Audiodoc
New Head-Fier
- Joined
- Sep 15, 2011
- Posts
- 32
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- 15
Need to add one more thing that I observed the transistor besides Q15 i.e. Q16 is cool. On the opposite side both the transistors are almost equally hot.
I auditioned an EHHA RevA made by local Head-fier BK8569er and loved how it sounded. I would describe it as sounding fast, clean, linear, airy. In comparing it to my SOHA1, I kept coming back to comparing the EHHA to the stax headphone sound while the SOHA had the more dynamic sound. Similar to Stax, my only complaint with this amp was it seemed to lack dynamic punch or a sense of weight on certain phones. But that's a minor quibble and not necessarily a bad thing. Other than dynamics I thought it clearly bettered the SOHA1 in every way and made the SOHA sound colored.
So I bought one on the forums made by a HF'er from a glassjar kit. I'm not here to name names, I know he's a good builder and the amp seems to be well done. But it doesn't sound nearly as good as the other EHHA I heard (and borrowed for a week). In fact, as far as I can tell my SOHA1 beats this EHHAreva in every way including speed and detail, things the other EHHA was clearly superior in before. BK8569er has been kind enough to check out the amp for me and do some tests for obvious problems and hasn't found anything glaring, and he confirmed it looked like a good build at least on the surface. He also lent me some tubes which didn't change much. I also tried switching from BJT's to Mosfets.
Maybe I just shouldn't be buying DIY amps if I know nothing about DIYing. But I like owning things that have so little marketing buzz behind them and instead have lots of love!
So I'm wondering if anyone here would be willing to have a look at it. If you own an EHHA it might be better so you can compare but not necessary. I'm not listening to it at all and not sure what else to do.
I'll add a bit of color since I apparrently own the "magic" RevA and also messed with rythmdevils unit at his place quite a bit.
With his original BJT setup I verified correct R17/22/23 and quiescent current. Heatsink temps were normal. I swapped in my GE/Amperex and later my Telefunken tubes for long term testing.
The output devices were socketed for easy changes, so we swapped in MOSFETS, changed to the appropriate R17/22/23, and adjusted the quiescent current per the setup instructions. Everything measured and behaved normally.
R13/14 is 75k, but R11 is 1.5k as opposed to the BOM value of 1.2k. jdkjake informs me that this will have the consequece of reducing the gain from ~9 to ~7.5 and increase NFB ~1.7dB.
The build itself is very well done with lots of attention to detail and solid workmanship. The grounding scheme is executed differently than mine, and this build employs an Alps pot and dual Avel-Lindberg transformers. FWIW, my own build closely follows the MOSFET BOM with individually sourced components and uses a TKD pot and a shielded SumR transformer.
I didn't do any critical listening, but to my ears, with his gear, rythmdevils unit functioned correctly and without major fault. It made music. Rythmdevils probably has some very senstive ears, but he reports that none of the changes we made (rolling tubes, BJT --> MOSFET, etc.) had any appreciable influence on the SQ. I find that a little surprising - as if something is being masked. As I recall the only source was a gamma-2 via optical. I think at this point he wants to turn it over to an expert to work some magic on it - any takers?
BK
The build itself is very well done with lots of attention to detail and solid workmanship. The grounding scheme is executed differently than mine, and this build employs an Alps pot and dual Avel-Lindberg transformers. FWIW, my own build closely follows the MOSFET BOM with individually sourced components and uses a TKD pot and a shielded SumR transformer.
What are the differences between the EHHA and BETA22 in terms of sound?
I'll add a bit of color since I apparrently own the "magic" RevA and also messed with rythmdevils unit at his place quite a bit.
With his original BJT setup I verified correct R17/22/23 and quiescent current. Heatsink temps were normal. I swapped in my GE/Amperex and later my Telefunken tubes for long term testing.
The output devices were socketed for easy changes, so we swapped in MOSFETS, changed to the appropriate R17/22/23, and adjusted the quiescent current per the setup instructions. Everything measured and behaved normally.
R13/14 is 75k, but R11 is 1.5k as opposed to the BOM value of 1.2k. jdkjake informs me that this will have the consequece of reducing the gain from ~9 to ~7.5 and increase NFB ~1.7dB.
The build itself is very well done with lots of attention to detail and solid workmanship. The grounding scheme is executed differently than mine, and this build employs an Alps pot and dual Avel-Lindberg transformers. FWIW, my own build closely follows the MOSFET BOM with individually sourced components and uses a TKD pot and a shielded SumR transformer.
I didn't do any critical listening, but to my ears, with his gear, rythmdevils unit functioned correctly and without major fault. It made music. Rythmdevils probably has some very senstive ears, but he reports that none of the changes we made (rolling tubes, BJT --> MOSFET, etc.) had any appreciable influence on the SQ. I find that a little surprising - as if something is being masked. As I recall the only source was a gamma-2 via optical. I think at this point he wants to turn it over to an expert to work some magic on it - any takers?
BK