[wiatrob]

It's got ~11-12 gain (5.5 or 6 x2) now. It has lower OL gain (10K or 33K) controlling the negative feedback. All these resistors are socketed.

Also, Larry - does it seem to have enough power? I think the amp as built produces about 18 Watts, but with MOSFETS and some tweaks it could go to 25W...

Yes, as it's setup, it does sound a bit B22 ish...

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif I don't know abut feedback or tubes - you'd have to ask Bill (wiatrob). Other details - I hooked it up to the PS Audio DLIII XLR out with anti-cables XLR IC, and the ZDT is hooked up to the PS Audio RCA out with anti-cables RCA IC, with Macbook as optical source. I believe the gain is set up as 2x7. It's similar to what I remember Naamanf's B22 sounding with his K1000, but that was back in February.

 

[jjazzyj]

Well, I'm enjoying my SOHA II so much, that it seems weird to want to build another amp, but I'm bored and I like electronics DIY. I want to use the EHHA as a headphone amp/preamp. Is the 3 channel version really that much better than the 2 channel version for headphones? It will mostly be used as a headphone amplifier as I haven't decided which power amp to build yet. I really like the FET Circlotron on the PassDIY site but I'd need to build a balanced EHHA and follow the wiring diagrams at the AMB site to convert my unbalanced source to balanced. But in any case, how well would the EHHA perform as a preamp and would it be limited to certain power amps?

 

[HeadphoneAddict]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif It's got ~11-12 gain (5.5 or 6 x2) now. It has lower OL gain (10K or 33K) controlling the negative feedback. All these resistors are socketed. Also, Larry - does it seem to have enough power? I think the amp as built produces about 18 Watts, but with MOSFETS and some tweaks it could go to 25W... Yes, as it's setup, it does sound a bit B22 ish...

I sent you some PM last night, and was planning to post some of those impressions when I am done listening to the EHHA.

It definitely has enough power vs the ZDT. I was worried the SAC KH1000 amp would have too much power for K1000 phones, but HiFlight assures me they can take it.

The EHHA with my re-cabled HD800 and PS Audio DL III DAC in 192Khz mode is a little bright sounding, while the ZDT is just right. The PSA tone changes with the 96K/192K up-sampling toggle and is less bright but also less expansive/wide sounding in 96K mode. So, if I switch the PSA DAC to 96K up-sampling then the EHHA soundstage closes in a little, while the brightness goes away and sounds better. At that point EHHA with PSA at 96K sounds very similar to the ZDT with the DAC still in 192K mode, in both freq response and sound stage width but not depth. As it was, the ZDT soundstage is a little deeper either way, and the ZDT was a little more refined and rich sounding as well. Maybe with the right tweaks making the EHHA useable with re-cabled HD800 + the PSA in 192K mode, the EHHA could have a little more expansive soundstage with more separation than the ZDT. But I don't know if the refinement and richness of the ZDT would be surpassed.

I can't guess which amp would be better without hearing the imaginary tweaks first. Regardless of HD800 or K1000, the EHHA is a great amp. It comes close to the ZDT with HD800, while driving the K1000 a little better than the ZDT. With K1000/EHHA the 192K mode in the PSA was much better than with the DLIII 96K mode. But it doesn't drive the K1000 quite as well as the SAC KH1000 amp but it is close, and the EHHA soundstage is still better than the SAC soundstage. The EHHA is tubier warmer richer than the SAC with K1000, but it is not quite as tight, detailed or extended as the SAC amp with K1000. The K1000 sound duller with the ZDT than EHHA, but even with the improved treble via EHHA the K1000 still sound duller with the EHHA than with the SAC amp. So, the EHHA splits the fence between the better K1000/SAC or better HD800/ZDT combo - being good with both but not the best with either.

Both the ZDT and the EHHA were a better match for my re-cabled HD800 than the SAC KH1000 amp which made the HD800 a bit bright and edgy, but I will try the HD800 stock cable to tame the SAC highs and see how that sounds tonight. And, I'll see if the stock HD800 cable allows me to use the DAC in 192K mode with the EHHA as well.

 

[funch]

Can someone give me the dimensions of the EHHA board?
Pleeeeeze?! And thank you.

 

[runeight]

It's approximately 4" x 3.5".

I was not as careful about board sizing back then as I am now.

I'd post the silkscreen but the pdf exceeds the attachment size of 19.5kB.

 

[digger945]

Zackly:

3.6425"(3 41/64") or 92.52mm
X
3.9800"(3 63/64") or 101.10mm

EDIT: Big un beat me to it LOL.

 

[funch]

Thanks, guys.

 

[wiatrob]

Quote:

Originally Posted by jjazzyj /img/forum/go_quote.gif Well, I'm enjoying my SOHA II so much, that it seems weird to want to build another amp, but I'm bored and I like electronics DIY. I want to use the EHHA as a headphone amp/preamp. Is the 3 channel version really that much better than the 2 channel version for headphones? It will mostly be used as a headphone amplifier as I haven't decided which power amp to build yet. I really like the FET Circlotron on the PassDIY site but I'd need to build a balanced EHHA and follow the wiring diagrams at the AMB site to convert my unbalanced source to balanced. But in any case, how well would the EHHA perform as a preamp and would it be limited to certain power amps?

There's some debate about the benefits of a three channel EHHA. I'v enever heard a two channel - only three and fully balanced with fully balanced sources. I think much of the benefits of this design coulod be realized in a two channel build.

That said I love my balanced BJT EHHA - but am thinking about building atwo/three channel MOSFET version to compare...(nuts? Yup!)

 

[johnwmclean]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif It's got ~11-12 gain (5.5 or 6 x2) now. It has lower OL gain (10K or 33K) controlling the negative feedback. All these resistors are socketed. Also, Larry - does it seem to have enough power? I think the amp as built produces about 18 Watts, but with MOSFETS and some tweaks it could go to 25W... Yes, as it's setup, it does sound a bit B22 ish...

wiatrob could you please let me know what value of the resistor for R13 for a gain of 5.5

 

[jjazzyj]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif There's some debate about the benefits of a three channel EHHA. I'v enever heard a two channel - only three and fully balanced with fully balanced sources. I think much of the benefits of this design coulod be realized in a two channel build. That said I love my balanced BJT EHHA - but am thinking about building atwo/three channel MOSFET version to compare...(nuts? Yup!)

Ok, I've been thinking about what I want to do. Because this amp is going to be upstairs, it is more than likely going to be doing triple duty. Light speaker amp and headphone amp. I'll probably include a pre/loop out just because. If I build a balanced EHHA will I need 4 S22's just like the B22? I'm thinking so.

I was planning on using a 500VA Xfmr with the 4 S22's (If I need them), it might need to be in a separate enclosure. The heater supply will be a 100VA Xfmr with LM338K To-3 based regulator circuit as the EHHA web page specifies.

All of the FET's on the EHHA boards and the S22 will be upgraded to 2.5" heatsinks.

Is this going to work okay for mostly headphone with light speaker/preamp duty?

 

[wiatrob]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif wiatrob could you please let me know what value of the resistor for R13 for a gain of 5.5

I made a spreadsheet that calculates arbitrary gains, let me find it and I'll send it on - there is a discussion earlier in this thread where the formula was mentioned.

 

[wiatrob]

Quote:

Originally Posted by jjazzyj /img/forum/go_quote.gif Ok, I've been thinking about what I want to do. Because this amp is going to be upstairs, it is more than likely going to be doing triple duty. Light speaker amp and headphone amp. I'll probably include a pre/loop out just because. If I build a balanced EHHA will I need 4 S22's just like the B22? I'm thinking so. I was planning on using a 500VA Xfmr with the 4 S22's (If I need them), it might need to be in a separate enclosure. The heater supply will be a 100VA Xfmr with LM338K To-3 based regulator circuit as the EHHA web page specifies. All of the FET's on the EHHA boards and the S22 will be upgraded to 2.5" heatsinks. Is this going to work okay for mostly headphone with light speaker/preamp duty?

You will need only a single S22 for a balanced EHHA. Pay attention to your heater supply though, especially if you plan on using 6H30s...

 

[jjazzyj]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif You will need only a single S22 for a balanced EHHA. Pay attention to your heater supply though, especially if you plan on using 6H30s...

Even if I'm planning on running speakers off the EHHA?

That's why the 100VA xmfr with the LM338K.

12v @ 4.3A and the LM338K handles a maximum of 5A So that should cover me.

 

[Ferrari]

Quote:

Originally Posted by jjazzyj /img/forum/go_quote.gif Even if I'm planning on running speakers off the EHHA? That's why the 100VA xmfr with the LM338K. 12v @ 4.3A and the LM338K handles a maximum of 5A So that should cover me.

Balanced EHHA with one σ22 PS is fine for headphones but for speakers duty… NO!!!
For speakers duty you are better off with 2 σ22 PS, with adequate heatsinking of course.

I’m driving AKG K1000 via my balanced EHHA with one σ22 PS, soundwise excellent performing however, the 2” heatsinks are getting very hot in the long run.

 

[jjazzyj]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif Balanced EHHA with one σ22 PS is fine for headphones but for speakers duty… NO!!! For speakers duty you are better off with 2 σ22 PS, with adequate heatsinking of course. I’m driving AKG K1000 via my balanced EHHA with one σ22 PS, soundwise excellent performing however, the 2” heatsinks are getting very hot in the long run.

I thought as much. I was reading the PS req's on the AMB site and figured that the same rules applied to the EHHA. I just bought a pair of AKG K240MKII and realized that with some surgery I won't be able to balance them

A 3 pin mini XLR can't be made into a balanced connection. The thought of being able to run two unbalanced Headphones with separate volume controls is a nice option when a friend comes over to watch movies/play games when the wife is sleeping though!!

So here's the plan:

4 EHHA channels with 2.5" heatsinks
500VA xfmr running 4 S22's with 2.5" heatsinks
100VA xfmr attached to a LM338K based regulated DC heater supply
2 Neutrik Combo XLR/TRS Jacks
Pre Out switch/Loop out Switch
Heaphone/Speaker output switch(es)

I think that will satisfy the power requirements, the only question will be if the 2.5" heatsinks are enough.

Anyone here have any input?