Ralph Power amplifier

[45drive45]

I only have this CCS scheme.

However I think I will be using Gary Pimm BMCCCS

[stigla]

"However I think I will be using Gary Pimm BMCCCS"

About that; The special CCS diodes, the 1N5294's seems to be imposible to source. At least anywhere in scandinavia... Anyone got'ny clues of where I could get some? (avoiding overseas orders...)


Stig

[45drive45]

The BMCCCS does not use that diode as far as I know.

only uses 15V zener diodes

http://home.pacifier.com/~gpimm/Battery_biased_ccs.htm

[stigla]

Hello, yet another time, I bring this tread to the top

I have been thinking allot of the idea of a fully symmetrical design, e.i. all PP stages.

I have been looking around for a cheap tranny to place at the ECC99 grids, doing the phase invertions, and then running the LL1660 in PP:PP. This means that there will be another 20mA to pull from my power tranny, but it will manage fine.

This means that the LL1660 must be connected in 2+2 : 2,25 + 2,25. What does this mean? why not 1+1 : 1,25+1,25?

Anyways, I think I have found a suitable phase splitter / input tranny in the lundahl catalog. Namely the LL1544A or the LL1554! (equal.)

What do you guy's think of this? Datasheet for the 1554 gives up a signal handling of +22dB. What does this mean? Currently I need around 2,4 volts to drive to full puwer.
It can be connected in 1 : 1+1 and has a amorphus core, and is much cheaper than the rather expensive Sowter 9100.

The tranny is stated as a general purpose audio transformer.

thanks in advance!

Stigla

[RichardJones]

I have a battery biased 6AQ8 as the driver tube in my 6B4G PP. Run them at 1.3v bias, parallel the sections for 20mA total...

sounds really good!

I have Electra-Print IT and Sovtek 6B4G's into EP OPT. Running Sylvania 5U4G's... wonderful sound.

Gonna pull the electrolytics from the power supply and replace the cathode bypass resistor / cap on the output with SLA batteries.



fun huh?

[Brett]

Originally posted by stigla
I have been thinking allot of the idea of a fully symmetrical design, e.i. all PP stages.

I have been looking around for a cheap tranny to place at the ECC99 grids, doing the phase invertions, and then running the LL1660 in PP:PP.

Sounds good Stig.
Why not use the 1635/5mA rather than the 1660? Unless you add a CCS into the cathodes and make the stage differential, rather than PP, the variations between even a well matched pair of triodes will be such that the core see a varying DC component and will saturate easily, as it has no air gap to allow for the DC at all. The 1635 is about the same price, and I beleive is the one Lundahl recommend for PP-PP applications.

This means that the LL1660 must be connected in 2+2 : 2,25 + 2,25. What does this mean? why not 1+1 : 1,25+1,25?

There are 4 windings on the primary of the 1660 and to be used in PP-PP it must be connected with all 4 windings in series (centre-tapped), as per the diagram in the datasheet. If the two winding on either side of the primary are paralleled the high frequency balance will not be maintained, and the primary inductance will be reduced by a factor of about 4.

If connected as per the datasheet, the primary has 4 winding in series, centre tapped, or 2+2. The number of turns on each secondary is 1.125 x (or 2.25/2) the ratio on each seriesed pair of primaries. It is not possible to have a 1:1.25 ratio on this trans in PP.

All of this is explained in the datasheets.

Anyways, I think I have found a suitable phase splitter / input tranny in the lundahl catalog. Namely the LL1544A or the LL1554! (equal.)

What do you guy's think of this? Datasheet for the 1554 gives up a signal handling of +22dB. What does this mean? Currently I need around 2,4 volts to drive to full puwer.
It can be connected in 1 : 1+1 and has a amorphus core, and is much cheaper than the rather expensive Sowter 9100.

The 1544(A) would be good in this app, and I've seen it recommended as such in other firums by Lundahl agents.

I've always accepted dBU to be dBV (U is always symbol for voltage in German publications for example) or dB relative to 1V. So +20dBV = 10V, so if you nedd 2.4V, you have a bit of headroom. It's best not to run cores in trans to the limit.

It is a heck of a lot cheaper than the 9100, but I don't know of any performance difference between them. The 9100 was a custom designed job at the request of Lynn Olson for the Raven preamp with the intent of having excellent HF balance. I don't know if the 1544 will be any worse (I doubt it).

I'd like to try the 1544 one day, but I have too many 1517's I got for about $2 ea, which I use as isolators for my AV gear, and no other need for them. Maybe later.

Cheers

[Carl Ekblom]

Hello,

Well, I think Lynn used LL 1554 in his first version of the Amnity Amp but I guess that the 1544 would be fine.

Carl

[stigla]

Thanks for replying guys!

The LL1544A does, according to the Lundahls page;

"Replaces LL1544 and LL1554", having a better core I think.

It's got an amazing 10Hz to 70Hz bandwith!



To brett:

I've already got the LL1660, so I thought it would be nice to use it instead of buying the LL1635....

I guess what I really was asking was; Can I use the LL1660 in a PP:PP configuration with the ECC99?

The LL1660 is very flexible so if I bought me a pair of LL1635 I can probably find some other use for the LL1660 in the future...

As you all probably know I have a working amp as per the schematic on page one, but the currents in the outputstage is different. (60mA)

I am very much in love with these amps right now, the music treated by them is just fantastic! I've had really few problems during the building.

But I guess I just want to explore more

I see before me a version of the Amity amp, just with 6B4G's on the outputs.

With a possibly investment in a CD player with a balanced output I started the idea with both XLR and RCA input connectors and thus the need for an input tranny for the RCA input.

So, Ill think about doing an investment in both a pair of LL1635 and a pair of LL1544A.

Anyone want some used LL1660? JUST KIDDING!!

Btw, the input tranny in the original Amity schematic is a Sowter 8920 I just realised... £40,69... about the same price as the LL1544A yes?... Anyone familiar with this Sowter Iron?


have a nice x-mas btw!..

stigla

[Brett]

Originally posted by stigla
I've already got the LL1660, so I thought it would be nice to use it instead of buying the LL1635....

I guess what I really was asking was; Can I use the LL1660 in a PP:PP configuration with the ECC99?

Yes, one one condition. As I explained (perhaps not very well) in my last answer, the LL1660PP cannot deal with any net DC current through it. With two even tightly matched ECC99 tubes as drivers they will not be close enough that they will bias exactly the same, and at some point(s) in the signal envelope there will be enough difference between the two to have a net offset and saturate the core.

The reason I suggested the LL1635/5mA, was it's gapped enough that it will allow a 5mA difference at least ( actually 9mA) between the two -99 stages without saturating. This is lots for tubes biassed at around 20mA each. This is why Lynn Olson uses the 1635/5 in the original Amity/Aurora. Later schematics use a pair of CCS as anode loads, with a 1635PP in parafeed. The CCS's can be controlled closely enough that no airgap is needed in the IT, so the -PP version can be used with it's higher inductance.

If you add a CCS in the tails of the ECC99's and make them a diff pair, rather than PP, the LL1660PP would be fine, otherwise you'll need the 1635. To add a CCS (use Gary Pimm's BBMCCS) connected at the bottom of the -99 cathode resistors and run to a negative supply of about -40V.

As you all probably know I have a working amp as per the schematic on page one, but the currents in the outputstage is different. (60mA)

This where they should be run.

But I guess I just want to explore more

Can be lots of fun, and once you have a box full of parts, quite inexpensive. Tubes, iron, passives, don't really go "off" from sitting on a shelf.

I see before me a version of the Amity amp, just with 6B4G's on the outputs.

Nice. That was my plan before I chose a slightly different path, but it's something I'd still like to investigate later.

With a possibly investment in a CD player with a balanced output I started the idea with both XLR and RCA input connectors and thus the need for an input tranny for the RCA input.

Big tip; get a Steven and Billington TX102 transformer volume control. The <i>best</i> volume control I've ever heard, and you get balancing as well for free.
http://www.stevens-billington.co.uk/TX102.htm

Cheers
Brett