of it.

Still the result is so so with my 90 dB tube-friendly speakers.
A smart chosen PP design can give better results with any speakers that has filters.

So now I changed my mindset. I am building a PP amp that will bring me into hifi heaven. Just to give you a hint, make something designed bij Olson, Gary Pimm or Allen Wright and everything wil come right at the end. I have learned the hard way.
Amen

[kevinkr]

I have had both two way (JBL Rhodes C37) and three way speaker systems, the latest my own design. (See the Onken thread) Both of these systems sound better with my 300B SE amplifier than any of the several PP amplifiers I have in the house.

Interestingly I heard some Luxman PP amplifiers recently with my Onkens and the sound was pretty good, although I still prefer the 300B SE amp..

I think it has a lot to do with the complexity of the cross-over and driver impedance variations over their passbands..

IMO A 90dB speaker system is not ideal for any SE, short of perhaps a 211, 845, GM70 or similar amplifier with >20Wrms per channel output. All of my speaker systems over the last 5yrs or so have ranged in the very high 90's to well over 100dBspl@1W/1M.

[Jaap]

with you kevinkr. But to be more precise, I did not say that any PP amp will sound better than se amps on speakers with filters. But there is a very good chance that the Tabor of Pimm, the Karna of Olson or the PP-amps of Allen Wright will sound better on your Onkens than the 300B se.
Of course, the better the behaviour of the speaker/filter combination, the less problems (on any amp I would think).