[SebastianL]

Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif The K75-10's used in conjunction with the T3 Teflons is a fabulous combo...it's my personal fav but the caps are huge and present an installation dilema (as you know from my efforts). Fortunately it's a minor dilema easily solved Peete.

Already got a pair of K75-10's. They are indeed HUGE!!

Sebastian

 

[SebastianL]

Mods that are comming up: replacing the resistors and the Phenix HiFi caps once I receive the parts. I ordered some AmpOhm caps and some Kiwame resistors.

Sebastian

 

[Budley007]

I doubt that I will ever own one of these amps. Nevertheless, this thread has been both enjoyable and informative. Thank you very much for your effort and time, folks.

 

[SebastianL]

Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif Personally I don't know why people like WIMA...I think they sound like crap (except the Black Box types which are PIO... ) in the signal pathways . Peete.

You're not the only one

:

Quote:

Originally Posted by Daroid /img/forum/go_quote.gif IMO the MKS4 is crap for audio, i didn't believe it was noticeable, and it was snake-oil but it really does sound harsh and rough compared to Evox CMK polycarbonate which is basically the same size (width is a bit larger). Difference between MKS2 and 4 is negligible, only the pin grid/spacing is different.QUOTE]

http://www.head-fi.org/forums/f6/wim...a-mks4-146231/

 

[SebastianL]

Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif Get some Caddock or Holcro 1/2 W or 1W (tighter tolerance the better) matched pairs for the gain sections.There is no need to go above 1W with 1/2 W being ideal in this particular part of the circuit. ----- EDIT: The large resistors in the B section of the photo look to be 2W...I would go with no less than 3W in these spots, again get the pairs matched and the tightest tolerances you can find.

To which degree should the resistors match? +/-10% or just as close as possible?

 

[Frihed89]

I would forget about the resistors, given the gains you've made, and see if there isn't anything you can do for the power supply to smooth the voltage better and/or make the rails bigger. Also, i am guessing it's SS rectified and he may have cut some corners, but you know I am not an LD owner.

I am really happy to hear about your successes.

 

[Pricklely Peete]

That is what the bypass caps for the large electrolytic caps will do Frihed89. There is only so much room in this chassis although I do believe the resistors in the signal path DO make a noticeable difference and are worth the effort and expense.

Sebastian...what I mean by matching is having both resistors measure the same value (if you need 4.7 ohms then a pair of 4.7 ohm resistors are culled from a batch as a matched pair). Tolerance has to do with how close to the stated value the parts actually are + or - .1 %/1%/5% etc...matching is making sure you haven't got a wide variation in value that when used in the gain section would yield a balance mismatch if the resistors are way off.

Peete.

 

[SebastianL]

Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif I already use the king of power tubes with it, a costly pair of 6H30Pi-DR's from the 1980's .... Peete.

Peete, how important are these expensive tubes? Did you do a direct comparison with the standard Sovtek 6H30s or the Electro Harmonix 6H30s? What are the differences soundwise, bass/treble extension, stereo perspective, depth, transparency, dynamics?
All in all are they really worth the huge price tag?
A local danish constructor of tubeamps with more than 20 years of experience, tells me that all the 6H30 type tube are exactly the same, made at the same factory. They only put different stamps on the tubes to justify the high pricetag.
He knows the specs of the 6H30 by heart - he's that much into tubes!
Of course I know that reportedly the 6H30Pi-DR's have been through intensive testing to meet mill. requirements, but are they worth it?

 

[SebastianL]

This is what I'm talking about:
"hello TG,

Jean Cristophe Morrison, the in-house tube wizard
at New Sensor has tested the Saratov against the
Sovtek. He told me that they are axactly the same.
From my own tests I agree with him.
In some application the Sovtek is better because of lower microphony.
BAT uses the original russian 6H30P-DR and not the Sovteks to realize a higher price."
6H30Pi variants [Archive] - diyAudio

 

[Frihed89]

Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif That is what the bypass caps for the large electrolytic caps will do Frihed89. There is only so much room in this chassis although I do believe the resistors in the signal path DO make a noticeable difference and are worth the effort and expense. Peete.

OK. You are the boss!

 

[SebastianL]

For those interested, by now I have done all of the planned modifications. Latest modification was subbing the output caps with the Russian PIO / FT3 Teflon combo. After the initial harshness had disappeared I did a comparison with the Ampohm caps and I did not notice any significant difference.
But according to my guide through this venture of modding, Prciklely Peete, the Teflons take about 700 hours to do a full burn in (the Ampohms as well take a long time).

Thus I’m in the tedious process of burning in the output caps the next couple of months. It wouldn’t be fair to draw any final conclusions until then.
But so far I can say that I’m very satisified with the mods I’ve done. Subbing the WIMA caps with the Jantzens being the most significant upgrade.

Discovering that exchanging the resistors was very difficult, I gave up less than halfway through this particular mod. The problem is that the existing pinholes in the PCB for the standard resistors were too small for the larger Kiwame and Holco resistors and I wouldn’t risk damaging the PCB. I managed to install a few Kiwame resistors in the signal path (both L and R of course). Luckily the three standard 5w ceramic resistors were quite large and I had no trouble replacing them with Kiwames. I measured of all the Kiwame and Holco resistors before installing them, and I managed to get matched pairs or very close to matched pairs with all of them. They were all very close to the stated value. Maybe I will eventually install the rest of the resistors with some sort of pin extension. That will have be a holiday job when I have nothing else to do since it’s a real PITA!

Some time ago I also replaced the original Sovtek 6H30П–EB with a pair of very cheap mil. spec. 6H6П. IMO a huge upgrade. Much better bass response and bass extension. (This is a bit off topic, I know) They sell for cheap in bundles on eBay.

 

[Pricklely Peete]

Quote:

Originally Posted by SebastianL /img/forum/go_quote.gif This is what I'm talking about: "hello TG, Jean Cristophe Morrison, the in-house tube wizard at New Sensor has tested the Saratov against the Sovtek. He told me that they are axactly the same. From my own tests I agree with him. In some application the Sovtek is better because of lower microphony. BAT uses the original russian 6H30P-DR and not the Sovteks to realize a higher price." 6H30Pi variants [Archive] - diyAudio

Your source is correct there is no sonic difference between the Sovtek or the EH Gold Pin. They are both built the same way with mostly the same materials. The DR's are another animal compared to the new production 6H30's, the NOS DR's are far better constructed and sound a little more extended and in control of the bass. The treble region has a little more sparkle with the mids being very smooth/creamy without sounding syrupy. I bet the Teflon/PIO caps are contributing a great deal to the overall sound so it's tough to gauge how much of the effect is attributed to the tubes or the new parts.....but,
It's been a while since I compared the NOS DR's vs the Sovteks ( I have both) so allow me to reacquaint myself with my LD MK III and I'll get back to you guys in few days with some fresh listening evaluations to report.

Good job thus far Sebastian, taking on a mod of this scope is commendable

....the hard part is waiting on the burn in of the Teflon/PLIO cap pairs. It's fun to listen along the way and take mental notes during the process.

Keep us informed as to your thoughts and progress

Peete.

 

[SebastianL]

Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif Your source is correct there is no sonic difference between the Sovtek or the EH Gold Pin. They are both built the same way with mostly the same materials. The DR's are another animal compared to the new production 6H30's, the NOS DR's are far better constructed and sound a little more extended and in control of the bass. The treble region has a little more sparkle with the mids being very smooth/creamy without sounding syrupy. I bet the Teflon/PIO caps are contributing a great deal to the overall sound so it's tough to gauge how much of the effect is attributed to the tubes or the new parts.....but, It's been a while since I compared the NOS DR's vs the Sovteks ( I have both) so allow me to reacquaint myself with my LD MK III and I'll get back to you guys in few days with some fresh listening evaluations to report. Good job thus far Sebastian, taking on a mod of this scope is commendable ....the hard part is waiting on the burn in of the Teflon/PLIO cap pairs. It's fun to listen along the way and take mental notes during the process. Keep us informed as to your thoughts and progress Peete.

I tried the 6H6П before I did the Teflon/PIO mod and it definitely had a serious impact. The 6H6П is not the leanest tube out there (soundwise), but that's what I like about it. Suddenly the acoustics of my classical recordings became much more apparent. The character of the room - much more like a vivid concert feeling. Tending a little bit towards the magnificent Stax combo I heard some weeks ago.

Anybody did a comparison between the 6H6П and the DRs?

 

[KMASCII]

Quote:

Originally Posted by SebastianL /img/forum/go_quote.gif Subbing the WIMAs with the Jantzens (the first mod I did) made a HUGE difference on the SQ. WOV! The annoying lack of treble (the biggest issue for me) was gone. Now, a lot of clear treble – maybe adding a tad too much emphasis on the high frequencies. But I was so content I was about to stop the modding process. However I had already bought or ordered a lot of other components. Thus, I went on tweaking.

I've ordered some caps to sample and swap for the WIMA's in my stock LD MKIII. Although I'd appreciate any added clarity and imaging, your comments about a prior lack of treble worry me a bit. I'm not wanting to take my LD any closer to a solid state sound than it already has. If anything, I'd look to toning down the lower high frequencies just a tad.

I listen to a mix of rock & acoustic through HD650's with GE 5654 5stars and 6H6n's. These are the tubes I'd finally settled on, and I find this combination just a smidgen bright at times. Other tubes I've tried turned out to be just a little dark or unrevealing for my liking.

I guess I'm looking for a more tubey sound, if you will. I wonder if I'll have to revisit some of my other tubes should replacing the WIMA caps expose too much of the highs. I'll try to remember to report back on my experiment and experience.

 

[SebastianL]

Quote:

Originally Posted by KMASCII /img/forum/go_quote.gif I've ordered some caps to sample and swap for the WIMA's in my stock LD MKIII. Although I'd appreciate any added clarity and imaging, your comments about a prior lack of treble worry me a bit. I'm not wanting to take my LD any closer to a solid state sound than it already has. If anything, I'd look to toning down the lower high frequencies just a tad.

Did you do a thorough burn in of the LD? It takes quite a while before the final sound settles in.
After the upgrades that I made, the amp doesn't sound like solid state. Still got the tube sound. In fact, before the upgrades I was disappointed with the lack of 'tubey' sound, and I think it will be difficult to kill that altogether.

I apologize for not posting a full report of the final results concerning the upgrades. It's due to lack of time. I'm still meaning to make a final conclusion once I get some time to do so.