Recommendations please for a really transparent 1:2 stepup transformer for a 2-stage 300b/2a3 amp. Input tube would be typically one with a mu of around 20 like ECC99, EL33 or EL84 in triode etc.
In my case please include input transformers available in the UK/Europe. However it's also possible to order from the USA or elsewhere and factor in the import/shipping cost, so all possibilities are on the table. Obvious examples would be:
Sowter
Lundahl
OEP
Slagle
Hammond broadcast range
Jensen
Cinemag
Other......
I'd be particularly interested in discussions of core material, e.g. amorphous, nickel, finemet etc. and which is best for transparency and clarity.
In my case please include input transformers available in the UK/Europe. However it's also possible to order from the USA or elsewhere and factor in the import/shipping cost, so all possibilities are on the table. Obvious examples would be:
Sowter
Lundahl
OEP
Slagle
Hammond broadcast range
Jensen
Cinemag
Other......
I'd be particularly interested in discussions of core material, e.g. amorphous, nickel, finemet etc. and which is best for transparency and clarity.
Hi Andy
As you may remember I use extensively the LL7903 for up to 1:8 and is a great SUT in my opinion for large signals. The LL7902 is also a very good one to consider.
My budget restricted me to the standard core version so haven’t tried silver not amorphous ones yet [emoji3]
I’m very happy with the LL7903 so will stick to it
Ale
As you may remember I use extensively the LL7903 for up to 1:8 and is a great SUT in my opinion for large signals. The LL7902 is also a very good one to consider.
My budget restricted me to the standard core version so haven’t tried silver not amorphous ones yet [emoji3]
I’m very happy with the LL7903 so will stick to it
Ale
Hello Ale,
Always good to hear from you. Yes, I know you like the LL7903. That's an obvious example.
Right now I have LL1540, LL1512 (similar), LL1554 (amorphous) and Hammond 124B which is 49% nickel. The LL1540 is a very standard part in Lundahl's range, mu-metal and on the cheaper end. The 124B is better than one might expect - on a quality level with the LL1540, maybe better because of more treble definition. It's a brighter sound with more treble emphasis despite the data sheet which suggests a falling HF response. I've just put it in circuit so will have to wait and see if the added HF emphasis is good or bad with extended listening. It's 1:3 stepup.
https://www.hammfg.com/files/parts/pdf/124B.pdf
Amorphous should be interesting - I haven't wired up the LL1554 yet.
Always good to hear from you. Yes, I know you like the LL7903. That's an obvious example.
Right now I have LL1540, LL1512 (similar), LL1554 (amorphous) and Hammond 124B which is 49% nickel. The LL1540 is a very standard part in Lundahl's range, mu-metal and on the cheaper end. The 124B is better than one might expect - on a quality level with the LL1540, maybe better because of more treble definition. It's a brighter sound with more treble emphasis despite the data sheet which suggests a falling HF response. I've just put it in circuit so will have to wait and see if the added HF emphasis is good or bad with extended listening. It's 1:3 stepup.
https://www.hammfg.com/files/parts/pdf/124B.pdf
Amorphous should be interesting - I haven't wired up the LL1554 yet.
Sowter 9063.
Pics:
Sowter
1:2 (parallel connected secondaries), 700R source, 10k load on secondary.
1:4 (series connected secondaries), 700R source, 10k load on both secondary.
vs.
LL1540 1:2 (series connected secondaries), 50R source, 10k load on both secondary
Pics:
Sowter
1:2 (parallel connected secondaries), 700R source, 10k load on secondary.
1:4 (series connected secondaries), 700R source, 10k load on both secondary.
vs.
LL1540 1:2 (series connected secondaries), 50R source, 10k load on both secondary
Attachments
Good performance of a step-up input transformer is dependent on how well the signal source can drive the input transformer.
Without a signal source that is fully capable, the very best input transformer will be a waste of money.
Without a signal source that is fully capable, the very best input transformer will be a waste of money.
Many thanks for that. The signal source is a NE5532 op-amp at the output of a AK4490 DAC.
How does that influence the choice of step-up transformer? Would a 600 ohm input be OK or does it require a higher impedance on the transformer input, and if so what?
No - it's a fairly cheap Chinese AK4490 DAC board no longer available. I have no specifications. As said, output is a NE5532 op-amp. I measure somewhere between 2 and 30 ohms resistance on the RCA outputs depending on the multimeter setting.
On the output of the Dac there are normally some resistors in series with the last active component to prevent damage when shorting the output. These need to be there but can be changed to a smaller value. So, "Yes You Can"! But why you want to use the transfomer in the first place? Not enough gain?
And second, why does it need to be that high grade?
The NE5532 is not worthy of this upgrade....
And second, why does it need to be that high grade?
The NE5532 is not worthy of this upgrade....
Andy - it is not clear to me whether you need an input or interstage transformer. Please clarify. The two types are very different in design.
Input - says so in the thread title!
Why do I need a good quality SUT? Because I could change DACs. No reason not to optimise the amplifier in its own right. Yes - not enough gain in the amplifier with EL33 driving 300b.
I can't change the DAC unfortunately since it's all surface mount. If it were leaded components I could increase the gain in the DAC for instance. Upgrading the DAC is certainly going to happen at some point but don't know to what yet. I'm not crazy about the NE5532, but two NE5534 start to be decent, and there are several possible substitutions.
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True, but then it would be best to build a suitable preamp instead and your gain issue is solved.
I tried a lot of different transformers but it always impoved if i could ommit the transformer and replace it by a good gain stage (tubes ;-)
I have a balanced audio system and therefore i used transformers as in some cases the source i used was not ballanced.
It doesn't sound bad with transformers just there is an improvement that's all.
I tried a lot of different transformers but it always impoved if i could ommit the transformer and replace it by a good gain stage (tubes ;-)
I have a balanced audio system and therefore i used transformers as in some cases the source i used was not ballanced.
It doesn't sound bad with transformers just there is an improvement that's all.
Attachments
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Then I can suggest UTC O-26 ouncer transformer. It has two 10 K ct windings. It has permalloy core. It allows for a little bit of DC offset, so can be connected to DAC without coupling capacitor. It sounds transparent at line level signal. It is not produced any more, but regularly appears on eBay for about $30.
It would only make sense to me if it replaced the op-amp in the DAC. At some point I'll upgrade the DAC so it's not impossible. But my only input is my DAC, so I don't need a preamp for anything else.
In your particular CD player (or your outboard DAC and Op amp):
What is the rated voltage output of the NE5532?
What is the rated current output of the NE5532?
What is the rated output impedance of the NE5532?
What is the lowest load that the NE5532 is rated to work with?
What is the rated distortion of the NE5532 when it drives 600 Ohms? (for example)
Many CD players put out 2.1Vrms, 3V peak, when the DAC is at full scale.
If the NE5532 puts out 3V peak, and drives 600 Ohms, it has to drive 5mA into the 600 Ohm load.
And, it has to drive 5mA at low distortion, or it will distort.
Does that give you any ideas?
This is probably better answered on the Solid State and/or Signal Sources threads on this forum.
Some of them may be more familiar with the NE5532.
Before trying to select an input transformer for a tube amplifier . . . Define all of the signal source parameters.
(would you put a small 4 cylinder engine on a large truck transmission; or put a 1 Horsepower electric motor on a hair dryer?)
What is the rated voltage output of the NE5532?
What is the rated current output of the NE5532?
What is the rated output impedance of the NE5532?
What is the lowest load that the NE5532 is rated to work with?
What is the rated distortion of the NE5532 when it drives 600 Ohms? (for example)
Many CD players put out 2.1Vrms, 3V peak, when the DAC is at full scale.
If the NE5532 puts out 3V peak, and drives 600 Ohms, it has to drive 5mA into the 600 Ohm load.
And, it has to drive 5mA at low distortion, or it will distort.
Does that give you any ideas?
This is probably better answered on the Solid State and/or Signal Sources threads on this forum.
Some of them may be more familiar with the NE5532.
Before trying to select an input transformer for a tube amplifier . . . Define all of the signal source parameters.
(would you put a small 4 cylinder engine on a large truck transmission; or put a 1 Horsepower electric motor on a hair dryer?)
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It is simple and doesn't need complications. If a DAC is driving a tube amp through 600 Ohm primary transformer, it doesn't see 600 Ohm load, it sees whatever the reflected amplifier input impedance is. Input transformer doesn't have its own impedance, it reflects impedances.