Dennis Had Inspire Amps

[BearCityUSA]

Originally Posted by Analog Addict

Great shape cosmetically and electronically are two different things. I also picked up a used Hickok (533) a few years back, and had it restored and professionally calibrated. Assuming it uses the same rectifiers, your 600 would use a 83 and a 5Y3 rectifier. First thing I would do is replace the rectifiers with known good ones, and potentially replace any electrolytics while you're underneath it. Then calibrate it or get it calibrated. Get a calibrated reference tube as well. Typically the Hickoks use a 6L6 as their reference calibration tube, although I use a 45 that measures exactly at 100%....

"good shape" of course is relative and I was not speaking of Cosmetics. The add read:

"For sale is a very nice Hickok 600A Tube Tester. All sockets have been cleaned and are tight. All wires in very good condition with no cracks in insulation. Instructions and tube data is included on a CD. The case is a little rough looking but solid. All caps and power cord have been replaced. The 83 tube has been replaced with a SS 83. The tester in great working condition. The one picture shows a 83 tube being tested. One picture shows the repair report for the tester. Please look at all pictures before bidding."

It arrived yesterday and I have had a little time to play with it today. I have not opened it up to verify what the seller claimed. Maybe I should though I do default to trusting people. Sometimes I regret it.

[Musica Amantem]

I'll be trying the following scenarios:

1. PRE: Shg CV-181 T, Silvertone 56's, Radiotron 80
AMP: Psvane CV-181 T-II, GL KT-77's, Brimar 5Z4

2. (1.) direct to AMP through ZBit (balanced), skipping PRE

3. (1.) and (2.) with VA 6550's, OTBE

4. (1.) and (2.) replacing SE 274B for Brimar 5Z4

5. (1.) and (2.) replacing Amperex 5AR4 for Brimar5 Z4

Plenty of combiinations to ID the best of the best in my stable, although all these sound great!

Who said anything about tube-rolling ?

[goldhorse]

Dennis Had Inspire first impressions:

I’ve had since Monday to listen to the LP-3a and Hot-Rod (stock KT66 valves).
Up until now I’ve been using a a 300B based SE integrated amp, and before that a LINN Majik DSM.
These are actually just my second set of tube amps so my impressions are mainly in comparison to the 300B amp.

The things that stood out were extended highs, a deeper and controlled bass, a more analytical and at the same time in your face sound presentation. In terms of power, while my 300B amp is rated at 8wpc, and the the Hot-Rod with the KT66 tubes 12wpc, I find I have to turn the volume on the Inspire about 20% higher to achieve the same volume level as the 300B. This is probably because the latter has more powerful transformers (judging from their size and weight which is almost twice that of the Hot-rod). Nevertheless, I seldom need to turn up the volume on the Inspire more than the 12 O’clock position, mostly on old classic recordings. The Harbeth Compact 7ES-3 they drive, despite their published inefficiency, always seem to work well with single end tube amps.

As my analog source, I use a Luxman PD-171A TT, Denon DL-103 MC, and an iFi micro iPhono2 phono stage. I have the iPhono2 set to 60db gain. I did try boosting the gain to 72db, but while this allowed me to listen comfortably with the volume at just around the 8 O’clock position, this resulted in clicking noises when I turn the volume, so I would rather turn up the volume on the amp than have unwanted noises.

As I mentioned earlier, I found the Inspire to sound more analytical and in your face. When I first listened to them I was surprised to hear nuances I did not notice before, the vocals or soloists practically leaping out at you, while instruments in the background are in their rightful positions. I almost whooped in delight. But frankly, after a time I found that I experienced hearing fatigue, maybe because I was used to the warmer, and laid back sound of the 300B. I made some adjustments in the phono stage (changed the load from 1K to 330), swapped out connection cables (silver to copper) and let time do the rest. I’ve had them running for at least 2 hours a day, and just left the power on practically for the whole day Now they are much less fatiguing (partly because I guess my ears have grown used to them) and needless to say a joy to listen to.

I’ll leave the stock tubes on for now, but I plan to try out other KT versions going forward. I guess one of the biggest reasons I got the Inspire is that they are so versatile, which means more options in tube usage. I wanted more control on the sound and these provide me more viable compared to my 300B, not to mention 300B can be quite expensive so I was just content to rolling the 12ax7 and 12au7 in the gain and driver stages.

BTW, I really like the iPhono2, it’s just so fun to be able to adjust load, gain, equalization, and I think it won’t shame itself connected to way expensive systems, but at the same time won’t break the bank. That being said, I eventually want a tube version to complete the set. I just got wind of Tavish Design Vintage, which is a 6SL7 based MM/MC phono stage, and almost same price range as the iPhono2. You can also get it as a kit, and save more. That being said I am still hoping that Dennis will get around to building the production version of his phono stage and hope it has MC as well. Last time I asked him about it, he seemed satisfied with his prototype, and just needed time to build the production version. Since I ordered my Hot-Rod he seems to have sold some more units in Ebay though so hey may be busy with that project still

[pstrisik]

Welcome goldhorse! And congratulations on the excellent acquisition!

New or used? If new, you will find some mellowing after some hours, both from acclimation of your perceptual system and from break in of caps and tubes (if they are new).

I would suggest grabbing a pair of new production Gold Lion KT-77's. I have found them to be tops in my Inspire as have some others here. They even out shine some of the preferred vintage types. If you have a newer model with the IIPS mod, the rectifier won't make a huge difference. Which driver type does it take? Mine is the 6922 family. Dennis seems to have moved away from that tube in later models. For this type, the Russian variants (usually 1970's-80's) do the best for me.

[BearCityUSA]

Originally Posted by Analog Addict

Great shape cosmetically and electronically are two different things. I also picked up a used Hickok (533) a few years back, and had it restored and professionally calibrated. Assuming it uses the same rectifiers, your 600 would use a 83 and a 5Y3 rectifier. First thing I would do is replace the rectifiers with known good ones, and potentially replace any electrolytics while you're underneath it. Then calibrate it or get it calibrated. Get a calibrated reference tube as well. Typically the Hickoks use a 6L6 as their reference calibration tube, although I use a 45 that measures exactly at 100%....

AA,

Thanks for the advice BTW. I re read my previous post and it reads a bit less than gracious. Anyway, where do you suggest getting the reference tube? I see Brent Jesse has a 6l6 but he seems to want a good amount for one. Likely the going rate retail.

[Bombadil]

Originally Posted by goldhorse

In terms of power, while my 300B amp is rated at 8wpc, and the the Hot-Rod with the KT66 tubes 12wpc, I find I have to turn the volume on the Inspire about 20% higher to achieve the same volume level as the 300B. This is probably because the latter has more powerful transformers (judging from their size and weight which is almost twice that of the Hot-rod).

One cannot judge power levels between two amps by the position of the volume control. Some amps are more sensitive than others. Some will reach full output power with a 1.0V input signal, others at 1.5V, and still others at 2.0V. You can have two amps, one rated at 20 wpc and the other at 30 wpc, and the 20 wpc amp could be louder at a volume setting at 10 o'clock because it reaches full power with a lower input voltage.

Both of my Inspire amps are less sensitive than all of my other amps.

[Bombadil]

Originally Posted by goldhorse

As I mentioned earlier, I found the Inspire to sound more analytical and in your face. When I first listened to them I was surprised to hear nuances I did not notice before, the vocals or soloists practically leaping out at you, while instruments in the background are in their rightful positions. I almost whooped in delight. But frankly, after a time I found that I experienced hearing fatigue, maybe because I was used to the warmer, and laid back sound of the 300B.

This has been true for me with some tube sets. If I have a 6SL7 sub'ed in for the stock 6SN7, I can't listen for more than 5-10 minutes before fatigue sets in. I can listen longer when using 6P3S-E output tubes, for up to an hour, but then the same. Longer still for 6V6 output tubes, but eventually they get to me. But with EL34 tubes, it has a very laid back sound, to the point of lacking sufficient detail. I like the sound with Gold Lion KT66s, these are detailed, but less so than others. I find that I like this level of clarity and imaging. Still swapping others in and out, and liking the sound of KT88s and KT120s.

[goldhorse]

Originally Posted by pstrisik

Welcome goldhorse! And congratulations on the excellent acquisition!

Thanks! I am glad I found your thread. It helped me a lot in making my decision.

Originally Posted by pstrisik

New or used? If new, you will find some mellowing after some hours, both from acclimation of your perceptual system and from break in of caps and tubes (if they are new).

They're new. I got the Hot-Rod off from ebay end of last month, then ordered the LP-3a directly right after. The power tubes I think are new, the rest of the tubes, not so sure. Dennis said he had these playing over a weekend before sending, plus a week since I had them so I think these have around 20-30 hours on them. Indeed I have noticed a mellowing the past couple of days, and have been able to listen for longer stretches of time.

Originally Posted by pstrisik

I would suggest grabbing a pair of new production Gold Lion KT-77's. I have found them to be tops in my Inspire as have some others here. They even out shine some of the preferred vintage types.

Thanks for your suggestions. I do plan on eventually getting all the KT in multiples of 11 I'll start with the KT77 then as they look to have positive feedback in this thread.

Originally Posted by pstrisik

If you have a newer model with the IIPS mod, the rectifier won't make a huge difference.

Yes, I have the IIPS mod. What's interesting though is that Dennis mentioned that while the choice of rectifier tube is not crucial, but if I did swap them, he told me to stick with directly heated types. Perhaps this is because of how the IIPS is wired.

Originally Posted by pstrisik

Which driver type does it take? Mine is the 6922 family. Dennis seems to have moved away from that tube in later models. For this type, the Russian variants (usually 1970's-80's) do the best for me.

Mine are 6SN7 based. The amps came with Philco tubes, and I think I'll stick with them for the meantime while I try out different power tubes. Then I am thinking of trying out Psvane CV-181s, if I can manage to fit them in. These have smaller footprints than the early Firebottles.

[goldhorse]

Originally Posted by Bombadil

One cannot judge power levels between two amps by the position of the volume control. Some amps are more sensitive than others. Some will reach full output power with a 1.0V input signal, others at 1.5V, and still others at 2.0V. You can have two amps, one rated at 20 wpc and the other at 30 wpc, and the 20 wpc amp could be louder at a volume setting at 10 o'clock because it reaches full power with a lower input voltage.

Both of my Inspire amps are less sensitive than all of my other amps.

Point taken. I've owned a number of amps before and I guess the Inspire's sensitivity seem to be the lowest one so far, my 300B included. Nevertheless they have sufficient power, and some to spare for my needs. The good thing that comes out of this though is that I am able to fine tune the volume better than my previous amps.

Originally Posted by Bombadil

This has been true for me with some tube sets. If I have a 6SL7 sub'ed in for the stock 6SN7, I can't listen for more than 5-10 minutes before fatigue sets in. I can listen longer when using 6P3S-E output tubes, for up to an hour, but then the same. Longer still for 6V6 output tubes, but eventually they get to me. But with EL34 tubes, it has a very laid back sound, to the point of lacking sufficient detail. I like the sound with Gold Lion KT66s, these are detailed, but less so than others. I find that I like this level of clarity and imaging. Still swapping others in and out, and liking the sound of KT88s and KT120s.

Dennis did suggest the 6SL7's if I wanted more sparkle on the high end. But judging from what I'm hearing, I may find them fatiguing too. After tweaking around with cables and phono loads, I seem to have found an equilibrium with the stock 6SN7 and KT66 combination. These do have sufficient details without being too clinical. I'm thinking of trying KT77's next, as they seem to be a nice compromise for the EL34.

[Bombadil]

I didn't find the 6SN7s to be "sparkling." It was more like aggressively forward in the upper midrange and treble. For a few minutes I found the increased detail to be interesting, I was hearing strings, percussion, piano like never before. Then after a few minutes I started getting a headache.