Mr. Lion's DIY Thread

[mordy]

So I got a bit more done tonight, including the amplifier feet, and holes drilled on each side panel for all 3 pairs of 10VA toroidal OPTs.

What's left - terminal strip mounting holes, ventilation holes (which I am still debating just how to do these nicely), front panel holes for power button, impedance rotary dial, stepped attenuator and 1/4" TRS out, then it'll be time to build within.

One other addition to the amp will be a pair of these NOS Simpson meters, one for each output tube to provide the plate current of each. These specific meters are from 1953.

WITHOUT COVER



WITH COVER






They are going to be placed in the general areas above. Debating if I use the black cover or the brass look without it - what do you guys think?

Would it be easier to see the readout of the meters on the face plate?

 

[Isaacc7]

No scale on the meter? I’m glad Tomas talked me in to getting the current meters. It is so much nicer to dial in the bias on the meters than fiddling with a multi meter.

 

[g0ldl10n]

Would it be easier to see the readout of the meters on the face plate?

Would be, but would be really tight with everything else on the front panel, so just going to place them there.

No scale on the meter? I’m glad Tomas talked me in to getting the current meters. It is so much nicer to dial in the bias on the meters than fiddling with a multi meter.

There is, just can't see it - up to 100mV (measurement taken over 1 ohm resistor) - I have tested these side by side with my DMM, and they are very accurate, although, I am not needing extreme accuracy, more along the lines of just always being able to know with a quick look that output plate current is normal and nothing weird is going on, without the need of using external MM probes / test points.

 

[LobalWarming]

So I got a bit more done tonight, including the amplifier feet, and holes drilled on each side panel for all 3 pairs of 10VA toroidal OPTs.

3 pairs?! Triple dual mono design? Wow!

What's left - terminal strip mounting holes, ventilation holes (which I am still debating just how to do these nicely), front panel holes for power button, impedance rotary dial, stepped attenuator and 1/4" TRS out, then it'll be time to build within.

One other addition to the amp will be a pair of these NOS Simpson meters, one for each output tube to provide the plate current of each. These specific meters are from 1953.

WITHOUT COVER



WITH COVER






They are going to be placed in the general areas above. Debating if I use the black cover or the brass look without it - what do you guys think?

Brass is classic, but black is more stylish and coherent for the product pictures when you list this design-breaking Triple Dual Mono amp on your internet store.

Although... if you kept the alternate desktop - the full unenclosed alligator-clipped desktop edition - then naked brass meters would be great. Just as long as they're placed in an inconvenient location.

 

[g0ldl10n]

3 pairs?! Triple dual mono design? Wow!

Bahahaha no - they are to run different impedance HPs more optimally, but don't give me any ideas!

Here's the breakdown

-10VA Antek toroidal PT repurposed as OPTs (specifics below - these all have dual primaries/secondaries, typically used as power transformers - both primary and secondaries wired in parallel).

High Impedance HPs (200-400 ohm) - AN-0115 - pri: 115v / sec: 15V
Medium Impedance HPs (80-150 ohm) - AN-0109 - pri: 115v / sec: 9V
Low Impedance HPs (20-80 ohm) - AN-0106 - pri: 115v / sec: 6V

Brass is classic, but black is more stylish and coherent for the product pictures when you list this design-breaking Triple Dual Mono amp on your internet store.

Although... if you kept the alternate desktop - the full unenclosed alligator-clipped desktop edition - then naked brass meters would be great. Just as long as they're placed in an inconvenient location.

I like the alligator clipped desktop edition idea!

 

[OctavianH]

They are going to be placed in the general areas above. Debating if I use the black cover or the brass look without it - what do you guys think?

Use the cover.

 

[g0ldl10n]

Today I figure how to calculate output impedance using the QA403 using two different known loads + some basic calculations via ohms law and my findings will likely bring a very slight change to the circuit.

Right now the following transformers being used for OPTs
High Impedance HPs (200-400 ohm) - AN-0115 - pri: 115v / sec: 15V
Medium Impedance HPs (80-150 ohm) - AN-0109 - pri: 115v / sec: 9V
Low Impedance HPs (20-80 ohm) - AN-0106 - pri: 115v / sec: 6V

I currently have the 9V transformers out of the test circuit so was only able to measure the output impedances of the 6V and 15V transformers, and I got the following output impedances.

High: 14 ohm
Low: 4.5 ohm

These aren't terrible, and function well, but I wanted to increase the output impedance of the 'High' setting for higher impedance HPs - well, I have a pair of 10VA 30V Antek transformers here so I threw those into the circuit took measurements and found output impedance at 40 ohms with those. So, the change likely coming will be throwing the 9V transformers out, and using the 6V, 15V and 30V transformers.

High Impedance HPs (200-400 ohm) - AN-0130 - pri: 115v / sec: 30V
Medium Impedance HPs (80-150 ohm) - AN-0115 - pri: 115v / sec: 15V
Low Impedance HPs (20-80 ohm) - AN-0106 - pri: 115v / sec: 6V

High: 40 ohm
Med: 14 ohm
Low: 4.5 ohm

I was a bit worried the gain would be raised to a point where noise floor was going to rise substantially with the 30V, but they are just as quite to my ears as the 15V transformers are paired with my high impedance HPs from ZMF (AO and VC), but provides significantly more gain/power than the 15V transformers did for those HPs.

 

[OctavianH]

Do not worry about output impedance Mr. Lion, Mr. Lobal has a magic box which makes any headphone happy with any amplifier. In fact, I am unsure if the amplifier needs to be a nice one. LOL

By the way, here is a nice example of how you can make those A and G1 detachable top caps. I'll borrow the photo:

 

[g0ldl10n]

Do not worry about output impedance Mr. Lion, Mr. Lobal has a magic box which makes any headphone happy with any amplifier. In fact, I am unsure if the amplifier needs to be a nice one. LOL

By the way, here is a nice example of how you can make those A and G1 detachable top caps. I'll borrow the photo:

Yes, I have seen @LobalWarming mention and discuss this on the forums - it's actually a wonderful solution for this issue, especially for OTLs.

Those look nice - it is one thing I can add without much complications once completely built, so we'll see exactly how I'd like to do it once the rest is built out.

Today, I have completed the front panel - I may end up going with a different power button style now that I see it on the front panel - it will have white LED around the ring and IO symbol, but not sure I am going to like it's style. But anyways, here's what the front panel looks like.

A few more holes in the top plate and assembly can begin. Slow and steady I suppose, and getting closer to completion.

 

[Isaacc7]

Yes, I have seen @LobalWarming mention and discuss this on the forums - it's actually a wonderful solution for this issue, especially for OTLs.

Those look nice - it is one thing I can add without much complications once completely built, so we'll see exactly how I'd like to do it once the rest is built out.

Today, I have completed the front panel - I may end up going with a different power button style now that I see it on the front panel - it will have white LED around the ring and IO symbol, but not sure I am going to like it's style. But anyways, here's what the front panel looks like.







A few more holes in the top plate and assembly can begin. Slow and steady I suppose, and getting closer to completion.

Which device? I’m afraid I’m out of the loop.

 

[g0ldl10n]

Which device? I’m afraid I’m out of the loop.

Oh, @LobalWarming has created a DIY external impedance box of sorts to use with main OTLs id imagine, so HPs with lower impedances can be used properly - he should be able to tell you more about it.

 

[Isaacc7]

Oh, @LobalWarming has created a DIY external impedance box of sorts to use with main OTLs id imagine, so HPs with lower impedances can be used properly - he should be able to tell you more about it.

Huh, sounds like a transformer lol.

 

[g0ldl10n]

Huh, sounds like a transformer lol.

Pretty sure that's what's in the external box - a few different transformers.

 

[LobalWarming]

Do not worry about output impedance Mr. Lion, Mr. Lobal has a magic box which makes any headphone happy with any amplifier. In fact, I am unsure if the amplifier needs to be a nice one. LOL

It's a transformation box. Makes a terrible amp sound nice. And a nice amp sound terrible. Transformers transform, right?

Yes, I have seen @LobalWarming mention and discuss this on the forums - it's actually a wonderful solution for this issue, especially for OTLs.

Yes, it was my (cheapskate) transformational solution, using a multi-tap 70V traffo.

Which device? I’m afraid I’m out of the loop.

Me too.

Oh, @LobalWarming has created a DIY external impedance box of sorts to use with main OTLs id imagine, so HPs with lower impedances can be used properly - he should be able to tell you more about it.

He should. But will he?

Huh, sounds like a transformer lol.

Sure does.

Pretty sure that's what's in the external box - a few different transformers.

Yes it is. Not different, just a pair of the same type - OSD Audio 70V line matching with 1KΩ, 500Ω, 375Ω and 250Ω taps for input and 4/8Ω output taps. See the mini-wire snake at this post.

No Triple Dual Mono Mojo.

But that sure is a tempting option. Wonder about a higher output impedance (80-120Ω) for high impedance phones... but appears their AN-130 is the top of the range.

However, since moving up the OTL sound train from coach to snob level, have found the TS 5998 or WE 421A can drive my Aryas and other low impedance phones very well without requiring electromagnetic transformative intermediation. In fact, the EL86 is pretty good as well. Although, I listen at reasonable levels and mainly small acoustic ensembles or solo instruments, so rarely need big loud boom boom power.

Still...to my ears. 'normal' AC regulator tubes like 6AS7/6080 do perform better with planars connected to a traffo-house.

 

[Isaacc7]

It's a transformation box. Makes a terrible amp sound nice. And a nice amp sound terrible. Transformers transform, right?

Yes, it was my (cheapskate) transformational solution, using a multi-tap 70V traffo.

Me too.

He should. But will he?

Sure does.

Yes it is. Not different, just a pair of the same type - OSD Audio 70V line matching with 1KΩ, 500Ω, 375Ω and 250Ω taps for input and 4/8Ω output taps. See the mini-wire snake at this post.

No Triple Dual Mono Mojo.

But that sure is a tempting option. Wonder about a higher output impedance (80-120Ω) for high impedance phones... but appears their AN-130 is the top of the range.

However, since moving up the OTL sound train from coach to snob level, have found the TS 5998 or WE 421A can drive my Aryas and other low impedance phones very well without requiring electromagnetic transformative intermediation. In fact, the EL86 is pretty good as well. Although, I listen at reasonable levels and mainly small acoustic ensembles or solo instruments, so rarely need big loud boom boom power.

Still...to my ears. 'normal' AC regulator tubes like 6AS7/6080 do perform better with planars connected to a traffo-house.

I have some limited exposure with OTL amps in the speaker world. The systems can sound wonderful but certainly limit your choices of speakers/headphones. Julias Futterman is rolling in his grave because of your contraption lol.