Sure, it's no work of art, though. I just hope the picture is clear enough. And thanks for all the help.
Attachments
You're running the input connections through all the mains AC wiring and through the supply wiring for the MOD86 boards. The former may induce some AC on the wiring. The latter will degrade performance near max output power. Just letting you know. Using a shielded cable here might work better.
I do suggest grounding the volume pot.
If you connect the amp to a source with a two-pin mains connection, you should have no issues with ground loops that I can tell.
Nice to see some MOD86 Rev. 1.0 boards in action, by the way.
An even better solution would have been to put the THAT Driver and the volume pot in a separate metal enclosure and use it as a preamp. What you have should work just fine, though.
Tom
I do suggest grounding the volume pot.
If you connect the amp to a source with a two-pin mains connection, you should have no issues with ground loops that I can tell.
Nice to see some MOD86 Rev. 1.0 boards in action, by the way.
An even better solution would have been to put the THAT Driver and the volume pot in a separate metal enclosure and use it as a preamp. What you have should work just fine, though.
Tom
Just played my Rev 1.0's for a few hours tonight and have been almost daily for creeping up on two years. Wonderful sound and very happy to see your product line and business expand. Well done.
I do have one question related to 1.0 boards:
Bill Shurv - you are the OP for what is now a massive thread - did you ever manage to finish your project?
Cheers
It is especially appreciated that stable aB amplifiers run more efficiently for both electric expenditures and expected output. Thanks for that!
The BOM that I maintain is with Mouser Electronics. They do deliver to Europe and from what I understand the shipping charges are quite reasonable. I usually get free shipping from Mouser as I order more than $100 worth at a time.
Should Mouser not suit your fancy, you can click the link to the Mouser project in Appendix A-1 of the design documentation and select "Export to Excel" on Mouser's website. This gives you an MS Excel document with the manufacturers and manufacturer part numbers. You can import this into RS, Farnell, etc. either automatically (if they support that) or manually.
It's actually quite a bit of work to keep up with the various parts going in and out of stock at Mouser. I'd hate to do it for multiple distributors. Sorry. Ain't gonna happen. I'd much rather focus on project development and other more fun activities.
Tom
Thanks Simon.
Actually I was on the verge of ordering boards and then had a listening session to all my amps. I concluded that my preference was:
KT88 PP valve amp
NAP200 clone (with EI core transformers)
Akitika GT101 (LM3886 with single polarity regulated supply)
P101 (with 1KVA toroid)
MJR7 Mk5 (2 stage mosfet amp with very low distortion)
So it looks like I like "high" distortion amps and therefore I decided to hold off on the Modulus.
Actually the MJR measurements seem to indicate extremely low distortion:
MJR7-Mk5 Test Results
In addition it has very low overshoot/ringing with a capacitive load. I would be surprised if an amp with 150dB of loop gain can achieve that (although maybe it doesn't matter in practice).
Actually I was on the verge of ordering boards and then had a listening session to all my amps. I concluded that my preference was:
KT88 PP valve amp
NAP200 clone (with EI core transformers)
Akitika GT101 (LM3886 with single polarity regulated supply)
P101 (with 1KVA toroid)
MJR7 Mk5 (2 stage mosfet amp with very low distortion)
So it looks like I like "high" distortion amps
and therefore I decided to hold off on the Modulus.Actually the MJR measurements seem to indicate extremely low distortion:
MJR7-Mk5 Test Results
In addition it has very low overshoot/ringing with a capacitive load. I would be surprised if an amp with 150dB of loop gain can achieve that (although maybe it doesn't matter in practice).
It works flawlessly in terms of noise and no switch on/off thumps. Soundwise it's pretty good, in a clean solid-state sort of way.
When I originally built it I seem to remember marginally preferring it with dual-mono unregulated supplies. However my system has changed a lot since then so perhaps that's not a reliable conclusion. Without the regulated supply it does produce some on/off noises though.
Interestingly the distortion figures measured for the Akitika seem quite close to the Mod-86 (see the spectrum at 53W):
GT-101 Measurements
Apologies for the OT content!
No. Actually the Modulus-86 is about 27-28 dB better than the Akitika based on the measurements shown for THD at 40 W (Modulus-86) and 53 W (Akitika).
Note that the graph for the Akitika is relative to 53 W, i.e. 0 dB on the graph is the voltage of the fundamental. The Modulus-86 measurement is in dBV. I.e. 0 dB on the graph is 1 V RMS. Thus, to compare the two graphs, subtract 25 dB from my measurement.
The result is:
Akitika THD: -97 dB (0.0014 %)
Modulus-86 THD: -124 dB (0.000061 %)
Tom
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Partially solved: Hum in Mod86 build
Played around with it some more. I did change the input wires to shielded wire; didn't make much difference. After trying some different sources, I found that the TIVO was definitely the worst. The best source WRT the buzz was my Mac laptop. When using the Mac I found that on one channel I got no buzz at all, just deep, dead and beautiful silence without input. On the other channel there was a very slight buzz.
As it happens, the offending channel was the one whose amp board is right next to the transformer. I wonder if that's the cause. I'm wondering if I can insert a metal plate between the transformer and the amp board to act as some sort of electrostatic shield.
In the meantime, I ditched the analog output from the TIVO, and connected its optical output to the amp via this optical to RCA converter. I also swapped out the RCA cables for some better ones. The result is the same as when using the Mac, no buzz on one channel and a very slight buzz on the other.
If anyone has any further suggestions, I'd be very happy to listen.
Played around with it some more. I did change the input wires to shielded wire; didn't make much difference. After trying some different sources, I found that the TIVO was definitely the worst. The best source WRT the buzz was my Mac laptop. When using the Mac I found that on one channel I got no buzz at all, just deep, dead and beautiful silence without input. On the other channel there was a very slight buzz.
As it happens, the offending channel was the one whose amp board is right next to the transformer. I wonder if that's the cause. I'm wondering if I can insert a metal plate between the transformer and the amp board to act as some sort of electrostatic shield.
In the meantime, I ditched the analog output from the TIVO, and connected its optical output to the amp via this optical to RCA converter. I also swapped out the RCA cables for some better ones. The result is the same as when using the Mac, no buzz on one channel and a very slight buzz on the other.
If anyone has any further suggestions, I'd be very happy to listen.