[L0rdGwyn]

Beautiful wiring! Would there be any magnetic coupling concerns shrinking down the depth of the chassis like below?



Is the chassis from Landfall Systems?

Assuming you can still do the rectifier mod with the resistors there?

TIA.

I wouldn't recommend putting the volume pot right next to the power switch, which is a source of 60Hz noise.

Edit - yeah, protection diodes will work just fine.

Yep, it is a Landfall chassis.

 

[L0rdGwyn]

I finished the amp, will post some pics shortly.

 

[L0rdGwyn]

Beautiful wiring! Would there be any magnetic coupling concerns shrinking down the depth of the chassis like below?



Is the chassis from Landfall Systems?

Assuming you can still do the rectifier mod with the resistors there?

TIA.

Oh I'm sorry those are protection diodes, disregard what I said, was out and about and just glanced at it. Yeah that should work fine!

 

[DenverW]

I finished the amp, will post some pics shortly.

Congrats! Tip a beverage back tonight in celebration as you play some tunes…

 

[L0rdGwyn]

Okay, amp is done. Didn't really feel like taking all of the test procedure photos, I'll do that at a later time. Input and output wiring done, all closed up.

 

[L0rdGwyn]

Next step will be to write everything up, step by step instructions with photos. I took over 300 pictures

 

[caryking]

I’m not an engineer; however, source impedance can help with headphone matching. I didn’t see it in the thread….

what is the source impedance of this amp?

 

[L0rdGwyn]

I’m not an engineer; however, source impedance can help with headphone matching. I didn’t see it in the thread….

what is the source impedance of this amp?

Output Z on the low setting with EL34 is 5ohm, on high Z setting 17ohms last time I measured. I would recommend low setting for 16-120ohm, high for 120ohm and up.

It should be able to run most any headphone well. The most demanding headphone I've tried with this amp is the Susvara. I thought it sounded great but I'm not a Susvara amplification connoisseur. We should have another opinion on that pairing soon.

 

[ScornDefeat]

Output Z on the low setting with EL34 is 5ohm, on high Z setting 17ohms last time I measured. I would recommend low setting for 16-120ohm, high for 120ohm and up.

It should be able to run most any headphone well. The most demanding headphone I've tried with this amp is the Susvara. I thought it sounded great but I'm not a Susvara amplification connoisseur. We should have another opinion on that pairing soon.

This is great information to know!

I believe @caryking was referencing the input impedance (source to amp) of the amp as opposed to its output impedance. I would assume it's probably 100k?

 

[L0rdGwyn]

This is great information to know!

I believe @caryking was referencing the input impedance (source to amp) of the amp as opposed to its output impedance. I would assume it's probably 100k?

Ahh well he did say headphone matching, so I assumed output impedance. The input impedance is 20K.

 

[ScornDefeat]

Ahh well he did say headphone matching, so I assumed output impedance. The input impedance is 20K.

Both figures are good to know, so appreciate it!

 

[caryking]

Actually, I read the following on Headphonesty:

The term ‘rule of eighths’ is used as a rough guide. Divide the headphone impedance by 8, and that is the maximum source output impedance (32 ohm headphones / 8 = 4 ohm maximum source output impedance). In practice, it isn’t that strict a rule and often success can be had with a greater range.

This ideal is based on the theory that regardless of how large an impedance spike is in the headphone driver’s response, a high enough damping factor prevents the frequency response from varying more than 1 dB (not typically audible).

“…if an amplifier’s output impedance is significantly more than an eighth of the headphone’s impedance, the frequency response and sound of the headphone can change. This results in bigger mismatches and creates more variation from the headphone’s default sound signature. The way that a headphone responds to an amplifier with output impedance higher than one eighth of the headphone can be entirely erratic – different headphones will respond in different ways, but generally the results will be negative.”

So, the amps source impedance is what I’m looking for, I think…

I use Audeze LCD-2F’s and watch to make sure I’m matching properly. I’m talking with an engineer that says his amp is a 1.5 ohm source impedance . He also says he will add pad resistors at the input jack, for the headphones, to lift his impedance to 9 ohms.

Now, he also has taps, on his output transformers, of 32 ohm and 68 ohm…

Thoughts?

 

[bcowen]

Actually, I read the following on Headphonesty:

The term ‘rule of eighths’ is used as a rough guide. Divide the headphone impedance by 8, and that is the maximum source output impedance (32 ohm headphones / 8 = 4 ohm maximum source output impedance). In practice, it isn’t that strict a rule and often success can be had with a greater range.

This ideal is based on the theory that regardless of how large an impedance spike is in the headphone driver’s response, a high enough damping factor prevents the frequency response from varying more than 1 dB (not typically audible).

“…if an amplifier’s output impedance is significantly more than an eighth of the headphone’s impedance, the frequency response and sound of the headphone can change. This results in bigger mismatches and creates more variation from the headphone’s default sound signature. The way that a headphone responds to an amplifier with output impedance higher than one eighth of the headphone can be entirely erratic – different headphones will respond in different ways, but generally the results will be negative.”

So, the amps source impedance is what I’m looking for, I think…

I use Audeze LCD-2F’s and watch to make sure I’m matching properly. I’m talking with an engineer that says his amp is a 1.5 ohm source impedance . He also says he will add pad resistors at the input jack, for the headphones, to lift his impedance to 9 ohms.

Now, he also has taps, on his output transformers, of 32 ohm and 68 ohm…

Thoughts?

This is just a terminology thing. The rule of eighths describes the relationship between an amplifier's output impedance and the headphone's input impedance. When he states the "1.5 ohm source impedance," he is presumably referring to the amplifier as the source for the headphones.

 

[L0rdGwyn]

Actually, I read the following on Headphonesty:

The term ‘rule of eighths’ is used as a rough guide. Divide the headphone impedance by 8, and that is the maximum source output impedance (32 ohm headphones / 8 = 4 ohm maximum source output impedance). In practice, it isn’t that strict a rule and often success can be had with a greater range.

This ideal is based on the theory that regardless of how large an impedance spike is in the headphone driver’s response, a high enough damping factor prevents the frequency response from varying more than 1 dB (not typically audible).

“…if an amplifier’s output impedance is significantly more than an eighth of the headphone’s impedance, the frequency response and sound of the headphone can change. This results in bigger mismatches and creates more variation from the headphone’s default sound signature. The way that a headphone responds to an amplifier with output impedance higher than one eighth of the headphone can be entirely erratic – different headphones will respond in different ways, but generally the results will be negative.”

So, the amps source impedance is what I’m looking for, I think…

I use Audeze LCD-2F’s and watch to make sure I’m matching properly. I’m talking with an engineer that says his amp is a 1.5 ohm source impedance . He also says he will add pad resistors at the input jack, for the headphones, to lift his impedance to 9 ohms.

Now, he also has taps, on his output transformers, of 32 ohm and 68 ohm…

Thoughts?

Source impedance and output impedance and synonymous in the context of a headphone amplifier. As far as I can see, LCD-2F is a 70ohm headphone, it will be well damped on the low Z tap.

 

[caryking]

So, the low Z tap on this amp is 5 ohm. Why would this engineer have a tap at 32 ohm and 68 ohm? Also, he has an 8 ohm tap being used for speakers. They appears to be closer than the other two impedances he’s offering, right?

What am I missing?