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mains_hum  HeadWize Fanatic Joined: Aug. 19, 2003 |  Message [#100] posted on: 11-12-2005 11:28 AM CST (US).   |  |  The transformer ( RS part 201-7038 ) is made by Block The RS site says its 26% regulation, yet that's not what the Farnell site says ... they reckon 69% regulation. Why might this matter ? ... in normal use it won't. But, if you power up the supply without the valve heater load B+ will sting if you touch it and 63V caps are a bit "iffy" if the 69% is correct whereas if 26% then the caps are OK. Why don't we just say that all 100uF are 100V rating ? Just a hint to you builders out there.... while I put together the parts for my "Cool Stoopid" ... coming soon .... [Edited by mains_hum on 11-12-2005 at 11:29 AM.] |
runeight Headphone Council Joined: Mar. 8, 2002 | Message [#101] posted on: 11-12-2005 12:18 PM CST (US). | | OK, I've changed all of the basic diagrams to use 100V caps. |
Blooze HeadWizer Joined: Jun. 28, 2005 | Message [#102] posted on: 11-13-2005 09:30 PM CST (US). | | Out of curiosity, are there any opinions about how the SOHA sounds compared to Sijosae's hybrid amp? I was thinking about building one or the other and they both look like excellent designs and would make a nice amp to use at work as well as being cost effective. |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#103] posted on: 11-13-2005 10:42 PM CST (US). | | It's hard to know without hearing both and since I'm one of the designers of the SOHA, I don't want to cheerlead for the SOHA too much, but am looking forward to the results that other builders will get. Mains and Batman did some testing on the SOHA with their prototypes. We purposely created the design to have a higher B+ on the tube because this where we believed the most improvement in the sound would come from. Batman has posted that when his B+ was around 20V or less the amp did not sound very good but that as he boosted the B+ to 40V the amp began to sound very good. In fact, it was equal to the sound of the CJ amp that he had. Mains has gotten similar listening results. So, if the design principle behind the SOHA is correct (raising the tube's B+), then it is likely that it will sound better than amps where tubes are running at 12-20V. Mains' and Batman's seem to verify this. They may have some additional comments. |
| Blooze HeadWizer Joined: Jun. 28, 2005 | Message [#104] posted on: 11-13-2005 11:00 PM CST (US). | | Thanks Runeight. I would think it would start to run more linear as you increased the B+, getting it a little out of the curve at the low end and eliminating some distortion that might be present. I may just have missed this in the posts, but is there a parts list made up for the SOHA? I also remember reading about a wiring diagram (I can do schematics, though it's always nice to be able to double check with a wiring diagram that everything is "in it's place". I see that transformers are mentioned, but is there any reason that a regulated wart couldn't be used here? It will be nice to give this a try and compare it to my Millett I'm finishing up. |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#105] posted on: 11-13-2005 11:12 PM CST (US). | | Yes, that was our thinking too. The more you can lift the B+ the more linear the tube will get. OTOH, increasing B+ too high misses the point of a hybrid amp. 40V seems to be a good sounding compromise. I don't think that anyone has created a parts list yet. Or a wiring diagram. When you say regulated Walwart, do you mean one with a DC output? If so, then this wouldn't work. The key part of the design is the voltage multiplier in the PS and this depends on having access to the secondary of the trafo. Batman is designing a PCB. This might be ready in a few days to a week. Hopefully he can find time to post here soon. |
| eric.w Headphone Council Joined: N/A | Message [#106] posted on: 11-13-2005 11:16 PM CST (US). | | If you used a wallwart it would have to be an AC output one, with a center tap connection, which are probably rare. Regulated DC won't work because the voltage doubler needs AC. [Edited by eric.w on 11-13-2005 at 11:17 PM.] |
| Blooze HeadWizer Joined: Jun. 28, 2005 | Message [#107] posted on: 11-13-2005 11:23 PM CST (US). | | I was thinking an AC wart with decent regulation compared to it's stated specs. Sorry. I've never done a PCB, but maybe this would be a good time to learn how. Or I could just continue to do p-2-p. Or maybe I could bribe someone to make me a PCB. LOL! The SOHA would work out quite well for me as I have a stack of old 12AU7's and their variants laying around. I've been collecting tubes here and there as I've come into them over the last 3-4 months in preparation for many years of pursuing this hobby. These low voltage designs are just what a guy learning needs to get his feet wet and I surely appreciate everyone's taking the time to design these amps. [Edited by Blooze on 11-13-2005 at 11:24 PM.] |
| Blooze HeadWizer Joined: Jun. 28, 2005 | Message [#108] posted on: 11-13-2005 11:37 PM CST (US). | | Did a quick search and the largest warts I could find were 16VAC that were center tapped. I've not dealt with AC adapters so I wasn't sure, but they are pretty scarce I guess. Tranny it is! |
| eric.w HeadWizer Joined: N/A | Message [#109] posted on: 11-14-2005 01:03 AM CST (US). | | Oh ok, sorry, I misunderstood you too..  Yeah, I love how the parts for this amp are cheap and common! From the leftovers of a multi-hybrid, plus some previous projects, and some 200V capacitors from switching power supplies, I should have everything I need to build one  |
| mains_hum HeadWize Fanatic Joined: Aug. 19, 2003 | Message [#110] posted on: 11-14-2005 01:05 PM CST (US). | | Yes!, a tranny it should be. A Walwart 16Vac CT won't do, whereas a 15-0-15 Vac or 15-0-15-0 Vac is just what's needed. 6VA is the minimum rating so don't forget this power aspect. Still, a suitable tranny is (or ought to be) cheap and that was one of the design goals. And yes, the design is meant to be something that sounds pretty good without any lethal voltages so folk can "get their feet wet" and check out the "tube sound" |
| Blooze HeadWizer Joined: Jun. 28, 2005 | Message [#111] posted on: 11-15-2005 11:10 AM CST (US). | | Has anyone tried the TSH22IN opamp from Mouser as a replacement for the 2134? I've used ST's opamps for replacements for the 2132 in Cmoys before with no problems, although this replacement may be a different beast all together. |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#112] posted on: 11-15-2005 11:19 AM CST (US). | | For the most part this opamp can sub for the 2134. But in this amp, because it is a bipolar opamp, it will have lower input impedance than the fet-input opamps. This will increase the loading on the tube and increase the distortion. But, since it seems to be pin compatible no reason you can't just pop it in and listen. Maybe it will sound better. |
| eVITAERC Headphone Council Joined: N/A | Message [#113] posted on: 11-16-2005 08:02 AM CST (US). | | Had anyone here built a Millet Hybrid as well? How is the sound of using "normal" tubes compared to those 12v counterparts? |
| Blooze HeadWizer Joined: Jun. 28, 2005 | Message [#114] posted on: 11-16-2005 08:42 AM CST (US). | |
I've built the Millett and am curious as to how they will compare also. I think the Millett sounds great and you can roll in a couple of different tubes for slightly different sounds. Speaking of rolling tubes, I've got some E81L's that are very cool looking that I would like to find out if they'd work triode strapped in a circuit such as the SOHA. You'd have to put one for each channel and do some PS changes I would think, but it has some nice curves when used as a triode. If someone has the inclination to check, I've doodled out some wiring schemes for the SOHA. |
ericj HeadWize Fanatic Joined: Aug. 1, 2005 | Message [#115] posted on: 11-16-2005 11:51 AM CST (US). | |
(Edit: Not in a SOHA, in another project. no new amp projects until my M3 is enclosed, which has been severely set back by circumstances beyond my control) It's a real nice little chip for the 68 cents paid. The faster version oughta be a peach. [Edited by ericj on 11-16-2005 at 11:57 AM.] |
| jbloudg20 HeadWize Fanatic Joined: N/A | Message [#116] posted on: 11-17-2005 12:03 AM CST (US). | | Does anyone have a Bill of Materials they would like to share? |
| Guitarsenal HeadWize Fanatic Joined: N/A | Message [#117] posted on: 11-17-2005 01:18 AM CST (US). | | Blooze, There may be a mistake in your power supply drawing. You are putting the entire power supply after the filimant dropping resistors. That might be a bad thing. |
| Guitarsenal HeadWize Fanatic Joined: N/A | Message [#118] posted on: 11-17-2005 01:26 AM CST (US). | | I just ordered this stuff from Mouser, but I'm kind of new to this so check my list carefully! Also, I have some caps here that aren't part of the SOHA and are intended for building a Meier natural crossfeed circuit. I am ordering a nice ALPS pot from Tangent, and I'll probably hit up Digi-Key for a better opamp... ~~~~~~~~~ Mouser 781-J113 J113 Vishay/Siliconix N-Channel FETs 511-L78L12ABD L78L12ABD ST Voltage Regulators 511-L79L12ACZ L79L12ACZ ST Voltage Regulators 511-TSH22IN TSH22IN ST Operational Amplifiers 652-3296W-1-202 3296W-1-202 Bourns Multi-Turn Trimmer Potentiometers 581-BF014D0104J BF014D0104J-- AVX Multi-Layer Film Capacitors 581-BF014D0224J BF014D0224J-- AVX Multi-Layer Film Capacitors 581-BF074D0474J BF074D0474J-- AVX Multi-Layer Film Capacitors 75-515D16V47 515D476M016JA6A Vishay/Sprague Radial Aluminum Electrolytic Capacitors - 85 Degree 75-515D35V470 515D477M035CG6A Vishay/Sprague Radial Aluminum Electrolytic Capacitors - 85 Degree 282-100 282-100 Xicon 2W 5% Small Metal Oxide Resistors 282-220 282-220 Xicon 2W 5% Small Metal Oxide Resistors 75-515D16V1000 515D108M016CG6A Vishay/Sprague Radial Aluminum Electrolytic Capacitors - 85 Degree 833-1N4148 1N4148 MCC Rectifiers - Switching 75-515D100V100 515D107M100DG6A Vishay/Sprague Radial Aluminum Electrolytic Capacitors - 85 Degree 161-R301SN 161-R301SN Kobiconn AC Connectors 633-HB16CKW01 HB16CKW01 NKK Pushbutton Switches 108-2MD1T1B1M1QE 108-2MD1T1B1M1QE Mountain Switch Ultra-Miniature Toggle Switches [Edited by Guitarsenal on 11-17-2005 at 01:27 AM.] |
| runeight Headphone Council Joined: Mar. 8, 2002 | Message [#119] posted on: 11-17-2005 08:34 AM CST (US). | | Blooze, Guitarsenal is correct. You have the entire PS coming after the filament droppers. Only the filmanent comes after these resistors. The rest of the PS should be connected directly to the trafo secondary. It's a simple rewiring on your diagram. Guitarsenal the parts list looks right assuming that you have the resistors not listed. [Edited by runeight on 11-17-2005 at 08:39 AM.] |
| Blooze HeadWizer Joined: Jun. 28, 2005 | Message [#120] posted on: 11-17-2005 08:37 AM CST (US). | |
Good call! Can't believe I missed that. That's why I like to have stuff checked first. Let's try again: |
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