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SOHA II Builders Thread - Page 27

post #391 of 1686
Quote:
Originally Posted by bmwpowere36m3 View Post
I ended using VitQ's in the C1 L/R positions, but I also chose to use "boutique" caps in other sections as well. I say the amp sounds wonderful and has great synergy with my Senn HD580's. However I can't compare it to the sound of the stock Wima's, just for that position: my SOHAII build

I'm curious has anyone listened to Grado's with this amp, specifically SR-80's. Yesterday I auditioned a pair of SR-80's and RS1 at an audio shop with their Grado RA1 amp. I got to take a pair of SR-80's back home for more auditioning with my setup (iMod DAC, SOHA II) and honestly the SR-80's aren't sounding too good. In the store, IIRC, they sounded pretty decent... yet different from my 580's.

At home, their pretty grainy, at time harsh treble, and peaky in the mid-bass and upper-mid treble... so details I hear in the HD580's are lost in the very projected, in your face sound.
I much prefer my Grado's (SR225) with the SOHAII to anything else I've used - CMOY, Creek OBH-11, CKKIII - while I find that the SOHAII/HD650 combination doesn't quite work for me. I've only the one tube type at the moment so this may be a factor, but while I agree the Grado sound is normally agressive, the tube sound tempers this to a degree and there is absolutely no harshness in the treble. By comparison, the Senns sound 'shut in' and dark, too soft and lazy, just comfy pipe-n-slippers presentation. However, I do enjoy them with the CKKIII and, since I upgraded the PSU and the opamp, I slightly prefer them on the Creek.



On the SOHAII
post #392 of 1686
I havent bulit a sohaII, but if you really want to tame grados then look for for some warm old valves (mullards etc). Certainly dont try the russians e.g. 6n1p.
post #393 of 1686
Quote:
Originally Posted by Uncle Bob View Post
I much prefer my Grado's (SR225) with the SOHAII to anything else I've used - CMOY, Creek OBH-11, CKKIII - while I find that the SOHAII/HD650 combination doesn't quite work for me. I've only the one tube type at the moment so this may be a factor, but while I agree the Grado sound is normally agressive, the tube sound tempers this to a degree and there is absolutely no harshness in the treble. By comparison, the Senns sound 'shut in' and dark, too soft and lazy, just comfy pipe-n-slippers presentation. However, I do enjoy them with the CKKIII and, since I upgraded the PSU and the opamp, I slightly prefer them on the Creek.



On the SOHAII
Huh, well maybe it's my choice of current tubes as well. Since both Holland and myself have noted that the Electro-Harmonix 12AU7's have a very aggressive, neutral, and clear presentation. Very well suited to "Metal" kind of music, but sound great with everything else I've throw at them. I'd say the combo of those tubes with "bright" Grado's, maybe overemphasizes those characteristics more.

Yes, the Senn's are little more laid back, but I think it's because they are so neutral. Whereas the Grado's have a funky peakiness in the upper-bass and upper midrange, so it really puts the music out there. I feel like I hear a lot more detail with the Senn's where the Grado's are overpowered by those to peaks. For example Hotel California, When Hell Freezes Over... with the Senn's my hearing focuses on Henley's vocals with everything else in balance. With the Grado's, I'm still sort of focused on Henley's vocals, but Walsh's guitar "licks" and Schmit's bassline kind of overpower the vocals...

Quote:
Originally Posted by adamus View Post
I havent bulit a sohaII, but if you really want to tame grados then look for for some warm old valves (mullards etc). Certainly dont try the russians e.g. 6n1p.
That what I was thinking, but I'm actually just trying out the Grado's currently. WHen I auditioned them in the store they sound better out of a Grado RA1 amp and I also listened to RS1's which had the characteristics of the SR80 but with a less harsh and overpowering treble and sweet mids.

Why no to the 6N1P's? That was actually the next tube I was going to get for the amp, Ferrari had some nice reviews about them.
post #394 of 1686
Quote:
Originally Posted by Hayduke View Post
Thanks Holland

That's what I'll use. Did you socket all the transistors? If not, which ones?
I socketed all of them, in case something happens to the regulators it's easier to access. I leave the heatsinks in, the only hard ones to reach are the regulators, but it's only because I am using much larger heatsinks (2.5" or 3" tall). The shorter heatsinks will still allow access to the bolts easily. The output transistors are in front and for me it's easy to access with a short screwdriver. I put the screws in the front side and the nuts in the back.
post #395 of 1686
Quote:
Originally Posted by Uncle Bob View Post
I've only the one tube type at the moment
Perhaps I missed it, but which tube are you using?
post #396 of 1686
First day progress - I was able today to solder all small signal diodes and resistors. I'm slow but I have the habit of double checking every solder joint and components value (R,C) or functionality (D,Q). Better safe than sorry.

I socketed R4 as I plan to eventually replace with Zeners then play with the tubes tail current. Anybody tried some zeners yet? Were they noisy and, if not, what brand did you use?

post #397 of 1686
Quote:
Originally Posted by wolf18t View Post
Anybody tried some zeners yet? Were they noisy and, if not, what brand did you use?
I have zeners installed in my amp, they are Fairchild Semiconductor 1N5248B's (Mouser 512-1N5248B). When I was building the amp, I asked here about the zeners and the response seemed to be that they increase the noise and most (all?) others had reverted to resistors. However, I am unable to hear any ill effects compared to the resistors with any of my headphones, so I decided to leave the zeners in. I think that they sound a bit better, but it's probably mostly psychoacoustics. =)
post #398 of 1686
Quote:
Originally Posted by holland View Post
Perhaps I missed it, but which tube are you using?
Currently, I'm using some Pinnacle (possibly made by Toshiba?) 13D5A's. I've got several spare, so if you're interested in trying a pair - drop me a PM

I've just bought a pair of Philips PCC88 off an ebay seller, so they'll be here in a few days. Once I've had chance to listen and compare - I'll put something in the SOHAII Tubes thread. There was little point before as I had nothing to compare with the 13D5A's.

I've got my eyes on some other tubes - mainly ECC81/82/83/88 but I won't pay silly money for tubes so I have to wait for the right deals to come around.
post #399 of 1686
Quote:
Originally Posted by Arkku View Post
I have zeners installed in my amp, they are Fairchild Semiconductor 1N5248B's (Mouser 512-1N5248B). When I was building the amp, I asked here about the zeners and the response seemed to be that they increase the noise and most (all?) others had reverted to resistors. However, I am unable to hear any ill effects compared to the resistors with any of my headphones, so I decided to leave the zeners in. I think that they sound a bit better, but it's probably mostly psychoacoustics. =)
Thank Arkku, I'll check if Digikey carry them. Did you experiment with the tail current to see if it change the sound somewhat?

If I understand correctly, that mod let you play with the triode plate current. Some tubes may benefit from rising it a little bit higher than 1 mA. The zener have the purpose of keeping the required near 19V voltage drop while you play with the tail current source pot.
post #400 of 1686
I might have good news...after replacing Q8R and Q7L and setting the idle currents I have about another full turn on each pot, does that sound right?

Thanks again for your patience and help
post #401 of 1686
Thread Starter 
Quote:
Originally Posted by wolf18t View Post
Thank Arkku, I'll check if Digikey carry them. Did you experiment with the tail current to see if it change the sound somewhat?

If I understand correctly, that mod let you play with the triode plate current. Some tubes may benefit from rising it a little bit higher than 1 mA. The zener have the purpose of keeping the required near 19V voltage drop while you play with the tail current source pot.
Yes. Correct.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #402 of 1686
Thread Starter 
Quote:
Originally Posted by DrkRipper View Post
I might have good news...after replacing Q8R and Q7L and setting the idle currents I have about another full turn on each pot, does that sound right?

Thanks again for your patience and help
So you can get 100mA in both channels with a little travel left over in the pot? Or are you dialing higher than this?

If 100mA it's hard to say if this is ok. You may have transistors which are outliers in their specs pushing your bias control to this limit, but normally you should get 100mA with about half travel or thereabouts.

What I am wondering is if there is still a transistor problem that will show up as poor audio quality. There would be no way to know this unless you had a companion unit.

The main thing on my mind is whether or not the current sources (Q7 and Q8) are indeed acting like a CCS. There is a way to look at this, but you probably don't want to fool with it.

How does it sound?
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #403 of 1686
I realize this is a very newbish question, but that's never stopped me from demonstrating how dumb I am before

Why do you need to insulate the RCA inputs (Mouser 502-3501FPX) if you use a metal face plate?

Seems like they are intended for use with a metal panel, so I'm confused

I know I'm asking a lot of questions before I've even ordered parts, but I'm trying to understand the logic behind the choice of every part. This also means I'll understand the amp better
post #404 of 1686
Quote:
Originally Posted by runeight View Post
So you can get 100mA in both channels with a little travel left over in the pot? Or are you dialing higher than this?
It is set at 100mA now, I was able to turn it up to ~120mA.

Quote:
Originally Posted by runeight View Post
The main thing on my mind is whether or not the current sources (Q7 and Q8) are indeed acting like a CCS. There is a way to look at this, but you probably don't want to fool with it.
What would be involved? I have access to an oscilloscope, if needed.

Quote:
Originally Posted by runeight View Post
How does it sound?
It sounds good, I certainly can't hear anything that sounds wrong.

*edit* A friend of mine was anxious to review it...so there will be some listening impressions posted soon.
post #405 of 1686
Quote:
Originally Posted by Hayduke View Post
Why do you need to insulate the RCA inputs (Mouser 502-3501FPX) if you use a metal face plate?

Seems like they are intended for use with a metal panel, so I'm confused
I believe that if the transformer is in the same case as the amp, then the case should be connected to your power earth/ground for safety. This means that signal ground should be isolated from the case to prevent ground loops that can cause hum.

If you were to put the transformer in a separate case, then the signal ground probably should be connected to the amp case.
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