Im interested in why you think the 'science' at the audioscience is a sham. Even without much knowledge i always felt that their pure objective stance is a bit dogmatic in itself so it would be nice to hear your expert opinion on the matter.
How does one get from audio "science" satire to sham?
AP measurements, if performed properly, are what they are, not sham per se. If someone were to misinterpret measurement results to mean something more than they really do, then the interpretation might be deemed as sham.
First a big caveat: I'm a complete amateur.
However, when designing Jam Jar I also did some experimenting with artificial loads on the drivers (in SPICE; I haven't built it yet). My conclusion was that the load resistors kept the H2/H3 ratio as the amp approaches full power; without them the H3 increases faster than the H2.
Based on this I designed the CFA front-end for Jam Jar with optional loading so I could experiment. Haven't built it yet though....
Increasing the feedback tightens up the sound and makes the amplifier play more like a typical hi-fi unit. Whether that's a good thing depends on your taste, I guess. My HPA-1 clone didn't blow me away with its brilliance, but you could always blame that on my implementation. I have no agenda or allegiances here. Having listened to the amplifier in its stock form, it was an obvious experiment to try this change. I will probably put the resistors back in, but choose values to give an intermediate level of feedback. With the 4.7K resistors in there as specified, I thought there was a little too much "color" for my liking. FYI, FWIW, and YMMV.
So after a couple build of whammy amp with very satisfying results I'm planning on building this amp. Being an absolute newbie I have a couple of questions as I was looking into sourcing the parts:
1. Since 2SD2081 is obsolete and hard to find I'm considering using 2SD2014/2SB1257 instead, eyeballing the datasheets I think the major difference is that 2SD2081 has higher maximum power ratings that this power supply doesn't need? An extremely rough estimate I think the transistor will operate at Vce ~ 10V and Ic < 0.5A so the replacement should be fine or am I missing anything here? (I also placed order for a couple samples of 2SD2081 on ebay but I don't have high hope for them to be genuine and I don't have real ones to compare, would appreciate if someone who has the real ones can help me identify
)
2. I think the actual output rail voltage will be Vf (D13) + Vz (D14) - Vbe (Q52) which should ideally be 24V, without knowing how to get the exactly number of these values, should I be worry about the actual rail voltage being slightly beyond +-24 which exceeds the maximum ratings of OPA2604/604?
many thanks!
1. Since 2SD2081 is obsolete and hard to find I'm considering using 2SD2014/2SB1257 instead, eyeballing the datasheets I think the major difference is that 2SD2081 has higher maximum power ratings that this power supply doesn't need? An extremely rough estimate I think the transistor will operate at Vce ~ 10V and Ic < 0.5A so the replacement should be fine or am I missing anything here? (I also placed order for a couple samples of 2SD2081 on ebay but I don't have high hope for them to be genuine and I don't have real ones to compare, would appreciate if someone who has the real ones can help me identify
)2. I think the actual output rail voltage will be Vf (D13) + Vz (D14) - Vbe (Q52) which should ideally be 24V, without knowing how to get the exactly number of these values, should I be worry about the actual rail voltage being slightly beyond +-24 which exceeds the maximum ratings of OPA2604/604?
many thanks!
Regarding 2SD2081, maybe one of the obsolete parts houses has what you want: https://octopart.com/2sd2081-sanken-2175204
thx. Yeah I tried to click thru Corestaff to order some yesterday, kind of a pain where minimum order of $50 required and $60 for shipping to the US unless spending above $300, also it seems both credit card transaction fee and paypal fee applies on top of that.
The rest of the listed distributors are all from China/Hongkong that I admit I'm not familiar with, does anyone have experience purchasing from any of them?
I don't know given that I only need a few of those at max and for what it's worth I feel getting substitute parts that are readily available in the US makes life much easier..
The rest of the listed distributors are all from China/Hongkong that I admit I'm not familiar with, does anyone have experience purchasing from any of them?
I don't know given that I only need a few of those at max and for what it's worth I feel getting substitute parts that are readily available in the US makes life much easier..
I have had pretty good results using the Sanken manufactured larger case Darlington output devices taken out of old receivers. For example SAP13N, SAP13P. There are a number of part numbers. Perhaps that is an option? (For outputs and supplies.)
Also for power supply use there are TIP122/127/142/147. (Which on the usual online sites are often fake along with the Sanken outputs.)
Also for power supply use there are TIP122/127/142/147. (Which on the usual online sites are often fake along with the Sanken outputs.)
Yeah there are beefier Sanken Darlingtons available too that come with different package, I'd like to stick with TO220 models tho such that it's easy to just use those on board heatsinks for TO220, since they ain't gonna dissipate all that much power.
Looks like TIP122/127 might also work, thanks for the recommendation, will keep that in mind as another alternative.
Looks like TIP122/127 might also work, thanks for the recommendation, will keep that in mind as another alternative.
B+D Enterprises have 2SD2081. They're very reliable.
https://www.bdent.com/2sd2081-sanken-darlington-transistor.html
https://www.bdent.com/2sd2081-sanken-darlington-transistor.html
